Microstructure Evolution and Composition Control During the Processing of Thin-Gage Metallic Foil

NASA Astrophysics Data System (ADS)

Semiatin, S. L.; Gross, M. E.; Matson, D. W.; Bennett, W. D.; Bonham, C. C.; Ustinov, A. I.; Ballard, D. L.

2012-12-01

The manufacture of thin-gage superalloy and gamma-titanium-aluminide foil products via near-conventional thermomechanical processing and two different vapor-deposition methods was investigated. Thermomechanical processing was based on hot-pack rolling of plate and sheet. Foils of the superalloy LSHR and the near-gamma titanium aluminide Ti-45.5Al-2Cr-2Nb made by this approach exhibited excellent gage control and fine two-phase microstructures. The vapor-phase techniques used magnetron sputtering (MS) of a target of the desired product composition or electron-beam physical vapor deposition (EBPVD) of separate targets of the specific alloying elements. Thin deposits of LSHR and Ti-48Al-2Cr-2Nb made by MS showed uniform thickness/composition and an ultrafine microstructure. However, systematic deviations from the specific target composition were found. During subsequent heat treatment, the microstructure of the MS samples showed various degrees of grain growth and coarsening. Foils of Ti-43Al and Ti-51Al-1V fabricated by EBPVD were fully dense. The microstructures developed during EBPVD were interpreted in terms of measured phase equilibria and the dependence of evaporant flux on temperature.

Review: Microstructure Engineering of Titanium Alloys via Small Boron Additions (Preprint)

DTIC Science & Technology

2011-07-01

small amount of boron to γ titanium aluminides (TiAl) has been found to improve room temperature ductility [12]. The principal effect of boron...AFRL-RX-WP-TP-2011-4298 REVIEW: MICROSTRUCTURE ENGINEERING OF TITANIUM ALLOYS VIA SMALL BORON ADDITIONS (Preprint) D.B. Miracle...2011 Journal Article Preprint 01 July 2011 – 01 July 2011 4. TITLE AND SUBTITLE REVIEW: MICROSTRUCTURE ENGINEERING OF TITANIUM ALLOYS VIA SMALL

International Conference on Mechanical Fatigue of Advanced Materials Held in Santa Barbara, California on 13-18 January 1991

DTIC Science & Technology

1991-02-15

been published on the basic microstructure of the monolithic alloys, particularly in the case of nickel and titanium aluminides , and several composite...34Initiation and Growth in Iniermetallic Compounds- N.S. Stoloff (invited) "Fatigue of Titanium Aluminides at Ambient and Elevated Ternperaiures" ). Bowen...applications such as life estimation for gas-turbine blades , the relevance of "small-crack" data is not fully appreciated. 3 Metal-Matrix Composites

Microstructure-Property-Design Relationships in the Simulation Era: An Introduction (PREPRINT)

DTIC Science & Technology

2010-01-01

Astronautics (AIAA) paper #1026. 20. Dimiduk DM (1998) Systems engineering of gamma titanium aluminides : impact of fundamentals on development strategy...microstructure-sensitive design tools for single-crystal turbine blades provides an accessible glimpse into future computational tools and their data...requirements. 15. SUBJECT TERMS single-crystal turbine blades , computational methods, integrated computational materials 16. SECURITY

Spark plasma sintering of titanium aluminide intermetallics and its composites

NASA Astrophysics Data System (ADS)

Aldoshan, Abdelhakim Ahmed

Titanium aluminide intermetallics are a distinct class of engineering materials having unique properties over conventional titanium alloys. gamma-TiAl compound possesses competitive physical and mechanical properties at elevated temperature applications compared to Ni-based superalloys. gamma-TiAl composite materials exhibit high melting point, low density, high strength and excellent corrosion resistance. Spark plasma sintering (SPS) is one of the powder metallurgy techniques where powder mixture undergoes simultaneous application of uniaxial pressure and pulsed direct current. Unlike other sintering techniques such as hot iso-static pressing and hot pressing, SPS compacts the materials in shorter time (< 10 min) with a lower temperature and leads to highly dense products. Reactive synthesis of titanium aluminide intermetallics is carried out using SPS. Reactive sintering takes place between liquid aluminum and solid titanium. In this work, reactive sintering through SPS was used to fabricate fully densified gamma-TiAl and titanium aluminide composites starting from elemental powders at different sintering temperatures. It was observed that sintering temperature played significant role in the densification of titanium aluminide composites. gamma-TiAl was the predominate phase at different temperatures. The effect of increasing sintering temperature on microhardness, microstructure, yield strength and wear behavior of titanium aluminide was studied. Addition of graphene nanoplatelets to titanium aluminide matrix resulted in change in microhardness. In Ti-Al-graphene composites, a noticeable decrease in coefficient of friction was observed due to the influence of self-lubrication caused by graphene.

Effect of Energy Input on Microstructure and Mechanical Properties of Titanium Aluminide Alloy Fabricated by the Additive Manufacturing Process of Electron Beam Melting

PubMed Central

Mohammad, Ashfaq; Alahmari, Abdulrahman M.; Mohammed, Muneer Khan; Renganayagalu, Ravi Kottan; Moiduddin, Khaja

2017-01-01

Titanium aluminides qualify adequately for advanced aero-engine applications in place of conventional nickel based superalloys. The combination of high temperature properties and lower density gives an edge to the titanium aluminide alloys. Nevertheless, challenges remain on how to process these essentially intermetallic alloys in to an actual product. Electron Beam Melting (EBM), an Additive Manufacturing Method, can build complex shaped solid parts from a given feedstock powder, thus overcoming the shortcomings of the conventional processing techniques such as machining and forging. The amount of energy supplied by the electron beam has considerable influence on the final build quality in the EBM process. Energy input is decided by the beam voltage, beam scan speed, beam current, and track offset distance. In the current work, beam current and track offset were varied to reflect three levels of energy input. Microstructural and mechanical properties were evaluated for these samples. The microstructure gradually coarsened from top to bottom along the build direction. Whereas higher energy favored lath microstructure, lower energy tended toward equiaxed grains. Computed tomography analysis revealed a greater amount of porosity in low energy samples. In addition, the lack of bonding defects led to premature failure in the tension test of low energy samples. Increase in energy to a medium level largely cancelled out the porosity, thereby increasing the strength. However, this trend did not continue with the high energy samples. Electron microscopy and X-ray diffraction investigations were carried out to understand this non-linear behavior of the strength in the three samples. Overall, the results of this work suggest that the input energy should be considered primarily whenever any new alloy system has to be processed through the EBM route. PMID:28772572

Effect of Energy Input on Microstructure and Mechanical Properties of Titanium Aluminide Alloy Fabricated by the Additive Manufacturing Process of Electron Beam Melting.

PubMed

Mohammad, Ashfaq; Alahmari, Abdulrahman M; Mohammed, Muneer Khan; Renganayagalu, Ravi Kottan; Moiduddin, Khaja

2017-02-21

Titanium aluminides qualify adequately for advanced aero-engine applications in place of conventional nickel based superalloys. The combination of high temperature properties and lower density gives an edge to the titanium aluminide alloys. Nevertheless, challenges remain on how to process these essentially intermetallic alloys in to an actual product. Electron Beam Melting (EBM), an Additive Manufacturing Method, can build complex shaped solid parts from a given feedstock powder, thus overcoming the shortcomings of the conventional processing techniques such as machining and forging. The amount of energy supplied by the electron beam has considerable influence on the final build quality in the EBM process. Energy input is decided by the beam voltage, beam scan speed, beam current, and track offset distance. In the current work, beam current and track offset were varied to reflect three levels of energy input. Microstructural and mechanical properties were evaluated for these samples. The microstructure gradually coarsened from top to bottom along the build direction. Whereas higher energy favored lath microstructure, lower energy tended toward equiaxed grains. Computed tomography analysis revealed a greater amount of porosity in low energy samples. In addition, the lack of bonding defects led to premature failure in the tension test of low energy samples. Increase in energy to a medium level largely cancelled out the porosity, thereby increasing the strength. However, this trend did not continue with the high energy samples. Electron microscopy and X-ray diffraction investigations were carried out to understand this non-linear behavior of the strength in the three samples. Overall, the results of this work suggest that the input energy should be considered primarily whenever any new alloy system has to be processed through the EBM route.

In-service testing of Ni{sub 3}Al coupons and trays in carburizing furnaces at Delphi Saginaw. CRADA final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sikka, V.K.; Santella, M.L.; Viswanathan, S.

1998-08-01

This Cooperative Research and Development Agreement (CRADA) report deals with the development of nickel aluminide alloy for improved longer life heat-resistant fixture assemblies for batch and continuous pusher carburizing furnaces. The nickel aluminide development was compared in both coupon and component testing with the currently used Fe-Ni-Cr heat-resisting alloy known as HU. The specific goals of the CRADA were: (1) casting process development, (2) characterization and possible modification of the alloy composition to optimize its manufacturing ability and performance under typical furnace operating conditions, and (3) testing and evaluation of specimens and prototype fixtures. In support of the CRADA objectives,more » coupons of nickel aluminide and the HU alloy were installed in both batch and pusher furnaces. The coupons were taken from two silicon levels and contained welds made with two different filler compositions (IC-221LA and IC-221W). Both nickel-aluminide and HU coupons were removed from the batch and pusher carburizing furnace at time intervals ranging from one month to one year. The exposed coupons were cut and mounted for metallographic, hardness, and microprobe analysis. The results of the microstructural analysis have been transmitted to General Motors Corporation, Saginaw Division (Delphi Saginaw) through reports that were presented at periodic CRADA review meetings. Based on coupon testing and verification of the coupon results with the testing of trays, Delphi Saginaw moved forward with the use of six additional trays in a batch furnace and two assemblies in a pusher furnace. Fifty percent of the trays and fixtures are in the as-cast condition and the remaining trays and fixtures are in the preoxidized condition. The successful operating experience of two assemblies in the pusher furnace for nearly a year formed the basis for a production run of 63 more assemblies. The production run required melting of 94 heats weighing 500 lb. each. Twenty-six of the 94 heats were from virgin stock, and 68 were from the revert that used 50% virgin and 50% revert. Detailed chemical analysis of the 94 heats reflected that the nickel aluminide can be cast into heat-treat fixtures under production conditions. In addition to the chemical analysis, the castings showed excellent dimensional reproducibility. A total of six batch furnace trays and 65 pusher furnace assemblies of nickel aluminide alloy IC-221M are currently operating in production furnaces at Delphi Saginaw. Two of the pusher furnace assemblies have completed two years of service without any failure. The CRADA has accomplished the goal of demonstrating that the nickel aluminide can be produced under commercial production conditions and it has superior performance over the currently used HU alloy in both batch and pusher furnaces.« less

Microstructure and properties of cryomilled nickel aluminide extruded with chromium or molybdenum

NASA Technical Reports Server (NTRS)

Aikin, Beverly J. M.; Dickerson, Robert M.; Dickerson, Patricia O.

1995-01-01

Previous results from high energy, attrition milled NiAl in liquid nitrogen (cryomilled) indicate that this process can produce high temperature, creep resistant AlN particulate reinforced materials. However, the low temperature toughness of such materials is below that preferred for structural applications in aerospace engines. In order to improve the toughness of these materials, prealloyed nickel aluminide (Ni-53 atomic percent Al) powder was cryomilled and mixed with chromium or molybdenum powders. The resulting materials were hot extruded and tested for room temperature toughness and 1300 K compressive strength.

Formation of microstructural features in hot-dip aluminized AISI 321 stainless steel

NASA Astrophysics Data System (ADS)

Huilgol, Prashant; Rajendra Udupa, K.; Udaya Bhat, K.

2018-02-01

Hot-dip aluminizing (HDA) is a proven surface coating technique for improving the oxidation and corrosion resistance of ferrous substrates. Although extensive studies on the HDA of plain carbon steels have been reported, studies on the HDA of stainless steels are limited. Because of the technological importance of stainless steels in high-temperature applications, studies of their microstructural development during HDA are needed. In the present investigation, the HDA of AISI 321 stainless steel was carried out in a pure Al bath. The microstructural features of the coating were studied using scanning electron microscopy and transmission electron microscopy. These studies revealed that the coating consists of two regions: an Al top coat and an aluminide layer at the interface between the steel and Al. The Al top coat was found to consist of intermetallic phases such as Al7Cr and Al3Fe dispersed in an Al matrix. Twinning was observed in both the Al7Cr and the Al3Fe phases. Furthermore, the aluminide layer comprised a mixture of nanocrystalline Fe2Al5, Al7Cr, and Al. Details of the microstructural features are presented, and their formation mechanisms are discussed.

A review of rapid solidification studies of intermetallic compounds

NASA Technical Reports Server (NTRS)

Koch, C. C.

1985-01-01

A review of rapid solidification studies of high-temperature ordered intermetallic compounds is presented. Emphasis is on the nickel - and iron- aluminides which are of potential interest as structural materials. The nickel-base aluminides which have been rapidly solidified exhibit changes in grain size, compositional segregation, and degree of long range order (as reflected in APB size and distribution) which markedly affect mechanical properties. Some experiments indicate the formation of a metastable L1(2) phase in rapidly solidified Fe-(Ni,Mn)-Al-C alloys, while other work observes only a metastable fcc phase in the same composition range. The metastable phases and/or microstructures in both nickel and iron aluminides are destroyed by annealing at temperatures above 750 K, with subsequent degradation of mechanical properties. Rapid solidification studies of several other intermetallic compounds are briefly noted.

Nonequilibrium Phase Chemistry in High Temperature Structure Alloys

NASA Technical Reports Server (NTRS)

Wang, R.

1991-01-01

Titanium and nickel aluminides of nonequilibrium microstructures and in thin gauge thickness were identified, characterized and produced for potential high temperature applications. A high rate sputter deposition technique for rapid surveillance of the microstructures and nonequilibrium phase is demonstrated. Alloys with specific compositions were synthesized with extended solid solutions, stable dispersoids, and specific phase boundaries associated with different heat treatments. Phase stability and mechanical behavior of these nonequilibrium alloys were investigated and compared.

Study of the Influence of Metallurgical Factors on Fatigue and Fracture of Aerospace Structural Materials

DTIC Science & Technology

1989-03-01

11 II. MICROSTRUCTURE/ PROPERTY RELATIONSHIPS IN ADVANCED 12 STRUCTURAL ALLOYS A. Research Objectives 12 B. Summary of Research Efforts 12 1. Fracture...relationship is needed. Figure 5. Correlation between crack growth rates and effective 7 AK for small and large fatigue cracks in a titanium aluminide ...Microstructural/ Property Relationships in Advanced Structural Alloys Table I. Tensile and Fracture Properties of A-Fe-X Alloys in the 13 LT

Micromechanical Characterization and Texture Analysis of Direct Cast Titanium Alloys Strips

NASA Technical Reports Server (NTRS)

2000-01-01

This research was conducted to determine a post-processing technique to optimize mechanical and material properties of a number of Titanium based alloys and aluminides processed via Melt Overflow Solidification Technique (MORST). This technique was developed by NASA for the development of thin sheet titanium and titanium aluminides used in high temperature applications. The materials investigated in this study included conventional titanium alloy strips and foils, Ti-1100, Ti-24Al-11Nb (Alpha-2), and Ti-48Al-2Ta (Gamma). The methodology used included micro-characterization, heat-treatment, mechanical processing and mechanical testing. Characterization techniques included optical, electron microscopy, and x-ray texture analysis. The processing included heat-treatment and mechanical deformation through cold rolling. The initial as-cast materials were evaluated for their microstructure and mechanical properties. Different heat-treatment and rolling steps were chosen to process these materials. The properties were evaluated further and a processing relationship was established in order to obtain an optimum processing condition. The results showed that the as-cast material exhibited a Widmanstatten (fine grain) microstructure that developed into a microstructure with larger grains through processing steps. The texture intensity showed little change for all processing performed in this investigation.

Preliminary investigation of inertia friction welding B2 aluminides

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Moore, Thomas J.; Kuruzar, Daniel L.

1987-01-01

An attempt is made to achieve inertia friction-welding in FeAl and NiAl samples, taking into account their intermetallics' compositions, extrusion parameters, and microstructural data. The energy required for the weld is stored in a rotating flywheel mass attached to one of the two pieces to be joined; when enough energy is introduced, the flywheel is disconnected and an axial load is applied which forces the spinning piece against the stationary one, converting the energy into heat by means of friction. Due to the inherent brittleness of the aluminides, a step-load program was used in which an initial, low-pressure heat buildup increased the work pieces' ductility.

1000 to 1300 K slow plastic compression properties of Al-deficient NiAl

NASA Technical Reports Server (NTRS)

Whittenberger, J. D.; Kumar, K. S.; Mannan, S. K.

1991-01-01

Nickel aluminides containing 37, 38.5 and 40 at. pct Al have been fabricated by XD synthesis and hot pressing. Such materials were compression tested in air under constant velocity conditions between 1000 and 1300 K. Examination of the microstructures of hot pressed and compression tested aluminides indicated that the structure consisted of two phases, gamma-prime and NiAl, for essentially all conditions, where gamma-prime was usually found on the NiAl grain boundaries. The stress-strain behavior of all three intermetallics was similar where flow at a nominally constant stress occurred after about two-percent plastic deformation. Furthermore, the 1000 to 1300 K flow stress-strain rate properties are nearly identical for these materials, and they are much lower than those for XD processed Ni-50Al. The overall deformation of the two phase nickel aluminides appears to be controlled by dislocation climb in NiAl rather than processes in gamma-prime.

Formation of Aluminide Coatings on Fe-Based Alloys by Chemical Vapor Deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Ying; Pint, Bruce A; Cooley, Kevin M

2008-01-01

Aluminide and Al-containing coatings were synthesized on commercial ferritic (P91) and austenitic (304L) alloys via a laboratory chemical vapor deposition (CVD) procedure for rigorous control over coating composition, purity and microstructure. The effect of the CVD aluminizing parameters such as temperature, Al activity, and post-aluminizing anneal on coating growth was investigated. Two procedures involving different Al activities were employed with and without including Cr-Al pellets in the CVD reactor to produce coatings with suitable thickness and composition for coating performance evaluation. The phase constitution of the as-synthesized coatings was assessed with the aid of a combination of X-ray diffraction, electronmore » probe microanalysis, and existing phase diagrams. The mechanisms of formation of these CVD coatings on the Fe-based alloys are discussed, and compared with nickel aluminide coatings on Ni-base superalloys. In addition, Cr-Al pellets were replaced with Fe-Al metals in some aluminizing process runs and similar coatings were achieved.« less

Influence of strain rate and temperature on the mechanical behavior of iron aluminide-based alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gray, G.T.

Iron aluminides are receiving increasing attention as potential high temperature structural materials due to their excellent oxidation and sulfidation resistance. Although the influence of strain rate on the microstructure/property relationships of pure iron and a variety of iron alloys and steels has been extensively studied, the effect of strain rate on the stress-strain and deformation response of iron aluminides remains poorly understood. In this paper the influence of strain rate, varied between 0.001 and 10{sup 4} s{sup {minus}1}, and temperature, between 77 & 1073{degree}K, on the mechanical behavior of Fe-40Al-0.1B and Fe-16.12Al-5.44Cr-0.11Zr-0.13C-1.07Mo-006Y, called FAP-Y, (both in at.%) is presented. Themore » rate sensitivity and work hardening of Fe-40Al and the disordered alloy based on Fe-16% Al are discussed as a function of strain rate and temperature.« less

Interface-related deformation phenomena in intermetallic γ-titanium aluminides

NASA Astrophysics Data System (ADS)

Appel, F.; Wagner, R.

1993-01-01

The development of titanium aluminides towards higher ductility concentrates on Ti-rich alloys which are composed of the intermetallic phases γ(TiAl) and α2(Ti3Al). The two phases form a lamellar microstructure with various types of interfaces. The deformation behaviour of these materials was investigated by compression tests, which were performed for different orientations of the interfacial boundaries with respect to the sample axis. With regard to the mechanical properties the structure of the interfaces and the micromechanisms of deformation were studied by conventional and high resolution electron microscopy. Accordingly, the interfacial boundaries impede the propagation of slip across the lamellae, leading to an athermal contribution to the flow stress.

Microgravity processing of particulate reinforced metal matrix composites

NASA Technical Reports Server (NTRS)

Morel, Donald E.; Stefanescu, Doru M.; Curreri, Peter A.

1989-01-01

The elimination of such gravity-related effects as buoyancy-driven sedimentation can yield more homogeneous microstructures in composite materials whose individual constituents have widely differing densities. A comparison of composite samples consisting of particulate ceramics in a nickel aluminide matrix solidified under gravity levels ranging from 0.01 to 1.8 G indicates that the G force normal to the growth direction plays a fundamental role in determining the distribution of the reinforcement in the matrix. Composites with extremely uniform microstructures can be produced by these methods.

Method of manufacturing iron aluminide by thermomechanical processing of elemental powders

DOEpatents

Deevi, Seetharama C.; Lilly, Jr., A. Clifton; Sikka, Vinod K.; Hajaligol, Mohammed R.

2000-01-01

A powder metallurgical process of preparing iron aluminide useful as electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 20 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1 % rare earth metal, .ltoreq.1% oxygen, and/or .ltoreq.3% Cu. The process includes forming a mixture of aluminum powder and iron powder, shaping the mixture into an article such as by cold rolling the mixture into a sheet, and sintering the article at a temperature sufficient to react the iron and aluminum powders and form iron aluminide. The sintering can be followed by hot or cold rolling to reduce porosity created during the sintering step and optional annealing steps in a vacuum or inert atmosphere.

Effects of In Situ Intermetallics on the Microstructural Array and Saline Corrosion Performance of Cast Al/WCp Composites

NASA Astrophysics Data System (ADS)

Lekatou, A. G.; Gkikas, N.; Gousia, V.; Lentzaris, K.; Karantzalis, A. E.

2018-06-01

Al-matrix composites, ex situ reinforced with WC nanoparticles and in situ reinforced with Al3(Ti,W), Al12W, Al5W and Al4W, have been fabricated by casting assisted by K2TiF6 wetting agent addition and mechanical stirring. A satisfactory particle incorporation and distribution accompanied by a high reactivity have been attained. The presence, topography, chemical composition of all included phases and their occurrence as clusters or single particles are clarified and justified. Al12W is the predominant aluminide phase at WC ≤ 1.5 vol.%. Al4W (primarily) and Al5W (secondarily) are the predominant aluminide phases at WC ≥ 2.0 vol.%. WC nanoparticles have acted as heterogeneous nucleation sites to Al3Ti particles. Reverse polarization tests in 3.5 wt.% NaCl show that the governing form of corrosion is intergranular corrosion of Al around Al3FeSi2 eutectic, fine plates. The corrosion steps/mechanisms are identified. Clusters of aluminides and carbide nanoparticles, as well as intergranular WC nano-dispersoids and their Al-matrix have remained corrosion-free. The role of the aluminides combined with WC remaining nano-cores as inhibitors of the eutectic Al3FeSi2 cathodic activity is highlighted.

9th Annual Science and Engineering Technology Conference

DTIC Science & Technology

2008-04-17

Disks Composite Technology Titanium Aluminides Processing Microstructure Properties Curve Generator Go-Forward: Integrated Materials & Process Models...Initiatives Current DPA/T3s: Atomic Layer Deposition Hermetic Coatings: ...domestic ALD for electronic components; transition to fabrication process ...Production windows estim • Process capability fully established >Production specifications in place >Supply chain established •All necessary property

Two phase titanium aluminide alloy

DOEpatents

Deevi, Seetharama C.; Liu, C. T.

2001-01-01

A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.

Recrystallization and grain growth in NiAl

NASA Technical Reports Server (NTRS)

Haff, G. R.; Schulson, E. M.

1982-01-01

Aluminide intermetallics, because of their strength, microstructural stability, and oxidation resistance at elevated temperatures, represent potential structural materials for use in advanced energy conversion systems. This inherent potential of the intermetallics can currently not be realized in connection with the general brittleness of the materials under ambient conditions. It is pointed out, however, that brittleness is not an inherent characteristic. Single crystals are ductile and polycrystals may be, too, if their grains are fine enough. The present investigation is concerned with an approach for reducing material brittleness, taking into account thermal-mechanically induced grain refinement in NiAl, a B2 aluminide which melts at 1638 C and which retains complete order to its melting point. Attention is given to the kinetics of recrystallization and grain growth of warm-worked, nickel-rich material.

Microstructural Evolution in Friction Stir Welding of Ti-5111

DTIC Science & Technology

2010-08-01

titanium and titanium aluminide alloys—an overview.” Materials Science and Engineering A243 (1998) 1-24 [Semiatin 1999] S.L. Semiatin, V...ABSTRACT Titanium and titanium alloys have shown excellent mechanical, physical, and corrosion properties. To address the needs of future naval...Texture; Phase Transformation Ti-5111 Titanium 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18. NUMBER OF PAGES 174 19a

The effect of microstructure on the tensile and fatigue behavior of Ti-22Al-23Nb in air and vacuum

NASA Astrophysics Data System (ADS)

Luetjering, Stephanie

Titanium aluminide alloys containing the ordered orthorhombic (O) phase, based on Ti2AlNb, exhibit high specific strengths at elevated temperature along with good room temperature tensile ductility and fracture toughness values. They are thus considered as potential materials for aerospace applications both in their monolithic form and as matrices in metal matrix composites. Microstructure/property relationships have been studied to a great extend with regard to tensile and creep properties. However, only little is known in the key areas of fatigue crack initiation, fatigue crack propagation and fatigue life. The main objective of this work therefore is to get a comprehensive understanding of the effects of microstructural parameters (such as volume fraction of the individual phases, their size and distribution) on the cyclic properties of O-based titanium aluminides. Furthermore, the performance of these alloys in aggressive environments, a critical issue for this alloy class, is being addressed. Tensile, isothermal fatigue, and fatigue crack growth (FCG) tests were conducted at 20°C and 540°C both in lab air and vacuum (pressure ≤ 1 x 10-6 torr) on three microstructural conditions of a representative O-based titanium alloy, Ti-22Al-23Nb. Results indicate a strong effect of microstructure on tensile and FCG properties, whereas only a slight influence of microstructure on the fatigue life is evident. The O phase contributes mainly to the material's yield stress. The tensile elongation is predominantly influenced by the beta phase volume fraction. The observed effect of microstructure on the FCG behavior is attributed to crack closure, crack front geometry and crystallographic texture. Environmental effects on the fatigue life are pronounced at elevated temperature and high applied stress amplitudes only. These conditions lead to premature crack initiation at the specimen's surface for testing in air, whereas testing in vacuum results in subsurface crack nucleation and an extended fatigue life of about two orders of magnitude. The FCG behavior is influenced by the environment at both 20°C and 540°C, proposing fatigue crack growth mechanisms enhanced by hydrogen embrittlement.

Continuous fiber-reinforced titanium aluminide composites

NASA Technical Reports Server (NTRS)

Mackay, R. A.; Brindley, P. K.; Froes, F. H.

1991-01-01

An account is given of the fabrication techniques, microstructural characteristics, and mechanical behavior of a lightweight, high service temperature SiC-reinforced alpha-2 Ti-14Al-21Nb intermetallic-matrix composite. Fabrication techniques under investigation to improve the low-temperature ductility and environmental resistance of this material system, while reducing manufacturing costs to competitive levels, encompass powder-cloth processing, foil-fiber-foil processing, and thermal-spray processing. Attention is given to composite microstructure problems associated with fiber distribution and fiber-matrix interfaces, as well as with mismatches of thermal-expansion coefficient; major improvements are noted to be required in tensile properties, thermal cycling effects, mechanical damage, creep, and environmental effects.

High-Temperature Deformation and Strengthening Mechanisms of Titanium Boride/nickel Aluminide Composites

NASA Astrophysics Data System (ADS)

Wang, Liqin

Intermetallic matrix composites, with ceramic particle reinforcements, are among the most important candidates for high-temperature structural applications. These composites, however, are not always stronger than their matrix materials at elevated temperatures. Some of the composites have much better high-temperature strength than their matrix materials, such as NiAl and FeAl, while others are just the opposite, e.g. TiAl, Ti_3Al, and Ni_3Al. The reasons for either the strengthening or the weakening observed in the discontinuous aluminide matrix composites are not obvious. The purpose of this research is to understand the mechanisms which caused the increase of the strength achieved by adding TiB_2 particulates to NiAl, and to recognize the fundamental principles of the deformation process in TiB_2/NiAl composites. In order to accomplish this objective, the mechanical properties and thermal activation parameters of the deformation process in TiB_2/NiAl composites have been systematically evaluated. The microstructures, dislocation structures and the interface structures of TiB _2/NiAl composites have been also thoroughly characterized before and after the deformation. Emphasis is placed on the relationship between the microstructures and mechanical properties of TiB_2/NiAl composites.

Plastic flow and microstructure of cast nickel aluminides at 1273 K

NASA Astrophysics Data System (ADS)

Schneibel, J. H.; Porter, W. D.; Horton, J. A.

1987-12-01

Chill-cast nickel aluminides based on Ni3Al were compression-tested in vacuum at 1273 K at strain rates ranging from 10-5 s-1 to 10-1 s-1. As the strain rate increases, the propensity for intergranular cracking increases. The ductile-to-brittle transition strain rate (DBTS) of as-cast Ni-22.5Al-0.5Hf-0.1B (at. pct) is approximately 10-1 s-1. Homogenization lowers this value by three orders of magnitude, to 10-4 s-1 (a homogenized specimen disintegrated completely at a rate of 10-3 s-1). The fine-grained structure of the as-cast alloy plays an important role in its relatively high DBTS. A hafnium-free alloy, Ni-24A1-0.1B, on the other hand, shows only a weak dependence of the DBTS on prior homogenization, and possible reasons for this finding are discussed.

Surface modification to improve fireside corrosion resistance of Fe-Cr ferritic steels

DOEpatents

Park, Jong-Hee; Natesan, Krishnamurti; Rink, David L.

2010-03-16

An article of manufacture and a method for providing an Fe--Cr ferritic steel article of manufacture having a surface layer modification for corrosion resistance. Fe--Cr ferritic steels can be modified to enhance their corrosion resistance to liquid coal ash and other chemical environments, which have chlorides or sulfates containing active species. The steel is modified to form an aluminide/silicide passivating layer to reduce such corrosion.

Successful Surface Treatments for Reducing Instabilities in Advanced Nickel-base Superalloys for Turbine Blades

NASA Technical Reports Server (NTRS)

Locci, Ivan E.; MacKay, Rebecca A.; Garg, Anita; Ritzert, Frank J.

2004-01-01

An optimized carburization treatment has been developed to mitigate instabilities that form in the microstructures of advanced turbine airfoil materials. Current turbine airfoils consist of a single crystal superalloy base that provides the mechanical performance of the airfoil, a thermal barrier coating (TBC) that reduces the temperature of the base superalloy, and a bondcoat between the superalloy and the TBC, that improves the oxidation and corrosion resistance of the base superalloy and the spallation resistance of the TBC. Advanced nickel-base superalloys containing high levels of refractory metals have been observed to develop an instability called secondary reaction zone (SRZ), which can form beneath diffusion aluminide bondcoats. This instability between the superalloy and the bondcoat has the potential of reducing the mechanical properties of thin-wall turbine airfoils. Controlled gas carburization treatments combined with a prior stress relief heat treatment and adequate surface preparation have been utilized effectively to minimize the formation of SRZ. These additional processing steps are employed before the aluminide bondcoat is deposited and are believed to change the local chemistry and local stresses of the surface of the superalloy. This paper presents the detailed processing steps used to reduce SRZ between platinum aluminide bondcoats and advanced single crystal superalloys.

Method of manufacturing aluminide sheet by thermomechanical processing of aluminide powders

DOEpatents

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleishhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2003-12-09

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Method of manufacturing aluminide sheet by thermomechanical processing of aluminide powders

DOEpatents

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2000-01-01

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr.ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Fundamental Concepts Relating Local Atomic Arrangements, Deformation, and Fracture of Intermetallic Alloys

DTIC Science & Technology

1993-06-01

Takahashi and H. Oikawa, J. Mater. Sci., 25 (1990) 629. 1 18. S.C. Huang and D.S. Shih, in Microstructure/Property Relationships in Titanium Aluminides and...driven development of directionally-solidified and single crystal superalloy turbine blades . Comparison of the deformation mechanism map for NiAI...1990) 35-44. 101. Bania, P.J. and Hall, J.A., in Titanium Science and Technology, Lutjering, G., Swicker, V., and Bunk, W. (eds.), Deutche

Effects of Processing and Powder Size on Microstructure and Reactivity in Arrested Reactive Milled Al + Ni

DTIC Science & Technology

2012-05-01

reactive milled (RM) experiments forming nickel aluminides [3,4,6,8–10,12,15,16,18,19], titanium - based alloys [5] and combustion reactions in metal...highly heterogeneous and is refined during processing until reaction occurs. The refinement process consists of the cold welding of powder grains within... welding at the surface of deforming particles, which pro-Table 2 Sample preparation measurements corresponding to the designed exper- iments presented

Microstructure of thermally grown and deposited alumina films probed with positrons

NASA Astrophysics Data System (ADS)

Somieski, Bertram; Hulett, Lester D.; Xu, Jun; Pint, Bruce A.; Tortorelli, Peter F.; Nielsen, Bent; Asoka-Kumar, Palakkal; Suzuki, Ryoichi; Ohdaira, Toshiyuki

1999-03-01

Aluminum oxide films used for corrosion protection of iron and nickel aluminides were generated by substrate oxidation as well as plasma and physical vapor depositions. The films grown by oxidation were crystalline. The others were amorphous. Defect structures of the films were studied by positron spectroscopy techniques. Lifetimes of the positrons, and Doppler broadening of the γ photons generated by their annihilation, were measured as functions of the energies with which they were injected. In this manner, densities and sizes of the defects were determined as functions of depths from the outer surfaces of the films. Alumina films generated by oxidation had high densities of open volume defects, mainly consisting of a few aggregated vacancies. In the outer regions of the films the structures of the defects did not depend on substrate compositions. Positron lifetime measurements, and the S and W parameters extracted from Doppler broadening spectra, showed uniform distributions of defects in the crystalline Al2O3 films grown on nickel aluminide substrates, but these data indicated intermediate layers of higher defect contents at the film/substrate interfaces of oxides grown on iron aluminide substrates. Amorphous films generated by plasma and physical vapor deposition had much larger open volume defects, which caused the average lifetimes of the injected positrons to be significantly longer. The plasma deposited film exhibited a high density of large cavities.

A heat treatment procedure to produce fine-grained lamellar microstructures in a P/M titanium aluminide alloy

NASA Astrophysics Data System (ADS)

Au, Peter

A process for fabricating advanced aerospace titanium aluminide alloys starting from metal powders (the hot isostatically consolidated P/M process) is presented in this thesis. This process does not suffer the difficulties of chemical inhomogeneities and coarse grain structure of castings. In addition heat treatments which take advantage of the refined structure of HIP processed materials are developed to achieve microstructure control and subsequent mechanical property control. It is shown that a better "property balance" is possible after the heat treatment of HIP consolidated materials than it is with alternative processing. It is well understood that the standard microstructures (near-gamma, duplex, nearly lamellar, and fully lamellar) do not have the balanced mechanical properties (tensile, yield, creep and fatigue strength, ductility and fracture toughness) necessary for optimal performance in aero engine and automotive applications. In this work a fine-grained fully lamellar (FGFL) microstructure is developed for property control and in particular for achieving a much improved property balance. A heat treatment procedure for this purpose which consists of cyclic processing in the alpha transus temperature region to achieve an FGFL structure with grain sizes in the range of 50 mum to 150 mum is presented. Compared with conventional duplex structured materials, the minimum creep rate is an order of magnitude lower with only a 10% loss in tensile yield strength. Moreover, a three-fold increase in tensile elongation is possible by converting to an FGFL structure with only a 30% loss in minimum creep rate. These are attractive trade-offs when considering the use of these alloys for aerospace purposes. A thorough literature review of the mechanisms of formation of standard microstructures and their deformation under mechanical loading is contained in the thesis. In addition, conventional techniques to produce FGFL microstructures in wrought and cast materials are discussed in detail. Beyond the review, the results of experiments are described for determining the alpha transus temperature, the phase transformation kinetics in this region and the effects of heat treatment time and cooling rate on microstructure. Based on this preliminary work, a heat treatment to achieve a FGFL microstructure with grain sizes in the range of 50 mum to 150 mum is proposed and confirmed. The room temperature and high temperature mechanical properties of these materials are compared with those of conventional duplex and fully lamellar structures. The results of this experimentation are discussed in terms of the fundamental mechanisms for controlling microstructure and mechanical properties in these materials. The potential for applying cyclic heat treatments to cast and wrought materials to improve the mechanical property balance in engineering practice is discussed.

Cost-Effective TiAl based Materials

NASA Technical Reports Server (NTRS)

Moxson, V. S.; Sun, Fusheng; Draper, Susan L.; Froes, F. H.; Duz, V.

2003-01-01

Because of their inherent low ductility, TiAl-based materials are difficult to fabricate, especially thin gage titanium gamma aluminide (TiAl) sheet and foil. In this paper, an innovative powder metallurgy approach for producing cost-effective thin gage TiAl sheets (with 356 mm long and 235 mm wide, and a thickness of 0.74, 1.09, 1.55, and 2.34 mm, respectively) is presented. The microstructures and tensile properties at room and elevated temperatures of the thin gage TiAl are studied. Results show that these TiAl sheets have a relatively homogenous chemistry, uniform microstructure, and acceptable mechanical properties. This work demonstrates a cost-effective method for producing both flat products (sheet/foil) and complex chunky parts of TiAl for various advanced applications including aerospace and automotive industries.

The fractography-modeling link in cleavage fracture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, A.W.

1997-12-31

Cleavage fracture has historically been modelled, out of necessity, in rather idealized terms. In real materials, however, there are a number of difficulties in linking such models with metallographic and fractographic observations. Some of the most vivid examples occur for {alpha}{sub 2} titanium aluminide alloys, in which, when the microstructure contains primary {alpha}{sub 2} particles, the primary particles crack first. When basketweave or Widmanstaetten structures of {alpha}{sub 2} laths comprise the microstructure, it appears that individual laths crack first. And in colony structures, cracking occurs first across the {alpha}{sub 2} lath colonies. Both detailed fractographic observations, and also a statisticalmore » model for brittle fracture by failure of weakest links, have been developed. The extent to which this can be interpreted in classical cleavage terms will be discussed.« less

Scanning and Transmission Electron Microscopy of High Temperature Materials

NASA Technical Reports Server (NTRS)

1994-01-01

Software and hardware updates to further extend the capability of the electron microscope were carried out. A range of materials such as intermetallics, metal-matrix composites, ceramic-matrix composites, ceramics and intermetallic compounds, based on refractory elements were examined under this research. Crystal structure, size, shape and volume fraction distribution of various phases which constitute the microstructures were examined. Deformed materials were studied to understand the effect of interfacial microstructure on the deformation and fracture behavior of these materials. Specimens tested for a range of mechanical property requirements, such as stress rupture, creep, low cycle fatigue, high cycle fatigue, thermomechanical fatigue, etc. were examined. Microstructural and microchemical stability of these materials exposed to simulated operating environments were investigated. The EOIM Shuttle post-flight samples were also examined to understand the influence of low gravity processing on microstructure. In addition, fractographic analyses of Nb-Zr-W, titanium aluminide, molybdenum silicide and silicon carbide samples were carried out. Extensive characterization of sapphire fibers in the fiber-reinforced composites made by powder cloth processing was made. Finally, pressure infiltration casting of metal-matrix composites was carried out.

Hot Rolling of Gamma Titanium Aluminide Foil (PREPRINT)

DTIC Science & Technology

2010-04-01

a proportionality constant between 0.84 and 1.14 for samples of Ti- 6Al - 4V (w/o) with fp ~ 0.2. In this former work, material with a range of grain...trend as that for Ti- 6Al - 4V (Figure 10). 4.2.2. Elimination of remnant lamellar colonies The elimination of colony remnants during heat...with previous observations for Ti- 6Al - 4V [29, 30]. Fig. 1. BSE images of the microstructure of the Ti-45.5Al-2Cr-2Nb (a/o) sheet used in the

Producing Foils From Direct Cast Titanium Alloy Strip

NASA Technical Reports Server (NTRS)

Stuart, T. A.; Gaspar, T. A.; Sukonnik, I. M.; Semiatan, S. L.; Batawi, E.; Peters, J. A.; Fraser, H. L.

1996-01-01

This research was undertaken to demonstrate the feasibility of producing high-quality, thin-gage, titanium foil from direct cast titanium strip. Melt Overflow Rapid Solidification Technology (MORST) was used to cast several different titanium alloys into 500 microns thick strip, 10 cm wide and up to 3 m long. The strip was then either ground, hot pack rolled or cold rolled, as appropriate, into foil. Gamma titanium aluminide (TiAl) was cast and ground to approximately 100 microns thick foil and alpha-2 titanium aluminide (Ti3AI) was cast and hot pack rolled to approximately 70 microns thick foil. CP Ti, Ti6Al2Sn4Zr2Mo, and Ti22AI23Nb (Orthorhombic), were successfully cast and cold-rolled into good quality foil (less than 125 microns thick). The foils were generally fully dense with smooth surfaces, had fine, uniform microstructures, and demonstrated mechanical properties equivalent to conventionally produced titanium. By eliminating many manufacturing steps, this technology has the potential to produce thin gage, titanium foil with good engineering properties at significantly reduced cost relative to conventional ingot metallurgy processing.

Nickel aluminides and nickel-iron aluminides for use in oxidizing environments

DOEpatents

Liu, Chain T.

1988-03-15

Nickel aluminides and nickel-iron aluminides treated with hafnium or zirconium, boron and cerium to which have been added chromium to significantly improve high temperature ductility, creep resistance and oxidation properties in oxidizing environments.

Comparison of orthorhombic and alpha-two titanium aluminides as matrices for continuous SiC-reinforced composites

NASA Astrophysics Data System (ADS)

Smith, P. R.; Graves, J. A.; Rhodes, Cg.

1994-06-01

The attributes of an orthorhombic Ti aluminide alloy, Ti-21Al-22Nb (at. pct), and an alpha-two Ti aluminide alloy, Ti-24Al-11Nb (at. pct), for use as a matrix with continuous SiC (SCS-6) fiber reinforcement have been compared. Foil-fiber-foil processing was used to produce both unreinforced (“neat”) and unidirectional “SCS-6” reinforced panels. Microstructure of the Ti-24A1-11Nb matrix consisted of ordered Ti3Al ( α 2) + disordered beta (β), while the Ti-21 Al-22Nb matrix contained three phases: α2, ordered beta ( β 0), and ordered orthorhombic (O). Fiber/ matrix interface reaction zone growth kinetics at 982 °C were examined for each composite system. Although both systems exhibited similar interface reaction products (i.e., mixed Ti carbides, silicides, and Ti-Al carbides), growth kinetics in the α 2 + β matrix composite were much more rapid than in the O + β 0 + α 2 matrix composite. Additionally, interfacial reaction in the α 2 + β} composite resulted in a relatively large brittle matrix zone, depleted of beta phase, which was not present in the O + β 0+ α 2 matrix composite. Mechanical property measurements included room and elevated temperature tensile, thermal stability, thermal fatigue, thermo-mechanical fatigue (TMF), and creep. The three-phase orthorhombic-based alloy outperformed the α2+ β alloy in all of these mechanical behavioral areas, on both an absolute and a specific (i.e., density corrected) basis.

Manufacturing Techniques for Titanium Aluminide Based Alloys and Metal Matrix Composites

DTIC Science & Technology

2010-01-01

aluminides are being used in the low pressure turbine (LPT) blades . In addition, titanium aluminides were also investigated for use in High Speed Civil... Titanium aluminides are also being used in General Electric’s GEnex gas turbine engine for the 6th and the 7th stage of the low pressure turbine blades ...ABSTRACT Title of Dissertation: MANUFACTURING TECHNIQUES FOR TITANIUM ALUMINIDE BASED ALLOYS AND METAL MATRIX COMPOSITES

Practical Implications of the Use of Aluminide Coatings for the Corrosion Protection of Superalloys in Gas Turbines

DTIC Science & Technology

1984-04-01

Strategic Materials Usage. Practical Implications of the Use of Aluminide Coatings for the Corrosion Protection of Superalloys in Gas Turbines. Coatings...requirements of using aluminide coatings, the processes currently commercially available, the compatabi1ity of aluminide coatings with...components, it is the intention of this paper to concentrate on those ed by reaction or diffusion type processes, In particular the aluminides

High Temperature Oxidation of Superalloys and Intermetallic Compounds

DTIC Science & Technology

2010-02-28

such as nickel aluminides (NisAI and NiAl), iron aluminides (FeAl, and Fe3AI) and titanium aluminides (TiAl and Ti3AI) are a class of advanced...80um by YAI2 phase segregation at grain boundaries preventing grain growth [6,8], other work has suggested that oxidation of titanium aluminides ...strengthened Titanium aluminides of similar composition. In this work, a study of the oxidation behavior of ingot-metallurgy processes titanium

Investigation of reaction kinetics and interfacial phase formation in Ti3Al + Nb composites

NASA Technical Reports Server (NTRS)

Wawner, F. E.; Gundel, D. B.

1992-01-01

Titanium aluminide metal matrix composites are prominent materials systems being considered for high temperature aerospace applications. One of the major problems with this material is the reactivity between existing reinforcements and the matrix after prolonged thermal exposure. This paper presents results from an investigation of reaction kinetics between Ti-14Al-21Nb (wt pct) and SCS-6 fibers and SiC fibers with surface coatings of TiB2, TiC, TiN, W, and Si. Microstructural evaluation of the reaction layers as well as matrix regions around the fibers is presented.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yablinsky, C. A.; Tippey, K. E.; Vaynman, S.

In this study, the development of oxide dispersion strengthened ferrous alloys has shown that microstructures designed for excellent irradiation resistance and thermal stability ideally contain stable nanoscale precipitates and dislocation sinks. Based upon this understanding, the microstructures of conventionally manufactured ferritic and ferritic-martensitic steels can be designed to include controlled volume fractions of fine, stable precipitates and dislocation sinks via specific alloying and processing paths. The concepts proposed here are categorized as advanced high-Cr ferritic-martensitic (AHCr-FM) and novel tailored precipitate ferritic (TPF) steels, which have the potential to improve the in-reactor performance of conventionally manufactured alloys. AHCr-FM steels have modifiedmore » alloy content relative to current reactor materials (such as alloy NF616/P92) to maximize desirable precipitates and control phase stability. TPF steels are designed to incorporate nickel aluminides, in addition to microalloy carbides, in a ferritic matrix to produce fine precipitate arrays with good thermal stability. Both alloying concepts may also benefit from thermomechanical processing to establish dislocation sinks and modify phase transformation behaviors. Alloying and processing paths toward designed microstructures are discussed for both AHCr-FM and TPF material classes.« less

Joining of Gamma Titanium Aluminides

DTIC Science & Technology

2002-09-01

AFRL-ML-WP-TR-2003-4036 JOINING OF GAMMA TITANIUM ALUMINIDES LTC William A. Baeslack, III Metals Branch (AFRL/MLLM) Metals, Ceramics, and...GAMMA TITANIUM ALUMINIDES 5c. PROGRAM ELEMENT NUMBER 62102F 5d. PROJECT NUMBER MO2R 5e. TASK NUMBER 10 6. AUTHOR(S) LTC William A...comparatively discusses the results of research and development performed on the joining of gamma titanium aluminides during the past two decades. Although

Thermal-Mechanical Fatigue Testing of a Titanium-Aluminide Alloy.

DTIC Science & Technology

1987-12-01

DIMSTRIBUTION STA Approved for pubi robing e% dQ *- AFIT/GAB/AA/87D-18 THERMAL-MECHANICAL FATIGUE TESTING OF A TITANIUM - ALUMINIDE ALLOY THESIS John J...THERMAL-MECHANICAL FATIGUE TESTING OF A TITANIUM - ALUMINIDE ALLOY THESIS Presented to the Faculty of the School of Engineering of the Air Force Institute...develop a Thermal-Mechanical Fatigue (TMF) testing system for titanium - aluminide compact tension specimens. I could not have accomplished this without the

Applicability and Performance Benefits of XD (Tradename) Titanium Aluminides to Expendable Gas Turbine Engines

DTIC Science & Technology

1993-08-01

analysis A dynamic analysis was conducted on the blades and splitters. The existing design for the compressor was used and XD® titanium aluminide property...AD-A272 998 ARMY RESEARCH LABORATORY Applicability and Performance Benefits of XD® Titanium Aluminides to Expendable Gas Turbine Engines Pamela...Benefits of XD® Contract # Titanium Aluminides to Expendable Gas Turbine DAAL04-91-C-0034 Fnginpq 6. AUTHOR(S) Pamela Sadler, K. Sharvan Kumar, John A. S

Thermo-Mechanical Fatigue of a Fiber Reinforced Titanium Aluminide Composite

DTIC Science & Technology

1991-03-01

Puiitr]on Air Foic. Base, Oiio 91 10 25 038 DTIC 4E L L E C :i<. THERMO- MECHAN I CAL FAT I GUE OF A FIBER REINFORCED TITANIUM ALUMINIDE COMPOSITE Thesis...reinforced titanium aluminide composite was investigated. Three test specimens were subjected to in-phase thermo- mechanical cycling and four to out-of...Unclassified UL ............................... AFIT/GAE/ENY/91S-1 THERMO- MECHANICAL FATIGUE OF A FIBER REINFORCED TITANIUM ALUMINIDE COMPOSITE THESIS

Degradation of nonmodified and rhodium modified aluminide coating deposited on CMSX 4 superalloy.

PubMed

Zagula-Yavorska, Maryana; Wierzbińska, Małgorzata; Gancarczyk, Kamil; Sieniawski, Jan

2016-07-01

The Ni-base superalloy CMSX 4 used in the turbine blades of aircraft engines was coated with rhodium layer (0.5-μm thick). Next coated CMSX 4 superalloy was aluminized by the CVD method. The rhodium modified aluminide coating and nonmodified aluminide coating were oxidized at 1100°C at the air atmosphere. The rhodium modified aluminide coating showed about twice better oxidation resistance than the nonmodified one. The spallation equal 62% of the total area was observed on the surface of the nonmodified coating whereas only 36% spallation area was observed on the surface of the rhodium modified aluminide coating after the oxidation test. The oxide layer formed on the surface of the nonmodified coating was composed of nonprotective (Ni,Cr)Al2 O4 and (Ni,Cr)O phases. Aluminium in the coating reacts with oxygen, forming a protective α-Al2 O3 oxide on the surface of the rhodium modified aluminide coating. When the oxide cracks and spalls due to oxidation, additional aluminium from the coating diffuses to the surface to form the oxide. The presence of protective Al2 O3 oxide on the surface of the rhodium modified aluminide coating slows coating degradation. Therefore, rhodium modified aluminide coating has better oxidation resistance than the nonmodified one. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

Utilization of gas-atomized titanium and titanium-aluminide powder

NASA Astrophysics Data System (ADS)

Moll, John H.

2000-05-01

A gas-atomization process has been developed producing clean, high-quality, prealloyed spherical titanium and titanium-aluminide powder. The powder is being used to manufacture hot-isostatically pressed consolidated shapes for aerospace and nonaerospace allocations. These include gamma titanium-aluminide sheet and orthorhombic titanium-aluminide wire as well as niche markets, such as x-ray drift standards and sputtering targets. The powder is also being used in specialized processes, including metal-matrix composites, laser forming, and metal-injection molding.

Identification of thermodynamically stable ceramic reinforcement materials for iron aluminide matrices

NASA Technical Reports Server (NTRS)

Misra, Ajay K.

1990-01-01

Aluminide-base intermetallic matrix composites are currently being considered as potential high-temperature materials. One of the key factors in the selection of a reinforcement material is its chemical stability in the matrix. In this study, chemical interactions between iron aluminides and several potential reinforcement materials, which include carbides, oxides, borides, and nitrides, are analyzed from thermodynamic considerations. Several chemically compatible reinforcement materials are identified for the iron aluminides with Al concentrations ranging from 40 to 50 at. pct.

Concepts for the development of nanoscale stable precipitation-strengthened steels manufactured by conventional methods

DOE PAGES

Yablinsky, C. A.; Tippey, K. E.; Vaynman, S.; ...

2014-11-11

In this study, the development of oxide dispersion strengthened ferrous alloys has shown that microstructures designed for excellent irradiation resistance and thermal stability ideally contain stable nanoscale precipitates and dislocation sinks. Based upon this understanding, the microstructures of conventionally manufactured ferritic and ferritic-martensitic steels can be designed to include controlled volume fractions of fine, stable precipitates and dislocation sinks via specific alloying and processing paths. The concepts proposed here are categorized as advanced high-Cr ferritic-martensitic (AHCr-FM) and novel tailored precipitate ferritic (TPF) steels, which have the potential to improve the in-reactor performance of conventionally manufactured alloys. AHCr-FM steels have modifiedmore » alloy content relative to current reactor materials (such as alloy NF616/P92) to maximize desirable precipitates and control phase stability. TPF steels are designed to incorporate nickel aluminides, in addition to microalloy carbides, in a ferritic matrix to produce fine precipitate arrays with good thermal stability. Both alloying concepts may also benefit from thermomechanical processing to establish dislocation sinks and modify phase transformation behaviors. Alloying and processing paths toward designed microstructures are discussed for both AHCr-FM and TPF material classes.« less

Effect of in-situ formed Al3Ti particles on the microstructure and mechanical properties of 6061 Al alloy

NASA Astrophysics Data System (ADS)

Gupta, Rahul; Chaudhari, G. P.; Daniel, B. S. S.

2018-03-01

In this study, in situ Titanium-tri-aluminide (Al3Ti) particles reinforced Al 6061 alloy matrix composites were fabricated by the reaction of potassium hexafluorotitanate (K2TiF6) inorganic salt with molten Al 6061 alloy via liquid metallurgy route. The development of in-situ Al3Ti particles and their effects on the mechanical properties such as yield strength (YS), ductility, ultimate tensile strength (UTS) and hardness, and microstructure of Al 6061 alloy were studied. It was observed from the results that in-situ formed Al3Ti particles were blocky in morphology whose average size was around 2.6 ± 1.1 μm. Microstructure studies showed that grain size of Al matrix was reduced due to the nucleating effect of Al3Ti particles. It was observed from the mechanical properties analysis that when the volume fraction of Al3Ti particles was increased, the hardness, UTS and YS of the composites were also increased as compared to that of Al 6061 alloy. An improvement in ductility was observed with the dispersion of Al3Ti particles in base alloy which is contrary to many other composites.

Effect of Processing Route on Strain Controlled Low Cycle Fatigue Behavior of Polycrystalline NiAl

NASA Technical Reports Server (NTRS)

Rao, K. Bhanu Sankara; Lerch, B. A.; Noebe, R. D.

1995-01-01

The present investigation examines the effects of manufacturing process on the total axial strain controlled low cycle fatigue behavior of polycrystalline NiAl at 1000 K, a temperature above the monotonic Brittle-to-Ductile Transition Temperature (BDTT). The nickel aluminide samples were produced by three different processing routes: hot isostatic pressing of pre- alloyed powders, extrusion of prealloyed powders, and extrusion of vacuum induction melted ingots. The LCF behavior of the cast plus extruded material was also determined at room temperature (below the BD77) for comparison to the high temperature data. The cyclic stress response, cyclic stress-strain behavior, and strain-life relationships were influenced by the alloy preparation technique and the testing temperature. Detailed characterization of the LCF tested samples was conducted by optical and electron microscopy to determine the variations in fracture and deformation modes and to determine any microstructural changes that occurred during LCF testing. The dependence of LCF properties on processing route was rationalized on the basis of starting microstructure, brittle-to-ductile transition temperature, deformation induced changes in the basic microstructure, deformation substructure, and synergistic interaction between the damage modes.

On Some Mechanical Properties and Wear Behavior of Sintered Bronze Based Composites Reinforced with Some Aluminides Microadditives

NASA Astrophysics Data System (ADS)

Feldshtein, E.; Kiełek, P.; Kiełek, T.; Dyachkova, L.; Letsko, A.

2017-05-01

In the paper, the changes in some mechanical properties and wear behavior of CuSn10 sintered bronze and MMCs based on this bronze reinforced with composite ultrafine aluminide powders FeAl/15 % Al2O3, NiAl/15 % Al2O3 and Ti-46Al-8Cr are described. It was observed that the presence of aluminides in the MMCs leads to an increase in the hardness, but the flexural strength may increase or decrease depending on the type of aluminide. The presence of aluminides in the MMC reduces the wear rate considerably. It is decreased in the direction of FeAl/15 % Al2O3 → NiAl/15 % Al2O3 → Ti-46Al-8Cr aluminides and for the best MMC composition the advantage is about 20 times. In the MMCs wear process, micro-craters are formed on the contact surface and it is the principal reason of a decrease in the wear rate.

Phase relations in Ti-Al-Nb alloys at 1200 degrees C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suryanarayana, C.; Lee, D.S.

1992-03-15

This paper reports that titanium aluminides based on both Ti{sub 3}Al ({alpha}{sub 2}) and TiAl ({gamma}) have received considerable attention during the past few years as potential candidates for high temperature structural applications in the aerospace industry. This has been due to the attractive combination of properties such as low density, high specific strength, elevated temperature strength and modulus retention, excellent creep resistance and high resistance to oxidation. A serious handicap in using these alloys has been their vary poor ductility. Refinement of grain size, addition of ternary and quaternary alloying elements (e.g., Nb, Mn and Ta) and microstructural refinementsmore » through either innovative heat treatments or by production of nanometer-sized grains through mechanical alloying or magnetron sputtering methods have been explored to increase the ductility. Amongst these approaches, addition of alloying elements, especially of niobium, has proven extremely beneficial. Thus, there have been several investigations in recent years on the constitution, microstructure and properties of ternary Ti-Al-Nb alloys.« less

R&D on Composition and Processing of Titanium Aluminide Alloys for Turbine Engines

DTIC Science & Technology

1982-07-01

45433. AUTHORITY AFWAL ltr, 6 Feb 1987 THIS PAGE IS UNCLASSIFIED AFWAL-TR-82-4086 R&D ON COMPOSITION AND PROCESSING4 OF TITANIUM ALUMINIDE ALLOYS FOR...TR-82-4086- 4. TITLE (and Subitfle) S TYPE OF REPORT I PERIOO COVEREO R&D ON COMPOSITION AND PROCESSING OF Interim Technical Report TITANIUM ALUMINIDE ...ILLUSTRATIONS FICURE PACE 1 As-received titanium aluminide ingots supplied 9 by RMI. (a) S/N 20007; (b) left to right, S/N 20008, S/N 20009, S/N 20010

Aluminide coatings for nickel base alloys

NASA Technical Reports Server (NTRS)

Fiedler, H. C.; Sieraski, R. J.

1971-01-01

The metalliding process was used to aluminide IN-100 and TD NiCr. Aluminum was deposited over a broad range of deposition rates, with two types of coating structures resulting. Chromium, silicon, titanium and yttrium were also individually deposited simutaneously with aluminum on IN-100. None of these had a marked effect on the oxidation resistance of the aluminide coating. Porosity-free aluminide coatings with good oxidation resistance were formed on TD NiCr providing the aluminum concentration did not exceed 8 percent, the limit of solubility in the gamma phase.

Cyclic oxidation of cobalt-chromium-aluminum-yttrium and aluminide coatings on IN-100 and VIA alloys in high velocity gases

NASA Technical Reports Server (NTRS)

Deadmore, D. L.

1972-01-01

Embedded-alumina-particle aluminide (EAPA) coated and CoCrAlY coated IN-100 and NASA-TRW-VIA specimens were cyclically oxidation tested in a high velocity (approximately Mach 1) gas flame at 1093 C (2000 F). The EAPA coatings on both alloys performed very similarly to commercial pack aluminide coatings with respect to weight change and thermal fatigue cracking. The CoCrAlY coating on IN-100 had weight changes similar to commercial pack aluminide coatings but no thermal fatigue cracks appeared at 300 hours. The CoCrAlY coating on VIA performed significantly better than the commercial aluminide coatings, providing oxidation protection (based on weight change) to 450 hours and thermal fatigue crack prevention to at least 600 hours.

Chromium and reactive element modified aluminide diffusion coatings on superalloys - Environmental testing

NASA Technical Reports Server (NTRS)

Bianco, Robert; Rapp, Robert A.; Smialek, James L.

1993-01-01

The high temperature performance of reactive element (RE)-doped and Cr/RE-modified aluminide diffusion coatings on commercial Ni-base alloy substrates was determined. In isothermal oxidation at 1100 C in air, RE-doped aluminide coatings on IN 713LC substrates formed a continuous slow-growing n-Al2O3 scale after 44 hrs of exposure. The coatings were protected by either an outer ridge Al2O3 scale with an inner compact Al2O3 scale rich in RE or by a continuous compact scale without any noticeable cracks or flaws. The cyclic oxidation behavior of Cr/RE-modified aluminide coatings on Rene 80 and IN 713LC alloys and of RE-doped aluminide coatings on IN 713LC alloys at 1100 C in static air was determined. Pack powder entrapment from the powder contacting (PC) process detracted significantly from the overall cyclic oxidation performance. Type I hot corrosion behavior of Cr/RE-modified aluminide coatings on Rene 80 and Mar-M247 alloy substrates at 900 C in a catalyzed 0.1 percent SO3/O3 gas mixture was determined. The modified coatings produced from the PC arrangement provided significantly better resistance to hot corrosion attack than commercial low-activity aluminide coatings produced by the above pack arrangement.

Titanium aluminide intermetallic alloys with improved wear resistance

DOEpatents

Qu, Jun; Lin, Hua-Tay; Blau, Peter J.; Sikka, Vinod K.

2014-07-08

The invention is directed to a method for producing a titanium aluminide intermetallic alloy composition having an improved wear resistance, the method comprising heating a titanium aluminide intermetallic alloy material in an oxygen-containing environment at a temperature and for a time sufficient to produce a top oxide layer and underlying oxygen-diffused layer, followed by removal of the top oxide layer such that the oxygen-diffused layer is exposed. The invention is also directed to the resulting oxygen-diffused titanium aluminide intermetallic alloy, as well as mechanical components or devices containing the improved alloy composition.

An investigation of the effect of surface impurities on the adsorption kinetics of hydrogen chemisorbed onto iron

NASA Technical Reports Server (NTRS)

Shanabarger, Mickey R.

1994-01-01

The goal of this program has been to develop an understanding of heterogeneous kinetic processes for those molecular species which produce gaseous hydrogen degradation of the mechanical properties of metallic structural materials. During the present program, the interaction of hydrogen with the surfaces of alpha-2 (Ti3Al) titanium aluminide, gamma (TiAl) titanium aluminide, and beryllium were studied. The interaction of low pressure hydrogen with gamma titanium aluminide and beryllium was found to be relatively weak. Weak in the sense that adsorption leads to a low surface concentration of dissociated hydrogen, i.e., the chemisorption process is reversible at room temperature (300 K) for gamma titanium aluminide and the sticking coefficient for chemisorption is extremely small for beryllium. Hydrogen was found to interact readily with alpha-2 titanium aluminide to form a stable surface hydride at 300 K. These results correlate well with other recent studies which show that the mechanical properties for alpha-2 titanium aluminide are readily degraded in hydrogen while gamma titanium aluminide exhibits less degradation and beryllium essentially no degradation. The interaction of oxygen with the surface of several of these materials was studied. More recently, preliminary hydrogen permeation studies were completed for three high temperature alloys, Incoloy 909, Mo-47.5Re (wt. %), and this past year, Haynes 188.

Laser-Based Surface Modification of Microstructure for Carbon Fiber-Reinforced Plastics

NASA Astrophysics Data System (ADS)

Yang, Wenfeng; Sun, Ting; Cao, Yu; Li, Shaolong; Liu, Chang; Tang, Qingru

2018-05-01

Bonding repair is a powerful feature of carbon fiber-reinforced plastics (CFRP). Based on the theory of interface bonding, the interface adhesion strength and reliability of the CFRP structure will be directly affected by the microscopic features of the CFRP surface, including the microstructure, physical, and chemical characteristics. In this paper, laser-based surface modification was compared to Peel-ply, grinding, and polishing to comparatively evaluate the surface microstructure of CFRP. The surface microstructure, morphology, fiber damage, height and space parameters were investigated by scanning electron microscopy (SEM) and laser confocal microscopy (LCM). Relative to the conventional grinding process, laser modification of the CFRP surface can result in more uniform resin removal and better processing control and repeatability. This decreases the adverse impact of surface fiber fractures and secondary damage. The surface properties were significantly optimized, which has been reflected such things as the obvious improvement of surface roughness, microstructure uniformity, and actual area. The improved surface microstructure based on laser modification is more conducive to interface bonding of CFRP structure repair. This can enhance the interfacial adhesion strength and reliability of repair.

The effect of cobalt content in U-700 type alloys on degradation of aluminide coatings

NASA Technical Reports Server (NTRS)

Zaplatynsky, I.

1985-01-01

The influence of cobalt content in U-700 type alloys on the behavior of aluminide coatings is studied in burner rig cyclic oxidation tests at 1100C. It is determined that aluminide coatings on alloys with higher cobalt offer better oxidation protection than the same coatings on alloys containing less cobalt.

An Oxidation-Resistant Coating Alloy for Gamma Titanium Aluminides

NASA Technical Reports Server (NTRS)

Brady, Michael P.; Smialek, James L.; Brindley, William J.

1997-01-01

Titanium aluminides based on the g-phase (TiAl) offer the potential for component weight savings of up to 50 percent over conventional superalloys in 600 to 850 C aerospace applications. Extensive development efforts over the past 10 years have led to the identification of "engineering" gamma-alloys, which offer a balance of room-temperature mechanical properties and high-temperature strength retention. The gamma class of titanium aluminides also offers oxidation and interstitial (oxygen and nitrogen) embrittlement resistance superior to that of the alpha(sub 2) (Ti3Al) and orthorhombic (Ti2AlNb) classes of titanium aluminides. However, environmental durability is still a concern, especially at temperatures above 750 to 800 C. Recent work at the NASA Lewis Research Center led to the development of an oxidation-resistant coating alloy that shows great promise for the protection of gamma titanium aluminides.

Iron aluminides and nickel aluminides as materials for chemical air separation

DOEpatents

Kang, Doohee

1991-01-01

The present invention is directed to a chemical air separation process using a molten salt solution of alkali metal nitrate and nitrite wherein the materials of construction of the containment for the process are chosen from intermetallic alloys of nickel and/or iron aluminide wherein the aluminum content is 28 atomic percent or greater to impart enhanced corrosion resistance.

International Workshop on Gamma Aluminide Alloy Technology. Section Three

DTIC Science & Technology

1997-04-18

Structure / Property Relationships General Mechanical Behavior Tensile Fracture Toughness Creep Fatigue; FCG, Inverse Ductility/FT Relationship...Workshop on Gamma Titanium Aluminide Alloy Technology. 1 May 1996-3 May 1996 The Topics covered include: Fundamental research issues for...understanding the emerging class of Gamma Titanium Aluminide Alloy Technologies 14. SUBJECT TERMS 15. NUMBER OF PAGES 16. PRICE CODE N/A 17. SECURITY

Iron aluminides and nickel aluminides as materials for chemical air separation

DOEpatents

Kang, D.

1991-01-29

The present invention is directed to a chemical air separation process using a molten salt solution of alkali metal nitrate and nitrite wherein the materials of construction of the containment for the process are chosen from intermetallic alloys of nickel and/or iron aluminide wherein the aluminum content is 28 atomic percent or greater to impart enhanced corrosion resistance.

In-situ observations of crack initiation and growth at notches in cast Ti-48Al-2Cr-2Nb

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pollock, T.M.; Muraleedharan, K.; Mumm, D.R.

1996-12-01

Gamma titanium aluminide alloys have recently received a great deal of attention due to their demonstrated potential for application in aircraft engines. Although a number of studies have been conducted on the fracture behavior of these alloys under conditions where relatively long pre-existing cracks are present, there is little information on the early stages of crack initiation and growth. The objective of the study reported here was to observe the initial development of cracks at the scale of the microstructure. To confine the process of interest to well-defined regions, notched specimens were utilized. Observations regarding the initiation, growth and themore » influence of environment on failure are discussed.« less

Effect of grain size on the high temperature properties of B2 aluminides

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel

1987-01-01

Measurements of the slow plastic flow behavior of cobalt, iron and nickel B2 crystal structure aluminides were conducted on materials fabricated by metallurical techniques. Due to this processing, the aluminides invariably had small equiaxed grains, ranging in size from about 3 to 60 microns in diameter. Grain size was dependent on the extrusion temperature used for powder consolidation, and it proved to be remarkably stable at elevated temperatures. Mechanical properties of all three aluminides were determined via constant velocity compression testing in air between 1000 and 1400 K at strain rates ranging from approx. 10 to the minus 3 power to 10 to the minus 7 power s (-1).

FY97 Materials & Processes Technology Area Plan

DTIC Science & Technology

1996-09-01

Offices ess has Center Technology Coun- ings, the first use ever of gamma (SPOs). In addition, we provide cil (CTCs) technology needs Titanium Aluminide ...300,000 in form- structive evaluation (NDE). Four Agreements (CRDAs) with 7 ing of Titanium Aluminide with Data EAchange Agreements more in negotiation and...Systems Aircraft Range with r 50% Decrease in Fuel Propulsion Syste s =Consumption Titanium Aluminides Cast Titanium 25000F Ceramic Matrix Transition

An Investigation of the Interatomic Bonding Characteristics of a Ti - 51at.% Al Alloy by X-Ray Diffraction

DTIC Science & Technology

1991-06-01

GROUP SUBGROUP X-ray Diffraction, XRD, TiAI, titanium , aluminum, bonding characteristics, titanium aluminides , Debye-Waller temperature factor...XRD Powder Particles (575X) .............. 47 viii I. INTRODUCTION Titanium aluminides are recognized for their high specific strength, particularly at...bonding characteristics of binary titanium aluminides . Upon the introduction of a third element to the system, a rearrangement of the valence

Research to Conduct an Exploratory Experimental and Analytical Investigation of Alloys

DTIC Science & Technology

1980-11-01

Properties of Forged and Heat 31 Treated Alpha-Two Titanium Aluminide Alloys 10 Effect of Interstitial Elements on Room 33 Temperature Notched (Kt-3.9...percent (three to five percent of engine weight) would be achieved with widespread application of the titanium aluminides in rotating hardwarei...vanadium substitution effect was also undertaken. One of the inconsistencies in the previous titanium aluminide investigations has been the poorer

Innovative Processing of Composites for Ultra-High Temperature Applications. Book 2

DTIC Science & Technology

1993-11-01

with dispersed aluminum and nickel particles [6). Successful toughening has also been observed in titanium aluminide [7] and molybdenum disilicide [g,9...2) Nb-based aluminides with the major focus on NbAl3. I Research Summary To achieve the goal of this program, the present investigation has been...toughening to produce hybrid composites. I Niobium aluminid Matrix Composites Reactive hot compaction (RHC) has been successfully utilized to produce

High-velocity-oxidation performance of metal-chromium-aluminum (MCrAl), cermet, and modified aluminide coatings on IN-100 and type VIA alloys at 1093 C

NASA Technical Reports Server (NTRS)

Deadmore, D. L.

1974-01-01

Cermet, MCrAl, and modified aluminide types of coatings applied to IN-100 and NASA-TRW-VIA alloy specimens were cyclically oxidation tested in a high velocity (Mach 1) gas flame at 1093 C. Several coating compositions of each type were evaluated for oxidation resistance. The modified aluminide coating, Pt-Al, applied to alloy 6A proved to be the best, providing oxidation protection to approximately 750 hours based on weight change measurements. The second best, a CoCrAlY coating applied to 6A, provided protection to 450 hours. The third best was a cermet + aluminide coating on 6A with a protection time to 385 hours.

United States Air Force Summer Research Program 1991. Summer Faculty Research Program (SFRP) Reports. Volume 5B. Wright Laboratory

DTIC Science & Technology

1992-01-09

interfaces of intermetallic-matrix composites (for example, with Ti-Il wt.% Al-14 wt.% Nb and other titanium aluminides combined with various fibers... titanium aluminide intermetallics should be processed, tested and characterized by TEM. These intermetallic-matrix composites (IMC) are important for...these titanium aluminides have a greater CTE mismatch and have been modelled to undergo significant plastic deformation as a result of thermal processing

Intermetallic alloy welding wires and method for fabricating the same

DOEpatents

Santella, M.L.; Sikka, V.K.

1996-06-11

Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined. 4 figs.

Intermetallic alloy welding wires and method for fabricating the same

DOEpatents

Santella, Michael L.; Sikka, Vinod K.

1996-01-01

Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined.

Research to Conduct an Exploratory Experimental and Analytical Investigation of Alloys

DTIC Science & Technology

1978-03-01

d« (f n«r««a«rv on« 149*111* hv *l«c* f*u0«««> Titanium Aluminides , Alloy Development, Mechemical Properties, Powder Metallurgy, Forging, Joining...Ccmpcsition of Titanium 79 Aluminida Alloy 9 Nuclear Metals Reported REP Titanium 80 Aluminide Powder Size Distribution 10 Phase I, Task I...137 141 24 Chemical Composition of Titanium Aluminide Alloy TMCA Heat 75301 Ti-13.5Al-21.4Nb 25 Isothermal Forging Results 26 Tensile Results

Advances in the Systems and Processes for the Production of Gamma Titanium Aluminide Bars and Powder

NASA Astrophysics Data System (ADS)

Haun, Robert E.

2017-12-01

A historical look at the melt processing of gamma titanium aluminides is presented first, followed by recent advances in melting equipment design by Retech to produce 50-mm and 100-mm-diameter ingots up to 1000 mm long. Equipment design for the economical production of gamma titanium aluminide powder is then discussed. The focus in industry has shifted away from basic research to cost-effective production of these titanium alloys for aerospace and automotive engine applications.

HCP to FCT + precipitate transformations in lamellar gamma-titanium aluminide alloys

NASA Astrophysics Data System (ADS)

Karadge, Mallikarjun Baburao

Fully lamellar gamma-TiAl [alpha2(HCP) + gamma(FCT)] based alloys are potential structural materials for aerospace engine applications. Lamellar structure stabilization and additional strengthening mechanisms are major issues in the ongoing development of titanium aluminides due to the microstructural instability resulting from decomposition of the strengthening alpha 2 phase. This work addresses characterization of multi-component TiAl systems to identify the mechanism of lamellar structure refinement and assess the effects of light element additions (C and Si) on creep deformation behavior. Transmission electron microscopy studies directly confirmed for the first time that, fine lamellar structure is formed by the nucleation and growth of a large number of basal stacking faults on the 1/6<112¯0> dislocations cross slipping repeatedly into and out of basal planes. This lamellar structure can be tailored by modifying jog heights through chemistry and thermal processing. alpha 2 → gamma transformation during heating (investigated by differential scanning calorimetry and X-ray diffraction) is a two step process involving the formation of a novel disordered FCC gamma' TiAl [with a(gamma') = c(gamma)] as an intermediate phase followed by ordering. Addition of carbon and silicon induced Ti2AlC H-type carbide precipitation inside the alpha2 lath and Ti 5(Al,Si)3 zeta-type silicide precipitation at the alpha 2/gamma interface. The H-carbides preserve alpha2/gamma type interfaces, while zeta-silicide precipitates restrict ledge growth and interfacial sliding enabling strong resistance to creep deformation.

Advanced ordered intermetallic alloy deployment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, C.T.; Maziasz, P.J.; Easton, D.S.

1997-04-01

The need for high-strength, high-temperature, and light-weight materials for structural applications has generated a great deal of interest in ordered intermetallic alloys, particularly in {gamma}-based titanium aluminides {gamma}-based TiAl alloys offer an attractive mix of low density ({approximately}4g/cm{sup 3}), good creep resistance, and high-temperature strength and oxidation resistance. For rotating or high-speed components. TiAl also has a high damping coefficient which minimizes vibrations and noise. These alloys generally contain two phases. {alpha}{sub 2} (DO{sub 19} structure) and {gamma} (L 1{sub 0}), at temperatures below 1120{degrees}C, the euticoid temperature. The mechanical properties of TiAl-based alloys are sensitive to both alloy compositionsmore » and microstructure. Depending on heat-treatment and thermomechanical processing, microstructures with near equiaxed {gamma}, a duplex structure (a mix of the {gamma} and {alpha}{sub 2} phases) can be developed in TiAl alloys containing 45 to 50 at. % Al. The major concern for structural use of TiAl alloys is their low ductility and poor fracture resistance at ambient temperatures. The purpose of this project is to improve the fracture toughness of TiAl-based alloys by controlling alloy composition, microstructure and thermomechanical treatment. This work is expected to lead to the development of TiAl alloys with significantly improved fracture toughness and tensile ductility for structural use.« less

Low Conductive Thermal Barrier Coatings Produced by Ion Beam Assisted EB-PVD with Controlled Porosity, Microstructure Refinement and Alloying Additions for High Temperature Applications

NASA Technical Reports Server (NTRS)

Wolfe, Douglas E.; Singh, Jogender

2005-01-01

Various advanced Hafnia-based thermal barrier coatings (TBC) were applied on nickel-based superalloy coupons by electron beam physical vapor deposition. In addition, microstructural modifications to the coating material were made in an effort to reduce the thermal conductivity of the coating materials. Various processing parameters and coating system modifications were made in order to deposit the alloyed TBC with the desired microstructure and thus coating performance, some of which include applying coatings at substrate temperatures of 1150 C on both PtAl and CoNiCrAlY bond coated samples, as well as using 8YSZ as a bond layer. In addition, various characterization techniques including thermal cyclic tests, scanning electron microscopy, x-ray diffraction, thermal conductivity, and reflectivity measurements were performed. Although the coating microstructure was never fully optimized due to funding being cut short, significant reductions in thermal conductivity were accomplished through both chemistry changes (composition) and microstructural modifications.

Oxidation of Slurry Aluminide Coatings on Cast Stainless Steel Alloy CF8C-Plus at 800oC in Water Vapor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haynes, James A; Armstrong, Beth L; Dryepondt, Sebastien N

A new, cast austenitic stainless steel, CF8C-Plus, has been developed for a wide range of high temperature applications, including diesel exhaust components, turbine casings and turbocharger housings. CF8C-Plus offers significant improvements in creep rupture life and creep rupture strength over standard CF8C steel. However, at higher temperatures and in more aggressive environments, such as those containing significant water vapor, an oxidation-resistant protective coating will be necessary. The oxidation behavior of alloys CF8C and CF8C-Plus with various aluminide coatings were compared at 800oC in air plus 10 vol% water vapor. Due to their affordability, slurry aluminides were the primary coating systemmore » of interest, although chemical vapor deposition (CVD) and pack cementation coatings were also compared. Additionally, a preliminary study of the low cycle fatigue behavior of aluminized CF8C-Plus was conducted at 800oC. Each type of coating provided substantial improvements in oxidation behavior, with simple slurry aluminides showing very good oxidation resistance after 4,000 h testing in water vapor. Preliminary low cycle fatigue results indicated that thicker aluminide coatings degraded high temperature fatigue properties of CF8C-Plus, whereas thinner coatings did not. Results suggest that appropriately designed slurry aluminide coatings are a viable option for economical, long-term oxidation protection of austenitic stainless steels in water vapor.« less

The study of in-situ formed alumina and aluminide intermetallic reinforced aluminum-based metal matrix composites

NASA Astrophysics Data System (ADS)

Yu, Peng

Aluminum-based metal matrix composites (MMCs) have been widely used as structural materials in the automobile and aerospace industry due to their specific properties. In this thesis, we report the fabrication of in-situ formed alumina and aluminide intermetallic reinforced aluminum-based metal matrix composites by the displacement reactions between Al and selected metal oxides (NiO, CuO and ZnO). These MMCs were produced when the Al-20wt% NiO, Al-20wt% CuO and Al-10wt% ZnO green compacts were reaction sintered in the tube furnaces. In this work, differential thermal analysis (DTA) was performed on the green samples. The green samples were then sintered separately in different tube furnaces for 30 minutes. In order to study the reaction mechanisms, the x-ray diffractometry (XRD) was used to obtain diffraction patterns of these sintered samples, the scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to study the microstructures of these samples. The elemental quantitative compositions of samples were determined by the energy dispersive x-ray spectrometry (EDX). In order to study the effect of cooling rate on the samples, the green samples were further sintered to 1000°C and cooled down to room temperature in different conditions: by furnace-cooling, air-quenching, oil-quenching or NaCl-solution-quenching. The SEM, TEM and atomic force microscopy (AFM) were conducted to investigate their microstructures. A microhardness tester was used to measure the hardness values of these samples. It was found that during sintering of the Al-20wt% NiO green sample, displacement reaction between Al and NiO initially occurred in solid-solid form and was soon halted by its products that separated the NiO particles from the Al matrix. The reaction then resumed in solid-liquid form as the temperature increased to the eutectic temperature of Al3Ni-Al when liquid (Al, Ni) phase appeared in the sample. After cooling, Al2O 3 particles, Al3Ni proeutectic phase and fiber-like Al 3Ni-Al eutectic were found in the sintered Al-MMC sample. (Abstract shortened by UMI.)

CVD aluminiding process for producing a modified platinum aluminide bond coat for improved high temperature performance

NASA Technical Reports Server (NTRS)

Nagaraj, Bangalore A. (Inventor); Williams, Jeffrey L. (Inventor)

2003-01-01

A method of depositing by chemical vapor deposition a modified platinum aluminide diffusion coating onto a superalloy substrate comprising the steps of applying a layer of a platinum group metal to the superalloy substrate; passing an externally generated aluminum halide gas through an internal gas generator which is integral with a retort, the internal gas generator generating a modified halide gas; and co-depositing aluminum and modifier onto the superalloy substrate. In one form, the modified halide gas is hafnium chloride and the modifier is hafnium with the modified platinum aluminum bond coat comprising a single phase additive layer of platinum aluminide with at least about 0.5 percent hafnium by weight percent and about 1 to about 15 weight percent of hafnium in the boundary between a diffusion layer and the additive layer. The bond coat produced by this method is also claimed.

Chromium modified nickel-iron aluminide useful in sulfur bearing environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cathcart, J.V.; Liu, C.T.

1989-06-13

This patent describes an improved nickel-iron aluminide containing chromium and molybdenum additions to improve resistance to sulfur attack. The corrosive effects of sulfur are discussed and the chemical composition of corrosion resistant alloys is illustrated.

Large Scale Evaluation fo Nickel Aluminide Rolls

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2005-09-01

This completed project was a joint effort between Oak Ridge National Laboratory and Bethlehem Steel (now Mittal Steel) to demonstrate the effectiveness of using nickel aluminide intermetallic alloy rolls as part of an updated, energy-efficient, commercial annealing furnace system.

Discontinuously reinforced intermetallic matrix composites via XD synthesis. [exothermal dispersion

NASA Technical Reports Server (NTRS)

Kumar, K. S.; Whittenberger, J. D.

1992-01-01

A review is given of recent results obtained for discontinuously reinforced intermetallic matrix composites produced using the XD process. Intermetallic matrices investigated include NiAl, multiphase NiAl + Ni2AlTi, CoAl, near-gamma titanium aluminides, and Ll2 trialuminides containing minor amounts of second phase. Such mechanical properties as low and high temperature strength, compressive and tensile creep, elastic modulus, ambient ductility, and fracture toughness are discussed as functions of reinforcement size, shape, and volume fraction. Microstructures before and after deformation are examined and correlated with measured properties. An observation of interest in many of the systems examined is 'dispersion weakening' at high temperatures and high strain rates. This behavior is not specific to the XD process; rather similar observations have been reported in other discontinuous composites. Proposed mechanisms for this behavior are presented.

Advances in Gammalloy Materials-Processes-Application Technology: Successes, Dilemmas, and Future

NASA Astrophysics Data System (ADS)

Kim, Young-Won; Kim, Sang-Lan

2018-04-01

For the last several years, gamma titanium aluminide ( γ-TiAl)-based alloys, called "gammalloys," in specific alloy-microstructure forms began to be implemented in civil aero-engines as cast or wrought low-pressure turbine (LPT) blades and in select ground vehicle engines as cast turbocharger rotors and wrought exhaust valves. Their operation temperatures are approximately up to 750°C for LPT blades and around 1000°C for turbocharger rotors. This article critically assesses current engineering gammalloys and their limitations and introduces eight strengthening pathways that can be adopted immediately for the development of advanced, higher temperature gammalloys. Intelligent integration of the pathways into the emerging application-specific research and development processes is emphasized as the key to the advancement of the gammalloy technology to the next higher engineering performance levels.

Mechanical alloying, characterization and consolidation of Ti-Al-Ni alloys

NASA Technical Reports Server (NTRS)

Nash, P.; Higgins, G. T.; Dillinger, N.; Hwang, S. J.; Kim, H.

1989-01-01

Mechanical alloying is being investigated as a processing route for the production of aluminide intermetallics. This program involves powder production and characterization, consolidation and thermal treatments and determination of microstructure-property relationships. An attritor mill is being used to produce powder in lots up to 1000 grams and the processing parameters are being systematically varied to establish the optimum milling conditions. The mill is being instrumented to generate data related to the processing to provide a basis for theoretical modeling. Powder is being characterized using thermal analysis, optical and electron microscopy and X-ray diffraction. Particle size distributions and powder density are being determined. Consolidation of the powder is being approached in several different ways including, cold isostatic pressing, sintering, extrusion and hot pressing. The results of the program so far will be presented and future directions discussed.

Iron aluminide useful as electrical resistance heating elements

DOEpatents

Sikka, V.K.; Deevi, S.C.; Fleischhauer, G.S.; Hajaligol, M.R.; Lilly, A.C. Jr.

1997-04-15

The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, {<=}1% Cr and either {>=}0.05% Zr or ZrO{sub 2} stringers extending perpendicular to an exposed surface of the heating element or {>=}0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, {<=}2% Ti, {<=}2% Mo, {<=}1% Zr, {<=}1% C, {<=}0.1% B, {<=}30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, {<=}1% rare earth metal, {<=}1% oxygen, {<=}3% Cu, balance Fe. 64 figs.

Ordered iron aluminide alloys having an improved room-temperature ductility and method thereof

DOEpatents

Sikka, Vinod K.

1992-01-01

A process is disclosed for improving the room temperature ductility and strength of iron aluminide intermetallic alloys. The process involves thermomechanically working an iron aluminide alloy by means which produce an elongated grain structure. The worked alloy is then heated at a temperature in the range of about 650.degree. C. to about 800.degree. C. to produce a B2-type crystal structure. The alloy is rapidly cooled in a moisture free atmosphere to retain the B2-type crystal structure at room temperature, thus providing an alloy having improved room temperature ductility and strength.

Metal matrix composite of an iron aluminide and ceramic particles and method thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneibel, Joachim H.

A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1450.degree. C. for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

Metal matrix composite of an iron aluminide and ceramic particles and method thereof

DOEpatents

Schneibel, J.H.

1997-06-10

A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1,450 C for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

Metal matrix composite of an iron aluminide and ceramic particles and method thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneibel, J.H.

A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1,450 C for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

Development of improved high temperature coatings for IN-792 + HF

NASA Technical Reports Server (NTRS)

Profant, D. D.; Naik, S. K.

1981-01-01

The development for t-55 l712 engine of high temperature for integral turbine nozzles with improved thermal fatigue resistance without sacrificing oxidation/corrosion protection is discussed. The program evaluated to coating systems which comprised one baseline plasma spray coating (12% Al-NiCoCrALY), three aluminide coatings including the baseline aluminide (701), two CoNiCrAly (6% Al) + aluminide systems and four NiCoCrY + aluminide coating were evaluated. The two-step coating processes were investigated since it offered the advantage of tailoring the composition as well as properly coating surfaces of an integral or segmented nozzle. Cyclic burner rig thermal fatigue and oxidation/corrosion tests were used to evaluate the candidate coating systems. The plasma sprayed 12% Al-NiCoCrAlY was rated the best coating in thermal fatigue resistance and outperformed all coatings by a factor between 1.4 to 2.5 in cycles to crack initiation. However, this coatings is not applicable to integral or segmented nozzles due to the line of sight limitation of the plasma spray process. The 6% Al-CoNiCrAlY + Mod. 701 aluminide (32 w/o Al) was rated the best coating in oxidation/corrosion resistance and was rated the second best in thermal fatigue resistance.

Development of Oxidation Protection Coatings for Gamma Titanium Aluminide Alloys

NASA Technical Reports Server (NTRS)

Wallace, T. A.; Bird, R. K.; Sankaran, S. N.

2003-01-01

Metallic material systems play a key role in meeting the stringent weight and durability requirements for reusable launch vehicle (RLV) airframe hot structures. Gamma titanium aluminides (gamma-TiAl) have been identified as high-payoff materials for high-temperature applications. The low density and good elevated temperature mechanical properties of gamma-TiAl alloys make them attractive candidates for durable lightweight hot structure and thermal protection systems at temperatures as high as 871 C. However, oxidation significantly degrades gamma-TiAl alloys under the high-temperature service conditions associated with the RLV operating environment. This paper discusses ongoing efforts at NASA Langley Research Center to develop durable ultrathin coatings for protecting gamma-TiAl alloys from high-temperature oxidation environments. In addition to offering oxidation protection, these multifunctional coatings are being engineered to provide thermal control features to help minimize heat input into the hot structures. This paper describes the coating development effort and discusses the effects of long-term high-temperature exposures on the microstructure of coated and uncoated gamma-TiAl alloys. The alloy of primary consideration was the Plansee alloy gamma-Met, but limited studies of the newer alloy gamma-Met-PX were also included. The oxidation behavior of the uncoated materials was evaluated over the temperature range of 704 C to 871 C. Sol-gel-based coatings were applied to the gamma-TiAl samples by dipping and spraying, and the performance evaluated at 871 C. Results showed that the coatings improve the oxidation resistance, but that further development is necessary.

Hot corrosion of the B2 nickel aluminides

NASA Technical Reports Server (NTRS)

Ellis, David L.

1993-01-01

The hot corrosion behavior of the B2 nickel aluminides was studied to determine the inherent hot corrosion resistance of the beta nickel aluminides and to develop a mechanism for the hot corrosion of the beta nickel aluminides. The effects of the prior processing of the material, small additions of zirconium, stoichiometry of the materials, and preoxidation of the samples were also examined. Additions of 2, 5, and 15 w/o chromium were used to determine the effect of chromium on the hot corrosion of the beta nickel aluminides and the minimum amount of chromium necessary for good hot corrosion resistance. The results indicate that the beta nickel aluminides have inferior inherent hot corrosion resistance despite their excellent oxidation resistance. Prior processing and zirconium additions had no discernible effect on the hot corrosion resistance of the alloys. Preoxidation extended the incubation period of the alloys only a few hours and was not considered to be an effective means of stopping hot corrosion. Stoichiometry was a major factor in determining the hot corrosion resistance of the alloys with the higher aluminum alloys having a definitely superior hot corrosion resistance. The addition of chromium to the alloys stopped the hot corrosion attack in the alloys tested. From a variety of experimental results, a complex hot corrosion mechanism was proposed. During the early stages of the hot corrosion of these alloys the corrosion is dominated by a local sulphidation/oxidation form of attack. During the intermediate stages of the hot corrosion, the aluminum depletion at the surface leads to a change in the oxidation mechanism from a protective external alumina layer to a mixed nickel-aluminum spinel and nickel oxide that can occur both externally and internally. The material undergoes extensive cracking during the later portions of the hot corrosion.

Oxidation resistant filler metals for direct brazing of structural ceramics

DOEpatents

Moorhead, Arthur J.

1986-01-01

A method of joining ceramics and metals to themselves and to one another is described using essentially pure trinickel aluminide and trinickel aluminide containing small amounts of carbon. This method produces strong joints that can withstand high service temperatures and oxidizing environments.

Diffusion coefficient of hydrogen in a cast gamma titanium aluminide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sundaram, P.A.; Wessel, E.; Ennis, P.J.

1999-06-04

Gamma titanium aluminides have the potential for high temperature applications because of their high specific strength and specific modulus. Their oxidation resistance is good, especially at intermediate temperatures and with suitable alloying additions, good oxidation resistance can be obtained up to 800 C. One critical area of application is in combustion engines in aero-space vehicles such as hypersonic airplanes and high speed civil transport airplanes. This entails the use of hydrogen as a fuel component and hence the effect of hydrogen on the mechanical properties of gamma titanium aluminides is of significant scientific and technological utility. The purpose of thismore » short investigation is to use an electrochemical method under galvanostatic conditions to determine the diffusion coefficient of hydrogen in a cast gamma titanium aluminide, a typical technical alloy with potential application in gas turbines under creep conditions. This result will be then compared with that obtained by microhardness profiling of electrolytically hydrogen precharged material.« less

Method for producing titanium aluminide weld rod

DOEpatents

Hansen, Jeffrey S.; Turner, Paul C.; Argetsinger, Edward R.

1995-01-01

A process for producing titanium aluminide weld rod comprising: attaching one end of a metal tube to a vacuum line; placing a means between said vacuum line and a junction of the metal tube to prevent powder from entering the vacuum line; inducing a vacuum within the tube; placing a mixture of titanium and aluminum powder in the tube and employing means to impact the powder in the tube to a filled tube; heating the tube in the vacuum at a temperature sufficient to initiate a high-temperature synthesis (SHS) reaction between the titanium and aluminum; and lowering the temperature to ambient temperature to obtain a intermetallic titanium aluminide alloy weld rod.

Evaluation of a Gamma Titanium Aluminide for Hypersonic Structural Applications

NASA Technical Reports Server (NTRS)

Johnson, W. Steven; Weeks, Carrell E.

2005-01-01

Titanium matrix composites (TMCs) have been extensively evaluated for their potential to replace conventional superalloys in high temperature structural applications, with significant weight-savings while maintaining comparable mechanical properties. New gamma titanium aluminide alloys and an appropriate fiber could offer an improved TMC for use in intermediate temperature applications (400-800 C). The purpose of this investigation is the evaluation of a gamma titanium aluminide alloy with nominal composition Ti-46.5Al-4(Cr,Nb,Ta,B)at.% as a structural material in future aerospace transportation systems, where very light-weight structures are necessary to meet the goals of advanced aerospace programs.

Castable nickel aluminide alloys for structural applications

DOEpatents

Liu, Chain T.

1992-01-01

The specification discloses nickel aluminide alloys which include as a component from about 0.5 to about 4 at. % of one or more of the elements selected from the group consisting of molybdenum or niobium to substantially improve the mechanical properties of the alloys in the cast condition.

Iridium Aluminide Coats For Protection Against Ox idation

NASA Technical Reports Server (NTRS)

Kaplan, Richard B.; Tuffias, Robert H.; La Ferla, Raffaele; Jang, Qin

1996-01-01

Iridium aluminide coats investigated for use in protecting some metallic substrates against oxidation at high temperatures. Investigation prompted by need for cost-effective anti-oxidation coats for walls of combustion chambers in rocket engines. Also useful in special terrestrial applications like laboratory combustion chambers and some chemical-processing chambers.

Food structure: Its formation and relationships with other properties.

PubMed

Joardder, Mohammad U H; Kumar, Chandan; Karim, M A

2017-04-13

Food materials are complex in nature as it has heterogeneous, amorphous, hygroscopic and porous properties. During processing, microstructure of food materials changes which significantly affects other properties of food. An appropriate understanding of the microstructure of the raw food material and its evolution during processing is critical in order to understand and accurately describe dehydration processes and quality anticipation. This review critically assesses the factors that influence the modification of microstructure in the course of drying of fruits and vegetables. The effect of simultaneous heat and mass transfer on microstructure in various drying methods is investigated. Effects of changes in microstructure on other functional properties of dried foods are discussed. After an extensive review of the literature, it is found that development of food structure significantly depends on fresh food properties and process parameters. Also, modification of microstructure influences the other properties of final product. An enhanced understanding of the relationships between food microstructure, drying process parameters and final product quality will facilitate the energy efficient optimum design of the food processor in order to achieve high-quality food.

Superalloy for high-temperature hydrogen environmental applications

NASA Technical Reports Server (NTRS)

McKannan, Eugene C. (Inventor); McPherson, William B. (Inventor); Ahmed, Shaffiq (Inventor); Chandler, Shirley S. (Inventor)

1991-01-01

A nickel-based superalloy is provided which is resistant to deterioration in hydrogen at high operating temperatures and pressures, and which thus can be used in hydrogen-fueled spacecraft such as the Space Shuttle. The superalloy is characterized by a two-phase microstructure and consists of a gamma-prime precipitated phase in a gamma matrix. The gamma matrix phase is a primary solid solution and the gamma precipitated phase will be an intermetallic compound of the type A.sub.3 B, such as nickel aluminide or titanide. Both phases are coherent, ordered, and compatible, and thus will retain most of their strength at elevated temperatures. The alloy consists essentially of (by weight): Ni 50-60%, Cr 10-20%, Al 2-6%, Co 2-5%, Ti 3-8%, W 5-12%, Mo 5-10%, Nb 1-3%, wherein the ratio W/MO is approximately equal to 1, and Ti/Al ranges from about 1 to about 2.

Iron aluminide useful as electrical resistance heating elements

DOEpatents

Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

1997-01-01

The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

Oxidation, carburization and/or sulfidation resistant iron aluminide alloy

DOEpatents

Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

2003-08-19

The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or Zro.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B. .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

Iron aluminide useful as electrical resistance heating elements

DOEpatents

Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

1999-01-01

The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

Iron aluminide useful as electrical resistance heating elements

DOEpatents

Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

2001-01-01

The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

Observations on the brittle to ductile transition temperatures of B2 nickel aluminides with and without zirconium

NASA Technical Reports Server (NTRS)

Raj, S. V.; Noebe, R. D.; Bowman, R.

1989-01-01

The effect of a zirconium addition (0.05 at. pct) to a stoichiometric NiAl alloy on the brittle-to-ductile transition temperature (BDTT) of this alloy was investigated. Constant velocity tensile tests were conducted to fracture between 300 and 1100 K under initial strain rate 0.00014/sec, and the true stress and true strain values were determined from plots of load vs time after subtracting the elastic strain. The inelastic strain was measured under a traveling microscope. Microstructural characterization of as-extruded and fractured specimens was carried out by SEM and TEM. It was found that, while the addition of 0.05 at. pct Zr strengthened the NiAl alloy, it increased its BDTT; this shift in the BDTT could not be attributed either to variations in grain size or to impurity contents. Little or no room-temperature ductility was observed for either alloy.

Synthesis, Microstructure and Properties of Nickel Aluminide Foams

NASA Technical Reports Server (NTRS)

Dunand, David C.

2003-01-01

Two Ph.D. students were involved in the project: Mr. Christopher Schuh (part-time, graduated in Spring 2001) and Ms. Andrea Hodge (full-time, graduated Summer 2002). One post-doctoral fellow, Dr. Heeman Choe, worked full-time on the project from July to December 2002. A new process to aluminize and chromize nickel foams was created. A kinetic aluminization model was developed. Creep testing was conducted on the foams. A finite-element model and a simplified analytical model for foam creep were produced. Four articles were written: one is published, two are accepted for publication, and one is in preparation. Ms. Hodge spent four months at NASA Glenn Research Center (9-12/2001 and 2-3/2002) under the supervision of Dr. Nathal. She conducted research on NiAl foam fabrication, mechanical testing and numerical modeling. She gave a talk at the ASM annual conference in November 2001 and presented her results at NASA in December 2001.

Polymer quenched prealloyed metal powder

DOEpatents

Hajaligol, Mohammad R.; Fleischhauer, Grier; German, Randall M.

2001-01-01

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3 % Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Thermomechanical processing of plasma sprayed intermetallic sheets

DOEpatents

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2001-01-01

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Three-dimensional nanometer scale analyses of precipitate structures and local compositions in titanium aluminide engineering alloys

NASA Astrophysics Data System (ADS)

Gerstl, Stephan S. A.

Titanium aluminide (TiAl) alloys are among the fastest developing class of materials for use in high temperature structural applications. Their low density and high strength make them excellent candidates for both engine and airframe applications. Creep properties of TiAl alloys, however, have been a limiting factor in applying the material to a larger commercial market. In this research, nanometer scale compositional and structural analyses of several TiAl alloys, ranging from model Ti-Al-C ternary alloys to putative commercial alloys with 10 components are investigated utilizing three dimensional atom probe (3DAP) and transmission electron microscopies. Nanometer sized borides, silicides, and carbide precipitates are involved in strengthening TiAl alloys, however, chemical partitioning measurements reveal oxygen concentrations up to 14 at. % within the precipitate phases, resulting in the realization of oxycarbide formation contributing to the precipitation strengthening of TiAl alloys. The local compositions of lamellar microstructures and a variety of precipitates in the TiAl system, including boride, silicide, binary carbides, and intermetallic carbides are investigated. Chemical partitioning of the microalloying elements between the alpha2/gamma lamellar phases, and the precipitate/gamma-matrix phases are determined. Both W and Hf have been shown to exhibit a near interfacial excess of 0.26 and 0.35 atoms nm-2 respectively within ca. 7 nm of lamellar interfaces in a complex TiAl alloy. In the case of needle-shaped perovskite Ti3AlC carbide precipitates, periodic domain boundaries are observed 5.3+/-0.8 nm apart along their growth axis parallel to the TiAl[001] crystallographic direction with concomitant composition variations after 24 hrs. at 800°C.

Method of protecting the surface of a substrate. [by applying aluminide coating

NASA Technical Reports Server (NTRS)

Gedwill, M. A. (Inventor); Grisaffe, S. J.

1974-01-01

The surface of a metallic base system is initially coated with a metallic alloy layer that is ductile and oxidation resistant. An aluminide coating is then applied to the metallic alloy layer. The chemistry of the metallic alloy layer is such that the oxidation resistance of the subsequently aluminized outermost layer is not seriously degraded.

Environmental Studies on Titanium Aluminide Alloys

NASA Technical Reports Server (NTRS)

Brindley, William J.; Bartolotta, Paul A.; Smialek, James L.; Brady, Michael P.

2005-01-01

Titanium aluminides are attractive alternatives to superalloys in moderate temperature applications (600 to 850 C) by virtue of their high strength-to-density ratio (high specific strength). These alloys are also more ductile than competing intermetallic systems. However, most Ti-based alloys tend to degrade through interstitial embrittlement and rapid oxidation during exposure to elevated temperatures. Therefore, their environmental behavior must be thoroughly investigated before they can be developed further. The goals of titanium aluminide environmental studies at the NASA Lewis Research Center are twofold: characterize the degradation mechanisms for advanced structural alloys and determine what means are available to minimize degradation. The studies to date have covered the alpha 2 (Ti3Al), orthorhombic (Ti2AlNb), and gamma (TiAl) classes of alloys.

Effect of Sr Additive Amount and Holding Time on Microstructure of A390 Aluminum Alloy

NASA Astrophysics Data System (ADS)

Zhang, J. H.; Xing, S. M.; Han, Q. Y.; Guo, Q.; Wang, R. F.

2017-11-01

The microstructure of A390 alloy under different Sr additive amounts and holding times was studied by means of direct reading spectrum analysis, energy spectrum analysis, optical microscope and electron microscope. The results show that Sr has a good modification to eutectic Si, while it has a negative effect on primary silicon. The Sr addition will increase the size of primary silicon. When the addition amount of Al-10Sr alloy is 0.6%, the modification of eutectic silicon is the optimum. The Sr has a short incubation period and a fine modification at 10min, but it is more serious burning rate in small furnace smelting, and the modification effect disappears basically after 100min.

Interdiffusion behaviors in doped molybdenum uranium and aluminum or aluminum silicon dispersion fuels: Effects of the microstructure

NASA Astrophysics Data System (ADS)

Allenou, J.; Tougait, O.; Pasturel, M.; Iltis, X.; Charollais, F.; Anselmet, M. C.; Lemoine, P.

2011-09-01

Si addition to Al is considered as a promising route to reduce (U,Mo)-Al interaction kinetics, due to its accumulation in the interaction layer, yielding the formation of silicide phases. The (U,Mo) alloy microstructure, and especially its homogenization state, could play a role on this accumulation process. The addition of a third element in γ(U,Mo) could also influence diffusion mechanisms of Al and Si. These two parameters were studied by means of diffusion couple experiments by joining γU based alloys with Al and (Al,Si) alloy. Chemical elements X added into γ(U,Mo) were thoroughly chosen on the following criteria: (i) the potential solubility of the alloying element into the γ(U,Mo) matrix, (ii) its capability to form the ternary aluminides based on the CeCr 2Al 20 and Ho 6Mo 4Al 43 - types, and (iii) the feasibility to control the microstructure of the alloys. On this basis, a test matrix is defined. It concerns γ(U80,Mo15,X5) alloys (in at.%) with X = Y, Cu, Zr, Ti or Cr. These alloys were homogenized and coupled with Al or (Al,Si) alloy. Results evidenced, first, the importance of the state of homogenization of the γ(U,Mo) binary alloy on interaction processes with (Al,Si) alloy, and the benefit on the diffusion of Si through the interaction layer, as observed on the elementary concentration profiles, when the third element X has some solubility into γ(U,Mo) alloy.

Microstructural Development in a Laser-Remelted Al-Zn-Si-Mg Coating.

PubMed

Godec, M; Podgornik, B; Nolan, D

2017-11-23

In the last five decades, there has been intense development in the field of Zn-Al galvanic coating modification. Recently, Mg was added to improve corrosion properties. Further improvements to the coating are possible with additional laser surface treatment. In this article, we focus on remelting the Al-Zn-Mg-Si layer, using a diode laser with a wide-beam format, concentrating on the microstructure development during extreme cooling rates. Laser remelting of the Al-Zn-Mg-Si coating and rapid self-quenching produces a finer grain size, and a microstructure that is substantially refined and homogenized with respect to the phase distribution. Using EBSD results, we are able to understand microstructure modification. The laser modified coating has some porosity and intergranular cracking which are difficult to avoid, however this does not seem to be detrimental to mechanical properties, such as ductility on bending. The newly developed technology has a high potential for improved corrosion performance due to highly refined microstructure.

An experimental, low-cost, silicon slurry/aluminide high-temperature coating for superalloys

NASA Technical Reports Server (NTRS)

Young, S. G.; Deadmore, D. L.

1979-01-01

A duplex silicon-slurry/aluminide coating has been developed and cyclically tested in Mach 1 combustion gases for oxidation and thermal fatigue resistance at 1093 C and in Mach 0.3 gases for hot-corrosion resistance at 900 C. The base-metal superalloys were VIA and B-1900. The coated B-1900 specimens performed much better in oxidation than similar specimens coated with aluminides and almost as well as the more-expensive Pt-Al and MCrAlY (where M is Ni and/or Co) coatings deposited by the physical vapor deposition process. The coating also provided good hot-corrosion protection. Metallographic, X-ray, and electron microprobe studies were made to characterize the coating, determine failure mechanisms, and study some of the changes due to exposure.

Titanium Aluminide Applications in the High Speed Civil Transport

NASA Technical Reports Server (NTRS)

Bartolotta, Paul A.; Krause, David L.

1999-01-01

It is projected that within the next two decades, overseas air travel will increase to over 600,000 passengers per day. The High Speed Civil Transport (HSCT) is a second-generation supersonic commercial aircraft proposed to meet this demand. The expected fleet of 500 to 1500 aircraft is required to meet EPA environmental goals; the HSCT propulsion system requires advanced technologies to reduce exhaust and noise pollution. A part of the resultant strategy for noise attenuation is the use of an extremely large exhaust nozzle. In the nozzle, several critical components are fabricated from titanium aluminide: the divergent nap uses wrought gamma; the nozzle sidewall is a hybrid fabrication of both wrought gamma face sheet and cast gamma substructure. This paper describes the HSCT program and the use of titanium aluminide for its components.

Mechanical properties of coated titanium Beta-21S after exposure to air at 700 and 800 C

NASA Technical Reports Server (NTRS)

Wiedemann, Karl E.; Bird, R. Keith; Wallace, Terryl A.; Clark, Ronald K.

1992-01-01

Mechanical properties of Beta-21S (Ti-15Mo-3Al-2.7Nb-0.2Si, wt percent) with glass, aluminide, and glass-on-aluminide coatings less than 3-micron thick were studied. Coatings were deposited by sol-gel processing or electron-beam evaporation onto 4.5-mil (113-micron) thick Beta-21S sheet from which, after oxidizing in air at 700 or 800 C, tensile test specimens were machined. Plastic elongation was the most severely degraded of the tensile properties; the glass-on-aluminide coatings were the most effective in preventing degradation. It was found that oxygen trapping by forming oxides in the coating, and reactions between the coatings and the Beta-21S alloy played significant roles.

Iron aluminide alloy container for solid oxide fuel cells

DOEpatents

Judkins, Roddie Reagan; Singh, Prabhakar; Sikka, Vinod Kumar

2000-01-01

A container for fuel cells is made from an iron aluminide alloy. The container alloy preferably includes from about 13 to about 22 weight percent Al, from about 2 to about 8 weight percent Cr, from about 0.1 to about 4 weight percent M selected from Zr and Hf, from about 0.005 to about 0.5 weight percent B or from about 0.001 to about 1 weight percent C, and the balance Fe and incidental impurities. The iron aluminide container alloy is extremely resistant to corrosion and metal loss when exposed to dual reducing and oxidizing atmospheres at elevated temperatures. The alloy is particularly useful for containment vessels for solid oxide fuel cells, as a replacement for stainless steel alloys which are currently used.

Effects of Nb Modification and Cooling Rate on the Microstructure in an Ultrahigh Carbon Steel

NASA Astrophysics Data System (ADS)

Hecht, Matthew D.; Webler, Bryan A.; Picard, Yoosuf N.

2018-04-01

In this study, two different melting methods were used to investigate effects of Nb modification on microstructure in ultrahigh carbon steel (UHCS). Nb-free and Nb-modified UHCS samples were produced by melting and resolidifying an industrially produced base UHCS with and without addition of Nb powder. Microstructure was characterized using scanning electron microscopy, X-ray diffraction, and electron dispersive spectroscopy. Equilibrium computations of phase fractions and compositions were utilized to help describe microstructural changes caused by the Nb additions. Nb combined with C to form NbC structures before and during austenite solidification, reducing the effective amount of carbon available for the other phases. Cementite network spacing in the Nb-free samples was controlled by the cooling rate during solidification (faster cooling led to a more refined network). Network spacing in the Nb-modified UHCS could be enlarged by NbC structures that formed cooperatively with austenite.

Effects of Nb Modification and Cooling Rate on the Microstructure in an Ultrahigh Carbon Steel

NASA Astrophysics Data System (ADS)

Hecht, Matthew D.; Webler, Bryan A.; Picard, Yoosuf N.

2018-06-01

In this study, two different melting methods were used to investigate effects of Nb modification on microstructure in ultrahigh carbon steel (UHCS). Nb-free and Nb-modified UHCS samples were produced by melting and resolidifying an industrially produced base UHCS with and without addition of Nb powder. Microstructure was characterized using scanning electron microscopy, X-ray diffraction, and electron dispersive spectroscopy. Equilibrium computations of phase fractions and compositions were utilized to help describe microstructural changes caused by the Nb additions. Nb combined with C to form NbC structures before and during austenite solidification, reducing the effective amount of carbon available for the other phases. Cementite network spacing in the Nb-free samples was controlled by the cooling rate during solidification (faster cooling led to a more refined network). Network spacing in the Nb-modified UHCS could be enlarged by NbC structures that formed cooperatively with austenite.

Breakthrough Air Force Capabilities Spawned By Basic Research

DTIC Science & Technology

2007-04-01

AboutAFOSR/about_history.htm>. 15 Ibid. 16 Ibid. 4 1990s • Titanium Aluminides . AFOSR-sponsored research looked at titanium aluminides , which are...the 1970s, AFOSR sponsored research on ways to increase the strength and fatigue resistance of titanium , aluminum, and nickel alloys used for...High-Efficiency Swept Shock Compressor Blades . AFOSR-sponsored research looked at making rotor blades in axial flow compressors more efficient

Repair welding of gamma titanium aluminide castings

NASA Astrophysics Data System (ADS)

Kelly, T. J.

This paper examines the GTA repair welding of cast Ti-48Al-2Cr-2Nb gamma titanium aluminide. Pre-weld heat treatment, preheat and welding parameters are evaluated and discussed. A wide range of GTAW parameters is demonstrated for use with this alloy and the resulting weld structure is examined. The effects of postweld heat treatment on the structure of the weld deposit is also determined.

Effects of Microalloying on the Microstructures and Mechanical Properties of Directionally Solidified Ni-33(at.%)Al-31Cr-3Mo Eutectic Alloys Investigated

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.

2002-01-01

Despite nickel aluminide (NiAl) alloys' attractive combination of oxidation and thermophysical properties, their development as replacements for superalloy airfoils in gas turbine engines has been largely limited by difficulties in developing alloys with an optimum combination of elevated-temperature creep resistance and room-temperature fracture toughness. Alternatively, research has focused on developing directionally solidified NiAl-based in situ eutectic composites composed of NiAl and (Cr,Mo) phases in order to obtain a desirable combination of properties a systematic investigation was undertaken at the NASA Glenn Research Center to examine the effects of small additions of 11 alloying elements (Co, Cu, Fe, Hf, Mn, Nb, Re, Si, Ta, Ti, and Zr) in amounts varying from 0.25 to 1.0 at.% on the elevated-temperature strength and room-temperature fracture toughness of directionally solidified Ni-33Al-31Cr-3Mo eutectic alloy. The alloys were grown at 12.7 mm/hr, where the unalloyed eutectic base alloy exhibited a planar eutectic microstructure. The different microstructures that formed because of these fifth-element additions are included in the table. The additions of these elements even in small amounts resulted in the formation of cellular microstructures, and in some cases, dendrites and third phases were observed. Most of these elemental additions did not improve either the elevated-temperature strength or the room-temperature fracture toughness over that of the base alloy. However, small improvements in the compression strength were observed between 1200 and 1400 K when 0.5 at.% Hf and 0.25 at.% Ti were added to the base alloy. The results of this study suggest that the microalloying of Ni-33Al-31Cr-3Mo will not significantly improve either its elevatedtemperature strength or its room-temperature fracture toughness. Thus, any improvements in these properties must be acquired by changing the processing conditions.

Welding of gamma titanium aluminide alloys

NASA Technical Reports Server (NTRS)

Smashey, Russell W. (Inventor); Snyder, John H. (Inventor); Kelly, Thomas J. (Inventor); Sheranko, Ronald L. (Inventor)

1998-01-01

An article made of a gamma titanium aluminide alloy is welded, as for example in the weld repair of surface cracks, by removing foreign matter from the area to be welded, first stress relieving the article, cooling the entire article to a welding temperature of from about 1000.degree. F. to about 1400.degree. F., welding a preselected region in an inert atmosphere at the welding temperature, and second stress relieving the article. Welding is preferably accomplished by striking an arc in the preselected region so as to locally melt the alloy in the preselected region, providing a filler metal having the same composition as the gamma titanium aluminide alloy of the article, and feeding the filler metal into the arc so that the filler metal is melted and fused with the article to form a weldment upon solidification.

Effect of niobium alloying level on the oxidation behavior of titanium aluminides at 850°C

NASA Astrophysics Data System (ADS)

Banu, Alexandra; Marcu, Maria; Petrescu, Simona; Ionescu, Nicolae; Paraschiv, Alexandru

2016-12-01

This work addresses the alloying of titanium aluminides used in aircraft engine applications and automobiles. The oxidation resistance behavior of two titanium aluminides of α2 + γ(Ti3Al + TiAl) and orthorhombic Ti2NbAl, recognized as candidates for high-temperature applications, was investigated by exposure of the alloys for 100 h in air. Thus, oxidation resistance was expressed as the mass gain rate, whereas surface aspects were analyzed using scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy, and the type of oxidation products was analyzed by X-ray diffraction and Raman spectroscopy. The orthorhombic Ti2NbAl alloy was embrittled, and pores and microcracks were formed as a result of oxygen diffusion through the external oxide layer formed during thermal oxidation for 100 h.

Effects of silicon additions on oxidation and mechanical behavior of the nickel-base superalloy B-1900

NASA Technical Reports Server (NTRS)

Miner, R. V., Jr.; Lowell, C. E.

1975-01-01

Test specimens with nominal additions of Si were tested in oxidation, thermal fatigue, sulfidation, tension, and stress rupture, and were also extensively studied metallographically. Alloy B-1900 modified with 0.6- or 1.2-wt% Si exhibited oxidation resistance equivalent to that of aluminide-coated B-1900 during cyclic, high-gas-velocity oxidation tests. Resistances to thermal fatigue and sulfidation were improved by the Si additions, but were not superior to aluminide-coated B-1900. Stress-rupture tests at 1000 C of specimens given the standard heat treatment to simulate an aluminide coating cycle showed Si to be detrimental. However, application of another heat treatment increased the rupture life of the alloy with 0.6-wt% Si to that of the unmodified B-1900 given the standard heat treatment.

Development of in-Situ Al-Si/CuAl₂ Metal Matrix Composites: Microstructure, Hardness, and Wear Behavior.

PubMed

Tash, Mahmoud M; Mahmoud, Essam R I

2016-06-02

In the present work, in-situ metal matrix composites were fabricated through squeeze casting. The copper particles were dispersed with different weight percentages (3%, 6%, 10%, and 15%) into Al-12% Si piston alloy. Also, heat treatments were performed at 380 °C and 450 °C for holding times of 6 and 18 h. The microstructures, X-ray diffractometer (XRD) pattern, hardness, and wear characteristics were evaluated. The results showed that these copper particles have reacted with the aluminum under all of the aforementioned processing conditions resulting in the formation of fine copper aluminide intermetallics. Most of the intermetallics were CuAl₂, while AlCu appeared in a small ratio. Additionally, these intermetallics were homogenously distributed within the alloy matrix with up to 6% Cu addition. The amounts of those intermetallics increased after performing heat treatment. Most of these intermetallics were CuAl₂ at 380 °C, while the Cu-rich intermetallics appeared at 450 °C. Increasing the holding time to 18 h, however, led to grain coarsening and resulted in the formation of some cracks. The hardness of the resulting composite materials was improved. The hardness value reached to about 170 HV after heat treating at 380 °C for 8 h. The wear resistance of the resulting composite materials was remarkably improved, especially at lower additions of Cu and at the lower heat treatment temperature.

Advanced Tomographic Imaging Methods for the Analysis of Materials

DTIC Science & Technology

1991-08-01

used in composite manufacture: aluminum, silicon carbide, and titanium aluminide . Also depicted in Fig. 2 are the energy intervals which can...SiC-fiber (SCS6) in a titanium - aluminide matrix. The contrast between SiC and AtIis only 10% over a broad eiaergy range. Therefore, distinguishing the...borehole logging, orrodent detection on turbine blades , kerogen analysis of shale, and contents of coals (sulfur, minerals, and btu). APSTNG

High-temperature fabricable nickel-iron aluminides

DOEpatents

Liu, Chain T.

1988-02-02

Nickel-iron aluminides are described that are based on Ni.sub.3 Al, and have significant iron content, to which additions of hafnium, boron, carbon and cerium are made resulting in Ni.sub.3 Al base alloys that can be fabricated at higher temperatures than similar alloys previously developed. Further addition of molybdenum improves oxidation and cracking resistance. These alloys possess the advantages of ductility, hot fabricability, strength, and oxidation resistance.

Anisotropic Damage Mechanics Modeling in Metal Matrix Composites

DTIC Science & Technology

1993-05-15

conducted on a titanium aluminide SiC-reinforced metal matrix composite. Center-cracked plates with laminate layups of (0/90) and (±45). were tested... interfacial damage mechanisms as debonding or delamination. Equations (2.14) and (2.15) represent the damage transformation equations for the stress... titanium aluminide SiC 46 continuous reinforced metal matrix composite. As a means of enforcing quality assurance, all manufacturing and cutting of the

Two-Phase (TiAl+TiCrAl) Coating Alloys for Titanium Aluminides

NASA Technical Reports Server (NTRS)

Brady, Michael P. (Inventor); Smialek, James L. (Inventor); Brindley, William J. (Inventor)

1998-01-01

A coating for protecting titanium aluminide alloys, including the TiAl gamma + Ti3Al (alpha(sub 2)) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C. is disclosed. This protective coating consists essentially of titanium, aluminum. and chromium in the following approximate atomic ratio: Ti(41.5-34.5)Al(49-53)Cr(9.5-12.5)

Aluminide coatings

DOEpatents

Henager, Jr; Charles, H [Kennewick, WA; Shin, Yongsoon [Richland, WA; Samuels, William D [Richland, WA

2009-08-18

Disclosed herein are aluminide coatings. In one embodiment coatings are used as a barrier coating to protect a metal substrate, such as a steel or a superalloy, from various chemical environments, including oxidizing, reducing and/or sulfidizing conditions. In addition, the disclosed coatings can be used, for example, to prevent the substantial diffusion of various elements, such as chromium, at elevated service temperatures. Related methods for preparing protective coatings on metal substrates are also described.

Elevated-Temperature Deformation Properties of a HfC Modified Ti-48Al-2Mn-2Nb Matrix Particulate Composite

NASA Technical Reports Server (NTRS)

Whittenberger, J. D.; Farmer, S. C.; Bors, D. A.; Ray, R.; Lee, D. S.

1994-01-01

Rapid solidification techniques in combination with HIPing have been used to produce Ti-48Al-2Mn-2Nb and a Ti-48Al-2Mn-2Nb+15 wt% HfC composite. While the composite does contain several second phases within the gamma + alpha(sub 2) matrix, none was identified to be HfC. The elevated-temperature properties were determined by constant velocity compression and constant load tensile testing in air between 1000 and 1173 K. Such testing indicated that the elevated temperature strengths of the HfC-modified aluminide was superior to those of the unreinforced matrix with the best 1100 K temperature slow strain rate properties for both materials being achieved after high-temperature annealing prior to testing. Examination of the microstructures after deformation in combination with the measured stress exponents and activation energies suggest that creep resistance of the HfC-modified form is due to solid-solution strengthening from carbon and hafnium rather than the presence of second phases.

Effects of Ultrasonic Nanocrystal Surface Modification on the Residual Stress, Microstructure, and Corrosion Resistance of 304 Stainless Steel Welds

NASA Astrophysics Data System (ADS)

Ye, Chang; Telang, Abhishek; Gill, Amrinder; Wen, Xingshuo; Mannava, Seetha R.; Qian, Dong; Vasudevan, Vijay K.

2018-03-01

In this study, ultrasonic nanocrystal surface modification (UNSM) of 304 stainless steel welds was carried out. UNSM effectively eliminates the tensile stress generated during welding and imparts beneficial compressive residual stresses. In addition, UNSM can effectively refine the grains and increase hardness in the near-surface region. Corrosion tests in boiling MgCl2 solution demonstrate that UNSM can significantly improve the corrosion resistance due to the compressive residual stresses and changes in the near-surface microstructure.

Development of re-crystallized W-1.1%TiC with enhanced room-temperature ductility and radiation performance

NASA Astrophysics Data System (ADS)

Kurishita, H.; Matsuo, S.; Arakawa, H.; Sakamoto, T.; Kobayashi, S.; Nakai, K.; Takida, T.; Kato, M.; Kawai, M.; Yoshida, N.

2010-03-01

Ultra-fine grained (UFG) W-TiC compacts fabricated by powder metallurgical methods utilizing mechanical alloying (MA) are very promising for use in irradiation environments. However, the assurance of room-temperature ductility and enhancement in surface resistances to low-energy hydrogen irradiation are unsettled issues. As an approach to solution to these, microstructural modification by hot plastic working has been applied to UFG W-TiC processed by MA in a purified Ar or H 2 atmosphere and hot isostatic pressing (HIP). Hot plastically worked compacts have been subjected to 3-point bend tests at room temperature and TEM microstructural examinations. It is found that the microstructural modification allows us to convert UFG W-1.1%TiC to compacts exhibiting a very high fracture strength and appreciable ductility at room temperature. The compacts of W-1.1%TiC/Ar (MA atmosphere: Ar) and W-1.1%TiC/H 2 (MA atmosphere: H 2) exhibit re-crystallized structures with approximately 0.5 and 1.5 μm in grain size, respectively. It is shown that the enhancement of fracture resistance by microstructural modifications is attributed to significant strengthening of weak grain boundaries in the re-crystallized state. As a result the modified compacts exhibit superior surface resistance to low-energy deuteron irradiation.

Enhanced Life Prediction Technology for Engine Rotor Life Extension (ERLE)

DTIC Science & Technology

2008-09-01

related a0 to dislocation pileups and mode II shear cracks, and found satisfactory agreement with small-crack data from titanium aluminides . Tanaka...Symp. Gamma Titanium Aluminides , TMS, 1999, pp. 517-525. [11] K. Tanaka, Y. Nakai, and M. Yamashita, “Fatigue Growth Threshold of Small Cracks...between his formulation and a variety of experimental data. While titanium was not included in the Tanaka comparisons, Brown and Taylor [12] have

Quantum Mechanical Approach to Understanding Structural, Electronic and Mechanical Properties of Intermetallics

DTIC Science & Technology

1989-01-26

Understanding Structural , Electronic and Mechanical Properties of Tntermetallics by A.J. Freeman, Principal Investigator ABSTRACT The primary goal of...like LI or Mg would lower EF into the minimum in the DOS and hence stabilize the L1 2 . A. Structural Phase Stability of Titanium Aluminides Most...34 Structural Stability Calculations in the Titanium -Aluminium System", Conf. on Titanium Aluminides , Wright-Patterson Air Force Base, Nov. 1986

Silicon-slurry/aluminide coating. [protecting gas turbine engine vanes and blades

NASA Technical Reports Server (NTRS)

Deadmore, D. L.; Young, S. G. (Inventor)

1983-01-01

A low cost coating protects metallic base system substrates from high temperatures, high gas velocity ovidation, thermal fatigue and hot corrosion and is particularly useful fo protecting vanes and blades in aircraft and land based gas turbine engines. A lacquer slurry comprising cellulose nitrate containing high purity silicon powder is sprayed onto the superalloy substrates. The silicon layer is then aluminized to complete the coating. The Si-Al coating is less costly to produce than advanced aluminides and protects the substrates from oxidation and thermal fatigue for a much longer period of time than the conventional aluminide coatings. While more expensive Pt-Al coatings and physical vapor deposited MCrAlY coatings may last longer or provide equal protection on certain substrates, the Si-Al coating exceeded the performance of both types of coatings on certain superalloys in high gas velocity oxidation and thermal fatigue and increased the resistance of certain superalloys to hot corrosion.

Internally coated air-cooled gas turbine blading

NASA Technical Reports Server (NTRS)

Hsu, L.; Stevens, W. G.; Stetson, A. R.

1979-01-01

Ten candidate modified nickel-aluminide coatings were developed using the slip pack process. These coatings contain additives such as silicon, chromium and columbium in a nickel-aluminum coating matrix with directionally solidified MAR-M200 + Hf as the substrate alloy. Following a series of screening tests which included strain tolerance, dynamic oxidation and hot corrosion testing, the Ni-19A1-1Cb (nominal composition) coating was selected for application to the internal passages of four first-stage turbine blades. Process development results indicate that a dry pack process is suitable for internal coating application resulting in 18 percent or less reduction in air flow. Coating uniformity, based on coated air-cooled blades, was within + or - 20 percent. Test results show that the presence of additives (silicon, chromium or columbium) appeared to improve significantly the ductility of the NiA1 matrix. However, the environmental resistance of these modified nickel-aluminides were generally inferior to the simple aluminides.

Performance of Diffusion Aluminide Coatings Applied on Alloy CF8C-Plus at 800oC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Deepak; Dryepondt, Sebastien N; Zhang, Ying

2012-01-01

High performance cast stainless steel, CF8C-Plus, is a low cost alloy with prospective applications ranging from covers and casings of small and medium size gas turbines to turbocharger housing and manifolds in internal combustion engines. Diffusion aluminide coatings were applied on this alloy as a potential strategy for improved oxidation resistance, particularly in wet air and steam. In this paper the performance of the aluminide coatings evaluated by cyclic oxidation experiments in air containing 10 vol.% H2O at 800 C and conventional tension-compression low-cycle-fatigue tests in air at 800 C with a strain range of 0.5% is presented. The resultsmore » show that specimens coated by a chemical vapor deposition process provide better oxidation resistance than those coated by an Al-slurry coating process. The application of a coating by pack cementation reduced the fatigue life by 15%.« less

High temperature properties of non-critical Fe-Al alloys doped by non critical or “slightly–critical” elements

NASA Astrophysics Data System (ADS)

Vodičková, Věra; Hanus, Pavel; Vlasák, Tomáš; Švec, Martin

2018-03-01

Iron aluminides were developed as an alternative to stainless steels after World War II. The main intended impact was to save strategic elements (chromium or nickel). The result of these investigations was development of registered alloys as Pyroferal (Czechoslovak Republic), Thugal (Soviet Union) or Thermagal (France). The investigation of these type alloys continued in the nineties thanks to technological progress. In this time iron aluminides seems to be promising material with very good corrosive and environment resistivity. The mechanical properties of binary iron aluminides (Fe-Al) are average at higher temperatures but strengthening effect of alloying elements is significant. The aim of the article is to show influence of non-critical additives (such as C, Ti, Zr) and also “slightly critical” elements as e.g. Ce, Nb on high temperature creep properties of alloys.

The Oxidation and Protection of Gamma Titanium Aluminides

NASA Technical Reports Server (NTRS)

Brady, Michael P.; Brindley, William J.; Smialek, James L.; Locci, Ivan E.

1996-01-01

The excellent density-specific properties of the gamma class of titanium aluminides make them attractive for intermediate-temperature (600-850 C) aerospace applications. The oxidation and embrittlement resistance of these alloys is superior to that of the alpha(sub 2) and orthorhombic classes of titanium aluminides. However, since gamma alloys form an intermixed Al2O3/TiO2 scale in air rather than the desired continuous Al2O3 scale, oxidation resistance is inadequate at the high end of this temperature range (i.e., greater than 750-800 C). For applications at such temperatures, an oxidation-resistant coating will be needed; however, a major drawback of the oxidation-resistant coatings currently available is severe degradation in fatigue life by the coating. A new class of oxidation-resistant coatings based in the Ti-Al-Cr system offers the potential for improved fatigue life.

Molybdeno-Aluminizing of Powder Metallurgy and Wrought Ti and Ti-6Al-4V alloys by Pack Cementation process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsipas, Sophia A., E-mail: stsipas@ing.uc3m.es; Go

Wear and high temperature oxidation resistance of some titanium-based alloys needs to be enhanced, and this can be effectively accomplished by surface treatment. Molybdenizing is a surface treatment where molybdenum is introduced into the surface of titanium alloys causing the formation of wear-resistant surface layers containing molybdenum, while aluminizing of titanium-based alloys has been reported to improve their high temperature oxidation properties. Whereas pack cementation and other surface modification methods have been used for molybdenizing or aluminizing of wrought and/or cast pure titanium and titanium alloys, such surface treatments have not been reported on titanium alloys produced by powder metallurgymore » (PM). Also a critical understanding of the process parameters for simultaneous one step molybdeno-aluminizing of titanium alloys by pack cementation and the predominant mechanism for this process have not been reported. The current research work describes the surface modification of titanium and Ti-6Al-4V prepared by PM by molybdeno-aluminizing and analyzes thermodynamic aspects of the deposition process. Similar coatings are also deposited to wrought Ti-6Al-4V and compared. Characterization of the coatings was carried out using scanning electron microscopy and x-ray diffraction. For both titanium and Ti-6Al-4V, the use of a powder pack containing ammonium chloride as activator leads to the deposition of molybdenum and aluminium into the surface but also introduces nitrogen causing the formation of a thin titanium nitride layer. In addition, various titanium aluminides and mixed titanium aluminium nitrides are formed. The appropriate conditions for molybdeno-aluminizing as well as the phases expected to be formed were successfully determined by thermodynamic equilibrium calculations. - Highlights: •Simultaneous co-deposition of Mo-Al onto powder metallurgy and wrought Ti alloy •Thermodynamic calculations were used to optimize deposition conditions •External TiN and internal a Mo-rich layer on all alloy substrates •Titanium aluminides and Ti-Al mixed nitrides are formed on Ti-6Al-4V •The presence of Al and V alloying elements modifies the diffusion of Mo.« less

Micro-structural integrity of dental enamel subjected to two tooth whitening regimes.

PubMed

Tanaka, Reina; Shibata, Yo; Manabe, Atsufumi; Miyazaki, Takashi

2010-04-01

Colour modification of tooth enamel has proven successful, but it is unclear how various bleaching applications affect micro-structural integrity of the whitened enamel. To investigate the internal structural integrity of human intact tooth enamel with the application of two commonly used whitening regimes (in-office power bleaching with 35% hydrogen peroxide and home bleaching with 10% carbamide peroxide), evaluations were performed on teeth of identical colour classification. After the bleaching applications, the enamel mineral density was quantified and visualised with micro-computed tomography. The micro-structural differences between the whitened tooth enamel samples were distinctive, though the colour parameter changes within the samples were equivalent. Home bleaching achieved colour modification by demineralisation, whereas in-office bleaching depended on redistribution of the minerals after treatment and subsequent enhanced mineralisation.

Defense Small Business Innovation Research Program (SBIR). Volume 3. Air Force Abstracts of Phase 1 Awards 1987.

DTIC Science & Technology

1988-04-01

RESISTANCE, AS WELL AS GUIDELINES FROM APPROPRIATE AEROSPACE SPECIFICATIONS; MATERIALS WILL INCLUDE ALUMINUM AND TITANIUM ALLOYS, PLUS A FEW STEELS...VAPOR SYNTHESIS OF NIOBIUM ALUMINIDES TOPIC# 105 OFFICE: AFWAL/ML DIRECT SYNTHESIS OF NbA1 ALLOY FOILS BY CHEMICAL VAPOR DEPOSITION ONTO INERT SUBSTRATES...GROWT OF GAMMA PRIME NICKEL ALUMINIDE (Ni3AI) %% TOPICt 104 OFFICE: AFWAL/ML . SMALL BUSINESS INNOVATION RESEARCH (SBIR) PROGRAM - PHASE 1 PAGE 555

Corrosion resistant iron aluminides exhibiting improved mechanical properties and corrosion resistance

DOEpatents

Liu, C.T.; McKamey, C.G.; Tortorelli, P.F.; David, S.A.

1994-06-14

The specification discloses a corrosion-resistant intermetallic alloy comprising, in atomic percent, an FeAl iron aluminide containing from about 30 to about 40% aluminum alloyed with from about 0.01 to 0.4% zirconium and from 0.01 to about 0.8% boron. The alloy exhibits considerably improved room temperature ductility for enhanced usefulness in structural applications. The high temperature strength and fabricability is improved by alloying with molybdenum, carbon, chromium and vanadium. 9 figs.

Electron Beam Welding to Join Gamma Titanium Aluminide Articles

NASA Technical Reports Server (NTRS)

Kelly, Thomas Joseph (Inventor)

2008-01-01

A method is provided for welding two gamma titanium aluminide articles together. The method includes preheating the two articles to a welding temperature of from about 1700 F to about 2100 F, thereafter electron beam welding the two articles together at the welding temperature and in a welding vacuum to form a welded structure, and thereafter annealing the welded structure at an annealing temperature of from about 1800 F to about 2200 F, to form a joined structure.

Corrosion resistant iron aluminides exhibiting improved mechanical properties and corrosion resistance

DOEpatents

Liu, Chain T.; McKamey, Claudette G.; Tortorelli, Peter F.; David, Stan A.

1994-01-01

The specification discloses a corrosion-resistant intermetallic alloy comprising, in atomic percent, an FeAl iron aluminide containing from about 30 to about 40% aluminum alloyed with from about 0.01 to 0.4% zirconium and from 0.01 to about 0.8% boron. The alloy exhibits considerably improved room temperature ductility for enhanced usefulness in structural applications. The high temperature strength and fabricability is improved by alloying with molybdenum, carbon, chromium and vanadium.

Influence of friction stir processing on the room temperature fatigue cracking mechanisms of A356 aluminum alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelaturu, Phalgun; Jana, Saumyadeep; Mishra, Rajiv S.

Here, failure by fatigue is a common problem associated with cast aluminum alloys due to defects like shrinkage porosities, non-metallic inclusions, etc. Friction stir processing (FSP) has recently emerged as an effective technique for local modification of microstructure. This study investigates the fatigue crack initiation and growth mechanisms in cast and FSPed A356 aluminum alloy. Two sets of parameters were used to friction stir the cast alloy resulting in the complete modification the cast microstructure to a wrought microstructure. Both the FSPed microstructures exhibited severe abnormal grain growth (AGG) after heat treatment leading to a multimodal grain size distribution –more » the grain sizes ranging from a few microns to a few millimeters. One of the FSP conditions displayed an excellent improvement in fatigue life by an order of magnitude, while the other condition displayed an unexpectedly large scatter in fatigue lives. Detailed study of the fractured fatigue specimens by electron back scattered diffraction (EBSD) revealed that both, fatigue crack initiation and propagation, were intimately tied to the grain size as well as the grain misorientations in the microstructure.« less

Influence of friction stir processing on the room temperature fatigue cracking mechanisms of A356 aluminum alloy

DOE PAGES

Nelaturu, Phalgun; Jana, Saumyadeep; Mishra, Rajiv S.; ...

2018-01-11

Here, failure by fatigue is a common problem associated with cast aluminum alloys due to defects like shrinkage porosities, non-metallic inclusions, etc. Friction stir processing (FSP) has recently emerged as an effective technique for local modification of microstructure. This study investigates the fatigue crack initiation and growth mechanisms in cast and FSPed A356 aluminum alloy. Two sets of parameters were used to friction stir the cast alloy resulting in the complete modification the cast microstructure to a wrought microstructure. Both the FSPed microstructures exhibited severe abnormal grain growth (AGG) after heat treatment leading to a multimodal grain size distribution –more » the grain sizes ranging from a few microns to a few millimeters. One of the FSP conditions displayed an excellent improvement in fatigue life by an order of magnitude, while the other condition displayed an unexpectedly large scatter in fatigue lives. Detailed study of the fractured fatigue specimens by electron back scattered diffraction (EBSD) revealed that both, fatigue crack initiation and propagation, were intimately tied to the grain size as well as the grain misorientations in the microstructure.« less

Experimental and Computational Study of Interphase Properties and Mechanics in Titanium Metal Matrix Composites at Elevated Temperatures

DTIC Science & Technology

2005-03-01

size of the interphase [22-24]. Yang and Jeng [45], in a study of the titanium aluminides Ti-24-11 and Ti-25-10, and a metastable beta titanium Ti-15-3... Titanium Aluminide Matrix Composites," Workshop proceedings on Titanium Matrix Components, P.R. Smith and W.C. Revelos, eds., Wright-Patterson AFB...Experimental and Computational Study of Interphase Properties and Mechanics in Titanium Metal Matrix Composites at Elevated Temperatures Final Report

Nickel aluminide alloy for high temperature structural use

DOEpatents

Liu, Chain T.; Sikka, Vinod K.

1991-01-01

The specification discloses nickel aluminide alloys including nickel, aluminum, chromium, zirconium and boron wherein the concentration of zirconium is maintained in the range of from about 0.05 to about 0.35 atomic percent to improve the ductility, strength and fabricability of the alloys at 1200.degree. C. Titanium may be added in an amount equal to about 0.2 to about 0.5 atomic percent to improve the mechanical properties of the alloys and the addition of a small amount of carbon further improves hot fabricability.

Effect of hydrogen on cathodic corrosion of titanium aluminide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, K.W.; Jin, J.W.; Qiao, L.J.

1996-01-01

Cathodic corrosion of titanium aluminide (TiAl) during hydrogen charging in various acidic aqueous solutions and in molten salt at 160 C was studied. At constant potential, the rate of cathodic corrosion (V) was much higher than during anodic dissolution, and V increased linearly with increasing current. V was 10 times higher in the acid solution than in the salt solution under the same current. Disruption of the surface film by local hydride formation during cathodic polarization was shown to be the key step.

Pack Cementation Aluminide Coatings on Superalloys: Codeposition of Cr and Reactive Elements (RE). Technical Report 1. Chromium and Reactive Element(RE)- Modified Aluminide Diffusion Coatings on Superalloys: Environmental Testing. Technical Report 2

DTIC Science & Technology

1992-11-01

Godlewska and K. Godlewski, Oxid. Met., 22 (1984) 117. 4. J.E. Restall, U.S. Patent #4,687,684 (1987). 5. P.N. Walsh, in Proceeding of the Fourth...McCarron, N.R. Lindblad, and D. Chatterji, Corrosion, 32 (1976) 476. 34 33. E. Godlewska and K. Godlewski, Oxid. Met., 22 (1984) 117. 34. B. Pieraggi

The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 5, Section 4: Processing: Matrices and Composites. Part 1

DTIC Science & Technology

1989-10-15

aluminides such as those in Ni, Fe, Nb and Ti systems have received considerable attention. In the development and evaluation of mechanical properties ...The first section in Book 1 is concerned with the properties and structure of bimaterial interfaces and the related problem of coating decohesion and...accomplished in a few hours. CONSOLIDATION - HIP consolidation of titanium aluminide powders produced by Rapid Solidification Rate (RSR) and Rotating

Multi-objective optimization of hole characteristics during pulsed Nd:YAG laser microdrilling of gamma-titanium aluminide alloy sheet

NASA Astrophysics Data System (ADS)

Biswas, R.; Kuar, A. S.; Mitra, S.

2014-09-01

Nd:YAG laser microdrilled holes on gamma-titanium aluminide, a newly developed alloy having wide applications in turbine blades, engine valves, cases, metal cutting tools, missile components, nuclear fuel and biomedical engineering, are important from the dimensional accuracy and quality of hole point of view. Keeping this in mind, a central composite design (CCD) based on response surface methodology (RSM) is employed for multi-objective optimization of pulsed Nd:YAG laser microdrilling operation on gamma-titanium aluminide alloy sheet to achieve optimum hole characteristics within existing resources. The three characteristics such as hole diameter at entry, hole diameter at exit and hole taper have been considered for simultaneous optimization. The individual optimization of all three responses has also been carried out. The input parameters considered are lamp current, pulse frequency, assist air pressure and thickness of the job. The responses at predicted optimum parameter level are in good agreement with the results of confirmation experiments conducted for verification tests.

Strengthening of Fe3Al Aluminides by One or Two Solute Elements

NASA Astrophysics Data System (ADS)

Kratochvíl, Petr; Daniš, Stanislav; Minárik, Peter; Pešička, Josef; Král, Robert

2017-09-01

The compressive yield stress of Fe-26Al with additives Ti (0.5 to 4 at. pct), Cr (0.5 to 8 at. pct), Mo (0.5 to 4 at. pct), and V (0.5 to 8 at. pct) at 1073 K (800 °C) has been determined. The effect of the concentration of diverse solutes on the yield stress at 1073 K (800 °C) was compared, and the additivity of the effects of solutes was tested. The effects in iron aluminides with two solutes (V and Ti, Ti and Cr, V and Cr) are compared with those of a single solute V, Ti, and Cr. It is found that the additivity of yield stress increments is valid only for lower solute concentrations. When the amount of the solute atoms increases, the yield stress increment is substantially higher than the sum of the yield stress increments of single solutes. This behavior is related to the high-temperature order in iron aluminides.

Method of protecting a surface with a silicon-slurry/aluminide coating. [coatings for gas turbine engine blades and vanes

NASA Technical Reports Server (NTRS)

Deadmore, D. L.; Young, S. G. (Inventor)

1982-01-01

A low cost coating for protecting metallic base system substrates from high temperatures, high gas velocity oxidation, thermal fatigue and hot corrosion is described. The coating is particularly useful for protecting vanes and blades in aircraft and land based gas turbine engines. A lacquer slurry comprising cellulose nitrate containing high purity silicon powder is sprayed onto the superalloy substrates. The silicon layer is then aluminized to complete the coating. The Si-Al coating is less costly to produce than advanced aluminides and protects the substrate from oxidation and thermal fatigue for a much longer period of time than the conventional aluminide coatings. While more expensive Pt-Al coatings and physical vapor deposited MCrAlY coatings may last longer or provide equal protection on certain substrates, the Si-Al coating exceeded the performance of both types of coatings on certain superalloys in high gas velocity oxidation and thermal fatigue. Also, the Si-Al coating increased the resistance of certain superalloys to hot corrosion.

Development of in-Situ Al-Si/CuAl2 Metal Matrix Composites: Microstructure, Hardness, and Wear Behavior

PubMed Central

Tash, Mahmoud M.; Mahmoud, Essam R. I.

2016-01-01

In the present work, in-situ metal matrix composites were fabricated through squeeze casting. The copper particles were dispersed with different weight percentages (3%, 6%, 10%, and 15%) into Al-12% Si piston alloy. Also, heat treatments were performed at 380 °C and 450 °C for holding times of 6 and 18 h. The microstructures, X-ray diffractometer (XRD) pattern, hardness, and wear characteristics were evaluated. The results showed that these copper particles have reacted with the aluminum under all of the aforementioned processing conditions resulting in the formation of fine copper aluminide intermetallics. Most of the intermetallics were CuAl2, while AlCu appeared in a small ratio. Additionally, these intermetallics were homogenously distributed within the alloy matrix with up to 6% Cu addition. The amounts of those intermetallics increased after performing heat treatment. Most of these intermetallics were CuAl2 at 380 °C, while the Cu-rich intermetallics appeared at 450 °C. Increasing the holding time to 18 h, however, led to grain coarsening and resulted in the formation of some cracks. The hardness of the resulting composite materials was improved. The hardness value reached to about 170 HV after heat treating at 380 °C for 8 h. The wear resistance of the resulting composite materials was remarkably improved, especially at lower additions of Cu and at the lower heat treatment temperature. PMID:28773564

Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides

NASA Technical Reports Server (NTRS)

Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)

1996-01-01

A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.

Chemical Vapor Synthesis of Titanium Aluminides by Reaction of Aluminum Subchloride and Titanium Tetrachloride

NASA Astrophysics Data System (ADS)

Zakirov, Roman A.; Parfenov, Oleg G.; Solovyov, Leonid A.

2018-02-01

A new process for developing titanium aluminides (TiAls) using chemical vapor synthesis was investigated in a laboratory experiment. Aluminum subchloride (AlCl) was used as the reducing agent in the reaction with TiCl4 and the source of aluminum for Ti-Al alloy. Two types of products, with large crystals and fine particles, were fabricated. The large crystals were determined to be TiAl, with small amounts of Ti and Ti3Al phases. The composition of fine particles, on the other hand, varied in wide range.

Thermodynamic analysis of chemical compatibility of several reinforcement materials with niobium aluminides

NASA Technical Reports Server (NTRS)

Misra, Ajay K.

1989-01-01

Chemical compatibility of several reinforcement materials with three niobium aluminides, Nb3Al, Nb2Al, and NbAl3, were examined from thermodynamic considerations. The reinforcement materials considered in this study include carbides, borides, nitrides, oxides, silicides, and Engel-Brewer compounds. Thermodynamics of the Nb-Al system were reviewed and activities of Nb and Al were derived at desired calculation temperatures. Criteria for chemical compatibility between the reinforcement material and Nb-Al compounds have been defined and several chemically compatible reinforcement materials have been identified.

Microstructural and strain rate effects on plastic deformation in aluminum 2219-T87

NASA Astrophysics Data System (ADS)

Rincon, Carlos D.

A fundamental investigation has been conducted on the effects of microstructure and strain rate on the plastic deformation of theta-prime-strengthened 2219 aluminum. The motivation for this work is based upon a previous study which showed inhomogeneous and locally extreme work hardening in the HAZ regions in VPPA 2219-T87 butt welds. This strongly suggests that the HAZ microstructure plays a major role in the deformation and fracture process in precipitation hardened aluminum alloy 2219. Tensile specimens of the weld joint exhibited more rapid work hardening in the heat-affected-zone (HAZ) at higher strain levels. Microhardness contour maps for these welds illustrated that late stage deformation was concentrated in two crossing bands at about 45sp° to the tensile axis. The width of the deformation bands and the ultimate tensile strength seemed to be dictated by the amount of work hardening in the HAZ. In this study, three different heat treatments were used to produce samples with different particle sizes and particle spacings, but all hardened by copper aluminide precipitates of the thetasp' structure. The heat treatments were categorized as being (A) as-received T87 condition, (B) T87 condition aged at approximately 204sp°C for 3 hours and (C) T87 over-aged at 204sp°C for 7 days. Uniaxial tensile tests consisted of two sets of experiments: (1) three heat treatments (A, B, and C) at two strain rates (0.02 minsp{-1} and 0.2 minsp{-1}) and (2) three heat treatments that were interrupted at select stress-strain levels (0.8% and 2% total strain) during the tensile tests at strain rate equal to 0.02 minsp{-1} at room temperature. Furthermore, a detailed transmission electron microscopy (TEM) study demonstrates the microstructural development during tensile deformation. The Voce equation of strain-hardening provides a slightly better fit to the tensile curves than the Ludwik-Hollomon equation. At higher strains, localized areas showed strain fields around thetasp' platelets had diminished. Lastly, in every treatment, both the yield and tensile strength were slightly higher for the higher strain rate, but only by 0.5 to 2.0 ksi.

Magnetic and microstructural characterisation of FeNi: Insight into the formation and impact history of the IAB parent body

NASA Astrophysics Data System (ADS)

Nichols, C. I. O.; Krakow, R.; Herrero-Albillos, J.; Kronast, F.; Northwood-Smith, G.; Harrison, R. J.

2017-12-01

The IABs represent one of only two groups of iron meteorites that did not form by fractional crystallization of liquid Fe-Ni in the core of a differentiated planetesimal. Instead, they are believed to originate from a partially differentiated body that was severely disrupted by one or more impacts during its early history. Paleomagnetic signals from two IABs, Toluca and Odessa, were investigated using X-ray magnetic circular dichroism (XMCD) and X-ray photoemission electron microscopy (X-PEEM) to image the magnetisation of the cloudy zone. The IABs do not appear to have experienced a magnetic field, consistent with the lack of a metallic core on the parent body. We also present a detailed microstructural and magnetic study of the observed FeNi microstructures, characterising their properties using XMCD and X-PEEM. The crystallographic architecture of the microstructures was analysed using electron backscatter diffraction (EBSD). Odessa and Toluca both exhibit a complex series of microstructures, requiring an unusual evolution during slow cooling. A conventional Widmanstätten sequence of kamacite, tetrataenite rim and cloudy zone developed via slow cooling to temperatures below 400 ºC. Subsequent modification of the microstructures resulted in the formation of pearlitic plessite and spheroidized plessite. Compositional and crystallographic analysis suggests that pearlitic and spheroidized plessite formed by impact modification of the cloudy zone and martensite, respectively. This study highlights the importance of characterising microstructures in order to corroborate paleomagnetic observations, as well as improving our understanding of the processes effecting planetary formation and evolution.

Development of weldable, corrosion-resistant iron-aluminide (FeAl) alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maziasz, P.J.; Goodwin, G.M.; Wang, X.L.

1997-04-01

A boron-microalloyed FeAl alloy (Fe-36Al-0.2Mo-0.05Zr-0.13C, at.%, with 100-400 appm B) with improved weldability and mechanical properties was developed in FY 1994. A new scale-up and industry technology development phase for this work began in FY 1995, pursuing two parallel paths. One path was developing monolithic FeAl component and application technology, and the other was developing coating/cladding technology for alloy steels, stainless steels and other Fe-Cr-Ni alloys. In FY 1995, it was found that cast FeAl alloys had good strength at 700-750{degrees}C, and some (2.5%) ductility in air at room-temperature. Hot-extruded FeAl with refined grain size was found to have ductilitymore » and to also have good impact-toughness at room-temperature. Further, it was discovered that powder-metallurgy (P/M) FeAl, consolidated by direct hot-extrusion at 950-1000{degrees}C to have an ultra fine-grained microstructure, had the highest ductility, strength and impact-toughness ever seen in such intermetallic alloys.« less

Defect structures in ordered intermetallics; grain boundaries and surfaces in FeAl, NiAl, CoAl and TiAl

NASA Astrophysics Data System (ADS)

Mutasa, Batsirai Manyara

Ordered intermetallics based on transition metal aluminides have been proposed as structural materials for advanced aerospace applications. The development of these materials, which have the advantages of low density and high operating temperatures, have been focused on the aluminides of titanium, nickel and iron. Though these materials exhibit attractive properties at elevated temperatures, their utilization is limited due to their propensity for low temperature fracture and susceptibility to decreased ductility due to environmental effects. A major embrittlement mechanism at ambient temperatures in these aluminides has been by the loss of cohesive strength at the interfaces (intergranular failure). This study focuses on this mechanism of failure, by undertaking a systematic study of the energies and structures of specific grain boundaries in some of these compounds. The relaxed atomistic grain boundary structures in B2 aluminides, FeAl, NiAl and CoAl and L10 gamma-TiAl were investigated using molecular statics and embedded atom potentials in order to explore general trends for a series of B2 compounds as well as TiAl. The potentials used correctly predict the proper mechanism of compositional disorder of these compounds. Using these potentials, point defects, free surface energies and various grain boundary structures of similar energies in three B2 compounds, FeAl, NiAl and CoAl were studied. These B2 alloys exhibited increasing anti-phase boundary energies respectively. The misorientations chosen for detailed study correspond to the Sigma5(310) and Sigma5(210) boundaries. These boundaries were investigated with consideration given to possible variations in the local chemical composition. The effects of both boundary stoichiometry and bulk stoichiometry on grain boundary energetics were also considered. Defect energies were calculated for boundaries contained in both stoichiometric and off-stoichiometric bulk. The surface energies for these aluminides were also calculated so that trends concerning the cohesive energy of the boundaries could be studied. The implications of stoichiometry, the multiplicity of the boundary structures and possible transformations between them for grain boundary brittleness are also discussed.

Very Long Term Oxidation of Ti-48Al-2Cr-2Nb at 704 C In Air

NASA Technical Reports Server (NTRS)

Locci, I. E.; Brady, M. P.; MacKay, R. A.; Smith, J. W.

1997-01-01

Introduction Titanium aluminides are of great interest for intermediate-temperature (600 C - 850 C) aerospace and power generation applications because of their high specific properties. Replacement of conventional superalloys by titanium aluminides offers the potential of significant weight savings. Extensive development efforts over the past IO years have led to the identification of y (TiAl) + alpha(sub 2) (Ti3Al) alloys, such as the G.E. alloy Ti48Al-2Cr-2Nb (all composition in at. %), which offer a balance of room temperature mechanical properties and high-temperature strength retention. The two phase gamma + alpha(sub 2) class of titanium aluminides also offers superior oxidation and embrittlement resistance compared to the alpha(sub 2) and orthorhombic classes of titanium aluminides. However, environmental durability is still a major concern. Significant progress has recently been made in understanding the fundamental aspects of the oxidation behavior of binary gamma + alpha(sub 2) Ti-Al alloys. However, most of this work has concentrated on short term (less than 1000 hours), high temperature (900 C - 1000 C) exposures. Also little data are available in the literature regarding the oxidation behavior of the quaternary and higher order gamma + alpha(sub 2) engineering alloys. This is especially true for the very long-term, low temperature conditions likely to be experienced during engineering applications. The present work addresses this regime to fill this gap by characterizing the oxidation behavior of Ti48Al-2Cr-2Nb for periods up to 9000 h at 704 C in air.

Evaluation of iron aluminide weld overlays for erosion - corrosion resistant boiler tube coatings in low NO{sub x} boilers

DOE Office of Scientific and Technical Information (OSTI.GOV)

DuPont, J.N.; Banovic, S.W.; Marder, A.R.

1996-08-01

Low NOx burners are being installed in many fossil fired power plants in order to comply with new Clean Air Regulations. Due to the operating characteristics of these burners, boiler tube sulfidation corrosion is often enhanced and premature tube failures can occur. Failures due to oxidation and solid particle erosion are also a concern. A program was initiated in early 1996 to evaluate the use of iron aluminide weld overlays for erosion/corrosion protection of boiler tubes in Low NOx boilers. Composite iron/aluminum wires will be used with the Gas Metal Arc Welding (GMAW) process to prepare overlays on boiler tubesmore » steels with aluminum contents from 8 to 16wt%. The weldability of the composite wires will be evaluated as a function of chemical composition and welding parameters. The effect of overlay composition on corrosion (oxidation and sulfidation) and solid particle erosion will also be evaluated. The laboratory studies will be complemented by field exposures of both iron aluminide weld overlays and co-extruded tubing under actual boiler conditions.« less

Microstructure and Property Modifications of Cold Rolled IF Steel by Local Laser Annealing

NASA Astrophysics Data System (ADS)

Hallberg, Håkan; Adamski, Frédéric; Baïz, Sarah; Castelnau, Olivier

2017-10-01

Laser annealing experiments are performed on cold rolled IF steel whereby highly localized microstructure and property modification are achieved. The microstructure is seen to develop by strongly heterogeneous recrystallization to provide steep gradients, across the submillimeter scale, of grain size and crystallographic texture. Hardness mapping by microindentation is used to reveal the corresponding gradients in macroscopic properties. A 2D level set model of the microstructure development is established as a tool to further optimize the method and to investigate, for example, the development of grain size variations due to the strong and transient thermal gradient. Particular focus is given to the evolution of the beneficial γ-fiber texture during laser annealing. The simulations indicate that the influence of selective growth based on anisotropic grain boundary properties only has a minor effect on texture evolution compared to heterogeneous stored energy, temperature variations, and nucleation conditions. It is also shown that although the α-fiber has an initial frequency advantage, the higher probability of γ-nucleation, in combination with a higher stored energy driving force in this fiber, promotes a stronger presence of the γ-fiber as also observed in experiments.

Phase Evaluation in Al2O3 Fiber-Reinforced Ti2AlC During Sintering in the 1300 degrees C-1500 degrees C Temperature Range

DTIC Science & Technology

2011-01-01

composition: 97% Al2O3 and 3% SiO2] fibers. In both cases, the fibers were chopped with a razor blade into 5 cm lengths. Mixing of the powder and...the presence of XRD amorphous Ti- aluminides (see below) or other phases cannot be ruled out at this juncture. When the XRD spectrum of the as-received...not shown). No peaks belonging to any Ti- aluminide were found suggesting them to be amorphous or at most nano-crystalline. A typical TEM micrograph of

International Workshop on Gamma Aluminide Alloy Technology. Section Four

DTIC Science & Technology

1997-04-18

a «—■ i— Q. O C (N i < 00 i H B £ 32 £ M U XI c o L. 4-» 5 Autogenous keyhole plasma weld in Ti-48Al-2Mn-2Nb casting, xlO...34: -, Sl Overview of joining gamma alloys P Threadgill J Lee, W A Baeslack and T J Kelly: Weld fusion zone phenomena in Ti (45-48)A1-Nb-Cr y...titanium aluminides, submitted to Welding Journal. a c 9 "" o « JL ° V GO I ■ CO ’ V ** K _ L

Filler metal alloy for welding cast nickel aluminide alloys

DOEpatents

Santella, Michael L.; Sikka, Vinod K.

1998-01-01

A filler metal alloy used as a filler for welding east nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and east in copper chill molds.

Hydrogen partitioning and transport in titanium aluminides

NASA Technical Reports Server (NTRS)

Han, Kwang S.; Lee, Weon S.

1993-01-01

This report gives the final summary of the research work perfomed from March 1, 1990 to August 28, 1993. Brief descriptions of the research findings are given on the surface variation of Ti-14Al-21Nb as a function of temperature under ultrahigh vacuum conditions; titanium aluminides: surface composition effects as a function of temperature; Auger electron intensity variation in oxygen-charged silver; and segregation of sulfur on a titanium surface studied by Auger electron spectroscopy. Each description details one or more of the attached corresponding figures. Published journal documents are provided as appendices to give further detail.

Friction Stir Processing of Particle Reinforced Composite Materials

PubMed Central

Gan, Yong X.; Solomon, Daniel; Reinbolt, Michael

2010-01-01

The objective of this article is to provide a review of friction stir processing (FSP) technology and its application for microstructure modification of particle reinforced composite materials. The main focus of FSP was on aluminum based alloys and composites. Recently, many researchers have investigated this technology for treating other alloys and materials including stainless steels, magnesium, titanium, and copper. It is shown that FSP technology is very effective in microstructure modification of reinforced metal matrix composite materials. FSP has also been used in the processing and structure modification of polymeric composite materials. Compared with other manufacturing processes, friction stir processing has the advantage of reducing distortion and defects in materials. The layout of this paper is as follows. The friction stir processing technology will be presented first. Then, the application of this technology in manufacturing and structure modification of particle reinforced composite materials will be introduced. Future application of friction stir processing in energy field, for example, for vanadium alloy and composites will be discussed. Finally, the challenges for improving friction stir processing technology will be mentioned.

Effect of Electropulsing-Assisted Ultrasonic Nanocrystalline Surface Modification on the Surface Mechanical Properties and Microstructure of Ti-6Al-4V Alloy

NASA Astrophysics Data System (ADS)

Ye, Yongda; Wang, Haibo; Tang, Guoyi; Song, Guolin

2018-05-01

The effect of electropulsing-assisted ultrasonic nanocrystalline surface modification (EP-UNSM) on surface mechanical properties and microstructure of Ti-6Al-4V alloy is investigated. Compared to conventional ultrasonic nanocrystalline surface modification (UNSM), EP-UNSM can effectively facilitate surface roughness and morphology, leading to excellent surface roughness (reduced from Ra 0.918 to Ra 0.028 μm by UNSM and Ra 0.019 μm by EP-UNSM) and smoother morphology with less cracks and defects. Surface friction coefficients are enhanced, resulting in lower and smoother friction coefficients. In addition, the surface-strengthened layer and ultra-refined grains are significantly enhanced with more severe plastic deformation and a greater surface hardness (a maximum hardness value of 407 HV and an effective depth of 550 μm, in comparison with the maximum hardness value of 364 HV and effective depth of 300 μm obtained by conventional UNSM). Remarkable enhancement of surface mechanical properties can be attributed to the refined gradient microstructure and the enhanced severe plastic deformation layer induced by coupling the effects of UNSM and electropulsing. The accelerated dislocation mobility and atom diffusion caused by the thermal and athermal effects of electropulsing treatment may be the primary intrinsic reasons for these improvements.

Corrosion behavior of binary titanium aluminide intermetallics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saffarian, H.M.; Gan, Q.; Hadkar, R.

1996-08-01

The corrosion behavior of arc-melted binary titanium aluminide intermetallics TiAl, Ti{sub 2}Al, and TiAl{sub 3} in aqueous sodium sulfate and sodium chloride solutions was measured and compared to that of pure Ti and Al. Effects of electrolyte composition (e.g., sulfate [0.25 M SO{sub 4}{sup 2}{sup {minus}}], chloride [0.1 to 1.0 M Cl{sup {minus}}], and pH [3 to 10]) were examined. Anodic polarization of titanium aluminides in aqueous SO{sub 4}{sup 2}{sup {minus}} solutions was similar (showing passive behavior), but no pitting or pitting potential (E{sub pit}) was observed. In aqueous NaCl, however, titanium aluminides were susceptible to pitting, and E{sub pit}more » decreased with increasing Al content (i.e., Ti{sub 3}Al had the highest E{sub pit} and, therefore, a greater resistance to pitting, followed by TiAl and TiAl{sub 3}). For TiAl, E{sub pit} was slightly dependent upon pH or Cl{sup {minus}} concentration. Pit morphology and E{sub pit} values were quite different for TiAl compared to Ti{sub 3}Al. TiAl showed numerous small pits, whereas Ti{sub 3}Al exhibited fewer but larger and deeper pits. The larger pit density for TiAl was associated with Al-rich interdendrite regions. One interesting feature of the anodic polarization curves for Ti{sub 3}Al was a small anodic peak frequently observed at {approximately}1.4 V{sub SCE} to 1.8 V{sub SCE}. Results suggested this peak was associated with pit initiation, since pitting initiated concurrently with the peak or immediately afterward.« less

Aqueous corrosion and corrosion-sensitive embrittlement of Fe{sub 3}Al-based and lean-aluminum iron aluminides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, J.G.; Buchanan, R.A.

Aqueous corrosion and corrosion-sensitive embrittlement of iron aluminides were characterized as functions of environment, alloying content, notch sensitivity, and strain rate. Polarization resistance and cyclic anodic polarization evaluations were performed in 3.5 wt % NaCl, 200 ppM Cl{sup {minus}} (pH = 4), and 1 N NaOH solutions. In the mild acid-chloride solution [200 ppM Cl{sup {minus}} (pH = 4)], the pitting-corrosion resistance of the new lean-aluminum iron aluminides (FAP-Y and CM-Mo) was comparable to that of the Fe{sub 3}Al-based FAL-Mo. In the higher-chloride 3.5 wt % NaCl, the resistance of CM-Mo was slightly less but FAP-Y showed quite similar behaviormore » to FAL-Mo. In 1 N NaOH solution, all materials exhibited ideal passive behavior. Under slow-strain-rate test conditions in the mild acid-chloride electrolyte, prior work had shown the ductilities (% elongations) of Fe{sub 3}Al-based materials to be {approximately}7% and {approximately}1% at the freely-corroding and hydrogen-charging potentials, respectively. Present studied on the lean-aluminum materials have shown the ductilities to be {approximately}17% and {approximately}5%, respectively. Thus, the present results indicate that these new materials have reasonably-good aqueous-corrosion properties in chloride environments and significantly-enhanced ductilities under aqueous corrosion conditions. The strain rate and notch sensitivities of high-aluminum iron aluminide (FA-129) were investigated by performing slow-strain-rate tests. The notch sensitivity was independent of strain rate and the notch sensitivity in the aqueous environment was similar to that in air.« less

Thermodynamics, Solubility, and Diffusivity of Oxygen in Titanium and Ti-Al Alloys

NASA Technical Reports Server (NTRS)

Mehrotra, Gopal M.

1992-01-01

Titanium aluminides and titanium aluminide-based composites are attractive candidate materials for high-temperature structural applications. As these materials may be exposed to oxidizing environments durine their use at elevated temperatures, it is essential that they possess a good oxidation resistance. Previous studies have shown that the oxidation resistance of Al-rich alloys in the Ti-Al system is superior to that of the Ti-rich alloys. The scales formed on the surface of the Al-rich and Ti-rich alloys have been reported to be predominantly Al2O3 and TiO2, respectively. Since the relative stabilities of the oxides of Al and Ti at various temperatures and oxygen pressures can be assessed from their thermodynamic data, it is possible, With the help of thermodynamic calculations, to determine the compositions of the alloys which would form scales of Al2O3, TiO(x) or a ternary oxide such as TiAl2O5 during oxidation at a given temperature. The thermodynamic calculations require reliable activity data for the Ti-Al system. These data have not been determined for the entire composition and temperature range of interest. Using the data available in the literature, recently performed thermodynamic calculations and concluded that the stable oxide changed from TiO to Al2O3 in the existence region of the tial phase. In the case of titanium aluminide-based composites, another major concern is the mutual chemical compatibility of the matrix material with the reinforcement phase. Fibers of SiC, TiB2 and Al2O3 are currently being investigated for reinforcement of titanium aluminide matrices.

Selective hierarchical patterning of silicon nanostructures via soft nanostencil lithography

NASA Astrophysics Data System (ADS)

Du, Ke; Ding, Junjun; Wathuthanthri, Ishan; Choi, Chang-Hwan

2017-11-01

It is challenging to hierarchically pattern high-aspect-ratio nanostructures on microstructures using conventional lithographic techniques, where photoresist (PR) film is not able to uniformly cover on the microstructures as the aspect ratio increases. Such non-uniformity causes poor definition of nanopatterns over the microstructures. Nanostencil lithography can provide an alternative means to hierarchically construct nanostructures on microstructures via direct deposition or plasma etching through a free-standing nanoporous membrane. In this work, we demonstrate the multiscale hierarchical fabrication of high-aspect-ratio nanostructures on microstructures of silicon using a free-standing nanostencil, which is a nanoporous membrane consisting of metal (Cr), PR, and anti-reflective coating. The nanostencil membrane is used as a deposition mask to define Cr nanodot patterns on the predefined silicon microstructures. Then, deep reactive ion etching is used to hierarchically create nanostructures on the microstructures using the Cr nanodots as an etch mask. With simple modification of the main fabrication processes, high-aspect-ratio nanopillars are selectively defined only on top of the microstructures, on bottom, or on both top and bottom.

Selective hierarchical patterning of silicon nanostructures via soft nanostencil lithography.

PubMed

Du, Ke; Ding, Junjun; Wathuthanthri, Ishan; Choi, Chang-Hwan

2017-11-17

It is challenging to hierarchically pattern high-aspect-ratio nanostructures on microstructures using conventional lithographic techniques, where photoresist (PR) film is not able to uniformly cover on the microstructures as the aspect ratio increases. Such non-uniformity causes poor definition of nanopatterns over the microstructures. Nanostencil lithography can provide an alternative means to hierarchically construct nanostructures on microstructures via direct deposition or plasma etching through a free-standing nanoporous membrane. In this work, we demonstrate the multiscale hierarchical fabrication of high-aspect-ratio nanostructures on microstructures of silicon using a free-standing nanostencil, which is a nanoporous membrane consisting of metal (Cr), PR, and anti-reflective coating. The nanostencil membrane is used as a deposition mask to define Cr nanodot patterns on the predefined silicon microstructures. Then, deep reactive ion etching is used to hierarchically create nanostructures on the microstructures using the Cr nanodots as an etch mask. With simple modification of the main fabrication processes, high-aspect-ratio nanopillars are selectively defined only on top of the microstructures, on bottom, or on both top and bottom.

Supplementary Microstructural Features Induced During Laser Surface Melting of Thermally Sprayed Inconel 625 Coatings

NASA Astrophysics Data System (ADS)

Ahmed, Nauman; Voisey, K. T.; McCartney, D. G.

2014-02-01

Laser surface melting of thermally sprayed coatings has the potential to enhance their corrosion properties by incorporating favorable microstructural changes. Besides homogenizing the as-sprayed structure, laser melting may induce certain microstructural modifications (i.e., supplementary features) in addition to those that directly improve the corrosion performance. Such features, being a direct result of the laser treatment process, are described in this paper which is part of a broader study in which high velocity oxy-fuel sprayed Inconel 625 coatings on mild-steel substrates were treated with a diode laser and the modified microstructure characterized using optical and scanning electron microscopy and x-ray diffraction. The laser treated coating features several different zones, including a region with a microstructure in which there is a continuous columnar dendritic structure through a network of retained oxide stringers.

Titanium Aluminide Scramjet Inlet Flap Subelement Benchmark Tested

NASA Technical Reports Server (NTRS)

Krause, David L.; Draper, Susan L.

2005-01-01

A subelement-level ultimate strength test was completed successfully at the NASA Glenn Research Center (http://www.nasa.gov/glenn/) on a large gamma titanium aluminide (TiAl) inlet flap demonstration piece. The test subjected the part to prototypical stress conditions by using unique fixtures that allowed both loading and support points to be located remote to the part itself (see the photograph). The resulting configuration produced shear, moment, and the consequent stress topology proportional to the design point. The test was conducted at room temperature, a harsh condition for the material because of reduced available ductility. Still, the peak experimental load-carrying capability exceeded original predictions.

Filler metal alloy for welding cast nickel aluminide alloys

DOEpatents

Santella, M.L.; Sikka, V.K.

1998-03-10

A filler metal alloy used as a filler for welding cast nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and cast in copper chill molds. 3 figs.

Thermodynamics and kinetics of pack aluminide coating formation on IN-100

NASA Technical Reports Server (NTRS)

Levine, S. R.; Caves, R. M.

1973-01-01

An investigation of the effects of pack variables on the formation of aluminide coatings on nickel-base superalloy IN-100 was conducted. Also, the thermodynamics and kinetics of coating formation were analyzed. Observed coating weights were in good agreement with predictions made from the analysis. Pack temperature rather than pack aluminum activity controls the principal coating phase formed. In 1 weight percent aluminum packs, aluminum weight gains were related to the halide pack activator. Solid-state nickel diffusion controlled coating formation from sodium fluoride and chloride and ammonium fluoride activated packs. In other ammonium and sodium halide activated 1 weight percent aluminum packs, gaseous diffusion controlled coating formation.

Piercing mandrel strengthening by surfacing with nickel aluminide-based alloy

NASA Astrophysics Data System (ADS)

Zorin, I. V.; Dubtsov, Yu N.; Sokolov, G. N.; Artem'ev, A. A.; Lysak, V. I.; Elsukov, S. N.

2017-02-01

Electrode composite wire (CW) was used for argon-arc surfacing of a thermal-resisting nickel aluminide-based alloy (Ni-Al-Cr-W-Mo-Ta system) on the butt-end surface of the non-water-cooled piercing mandrel. It was shown that multipassing surfacing forms a defect-free deposited metal based on the γ’-Ni3Al phase of various structural origins. Using high-temperature sclerometry and thermal fatigue testing methods, the metal deposited with CW containing ultrafine particle of 0.3-0.4 % wt. WC carbide features increased resistance to thermal and force effects at temperatures up to 1200 °C.

Laser Powder Welding of a Ti52Al46.8Cr1Si0.2Titanium Aluminide Alloy at Elevated Temperature

NASA Astrophysics Data System (ADS)

Smal, C. A.; Meacock, C. G.; Rossouw, H. J.

2011-04-01

A method for the joining of a Ti52Al46.8Cr1Si0.2Titanium Aluminide alloy by laser powder welding is presented. The technique acts to join materials by consolidating powder with focused laser beam to form weld beads that fill a V joint. In order to avoid the occurrence of residual thermal stresses and hence cracking of the brittle material, the weld plates were heated to a temperature of 1173 K (= 900 °C) by an ohmic heating device, welded and then slowly cooled to produce pore and crack free welds.

Long-Term Cyclic Oxidation Behavior of Uncoated and Coated Re-108 and In-939 at 980 and 870 C

NASA Technical Reports Server (NTRS)

Lee, K. N.; Barrett, C. A.; Smith, J.

1999-01-01

Very long-term cyclic oxidation behavior of Re-108 and ln-939 with and without a protective coating was evaluated at 980 and 870 C, respectively. Re-108 and ln-939 without a protective coating began to show rapid weight loss at 3000 h due to scale spallation, indicating the need for an oxidation protective coating for longer than thousands of hours of oxidative life. NiAl-base coatings of a vapor phase aluminide (VPA), a pack aluminide (CODEP), and a slurry paint aluminide (SERMALOY J) were applied on Re-108 and ln-939. VPA and CODEP on Re-108 and all three coatings on ln-939 showed excellent cyclic oxidation resistance out to 10000 hr. Coated alloys were annealed in an inert atmosphere to determine the loss of Al from the coating into the alloy substrate through diffusion. The Al loss from the coating through diffusion was twice as great as the Al loss through oxidation after 10000 h of cyclic exposure. Oxidation life of VPA-coated Re-108 was estimated by calculating the amount of Al initially available for protective oxidation and the amount of Al lost through oxidation and diffusion.

Iron aluminide alloy coatings and joints, and methods of forming

DOEpatents

Wright, Richard N.; Wright, Julie K.; Moore, Glenn A.

1994-01-01

A method of joining two bodies together, at least one of the bodies being predominantly composed of metal, the two bodies each having a respective joint surface for joining with the joint surface of the other body, the two bodies having a respective melting point, includes the following steps: a) providing aluminum metal and iron metal on at least one of the joint surfaces of the two bodies; b) after providing the aluminum metal and iron metal on the one joint surface, positioning the joint surfaces of the two bodies in juxtaposition against one another with the aluminum and iron positioned therebetween; c) heating the aluminum and iron on the juxtaposed bodies to a temperature from greater than or equal to 600.degree. C. to less than the melting point of the lower melting point body; d) applying pressure on the juxtaposed surfaces; and e) maintaining the pressure and the temperature for a time period effective to form the aluminum and iron into an iron aluminide alloy joint which bonds the juxtaposed surfaces and correspondingly the two bodies together. The method can also effectively be used to coat a body with an iron aluminide coating.

Enriched aluminide coatings for dispersion strengthened nickel materials

NASA Technical Reports Server (NTRS)

Levinstein, M. A.

1973-01-01

Improved aluminide/barrier coating combinations for dispersion strengthened nickel materials were investigated. The barrier materials involved alloys with refractory metal content to limit interdiffusion between the coating and the substrate, thereby minimizing void formation. Improved aluminide coatings involved the dispersion of aluminum-rich compounds. Coatings were tested in argon at 1533 K (2300 F) for 100 hours and in cyclic oxidation at 1422 K (2100 F). Two coatings on TDNiCr completed 300 hours of oxidation testing, none on TDNi. Selected coating combinations were evaluated in Mach 1 burner rig testing using JP-4 fuel and air at 1422 K (2100 F) and 1477 K (2200 F) for 350 and 100 hours, respectively. Static oxidation in 1-hour cycles was conducted at 1533 K (2300 F) for 100 hours. For comparison purposes a physical vapor deposition (PVD) NiCrAlY coating was tested concurrently. Only the NiCrA1Y coating survived the 1477 K (2200 F)/100-hour burner rig test and 275 hours of the 350-hour 1422 K (2100 F) test. Elevated temperature exposure reduced room temperature tensile properties but had little effect on elevated temperature properties.

Iron aluminide alloy coatings and joints, and methods of forming

DOEpatents

Wright, R.N.; Wright, J.K.; Moore, G.A.

1994-09-27

Disclosed is a method of joining two bodies together, at least one of the bodies being predominantly composed of metal, the two bodies each having a respective joint surface for joining with the joint surface of the other body, the two bodies having a respective melting point, includes the following steps: (a) providing aluminum metal and iron metal on at least one of the joint surfaces of the two bodies; (b) after providing the aluminum metal and iron metal on the one joint surface, positioning the joint surfaces of the two bodies in juxtaposition against one another with the aluminum and iron positioned therebetween; (c) heating the aluminum and iron on the juxtaposed bodies to a temperature from greater than or equal to 600 C to less than the melting point of the lower melting point body; (d) applying pressure on the juxtaposed surfaces; and (e) maintaining the pressure and the temperature for a time period effective to form the aluminum and iron into an iron aluminide alloy joint which bonds the juxtaposed surfaces and correspondingly the two bodies together. The method can also effectively be used to coat a body with an iron aluminide coating.

Laser Surface Treatment and Modification of Aluminum Alloy Matrix Composites

NASA Astrophysics Data System (ADS)

Abbass, Muna Khethier

2018-02-01

The present work aimed to study the laser surface treatment and modification of Al-4.0%Cu-1.0%Mg alloy matrix composite reinforced with 10%SiC particles produced by stir casting. The specimens of the base alloy and composite were irradiated with an Nd:YAG laser of 1000 mJ, 1064 nm and 3 Hz . Dry wear test using the pin-on -disc technique at different sliding times (5-30 min) at a constant applied load and sliding speed were performed before and after laser treatment. Micro hardness and wear resistance were increased for all samples after laser hardening treatment. The improvement of these properties is explained by microstructural homogenization and grain refinement of the laser treated surface. Modification and refinement of SiC particles and grain refinement in the microstructure of the aluminum alloy matrix (α-Al) were observed by optical and SEM micrographs. The highest increase in hardness was 21.4% and 26.2% for the base alloy and composite sample respectively.

Effect of cryogenic treatment on microstructure, mechanical and wear behaviors of AISI H13 hot work tool steel

NASA Astrophysics Data System (ADS)

Koneshlou, Mahdi; Meshinchi Asl, Kaveh; Khomamizadeh, Farzad

2011-01-01

This paper focuses on the effects of low temperature (subzero) treatments on microstructure and mechanical properties of H13 hot work tool steel. Cryogenic treatment at -72 °C and deep cryogenic treatment at -196 °C were applied and it was found that by applying the subzero treatments, the retained austenite was transformed to martensite. As the temperature was decreased more retained austenite was transformed to martensite and it also led to smaller and more uniform martensite laths distributed in the microstructure. The deep cryogenic treatment also resulted in precipitation of more uniform and very fine carbide particles. The microstructural modification resulted in a significant improvement on the mechanical properties of the H13 tool steel.

Development and Processing of Nickel Aluminide-Carbide Alloys

NASA Technical Reports Server (NTRS)

Newport, Timothy Scott

1996-01-01

With the upper temperature limit of the Ni-based superalloys attained, a new class of materials is required. Intermetallics appear as likely candidates because of their attractive physical properties. With a relatively low density, high thermal conductivity, excellent oxidation resistance, high melting point, and simple crystal structure, nickel aluminide (NiAl) appears to be a potential candidate. However, NiAl is limited in structural applications due to its low room temperature fracture toughness and poor elevated temperature strength. One approach to improving these properties has been through the application of eutectic composites. Researchers have shown that containerless directional solidification of NiAl-based eutectic alloys can provide improvement in both the creep strength and fracture toughness. Although these systems have shown improvements in the mechanical properties, the presence of refractory metals increases the density significantly in some alloys. Lower density systems, such as the carbides, nitrides, and borides, may provide NiAl-based eutectic structure. With little or no information available on these systems, experimental investigation is required. The objective of this research was to locate and develop NiAl-carbide eutectic alloys. Exploratory arc-melts were performed in NiAl-refractory metal-C systems. Refractory metal systems investigated included Co, Cr, Fe, Hf, Mo, Nb, Ta, Ti, W, and Zr. Systems containing carbides with excellent stability (i.e.,HfC, NbC, TaC, TiC, and ZrC) produced large blocky cubic carbides in an NiAl matrix. The carbides appeared to have formed in the liquid state and were randomly distributed throughout the polycrystalline NiAl. The Co, Cr, Fe, Mo, and W systems contained NiAl dendrites with a two-phase interdendritic microconstituent present. Of these systems, the NiAl-Mo-C system had the most promising microstructure for in-situ composites. Three processing techniques were used to evaluate the NiAl-Mo-C system: arc-melting, slow cooling, and containerless directional solidification. Arc-melting provided a wide range of compositions in an economical and simple fashion. The slow cooled ingots provided larger ingots and slower cooling rates than arc-melting. Directional solidification was used to produce in-situ composites consisting of NiAl reinforced with molybdenum carbides.

Deformation and fracture behavior of titanium-aluminum-niobium-(chromium,molybdenum) alloys with a gamma+sigma microstructure at ambient temperature

NASA Astrophysics Data System (ADS)

Kesler, Michael Steiner

Titanium aluminides are of interest as a candidate material for aerospace turbine applications due to their high strength to weight ratio. gamma-TiAl + alpha2-Ti3Al alloys have recently been incorporated in the low pressure turbine region but their loss of strength near 750C limits their high temperature use. Additions of Nb have been shown to have several beneficial effects in gamma+alpha2 alloys, including enhancements in strength and ductility of the gamma-phase, along with the stabilization of the cubic BCC beta-phase at forging temperatures allowing for thermomechanical processing. In the ternary Ti-Al-Nb system at high Nb-contents above approximately 10at%, there exists a two-phase gamma-TiAl + sigma-Nb2Al region at and above current service temperature for the target application. Limited research has been conducted on the mechanical properties of alloys with this microstructure, though they have demonstrated excellent high temperature strength, superior to that of gamma+alpha2 alloys. Because the sigma-phase does not deform at room temperature, high volume fractions of this phase result in poor toughness and no tensile elongation. Controlling the microstructural morphology by disconnecting the brittle matrix through heat treatments has improved the toughness at room temperature. In this study, attempts to further improve the mechanical properties of these alloys were undertaken by reducing the volume fraction of the sigma-phase and controlling the scale of the gamma+sigma microstructure through the aging of a meta-stable parent phase, the beta- phase, that was quenched-in to room temperature. Additions of beta-stabilizing elements, Cr and Mo, were needed in order to quench-in the beta-phase. The room temperature mechanical properties were evaluated by compression, Vickers' indentation and single edge notch bend tests at room temperature. The formation of the large gamma-laths at prior beta- phase grain boundaries was found to be detrimental to ductility due to strain localization in this coarsened region of the microstructure. Furthermore, samples aged from beta- phase single crystals proved to have excellent combinations of strength and ductility under compression. In the single crystals, microcracking did not develop until much larger plastic strains were reached. Lowering the volume fraction of the sigma-phase proved to enhance the fracture toughness in these alloys. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)

ZnO nanostructures directly grown on paper and bacterial cellulose substrates without any surface modification layer.

PubMed

Costa, Saionara V; Gonçalves, Agnaldo S; Zaguete, Maria A; Mazon, Talita; Nogueira, Ana F

2013-09-21

In this report, hierarchical ZnO nano- and microstructures were directly grown for the first time on a bacterial cellulose substrate and on two additional different papers by hydrothermal synthesis without any surface modification layer. Compactness and smoothness of the substrates are two important parameters that allow the growth of oriented structures.

Microstructural modification of pure Mg for improving mechanical and biocorrosion properties.

PubMed

Ahmadkhaniha, D; Järvenpää, A; Jaskari, M; Sohi, M Heydarzadeh; Zarei-Hanzaki, A; Fedel, M; Deflorian, F; Karjalainen, L P

2016-08-01

In this study, the effect of microstructural modification on mechanical properties and biocorrosion resistance of pure Mg was investigated for tailoring a load-bearing orthopedic biodegradable implant material. This was performed utilizing the friction stir processing (FSP) in 1-3 passes to refine the grain size. Microstructure was examined in an optical microscope and scanning electron microscope with an electron backscatter diffraction unit. X-ray diffraction method was used to identify the texture. Mechanical properties were measured by microhardness and tensile testing. Electrochemical impedance spectroscopy was applied to evaluate corrosion behavior. The results indicate that even applying a single pass of FSP refined the grain size significantly. Increasing the number of FSP passes further refined the structure, increased the mechanical strength and intensified the dominating basal texture. The best combination of mechanical properties and corrosion resistance were achieved after three FSP passes. In this case, the yield strength was about six times higher than that of the as-cast Mg and the corrosion resistance was also improved compared to that in the as-cast condition. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of Ti and La Additions on the Microstructures and Mechanical Properties of B-Refined and Sr-Modified Al-11Si Alloys

NASA Astrophysics Data System (ADS)

Li, Chenlin; Pan, Ye; Lu, Tao; Jing, Lijun; Pi, Jinhong

2018-03-01

The effects of Ti and La additions on the microstructures and mechanical properties of B-refined and Sr-modified Al-11Si alloys were investigated in the present work. The interactions among Ti, La, B and Sr elements were discussed employing microstructure observation, thermal analysis and tensile test, respectively. It was found that the addition of 0.05 wt% B induces a transformation of eutectic Si from finely fibrous to coarsely plate-like morphology in the Al-11Si alloy with 0.02 wt%Sr modification, owing to the poisoning of IIT mechanism, and the eutectic Si grows only with TPRE mechanism. Both titanium and lanthanum can neutralize the co-poisoning effect between Sr and B in the Al-11Si alloy, but the neutralizing effect of La is dependent on the addition sequence. The combinative addition of La and B elements promotes the effective refinement of α-Al grains, but an inhomogeneous modification of eutectic Si phases is also observed, leading to a slightly decrease in the elongation.

Influence of Carbide Modifications on the Mechanical Properties of Ultra-High-Strength Stainless Steels

NASA Astrophysics Data System (ADS)

Seo, Joo-Young; Park, Soo-Keun; Kwon, Hoon; Cho, Ki-Sub

2017-10-01

The mechanical properties of ultra-high-strength secondary hardened stainless steels with varying Co, V, and C contents have been studied. A reduced-Co alloy based on the chemical composition of Ferrium S53 was made by increasing the V and C content. This changed the M2C-strengthened microstructure to a MC plus M2C-strengthened microstructure, and no deteriorative effects were observed for peak-aged and over-aged samples despite the large reduction in Co content from 14 to 7 wt pct. The mechanical properties according to alloying modification were associated with carbide precipitation kinetics, which was clearly outlined by combining analytical tools including small-angle neutron scattering (SANS) as well as an analytical TEM with computational simulation.

Nanostructure of vortex during explosion welding.

PubMed

Rybin, V V; Greenberg, B A; Ivanov, M A; Patselov, A M; Antonova, O V; Elkina, O A; Inozemtsev, A V; Salishchev, G A

2011-10-01

The microstructure of a bimetallic joint made by explosion welding of orthorhombic titanium aluminide (Ti-30Al-16Nb-1Zr-1Mo) with commercially pure titanium is studied. It is found that the welded joint has a multilayered structure including a severely deformed zone observed in both materials, a recrystallized zone of titanium, and a transition zone near the interface. Typical elements of the transition zone-a wavy interface, macrorotations of the lattice, vortices and tracks of fragments of the initial materials-are determined. It is shown that the observed vortices are formed most probably due to local melting of the material near the contact surface. Evidence for this assumption is deduced from the presence of dipoles, which consist of two vortices of different helicity and an ultrafine duplex structure of the vortex. Also, high mixing of the material near the vortex is only possible by the turbulent transport whose coefficient is several orders of magnitude larger than the coefficient of atomic diffusion in liquids. The role played by fragmentation in both the formation of lattice macrorotations and the passage of coarse particles of one material through the bulk of the other is determined.

The reactive element effect of ceria particle dispersion on alumina growth: A model based on microstructural observations

PubMed Central

Wang, X.; Peng, X.; Tan, X.; Wang, F.

2016-01-01

The oxidation kinetics of alumina-forming metals can be affected by adding a small amount of a reactive (normally rare earth) element oxide (RExOy) and the segregation of the reactive element (RE) ions to the growing alumina grain boundaries (GBs) has been considered as a responsible reason. However, this interpretation remains a controversial issue as to how RE ions are produced by RExOy which is thermodynamically and chemically stable in metals. The question is answered by a model that is based on transmission electron microscopy (TEM) investigation of a CeO2-dispersed nickel aluminide oxidized in air at 1100 °C. The CeO2 dispersion is incorporated into the alumina scale by the inward growth of inner α-Al2O3, where it partially dissolves producing tetravalent Ce cations which then transform to trivalent cations by trapping electrons. The trivalent cations segregate to the α-Al2O3 GBs and diffuse outward along first the GBs and later the twin boundaries (TBs) in the outer γ-Al2O3 layer, being precipitated as Ce2O3 particles near surface. PMID:27406938

Creep fatigue life prediction for engine hot section materials (isotropic)

NASA Technical Reports Server (NTRS)

Nelson, R. S.; Levan, G. W.; Schoendorf, J. F.

1992-01-01

A series of high temperature strain controlled fatigue tests have been completed to study the effects of thermomechanical fatigue, multiaxial loading, reactive environments, and imposed mean stresses. The baseline alloy used in these tests was cast B1900+Hf (with and without coatings); a small number of tests of wrought INCO 718 are also included. A strong path dependence was demonstrated during the thermomechanical fatigue testing, using in-phase, out-phase, and non-proportional (elliptical and 'dogleg') strain-temperature cycles. The multiaxial tests also demonstrated cycle path to be a significant variable, using both proportional and non-proportional tension-torsion loading. Environmental screening tests were conducted in moderate pressure oxygen and purified argon; the oxygen reduced the specimen lives by two, while the argon testing produced ambiguous data. Both NiCoCrAlY overlay and diffusion aluminide coatings were evaluated under isothermal and TMF conditions; in general, the lives of the coated specimens were higher that those of uncoated specimens. Controlled mean stress TMF tests showed that small mean stress changes could change initiation lives by orders of magnitude; these results are not conservatively predicted using traditional linear damage summation rules. Microstructures were evaluated using optical, SEM and TEM methods.

Investigation of moisture-induced embrittlement of iron aluminides. Interim report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castagna, A.; Stoloff, N.S.

Alloy FA-129 undergoes an increase in crack propagation rate and a loss of fracture toughness in moisture-bearing and hydrogen gas environments. A similar effect is seen on ductility of FA-129 in tensile tests. The embrittling effect in air is attributed to oxidation of aluminum in the alloy by water vapor to produce Al{sub 2}O{sub 3} and hydrogen gas. Alloy FAP-Y, which is disordered and contains only 16 a%Al is embrittled by hydrogen gas in a manner similar to that of FA-129. However, laboratory air had little effect on the crack growth rates, fracture toughness, or tensile ductility. The lower aluminummore » content apparently is insufficient to induce the Al-H{sub 2}O reaction. TEM and SEM analyses of microstructure and fracture surfaces were consistent with the change in fracture toughness with order and environment. Testing at elevated temperatures reduces crack growth rates in FA-129, and increases fracture toughness and ductility. This is consistent with the well documented peak in hydrogen embrittlement in structural alloys at or near room temperature. Elevated temperature affects the degree of embrittlement in a complex manner, possibly changing the rates of several of the processes involved.« less

A low-cost, high-efficiency and high-flexibility surface modification technology for a black bisphenol A polycarbonate board

NASA Astrophysics Data System (ADS)

Wang, Suhuan; Liu, Jianguo; Lv, Ming; Zeng, Xiaoyan

2014-09-01

In this paper, a low-cost, high-efficiency and high-flexibility surface modification technology for polymer materials was achieved at high laser scanning speeds (600-1000 mm s-1) and using an all-solid state, Q-switched, high-average power, and nanosecond pulse ultraviolet (355 nm wavelength) laser. During the surface modification of a very important engineering plastic, i.e., black bisphenol A polycarbonate (BAPC) board, it was found that different laser parameters (e.g., laser fluence and pulse frequency) were able to result in different surface microstructures (e.g., many tiny protuberances or a porous microstructure with periodical V-type grooves). After the modification, although the total relative content of the oxygen-containing groups (e.g., Csbnd O and COO-) on the BAPC surface increased, however, the special microstructures played a deciding role in the surface properties (e.g., contact angle and surface energy) of the BAPC. The change trend of the water contact angle on the BAPC surface was with an obvious increase, that of the diiodomethane contact angle was with a most decrease, and that of the ethylene glycol contact angle was between the above two. It showed that the wetting properties of the three liquids on the modified BAPC surface were different. Basing on the measurements of the contact angles of the three liquids, and according to the Young equation and the Lifshitz van der Waals and Lewis acid-base theory, the BAPC surface energy after the modification was calculated. The results were that, in a broad range of laser fluences, pulse frequencies and scanning speeds, the surface energy had a significant increase (e.g., from the original of about 44 mJ m-2 to the maximum of about 70 mJ m-2), and the higher the laser pulse frequency, the more significant the increase. This would be very advantageous to fabricate the high-quality micro-devices and micro-systems on the modified surface.

Impact resistance and energies of intermetallic bonded diamond composites and polycrystalline diamond compacts and their comparison

NASA Astrophysics Data System (ADS)

Gorla, Sai Prasanth

Chemistry of intermetallic bonded diamond is studied. The impact resistance and energies of intermetallic bonded diamond is compared to current poly crystalline diamond compacts. IBD's are found to have high standards of hardness and have more impact energies absorbed. Intermetallic bonded diamond composite comprises of diamond particles dispersed in Tungsten carbide using Nickel aluminide (Ni3Al) as binder. In previous research conducted on IBD's, diamonds are successfully dispersed in intermetallic alloy of nickel aluminide and processed at 1350°C such that diamond particles remain intact without forming graphite. Composites are formed by milling, pressing the intermetallic binder and diamond particles and sintering at high temperature conditions.

High-temperature corrosion-resistant iron-aluminide (FeAl) alloys exhibiting improved weldability

DOEpatents

Maziasz, P.J.; Goodwin, G.M.; Liu, C.T.

1996-08-13

This invention relates to improved corrosion-resistant iron-aluminide intermetallic alloys. The alloys of this invention comprise, in atomic percent, from about 30% to about 40% aluminum alloyed with from about 0.1% to about 0.5% carbon, no more than about 0.04% boron such that the atomic weight ratio of boron to carbon in the alloy is in the range of from about 0.01:1 to about 0.08:1, from about 0.01 to about 3.5% of one or more transition metals selected from Group IVB, VB, and VIB elements and the balance iron wherein the alloy exhibits improved resistance to hot cracking during welding. 13 figs.

High-temperature corrosion-resistant iron-aluminide (FeAl) alloys exhibiting improved weldability

DOEpatents

Maziasz, Philip J.; Goodwin, Gene M.; Liu, Chain T.

1996-01-01

This invention relates to improved corrosion-resistant iron-aluminide intermetallic alloys. The alloys of this invention comprise, in atomic percent, from about 30% to about 40% aluminum alloyed with from about 0.1% to about 0.5% carbon, no more than about 0.04% boron such that the atomic weight ratio of boron to carbon in the alloy is in the range of from about 0.01:1 to about 0.08:1, from about 0.01 to about 3.5% of one or more transition metals selected from Group IVB, VB, and VIB elements and the balance iron wherein the alloy exhibits improved resistance to hot cracking during welding.

Thin coatings for protecting titanium aluminides in high-temperature oxidizing environments

NASA Technical Reports Server (NTRS)

Wiedemann, K. E.; Taylor, P. J.; Clark, R. K.; Wallace, T. A.

1991-01-01

Titanium aluminides have high specific strengths at high temperatures but are susceptible to environmental attack. Their use in many aerospace applications would require that they be protected with coatings that, for structural efficiency, must be thin. It is conceivable that acceptable coatings might be found in several oxide systems, and consequently, oxide coatings of many compositions were prepared from sol-gels for study. Response-surface methodology was used to refine coating compositions and factorial experiments were used to develop coating strategies. Oxygen permeability diagrams of two-layer coatings for several oxide systems, an analysis of multiple-layer coatings on rough and polished surfaces, and modeling of the oxidation weight gain are presented.

Magnetohydrodynamic electrode

DOEpatents

Marchant, David D.; Killpatrick, Don H.

1978-01-01

An electrode capable of withstanding high temperatures and suitable for use as a current collector in the channel of a magnetohydrodynamic (MHD) generator consists of a sintered powdered metal base portion, the upper surface of the base being coated with a first layer of nickel aluminide, an intermediate layer of a mixture of nickel aluminide - refractory ceramic on the first layer and a third or outer layer of a refractory ceramic material on the intermediate layer. The sintered powdered metal base resists spalling by the ceramic coatings and permits greater electrode compliance to thermal shock. The density of the powdered metal base can be varied to allow optimization of the thermal conductivity of the electrode and prevent excess heat loss from the channel.

Microstructure and Mechanical Properties of a Tempered High Cr Martensitic Steel

NASA Astrophysics Data System (ADS)

Guerra-Fuentes, L.; Hernandez-Rodriguez, M. A. L.; Zambrano-Robledo, P.; Salinas-Rodriguez, A.; Garcia-Sanchez, E.

2017-07-01

Microstructural and mechanical studies have been performed in a high Cr martensitic steel Firth-Vickers (FV535) to analyze the tempering of martensite. Nanoindentation technique was used to determine the hardness and elastic modulus through systematic measurements on martensite and tempered martensite. On the other hand, microscopic studies were carried out to analyze the material in the same condition as received and subsequently observe the microstructural modifications after heat treatment. The precipitation presented in the last stage of tempering was observed by transmission electron microscopy. The results showed the effect of the martensite decomposition on the mechanical and nanomechanical properties of FV535.

Nanoscale microstructure effects on hydrogen behavior in rapidly solidified aluminum alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tashlykova-Bushkevich, Iya I.

2015-12-31

The present work summarizes recent progress in the investigation of nanoscale microstructure effects on hydrogen behavior in rapidly solidified aluminum alloys foils produced at exceptionally high cooling rates. We focus here on the potential of modification of hydrogen desorption kinetics in respect to weak and strong trapping sites that could serve as hydrogen sinks in Al materials. It is shown that it is important to elucidate the surface microstructure of the Al alloy foils at the submicrometer scale because rapidly solidified microstructural features affect hydrogen trapping at nanostructured defects. We discuss the profound influence of solute atoms on hydrogen−lattice defectmore » interactions in the alloys. with emphasis on role of vacancies in hydrogen evolution; both rapidly solidified pure Al and conventionally processed aluminum samples are considered.« less

Long-Term Cyclic Oxidation Behavior of Uncoated and Coated Re-108 and In-939 at 980 and 870 C

NASA Technical Reports Server (NTRS)

Lee, K. N.; Barrett, C. A.; Smith, J.

2000-01-01

Very long-term cyclic oxidation behavior of Re108 and In939 with and without a protective coating was evaluated at 980 and 870 C, respectively. Re-108 and In-939 without a protective coating began to show a rapid weight loss at 3000 h due to scale spallation, indicating the need for an oxidation protective coating for longer than thousands of hours of oxidative life. NiAl-base coatings of a vapor phase aluminide (VPA), a pack aluminide (CODEP), and a slurry paint aluminide (SERMALOY J) were applied on Re-108 and In-939. The VPA and CODEP on Re-108 and all three coatings on In-939 showed excellent cyclic oxidation resistance out to 10,000 h. Coated alloys were annealed in an inert atmosphere to determine the loss of Al from the coating into the alloy substrate through diffusion. The Al loss from the coating through diffusion was twice as great as the Al loss through oxidation after 10,000 h of cyclic exposure. The oxidation life of VPA-coated Re-108 was estimated by calculating the amount of Al initially available for protective oxidation and the amount of Al lost through oxidation and diffusion.

An evaluation of fiber-reinforced titanium matrix composites for advanced high-temperature aerospace applications

NASA Astrophysics Data System (ADS)

Larsen, James M.; Russ, Stephan M.; Jones, J. W.

1995-12-01

The current capabilities of continuous silicon-carbide fiber-reinforced titanium matrix composites (TMCs) are reviewed with respect to application needs and compared to the capabilities of conventional high-temperature monolithic alloys and aluminides. In particular, the properties of a firstgeneration titanium aluminide composite, SCS-6/Ti-24Al-11Nb, and a second-generation metastable beta alloy composite, SCS-6/TIMETAL 21S, are compared with the nickel-base superalloy IN100, the high-temperature titanium alloy Ti-1100, and a relatively new titanium aluminide alloy. Emphasis is given to life-limiting cyclic and monotonie properties and to the influence of time-dependent deformation and environmental effects on these properties. The composite materials offer a wide range of performance capabilities, depending on laminate architecture. In many instances, unidirectional composites exhibit outstanding properties, although the same materials loaded transverse to the fiber direction typically exhibit very poor properties, primarily due to the weak fiber/matrix interface. Depending on the specific mechanical property under consideration, composite cross-ply laminates often show no improvement over the capability of conventional monolithic materials. Thus, it is essential that these composite materials be tailored to achieve a balance of properties suitable to the specific application needs if these materials are to be attractive candidates to replace more conventional materials.

PFB Coal Fired Combined Cycle Development Program. Quarterly report, July-September 1978

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1978-01-01

The System Analysis report was completed and is currently undergoing internal review prior to submission to DOE. Exposures of up to 6000 hours in the small burner rigs during Phase II identified PFB-5PM, aluminided PFB-6PM and GE-2541 as the most corrosion resistant cladding alloys. Three alloy modifications each of GE-2541 and PFB-5PM have been ordered as prealloyed powder to evaluate the effect of the modifications. Test 9 at CURL was terminated after twenty-one hours' operation due to a failure in the bellows between the combustor and Aerodyne cyclone. Initial data reduction of the total ninety-one hours of testing (combined Testsmore » 8 and 9) is in progress. All 24 mini-airfoil specimens exposed in the four cascades of the 91 hours CURL PFB Tests 8/9 were received for evaluation. The Aerodyne two-in-one cyclone was removed from the CURL facility and disassembled in order to determine the cause of the anomalies which occurred during Tests number 8 and number 9. The consensus after review and investigation by representatives from Aerodyne, CURL, and GE indicated a number of causes which are detailed. Test planning for the upcoming 1000 hour test at CURL was initiated. Effort is concentrated at integrating the test objectives of the program participants (DOE, EPRI, CURL, GE, AEP, Stal Laval, and B and W Ltd.).« less

An investigation of the effect of surface impurities on the adsorption kinetics of hydrogen chemisorbed onto iron

NASA Technical Reports Server (NTRS)

Shanabarger, Mickey R.

1993-01-01

The goal of this program was to develop an understanding of heterogeneous kinetic processes for those molecular species which produce gaseous hydrogen degradation of the mechanical properties of metallic structural materials. Although hydrogen degradation of metallic materials is believed to result from dissolved protonic hydrogen, the heterogeneous hydrogen interface transport processes often dominate the kinetics of degradation. The initial step in the interface transport process is the dissociative chemisorption of the molecular species at the metal surface followed by hydrogen absorption into and transport through the bulk. The interaction of hydrogen with the surfaces of alpha-2(Ti3Al) titanium aluminide, gamma(TiAl) titanium aluminide, and beryllium were studied.

Iron aluminide alloys with improved properties for high temperature applications

DOEpatents

McKamey, Claudette G.; Liu, Chain T.

1990-01-01

An improved iron aluminide alloy of the DO.sub.3 type that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy corrosion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26-30 at. % aluminum, 0.5-10 at. % chromium, 0.02-0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron.

Iron aluminide alloys with improved properties for high temperature applications

DOEpatents

McKamey, C.G.; Liu, C.T.

1990-10-09

An improved iron aluminide alloy of the DO[sub 3] type is described that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy conversion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26--30 at. % aluminum, 0.5--10 at. % chromium, 0.02--0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron. 3 figs.

Effects of a High Magnetic Field on the Microstructure of Ni-Based Single-Crystal Superalloys During Directional Solidification

NASA Astrophysics Data System (ADS)

Xuan, Weidong; Lan, Jian; Liu, Huan; Li, Chuanjun; Wang, Jiang; Ren, Weili; Zhong, Yunbo; Li, Xi; Ren, Zhongming

2017-08-01

High magnetic fields are widely used to improve the microstructure and properties of materials during the solidification process. During the preparation of single-crystal turbine blades, the microstructure of the superalloy is the main factor that determines its mechanical properties. In this work, the effects of a high magnetic field on the microstructure of Ni-based single-crystal superalloys PWA1483 and CMSX-4 during directional solidification were investigated experimentally. The results showed that the magnetic field modified the primary dendrite arm spacing, γ' phase size, and microsegregation of the superalloys. In addition, the size and volume fractions of γ/ γ' eutectic and the microporosity were decreased in a high magnetic field. Analysis of variance (ANOVA) results showed that the effect of a high magnetic field on the microstructure during directional solidification was significant ( p < 0.05). Based on both experimental results and theoretical analysis, the modification of microstructure was attributed to thermoelectric magnetic convection occurring in the interdendritic regions under a high magnetic field. The present work provides a new method to optimize the microstructure of Ni-based single-crystal superalloy blades by applying a high magnetic field.

Hydrocarbon-Based Polymer Electrolyte Membranes: Importance of Morphology on Ion Transport and Membrane Stability.

PubMed

Shin, Dong Won; Guiver, Michael D; Lee, Young Moo

2017-03-22

A fundamental understanding of polymer microstructure is important in order to design novel polymer electrolyte membranes (PEMs) with excellent electrochemical performance and stabilities. Hydrocarbon-based polymers have distinct microstructure according to their chemical structure. The ionic clusters and/or channels play a critical role in PEMs, affecting ion conductivity and water transport, especially at medium temperature and low relative humidity (RH). In addition, physical properties such as water uptake and dimensional swelling behavior depend strongly on polymer morphology. Over the past few decades, much research has focused on the synthetic development and microstructural characterization of hydrocarbon-based PEM materials. Furthermore, blends, composites, pressing, shear field, electrical field, surface modification, and cross-linking have also been shown to be effective approaches to obtain/maintain well-defined PEM microstructure. This review summarizes recent work on developments in advanced PEMs with various chemical structures and architecture and the resulting polymer microstructures and morphologies that arise for potential application in fuel cell, lithium ion battery, redox flow battery, actuators, and electrodialysis.

Effect of annealing conditions on the microstructure and magnetic properties of sintered Nd-Fe-B magnets as seen by magnetic small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Périgo, Élio A.; Titov, Ivan; Weber, Raoul; Mettus, Denis; Peral, Inma; Vallcorba, Oriol; Honecker, Dirk; Feoktystov, Artem; Michels, Andreas

2018-03-01

We have investigated the effect of the annealing conditions (heating rate and temperature) on the magnetic microstructure of sintered Nd-Fe-B magnets by means of magnetometry, scanning electron microscopy, high-energy synchrotron x-ray diffraction, and small-angle neutron scattering (SANS). While the temperature treatment has a strong effect on the coercivity (reduction by about 50% on annealing), the associated changes in the microstructure do surprisingly not show up (or at best only very weakly) in the neutron-scattering signal, which probes a mesoscopic real-space length scale ranging between about 1–300 nm. On the other hand, the x-ray data reveal microstructural changes in the Nd-rich phases, presumably due to modifications in grain-boundary regions. Moreover, we observe an unusual diamond-shaped angular anisotropy in the SANS cross section, which strongly points towards the existence of texture in the nuclear microstructure.

Optimization of laser energy deposition for single-shot high aspect-ratio microstructuring of thick BK7 glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garzillo, Valerio; Grigutis, Robertas; Jukna, Vytautas

We investigate the generation of high aspect ratio microstructures across 0.7 mm thick glass by means of single shot Bessel beam laser direct writing. We study the effect on the photoinscription of the cone angle, as well as of the energy and duration of the ultrashort laser pulse. The aim of the study is to optimize the parameters for the writing of a regular microstructure due to index modification along the whole sample thickness. By using a spectrally resolved single pulse transmission diagnostics at the output surface of the glass, we correlate the single shot material modification with observations of themore » absorption in different portions of the retrieved spectra, and with the absence or presence of spectral modulation. Numerical simulations of the evolution of the Bessel pulse intensity and of the energy deposition inside the sample help us interpret the experimental results that suggest to use picosecond pulses for an efficient and more regular energy deposition. Picosecond pulses take advantage of nonlinear plasma absorption and avoid temporal dynamics effects which can compromise the stationarity of the Bessel beam propagation.« less

Wettability modification of porous PET by atmospheric femtosecond PLD

NASA Astrophysics Data System (ADS)

Assaf, Youssef; Forstmann, Guillaume; Kietzig, Anne-Marie

2018-04-01

In this study, porous structures were created on poly(ethylene terephthalate) (PET) by femtosecond (fs) laser micromachining. While such structures offer a texture that is desirable for several applications, their wettability does not always match the application in question. The aim of this investigation is to tune the wettability of such surfaces by incorporating a controlled amount of nanoparticles into the structure. The machined PET samples were thus used as substrates for fs pulsed laser deposition (PLD) of titanium under ambient conditions. The nanoparticles were deposited as nanochain clusters due to the formation of an oxide layer between individual nanoparticles. The stability of nanoparticle incorporation was tested by placing the samples in an ultrasonic ethanol bath. Results indicated that nanoparticles were still successfully incorporated into the microstructure after sonication. Nanoparticle surface coverage was observed to be controllable through the operating fluence. The dynamic contact angles of the resulting composite surface were observed to decrease with increasing titanium incorporation. Therefore, this work highlights atmospheric fs PLD as a method for wettability modification of high surface area microstructures without undermining their topology. In addition, this technique uses almost the same equipment as the machining process by which the microstructures are initially created, further highlighting its practicality.

Recent advances in the chemical modification of unsaturated polymers

NASA Technical Reports Server (NTRS)

Schulz, D. N.; Turner, S. R.; Golub, M. A.

1982-01-01

The present discussion has the objective to update the most comprehensive reviews on the considered subject and to fill in the gaps of less complete, but more modern treatments. Only simple chemical functionalization or structural modification of unsaturated polymers are covered, and the literature of diene polymer modification since 1974 is emphasized. Attention is given to hydrogenation, halogenation and hydrohalogenation, cyclization, cis-trans isomerization, epoxidation, ene and other cycloaddition reactions, sulfonation, carboxylation, phosphonylation, sulfenyl chloride addition, carbene addition, metalation, and silylation. It is pointed out that modern synthetic reagents and catalysts have been advantageously employed to improve process and/or product quality. Synthetic techniques have been refined to allow the selective modification of specific polymer microstructures or blocks.

Microstructural Modification of Sn-0.7Cu Solder Alloys by Fe/Bi-Addition for Achieving High Mechanical Performance

NASA Astrophysics Data System (ADS)

Ali, Bakhtiar; Sabri, Mohd Faizul Mohd; Said, Suhana Mohd; Mahdavifard, Mohammad Hossein; Sukiman, Nazatul Liana; Jauhari, Iswadi

2017-08-01

In this work, we studied the Fe/Bi-bearing tin-copper (Sn-0.7Cu) solders for their microstructural and mechanical properties. The microstructure was studied using field emission scanning electron microscopy (FESEM) with a backscattered electron (BSE) detector, x-ray diffraction (XRD) analysis, and energy-dispersive x-ray spectroscopy (EDX). The microstructure study showed that Fe forms very few FeSn2 intermetallic compounds (IMCs) and does not significantly alter the microstructure of Sn-0.7Cu, whereas Bi controls the size of inter-dendritic regions containing Cu6Sn5 and Ag3Sn IMCs of the alloy, as well as significantly refines its primary β-Sn dendrites. Moreover, Bi atoms dissolve in β-Sn matrix, which in turn strengthen the solder by the Bi solid solution strengthening mechanism. Such microstructural modification leads to significant improvements in various mechanical properties of the alloy, including shear strength, impact toughness, and hardness values. Shear tests were performed with a 0.25 mm/min shear speed. The results showed that shear strength improves from 16.57 MPa to 38.36 MPa with the addition of Fe/Bi to Sn-0.7Cu, raising by about 130%. The energy absorbed during impact tests was measured for samples with the help of a Charpy impact testing machine with a 5.4 m/s impact speed. The results revealed that the addition of Fe/Bi to Sn-0.7Cu improves its impact absorbed energy by over 35%, increasing it from 7.5 J to 10.3 J. Vickers hardness tests were carried out for the test samples with a 245.2 mN applied load and 10 s dwell time. The results showed that the hardness number improves from 9.89 to 24.13 with Fe/Bi to Sn-0.7Cu, increasing by about 140%.

Characterization and Electrical Response to Humidity of Sintered Polymeric Electrospun Fibers of Vanadium Oxide-({TiO}_{{2}} /{WO}_{{3}} )

NASA Astrophysics Data System (ADS)

Araújo, E. S.; Libardi, J.; Faia, P. M.; de Oliveira, H. P.

2018-02-01

Metal oxide composites have attracted much consideration due to their promising applications in humidity sensors in response to the physical and chemical property modifications of the resulting materials. This work focused on the preparation, microstructural characterization and analysis of humidity-dependent electrical properties of undoped and vanadium oxide (V2O5)-doped titanium oxide/tungsten oxide (TiO2/WO3) sintered ceramic films obtained by electrospinning. The electrical properties were investigated by impedance spectroscopy (400 Hz-40 MHz) as a function of relative humidity (RH). The results revealed a typical transition in the transport mechanisms controlled by the appropriated doping level of V2O5, which introduces important advantages to RH detection due to the atomic substitution of titanium by vanadium atoms in highly doped structures. These aspects are directly related to the microstructure modification and structure fabrication procedure.

Experimental studies on mechanical properties of T6 treated Al25Mg2Si2Cu4Fe alloy

NASA Astrophysics Data System (ADS)

Sondur, D. G.; Mallapur, D. G.; Udupa, K. Rajendra

2018-04-01

Effect of T6 treatment on the mechanical properties of Al25Mg2Si2Cu4Fe alloy was evaluated by conducting mechanical tests on test pieces using universal testing machine. Increase in the mechanical properties such as ultimate tensile strength, hardness and % elongation was observed. Microstructure characterization revealed the modification in the size and shapes of the precipitates formed during the homogenization process. This modification increases the anisotropy of the microstructure and the stresses in the as cast structure. The increase in the hardness of T6 treated alloy is due to the partial recrystallization, fragmentation and redistribution of primary Mg2Si phase, precipitation of fine θ, Q phases. The high volume fractions of uniformly dispersed hard β-particles greatly increase the flow stress and provide an appreciable impediment to plastic deformation. Thus increasing the hardness of the alloy.

Micro- and nanostructure of a titanium surface electric-spark-doped with tantalum and modified by high-frequency currents

NASA Astrophysics Data System (ADS)

Fomin, A. A.; Fomina, M. A.; Koshuro, V. A.; Rodionov, I. V.; Voiko, A. V.; Zakharevich, A. M.; Aman, A.; Oseev, A.; Hirsch, S.; Majcherek, S.

2016-09-01

We have studied the characteristics of the porous microstructure of tantalum coatings obtained by means of electric spark spraying on the surface of commercial grade titanium. It is established that, at an electric spark current within 0.8-2.2 A, a mechanically strong tantalum coating microstructure is formed with an average protrusion size of 5.1-5.4 µm and pore sizes from 3.5 to 9.2 µm. On the nanoscale, a structurally heterogeneous state of coatings has been achieved by subsequent thermal modification at 800-830°C with the aid of high-frequency currents. A metal oxide nanostructure with grain sizes from 40 to 120 nm is formed by short-time (~30 s) thermal modification. The coating hardness reaches 9.5-10.5 GPa at an elastic modulus of 400-550 GPa.

High-temperature ultrasonic characterization of the mechanical and microstructural behavior of a fibrous composite with a magnesium lithium aluminum silicate glass-ceramic matrix

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cutard, T.; Huger, M.; Fargeot, D.

The mechanical behavior and the microstructural modifications of a SiC-fiber-reinforced magnesium lithium aluminum silicate glass-ceramic (SiC/MASL) have been characterized by ultrasonic measurement of uniaxial Young`s modulus at high temperature. Under vacuum, long isothermal agings in the 750--1,000 C temperature range have shown matrix modifications in terms of crystallization of residual glassy phases, and of phase transformations in the Li{sub 2}O-Al{sub 2}O{sub 3}-SiO{sub 2} system. In air, long isothermal agings performed under the same conditions have led to the same matrix transformations but in competition with oxidation mechanisms of the carbon fiber-matrix interphase. All of these matrix and/or interface transformations havemore » been confirmed by X-ray diffraction analysis, scanning electron microscopy, scanning acoustic microscopy, and microindentation tests.« less

Microstructure modification and performance improvement of Mg-RE alloys by friction stir processing

NASA Astrophysics Data System (ADS)

Wu, Yujuan; Peng, Liming; Zheng, Feiyan; Li, Xuewen; Li, Dejiang; Ding, Wenjiang

Friction stir processing (FSP) is a severe plastic deformation (SPD) processing, which is very useful to refine grain size and secondary phase as well as change the texture of metal materials. Many FSP research were focused on aluminum alloys, while there are few reports on FSP of magnesium alloys, esp. on precipitation-hardening Mg-RE alloys. This paper overviewed the micro structures and mechanical properties of several FSPed Mg-RE alloys, such as Mg-Gd-Zn-Zr, Mg-Gd-Ag-Zr, and Mg-Nd-Zn-Zr with or without long period stacking ordering (LPSO) structure. The effects of processing parameters, such as rotation rate and traversing speed, on microstructure and mechanical properties were evaluated. It shows that FSP can effectively lend to performance improvement by micro structure modification, including obtaining remarkable finer and more homogenized grains, changing distribution and volume percentage of secondary phase etc.

Very Long Term Oxidation of Titanium Aluminides Investigated

NASA Technical Reports Server (NTRS)

Locci, Ivan E.; Brady, Michael P.; Smialek, James L.; Retallick, William B.

2000-01-01

Titanium aluminides (TiAl) are of great interest for intermediate-temperature (600 to 850 C) aerospace and power-generation applications because they offer significant weight savings over today's nickel alloys. TiAl alloys are being investigated for low-pressure turbine blade applications, exhaust nozzle components, and compressor cases in advanced subsonic and supersonic engines. Significant progress has been made in understanding the fundamental aspects of the oxidation behavior of binary TiAl alloys. However, most of this work has concentrated on short term (<1000 hr), high-temperature (900 to 1000 C) exposures. Also, there is not much data available in the literature regarding the oxidation behavior of the quaternary and higher order engineering alloys. This is especially true for the very long term, low-temperature conditions likely to be experienced during aerospace applications. An investigation at the NASA Glenn Research Center at Lewis Field was undertaken to characterize the long-term oxidation behavior of various model and advanced titanium aluminides for periods up to 7000 hr at 704 C in air using a high-resolution field emission scanning electron microscope. Also, a unique surface treatment technique developed to improve the oxidation resistance of TiAl was evaluated. The alloys included in this investigation are listed in the table. The table also shows typical alloy compositions and the specific weight changes and scale thickness measured for each alloy after exposure to 700 C for 7000 hr in air.

Thermal and Irradiation Creep Behavior of a Titanium Aluminide in Advanced Nuclear Plant Environments

NASA Astrophysics Data System (ADS)

Magnusson, Per; Chen, Jiachao; Hoffelner, Wolfgang

2009-12-01

Titanium aluminides are well-accepted elevated temperature materials. In conventional applications, their poor oxidation resistance limits the maximum operating temperature. Advanced reactors operate in nonoxidizing environments. This could enlarge the applicability of these materials to higher temperatures. The behavior of a cast gamma-alpha-2 TiAl was investigated under thermal and irradiation conditions. Irradiation creep was studied in beam using helium implantation. Dog-bone samples of dimensions 10 × 2 × 0.2 mm3 were investigated in a temperature range of 300 °C to 500 °C under irradiation, and significant creep strains were detected. At temperatures above 500 °C, thermal creep becomes the predominant mechanism. Thermal creep was investigated at temperatures up to 900 °C without irradiation with samples of the same geometry. The results are compared with other materials considered for advanced fission applications. These are a ferritic oxide-dispersion-strengthened material (PM2000) and the nickel-base superalloy IN617. A better thermal creep behavior than IN617 was found in the entire temperature range. Up to 900 °C, the expected 104 hour stress rupture properties exceeded even those of the ODS alloy. The irradiation creep performance of the titanium aluminide was comparable with the ODS steels. For IN617, no irradiation creep experiments were performed due to the expected low irradiation resistance (swelling, helium embrittlement) of nickel-base alloys.

Dynamic Fracture Initiation Toughness at Elevated Temperatures With Application to the New Generation of Titanium Aluminide Alloys. Chapter 8

NASA Technical Reports Server (NTRS)

Shazly, Mostafa; Prakash, Vikas; Draper, Susan; Shukla, Arun (Editor)

2006-01-01

Recently, a new generation of titanium aluminide alloy, named Gamma-Met PX, has been developed with better rolling and post-rolling characteristics. I'revious work on this alloy has shown the material to have higher strengths at room and elevated temperatures when compared with other gamma titanium aluminides. In particular, this new alloy has shown increased ductility at elevated temperatures under both quasi-static and high strain rate uniaxial compressive loading. However, its high strain rate tensile ductility at room and elevated temperatures is limited to approx. 1%. In the present chapter, results of a study to investigate the effects of loading rate and test temperature on the dynamic fracture initiation toughness in Gamma-Met PX are presented. Modified split Hopkinson pressure bar was used along with high-speed photography to determine the crack initiation time. Three-point bend dynamic fracture experiments were conducted at impact speeds of approx. 1 m/s and tests temperatures of up-to 1200 C. The results show that thc dynamic fracture initiation toughness decreases with increasing test temperatures beyond 600 C. Furthermore, thc effect of long time high temperature air exposure on the fracture toughness was investigated. The dynamic fracture initiation toughness was found to decrease with increasing exposure time. The reasons behind this drop are analyzed and discussed.

Insoluble Coatings for Stirling Engine Heat Pipe Condenser Surfaces

NASA Technical Reports Server (NTRS)

Dussinger, Peter M.; Lindemuth, James E.

1997-01-01

The principal objective of this Phase 2 SBIR program was to develop and demonstrate a practically insoluble coating for nickel-based superalloys for Stirling engine heat pipe applications. Specific technical objectives of the program were: (1) Determine the solubility corrosion rates for Nickel 200, Inconel 718, and Udimet 72OLI in a simulated Stirling engine heat pipe environment, (2) Develop coating processes and techniques for capillary groove and screen wick structures, (3) Evaluate the durability and solubility corrosion rates for capillary groove and screen wick structures coated with an insoluble coating in cylindrical heat pipes operating under Stirling engine conditions, and (4) Design and fabricate a coated full-scale, partial segment of the current Stirling engine heat pipe for the Stirling Space Power Convertor program. The work effort successfully demonstrated a two-step nickel aluminide coating process for groove wick structures and interior wall surfaces in contact with liquid metals; demonstrated a one-step nickel aluminide coating process for nickel screen wick structures; and developed and demonstrated a two-step aluminum-to-nickel aluminide coating process for nickel screen wick structures. In addition, the full-scale, partial segment was fabricated and the interior surfaces and wick structures were coated. The heat pipe was charged with sodium, processed, and scheduled to be life tested for up to ten years as a Phase 3 effort.

Development of high toughness, high strength aluminide-bonded carbide ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Becher, P.F.; Plucknett, K.P.; Tiegs, T.N.

1997-04-01

Cemented carbides are widely used in applications where resistance to abrasion and wear are important, particularly in combination with high strength and stiffness. In the present case, ductile aluminides have been used as a binder phase to fabricate dense carbide cermets by either sintering of mixed powders or a melt-infiltration sintering process. The choice of an aluminide binder was based on the exceptional high temperature strength and chemical stability exhibited by these alloys. For example, TiC-based composites with a Ni{sub 3}Al binder phase exhibit improved oxidation resistance, Young`s moduli > 375 GPa, high fracture strengths (> 1 GPa) that aremore » retained to {ge} 900{degrees}C, and fracture toughness values of 10 to 15 MPa{radical}m, identical to that measured in commercial cobalt-bonded WC with the same test method. The thermal diffusivity values at 200{degrees}C for these composites are {approximately} 0.070 to 0.075 cm{sup 2}/s while the thermal expansion coefficients rise with Ni3Al content from {approximately} 8 to {approximately}11 x 10{sup {minus}6}/{degrees}C over the range of 8 to 40 vol. % Ni{sub 3}Al. The oxidation and acidic corrosion resistances are quite promising as well. Finally, these materials also exhibit good electrical conductivity allowing them to be sectioned and shaped by electrical discharge machining (EDM) processes.« less

Microstructure representations for sound absorbing fibrous media: 3D and 2D multiscale modelling and experiments

NASA Astrophysics Data System (ADS)

Zieliński, Tomasz G.

2017-11-01

The paper proposes and investigates computationally-efficient microstructure representations for sound absorbing fibrous media. Three-dimensional volume elements involving non-trivial periodic arrangements of straight fibres are examined as well as simple two-dimensional cells. It has been found that a simple 2D quasi-representative cell can provide similar predictions as a volume element which is in general much more geometrically accurate for typical fibrous materials. The multiscale modelling allowed to determine the effective speeds and damping of acoustic waves propagating in such media, which brings up a discussion on the correlation between the speed, penetration range and attenuation of sound waves. Original experiments on manufactured copper-wire samples are presented and the microstructure-based calculations of acoustic absorption are compared with the corresponding experimental results. In fact, the comparison suggested the microstructure modifications leading to representations with non-uniformly distributed fibres.

The effect of scandium addition on microstructure and mechanical properties of Al–Si–Mg alloy: A multi-refinement modifier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Cong, E-mail: xucong55555@gmail.com; Xiao, Wenlong, E-mail: wlxiao@buaa.edu.cn; Hanada, Shuji

2015-12-15

Effect of scandium (Sc) additions on the microstructure, mechanical properties and fracture behavior of Al–Si–Mg casting alloy (F357) were systematically investigated. It was found that Sc addition caused a multi-refining efficiency on the microstructure of as-cast F357 alloy, including refinement of grains and secondary dendrite arm spacing (SDAS), modification of eutectic Si and harmless disposal of β-Al{sub 5}FeSi phase. Subsequent T6 heat treatment had further induced the complete spheroidization of eutectic Si and precipitation of fine secondary Al{sub 3}Sc dispersoids in the Sc modified alloys. Thus the mechanical properties, especially the ductility, were significantly enhanced by the addition of Scmore » combined with the heat treatment. The highest ultimate tensile strength, yield strength and elongation were achieved in 0.8 wt.% Sc modified F357 alloy combined with T6 heat treatment. Furthermore, fractographic examinations indicated that the ductile fracture mechanism served as a dominate role in the modified alloys due to the formation of fine, deep and uniformly distributed dimples. - Highlights: • Detailed characterization of the multi-refining microstructure of Sc modified F357 alloy was performed. • The multi-refinement was proposed to refine grain and SDAS, modify eutectic Si and β-phase. • Sc modifier combined with T6 treatment is effective in improving tensile properties. • Modification of eutectic Si in F357 alloy with Sc is consistent with the IIT mechanism.« less

Titanium Aluminide Technologies Successfully Transferred From HSR Program to RLV VentureStar Program

NASA Technical Reports Server (NTRS)

Bartolotta, Paul A.

2000-01-01

Through a cost-share contract, BFGoodrich Aerostructures group successfully fabricated three titanium aluminide (gamma TiAl) truss core structures using technologies pioneered in the High-Speed Research (HSR) program at the NASA Glenn Research Center at Lewis Field. The truss core subelement is approximately 60-cm (24-in.) long by 14-cm (5.5-in.) wide by 6-cm (2.5-in.) deep. To fabricate this subelement, BFGoodrich first obtained gamma TiAl sheets from Plansee (Austria) which produced the sheets using techniques developed collaboratively by Glenn, Pratt & Whitney, and Plansee. This new gamma TiAl production technology has significantly lowered the cost of gamma TiAl sheet (approx. 75-percent decrease) and has made the production of larger gamma TiAl sheets possible (approx. 60-percent increase).

Coatings for directional eutectics. [for corrosion and oxidation resistance

NASA Technical Reports Server (NTRS)

Felten, E. J.; Strangman, T. E.; Ulion, N. E.

1974-01-01

Eleven coating systems based on MCrAlY overlay and diffusion aluminide prototypes were evaluated to determine their capability for protecting the gamma/gamma prime-delta directionally solidified eutectic alloy (Ni-20Cb-6Cr-2.5Al) in gas turbine engine applications. Furnace oxidation and hot corrosion, Mach 0.37 burner-rig, tensile ductility, stress-rupture and thermomechanical fatigue tests were used to evaluate the coated gamma/gamma prime-delta alloy. The diffusion aluminide coatings provided adequate oxidation resistance at 1144 K (1600 F) but offered very limited protection in 114 K (1600 F) hot corrosion and 1366 K (2000 F) oxidation tests. A platinum modified NiCrAlY overlay coating exhibited excellent performance in oxidation testing and had no adverse effects upon the eutectic alloy.

Effects of Heat Treatments and Compositional Modification on Carbide Network and Matrix Microstructure in Ultrahigh Carbon Steels

NASA Astrophysics Data System (ADS)

Hecht, Matthew David

This dissertation investigates microstructure/property relations in ultrahigh carbon steel (UHCS) with the aim of improving toughness while retaining high hardness. Due to high C contents (ranging from 1 to 2 wt%), UHCS exhibit high strength, hardness, and wear resistance. Despite this, applications for UHCS are currently limited because they typically contain a continuous network of proeutectoid cementite that greatly reduces ductility and toughness. In previous research, thermomechanic processing had seen considerable success in breaking up the network. However, the processing is difficult and has thus far seen very limited industrial application. Chemical modification of the steel composition has also seen some success in network break-up, but is still not well understood. There have been relatively few fundamental studies of microstructure evolution in UHCS; studies in the literature typically focused on lower C steels (up to 1 wt% C) or on cast irons (>2.1 wt% C). Thus, this work was undertaken to gain a better understanding of microstructural changes that occur during heat treatment and/or chemical modification of UHCS with a focus on the distribution of proeutectoid cementite within the microstructure. This dissertation is composed of eight chapters. The first chapter presents an introduction to phases found in UHCS, descriptions of research materials used in each chapter, and the hypotheses and objectives guiding the work. The second chapter describes a study of the microstructure found in a 2C-4Cr UHCS before and after an industrial-scale austenitizating heat treatment that increased hardness and toughness and also produced discrete carbide particles in the matrix. The third chapter establishes and demonstrates a metric for measuring connectivity in carbide networks. The fourth chapter describes a series of heat treatments designed to investigate kinetics of spheroidization and coarsening of carbide particles and denuded zones near cementite network branches in 2C-4Cr UHCS. The fifth chapter describes an additional series of heat treatments comparing coarsening kinetics in 2C-1Cr and 2C-4Cr UHCS. Lowering the Cr content caused clustering of cementite particles near grain boundaries, in contrast to the denuded zones observed in the higher Cr UHCS. The fifth chapter details four in situ confocal laser scanning microscopy heat treatments of 2C-4Cr UHCS. The seventh chapter investigates the effects of a 2wt% Nb addition on 2C-4Cr UHCS. The eighth and final chapter summarizes the findings of all the experiments of the previous chapters and revisits the objectives and conclusions.

Chemically-modified cellulose paper as a microstructured catalytic reactor.

PubMed

Koga, Hirotaka; Kitaoka, Takuya; Isogai, Akira

2015-01-15

We discuss the successful use of chemically-modified cellulose paper as a microstructured catalytic reactor for the production of useful chemicals. The chemical modification of cellulose paper was achieved using a silane-coupling technique. Amine-modified paper was directly used as a base catalyst for the Knoevenagel condensation reaction. Methacrylate-modified paper was used for the immobilization of lipase and then in nonaqueous transesterification processes. These catalytic paper materials offer high reaction efficiencies and have excellent practical properties. We suggest that the paper-specific interconnected microstructure with pulp fiber networks provides fast mixing of the reactants and efficient transport of the reactants to the catalytically-active sites. This concept is expected to be a promising route to green and sustainable chemistry.

Crystallographic Characterization on Polycrystalline Ni-Mn-Ga Alloys with Strong Preferred Orientation.

PubMed

Li, Zongbin; Yang, Bo; Zou, Naifu; Zhang, Yudong; Esling, Claude; Gan, Weimin; Zhao, Xiang; Zuo, Liang

2017-04-27

Heusler type Ni-Mn-Ga ferromagnetic shape memory alloys can demonstrate excellent magnetic shape memory effect in single crystals. However, such effect in polycrystalline alloys is greatly weakened due to the random distribution of crystallographic orientation. Microstructure optimization and texture control are of great significance and challenge to improve the functional behaviors of polycrystalline alloys. In this paper, we summarize our recent progress on the microstructure control in polycrystalline Ni-Mn-Ga alloys in the form of bulk alloys, melt-spun ribbons and thin films, based on the detailed crystallographic characterizations through neutron diffraction, X-ray diffraction and electron backscatter diffraction. The presented results are expected to offer some guidelines for the microstructure modification and functional performance control of ferromagnetic shape memory alloys.

Measurement and Simulation of Thermal Conductivity of Hafnium-Aluminum Thermal Neutron Absorber Material

DOE PAGES

Guillen, Donna Post; Harris, William H.

2016-05-11

A metal matrix composite (MMC) material comprised of hafnium aluminide (Al3Hf) intermetallic particles in an aluminum matrix has been identified as a promising material for fast-flux irradiation testing applications. This material can filter thermal neutrons while simultaneously providing high rates of conductive cooling for experiment capsules. Our purpose is to investigate effects of Hf-Al material composition and neutron irradiation on thermophysical properties, which were measured before and after irradiation. When performing differential scanning calorimetry (DSC) on the irradiated specimens, a large exotherm corresponding to material annealment was observed. Thus, a test procedure was developed to perform DSC and laser flashmore » analysis (LFA) to obtain the specific heat and thermal diffusivity of pre- and post-annealment specimens. This paper presents the thermal properties for three states of the MMC material: (1) unirradiated, (2) as-irradiated, and (3) irradiated and annealed. Microstructure-property relationships were obtained for the thermal conductivity. These relationships are useful for designing components from this material to operate in irradiation environments. Furthermore, the ability of this material to effectively conduct heat as a function of temperature, volume fraction Al 3Hf, radiation damage and annealing is assessed using the MOOSE suite of computational tools.« less

Accessing Colony Boundary Strengthening of Fully Lamellar TiAl Alloys via Micromechanical Modeling

PubMed Central

Bargmann, Swantje

2017-01-01

In this article, we present a strategy to decouple the relative influences of colony, domain and lamella boundary strengthening in fully lamellar titanium aluminide alloys, using a physics-based crystal plasticity modeling strategy. While lamella and domain boundary strengthening can be isolated in experiments using polysynthetically twinned crystals or mircomechanical testing, colony boundary strengthening can only be investigated in specimens in which all three strengthening mechanisms act simultaneously. Thus, isolating the colony boundary strengthening Hall–Petch coefficient KC experimentally requires a sufficient number of specimens with different colony sizes λC but constant lamella thickness λL and domain size λD, difficult to produce even with sophisticated alloying techniques. The here presented crystal plasticity model enables identification of the colony boundary strengthening coefficient KC as a function of lamella thickness λL. The constitutive description is based on the model of a polysynthetically twinned crystal which is adopted to a representative volume element of a fully lamellar microstructure. In order to capture the micro yield and subsequent micro hardening in weakly oriented colonies prior to macroscopic yield, the hardening relations of the adopted model are revised and calibrated against experiments with polysynthetically twinned crystals for plastic strains up to 15%. PMID:28771218

Accessing Colony Boundary Strengthening of Fully Lamellar TiAl Alloys via Micromechanical Modeling.

PubMed

Schnabel, Jan Eike; Bargmann, Swantje

2017-08-03

In this article, we present a strategy to decouple the relative influences of colony, domain and lamella boundary strengthening in fully lamellar titanium aluminide alloys, using a physics-based crystal plasticity modeling strategy. While lamella and domain boundary strengthening can be isolated in experiments using polysynthetically twinned crystals or mircomechanical testing, colony boundary strengthening can only be investigated in specimens in which all three strengthening mechanisms act simultaneously. Thus, isolating the colony boundary strengthening Hall-Petch coefficient K C experimentally requires a sufficient number of specimens with different colony sizes λ C but constant lamella thickness λ L and domain size λ D , difficult to produce even with sophisticated alloying techniques. The here presented crystal plasticity model enables identification of the colony boundary strengthening coefficient K C as a function of lamella thickness λ L . The constitutive description is based on the model of a polysynthetically twinned crystal which is adopted to a representative volume element of a fully lamellar microstructure. In order to capture the micro yield and subsequent micro hardening in weakly oriented colonies prior to macroscopic yield, the hardening relations of the adopted model are revised and calibrated against experiments with polysynthetically twinned crystals for plastic strains up to 15%.

Evaluation of the Transient Liquid Phase (TLP) Bonding Process for Ti3Al-Based Honeycomb Core Sandwich Structure

NASA Technical Reports Server (NTRS)

Bird, R. Keith; Hoffman, Eric K.

1998-01-01

The suitability of using transient liquid phase (TLP) bonding to fabricate honeycomb core sandwich panels with Ti-14Al-21Nb (wt%) titanium aluminide (T3Al) face sheets for high-temperature hypersonic vehicle applications was evaluated. Three titanium alloy honeycomb cores and one Ti3Al alloy honeycomb core were investigated. Edgewise compression (EWC) and flatwise tension (FWT) tests on honeycomb core sandwich specimens and tensile tests of the face sheet material were conducted at temperatures ranging from room temperature to 1500 F. EWC tests indicated that the honeycomb cores and diffusion bonded joints were able to stabilize the face sheets up to and beyond the face sheet compressive yield strength for all temperatures investigated. The specimens with the T3Al honeycomb core produced the highest FWT strengths at temperatures above 1000 F. Tensile tests indicated that TLP processing conditions resulted in decreases in ductility of the Ti-14Al-21Nb face sheets. Microstructural examination showed that the side of the face sheets to which the filler metals had been applied was transformed from equiaxed alpha2 grains to coarse plates of alpha2 with intergranular Beta. Fractographic examination of the tensile specimens showed that this transformed region was dominated by brittle fracture.

Effect of CeO2 addition on the properties of FeAl based alloy produced by mechanical alloying technique

NASA Astrophysics Data System (ADS)

Khaerudini, Deni S.; Muljadi, Sardjono, P.; Tetuko, Anggito P.; Sebayang, P.; Ginting, M.

2013-09-01

Iron aluminides based on FeAl is notable for their low materials cost, ease of fabrication and good corrosion, suffixation and oxidation resistance. However, the application based on these unique properties still require the development of Fe-Al based alloy since it shows some drawbacks such as a lack of high temperature strength and low ductility. To improve the mechanical properties of FeAl based alloy, ceria (CeO2) will be added to this compound. FeAl based alloy produced by the mechanical alloying (MA) technique. The developed specimens then assessed with respect to oxidation behaviour in high temperature, scale microstructure and hardness. The surface morphologies of the alloy evaluated and observed using scanning electron microscopy (SEM) with an energy dispersive X-ray spectroscopy (EDX). The phase structures of oxide scale formed on them were identified by X-ray diffraction (XRD). The results found that the FeAl intermetallic compound containing CeO2 0.5 wt.% is less pores and CeO2 1.0 wt.% is more homogen in powder and solid form, higher hardness and increase in their resistance to oxidation behaviour in high temperature compared with another percentage of CeO2.

High temperature behavior of B2-based ruthenium aluminide systems

NASA Astrophysics Data System (ADS)

Cao, Fang

Ru-modified NiAl-based bond coats have the potential to improve the durability of Superalloy-Thermal Barrier Coating systems (TBCs) for advanced gas turbine engines. A fundamental understanding of the high temperature mechanical behavior across the Ni-Al-Ru B2 phase field can provide direction for the development of these new bond coats for TBCs. The purpose of this study has been to describe the fundamental processes of creep deformation in single phase B2 Ru-Al-Ni ternary alloys which would form the basis for the bond coats. To accomplish this, five ternary alloys with compositions located within the B2 field across the NiAl-RuAl phase region were fabricated and investigated. Special emphasis was placed on characterizing creep deformation and describing the operative creep mechanisms in these alloys. At room temperature, brittle failure was observed in the Ni-rich alloys in compression, while improved strength and ductility were displayed in two Ru-rich ternary alloys at temperatures up to 700°C. Exceptional creep strength was observed in these alloys, as compared to other high melting temperature B2 intermetallics. A continuous increase of the melting temperature and creep resistance with the increasing of the Ru/Ni ratio in these alloys was observed. Post-creep dislocation analyses identified the presence of <100> and <110> edge dislocations in the Ni-rich alloys, while uniformly distributed jogged <100> screw dislocations predominated in the Ru-rich ternary alloys. A transition of the creep mechanism from viscous glide controlled to jogged screw motion in these Ru-Al-Ni ternary B2 alloys with increasing Ru/Ni ratio is demonstrated by the characteristics of the creep deformation process, stress change creep tests, post-creep dislocation analyses, and numerical modeling. Additionally, the knowledge of the cyclic oxidation behavior of ruthenium aluminide-based alloy is essential, as many high-temperature applications for which this intermetallic might be utilized undergo repeated severe thermal cycling. Thus the second portion of this thesis focuses on the characterization of the cyclic oxidation properties of RuAl-based alloys. The cyclic oxidation behavior of six RuAl-based alloys was studied in air over the temperature range of 1000°C to 1300°C. Oxidation kinetics have been shown to be influenced by microstructure as well as the addition of platinum.

Investigation of porous asphalt microstructure using optical and electron microscopy.

PubMed

Poulikakos, L D; Partl, M N

2010-11-01

Direct observations of porous asphalt concrete samples in their natural state using optical and electron microscopy techniques led to useful information regarding the microstructure of two mixes and indicated a relationship between microstructure and in situ performance. This paper presents evidence that suboptimal microstructure can lead to premature failure thus making a first step in defining well or suboptimal performing pavements with a bottom-up approach (microstructure). Laboratory and field compaction produce different samples in terms of the microstructure. Laboratory compaction using the gyratory method has produced more microcracks in mineral aggregates after the binder had cooled. Well-performing mixes used polymer-modified binders, had a more homogeneous void structure with fewer elongated voids and better interlocking of the aggregates. Furthermore, well-performing mixes showed better distribution of the mastic and better coverage of the aggregates with bitumen. Low vacuum scanning electron microscopy showed that styrene butadiene styrene polymer modification in binder exists in the form of discontinuous globules and not continuous networks. A reduction in the polymer phase was observed as a result of aging and in-service use. © 2010 The Authors Journal compilation © 2010 The Royal Microscopical Society.

Starch: chemistry, microstructure, processing and enzymatic degradation

USDA-ARS?s Scientific Manuscript database

Starch is recognized as one of the most abundant and important commodities containing value added attributes for a vast number of industrial applications. Its chemistry, structure, property and susceptibility to various chemical, physical and enzymatic modifications offer a high technological value ...

Microstructure and tensile properties after thermohydrogen processing of Ti-6 Al-4V.

PubMed

Guitar, A; Vigna, G; Luppo, M I

2009-04-01

Thermohydrogen processing (THP), a technique in which hydrogen is used as a temporary alloying element, can refine the microstructure and improve the final mechanical properties of the Ti-6 Al-4V alloy. THP allows microstructural modification of titanium alloys near net shape such as biomaterial components obtained by powder metallurgy and castings, since it does not require mechanical working. Two THP, called THP-A and THP-B, have been evaluated in samples of Ti-6Al-4V with a coarse and lamellar microstructure typical of castings and powder metallurgy. The THP-A is based in the eutectoid decomposition of the beta(H) phase to alpha phase and hydride phase. The THP-B is based in the isothermal decomposition of alpha('') martensite phase, obtained by quenching of hydrogenated samples. The refinement of the microstructure due to THP has been evaluated by means of optical and electron microscopy. Tensile tests showed that while both processes were able to increase the strength of the alloy as compared with the starting material, the ductility in samples subjected to THP-B was severely reduced.

Microstructural characterisation of Al-Si cast alloys containing rare earth additions

NASA Astrophysics Data System (ADS)

Elgallad, E. M.; Ibrahim, M. F.; Doty, H. W.; Samuel, F. H.

2018-05-01

This paper presents a thorough study on the effect of rare earth elements, specifically La and Ce, on the microstructure characteristics of non-modified and Sr-modified A356 and A413 alloys. Several alloys were prepared by adding 1% La and 1% Ce either individually or in combination. Microstructural characterisation was carried out using optical microscopy, scanning electron microscopy and electron probe microanalysis as well as differential scanning calorimetry (DSC) analysis. The results showed that the individual and combined additions of La and Ce did not bring about any modification or even refinement in the eutectic Si structure. Moreover, these additions were found to negate the modification effect of Sr, particularly in the presence of La. The A356 and A413 alloys containing La and/or Ce displayed high phase volume fractions owing to the formation of Al-Si-La/Ce/(La,Ce) and Al-Ti-La/Ce intermetallic phases. DSC analysis revealed that the formation temperatures of these phases varied from 560 to 568 °C and 568 to 574 °C, respectively. This analysis also showed that the addition of La and Ce whether individually or in combination resulted in a depression in the eutectic temperature and a considerable increase in the solidification range, particularly for the A413 alloy.

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses.

PubMed

Miglierini, Marcel B; Procházka, Vít; Vrba, Vlastimil; Švec, Peter; Janičkovič, Dušan; Matúš, Peter

2018-06-07

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic glasses (MGs). Despite their amorphous nature, the identification of hyperfine interactions unveils faint structural modifications. For this purpose, we have employed two techniques that utilize nuclear resonance among nuclear levels of a stable 57 Fe isotope, namely Mössbauer spectrometry and nuclear forward scattering (NFS) of synchrotron radiation. The effects of heat treatment upon (Fe2.85Co1)77Mo8Cu1B14 MG are discussed using the results of ex situ and in situ experiments, respectively. As both methods are sensitive to hyperfine interactions, information on structural arrangement as well as on magnetic microstructure is readily available. Mössbauer spectrometry performed ex situ describes how the structural arrangement and magnetic microstructure appears at room temperature after the annealing under certain conditions (temperature, time), and thus this technique inspects steady states. On the other hand, NFS data are recorded in situ during dynamically changing temperature and NFS examines transient states. The use of both techniques provides complementary information. In general, they can be applied to any suitable system in which it is important to know its steady state but also transient states.

Grain boundary engineering: fatigue fracture

NASA Astrophysics Data System (ADS)

Das, Arpan

2017-04-01

Grain boundary engineering has revealed significant enhancement of material properties by modifying the populations and connectivity of different types of grain boundaries within the polycrystals. The character and connectivity of grain boundaries in polycrystalline microstructures control the corrosion and mechanical behaviour of materials. A comprehensive review of the previous researches has been carried out to understand this philosophy. Present research thoroughly explores the effect of total strain amplitude on phase transformation, fatigue fracture features, grain size, annealing twinning, different grain connectivity and grain boundary network after strain controlled low cycle fatigue deformation of austenitic stainless steel under ambient temperature. Electron backscatter diffraction technique has been used extensively to investigate the grain boundary characteristics and morphologies. The nominal variation of strain amplitude through cyclic plastic deformation is quantitatively demonstrated completely in connection with the grain boundary microstructure and fractographic features to reveal the mechanism of fatigue fracture of polycrystalline austenite. The extent of boundary modifications has been found to be a function of the number of applied loading cycles and strain amplitudes. It is also investigated that cyclic plasticity induced martensitic transformation strongly influences grain boundary characteristics and modifications of the material's microstructure/microtexture as a function of strain amplitudes. The experimental results presented here suggest a path to grain boundary engineering during fatigue fracture of austenite polycrystals.

Low cost high temperature, duplex coating for superalloys

NASA Technical Reports Server (NTRS)

Young, S. G.; Deadmore, D. L.

1981-01-01

Duplex silicon-slurry/aluminide coating substantially improves high temperature resistance to oxidation and corrosion of nickel base alloys. Coating used in critical sections of power systems like turbojet engines extends their operating capabilities.

The effect of Cr, Co, Al, Mo and Ta on a series of cast Ni-base superalloys on the stability of an aluminide coating during cyclic oxidation in Mach 0.3 burner rig

NASA Technical Reports Server (NTRS)

Zaplatynsky, I.; Barrett, C. A.

1986-01-01

The influence of varying the content of Co, Cr, Mo, Ta, and Al in a series of cast Ni-based gamma/gamma'superalloys on the behavior of aluminide coatings was studied in burner rig cyclic oxidation tests at 1100 C. The alloys had nominally fixed levels of Ti, W, Cb, Zr, C, and B. The alloy compositions were based on a full 2(sup 5)-fractional statistical design supplemented by 10 star point alloys and a center point alloy. This full central composite design of 43 alloys plus two additional alloys with extreme Al levels allowed a complete second degree estimating equation to be derived from the 5-compositional variables. The weight change/time data for the coated samples fitted well to the paralinear oxidation model and enabled a modified oxidation attack parameter, K'(sub a) to be derived to rank the alloys and log K' (sub a ) to be used as the dependent variable in the estimating equation to determine the oxidation resistance of the coating as a function of the underlying alloy content. The most protective aluminide coatings are associated with the highest possible base ally contents of CR and Al and at a 4 percent Ta level. The Mo and Co effects interact but at fixed levels of 0, 5, or 10% Co. A 4% Mo level is optimum.

Modeling of High-Strain-Rate Deformation, Fracture, and Impact Behavior of Advanced Gas Turbine Engine Materials at Low and Elevated Temperatures

NASA Technical Reports Server (NTRS)

Shazly, Mostafa; Nathenson, David; Prakash, Vikas

2003-01-01

Gamma titanium aluminides have received considerable attention over the last decade. These alloys are known to have low density, good high temperature strength retention, and good oxidation and corrosion resistance. However, poor ductility and low fracture toughness have been the key limiting factors in the full utilization of these alloys. More recently, Gamma-met PX has been developed by GKSS, Germany. These alloys have been observed to have superior strengths at elevated temperatures and quasi-static deformation rates and good oxidation resistance at elevated temperatures when compared with other gamma titanium aluminides. The present paper discusses results of a study to understand dynamic response of gamma-met PX in uniaxial compression. The experiments were conducted by using a modified split Hopkinson pressure bar between room temperature and 900 C and strain rates of up to 3500 per second. The Gamma met PX alloy showed superior strength when compared to nickel based superalloys and other gamma titanium aluminides at all test temperatures. It also showed strain and strain-rate hardening at all levels of strain rates and temperatures and without yield anomaly up to 900 C. After approximately 600 C, thermal softening is observed at all strain rates with the rate of thermal softening increasing dramatically between 800 and 900 C. However, these flow stress levels are comparatively higher in Gamma met PX than those observed for other TiAl alloys.

Microstructural modifications induced by accelerated aging and lipid absorption in remelted and annealed UHMWPEs for total hip arthroplasty

PubMed Central

Puppulin, Leonardo; Zhu, Wenliang; Sugano, Nobuhiko

2014-01-01

Three types of commercially available ultra-high molecular weight polyethylene (UHMWPE) acetabular cups currently used in total hip arthroplasty have been studied by means of Raman micro-spectroscopy to unfold the microstructural modification induced by the oxidative degradation after accelerated aging with and without lipid absorption. The three investigated materials were produced by three different manufacturing procedures, as follows: irradiation followed by remelting, one-step irradiation followed by annealing, 3-step irradiation and annealing. Clear microstructural differences were observed in terms of phase contents (i.e. amorphous, crystalline and intermediate phase fraction). The three-step annealed material showed the highest crystallinity fraction in the bulk, while the remelted polyethylene is clearly characterized by the lowest content of crystalline phase and the highest content of amorphous phase. After accelerated aging either with or without lipids, the amount of amorphous phase decreased in all the samples as a consequence of the oxidation-induced recrystallization. The most remarkable variations of phase contents were detected in the remelted and in the single-step annealed materials. The presence of lipids triggered oxidative degradation especially in the remelted polyethylene. Such experimental evidence might be explained by the highest amount of amorphous phase in which lipids can be absorbed prior to accelerated aging. The results of these spectroscopic characterizations help to rationalize the complex effect of different irradiation and post-irradiation treatments on the UHMWPE microstructure and gives useful information on how significantly any single step of the manufacturing procedures might affect the oxidative degradation of the polymer. PMID:25179830

Study of Al-Si Alloy Oxygen Saturation on Its Microstructure and Mechanical Properties.

PubMed

Finkelstein, Arkady; Schaefer, Arseny; Chikova, Оlga; Borodianskiy, Konstantin

2017-07-11

One of the main goals of modern materials research is obtaining different microstructures and studying their influence on the mechanical properties of metals; aluminum alloys are particularly of interest due to their advanced performance. Traditionally, their required properties are obtained by alloying process, modification, or physical influence during solidification. The present work describes a saturation of the overheated AlSi₇Fe₁ casting alloy by oxides using oxygen blowing approach in overheated alloy. Changes in metals' microstructural and mechanical properties are also described in the work. An Al 10 SiFe intermetallic complex compound was obtained as a preferable component to Al₂O₃ precipitation on it, and its morphology was investigated by scanning electron microscopy. The mechanical properties of the alloy after the oxygen blowing treatment are discussed in this work.

Large area ultraviolet photodetector on surface modified Si:GaN layers

NASA Astrophysics Data System (ADS)

Anitha, R.; R., Ramesh; Loganathan, R.; Vavilapalli, Durga Sankar; Baskar, K.; Singh, Shubra

2018-03-01

Unique features of semiconductor based heterostructured photoelectric devices have drawn considerable attention in the recent past. In the present work, large area UV photodetector has been fabricated utilizing interesting Zinc oxide microstructures on etched Si:GaN layers. The surface of Si:GaN layer grown by metal organic chemical vapor deposition method on sapphire has been modified by chemical etching to control the microstructure. The photodetector exhibits response to Ultraviolet light only. Optimum etching of Si:GaN was required to exhibit higher responsivity (0.96 A/W) and detectivity (∼4.87 × 109 Jones), the two important parameters for a photodetector. Present method offers a tunable functionality of photodetector through modification of top layer microstructure. A comparison with state of art materials has also been presented.

Microstructural Parameters in 8 MeV Electron-Irradiated BOMBYX MORI Silk Fibers by Wide-ANGLE X-Ray Scattering Studies (waxs)

NASA Astrophysics Data System (ADS)

Sangappa, Asha, S.; Sanjeev, Ganesh; Subramanya, G.; Parameswara, P.; Somashekar, R.

2010-01-01

The present work looks into the microstructural modification in electron irradiated Bombyx mori P31 silk fibers. The irradiation process was performed in air at room temperature using 8 MeV electron accelerator at different doses: 0, 25, 50 and 100 kGy. Irradiation of polymer is used to cross-link or degrade the desired component or to fix the polymer morphology. The changes in microstructural parameters in these natural polymer fibers have been computed using wide angle X-ray scattering (WAXS) data and employing line profile analysis (LPA) using Fourier transform technique of Warren. Exponential, Lognormal and Reinhold functions for the column length distributions have been used for the determination of crystal size, lattice strain and enthalpy parameters.

Crystallographic Characterization on Polycrystalline Ni-Mn-Ga Alloys with Strong Preferred Orientation

PubMed Central

Li, Zongbin; Yang, Bo; Zou, Naifu; Zhang, Yudong; Esling, Claude; Gan, Weimin; Zhao, Xiang; Zuo, Liang

2017-01-01

Heusler type Ni-Mn-Ga ferromagnetic shape memory alloys can demonstrate excellent magnetic shape memory effect in single crystals. However, such effect in polycrystalline alloys is greatly weakened due to the random distribution of crystallographic orientation. Microstructure optimization and texture control are of great significance and challenge to improve the functional behaviors of polycrystalline alloys. In this paper, we summarize our recent progress on the microstructure control in polycrystalline Ni-Mn-Ga alloys in the form of bulk alloys, melt-spun ribbons and thin films, based on the detailed crystallographic characterizations through neutron diffraction, X-ray diffraction and electron backscatter diffraction. The presented results are expected to offer some guidelines for the microstructure modification and functional performance control of ferromagnetic shape memory alloys. PMID:28772826

Implications of recent research on microstructure modifications, through heat-related processing and trait alteration to bio-functions, molecular thermal stability and mobility, metabolic characteristics and nutrition in cool-climate cereal grains and other types of seeds with advanced molecular techniques.

PubMed

Ying, Yuguang; Zhang, Huihua; Yu, Peiqiang

2018-02-16

The cutting-edge synchrotron radiation based and globar-sourced vibrational infrared microspectroscopy have recently been developed. These novel techniques are able to reveal structure features at cellular and molecular levels with the tested tissues being intact. However, to date, the advanced techniques are unfamiliar or unknown to food and feed scientists and have not been used to study the molecular structure changes in cool-climate cereal grain seeds and other types of bio-oil and bioenergy seeds. This article aims to provide some recent research in cool-climate cereal grains and other types of seeds on molecular structures and metabolic characteristics of carbohydrate and protein, and implication of microstructure modification through heat-related processing and trait alteration to bio-functions, molecular thermal stability and mobility, and nutrition with advanced molecular techniques- synchrotron radiation based and globar-sourced vibrational infrared microspectroscopy in the areas of (1) Inherent microstructure of cereal grain seeds; (2) The nutritional values of cereal grains; (3) Impact and modification of heat-related processing to cereal grain; (4) Conventional nutrition evaluation methodology; (5) Synchrotron radiation-based and globar-sourced vibrational (micro)-spectroscopy for molecular structure study and molecular thermal stability and mobility, and (6) Recent molecular spectroscopic technique applications in research on raw, traits altered and processed cool-climate cereal grains and other types of seeds. The information described in this article gives better insights of research progress and update in cool-climate cereal grains and other seeds with advanced molecular techniques.

YBa_2Cu_3O_{7-δ} : in pursuit of the ideal microstructure

NASA Astrophysics Data System (ADS)

Smith, D. S.; Suasmoro, S.; Lejeune, M.; Rabier, J.; Denanot, M. F.; Heintz, J. M.; Magro, C.; Bonnet, J. P.

1992-02-01

This paper examines the role of different factors in the microstructure of ceramic YBa2Cu3O{7-δ} with emphasis on its electrical response. In particular we discuss : 1. the effect of microstructural variations on j_c and ρ_{300}, 2. measurement of j_c, 3. the presence of minor phases and carbonates, 4. oxygen uptake and microcracks, 5. plastic deformation and related structural defects. Dans cet article, nous examinons d'une part la réponse électrique de céramiques supraconductrices massives de type YBa2Cu3O{7-δ} et d'autre part sa relation avec la microstructure. Nous présenterons successivement : 1. L'incidence de modifications microstructurales sur les valeurs de j_c et ρ_{300}, 2. les mesures expérimentales de j_c, 3. la présence de phases minoritaires et de carbonates, 4. la reprise d'oxygène et la microfissuration, 5. la déformation plastique et les défauts structuraux associés.

Characterization of a cold-rolled 2101 lean duplex stainless steel.

PubMed

Bassani, Paola; Breda, Marco; Brunelli, Katya; Mészáros, Istvan; Passaretti, Francesca; Zanellato, Michela; Calliari, Irene

2013-08-01

Duplex stainless steels (DSS) may be defined as a category of steels with a two-phase ferritic-austenitic microstructure, which combines good mechanical and corrosion properties. However, these steels can undergo significant microstructural modification as a consequence of either thermo-mechanical treatments (ferrite decomposition, which causes σ- and χ-phase formation and nitride precipitation) or plastic deformation at room temperature [austenite transformation into strain-induced martensite (SIM)]. These secondary phases noticeably affect the properties of DSS, and therefore are of huge industrial interest. In the present work, SIM formation was investigated in a 2101 lean DSS. The material was subjected to cold rolling at various degrees of deformation (from 10 to 80% thickness reduction) and the microstructure developed after plastic deformation was investigated by electron backscattered diffraction, X-ray diffraction measurements, and hardness and magnetic tests. It was observed that SIM formed as a consequence of deformations higher than ~20% and residual austenite was still observed at 80% of thickness reduction. Furthermore, a direct relationship was found between microstructure and magnetic properties.

Exploration of alloy surface and slurry modification to improve oxidation life of fused silicide coated niobium alloys

NASA Technical Reports Server (NTRS)

Levine, S. R.; Grisaffe, S. J.

1972-01-01

Edge and surface modifications of niobium alloys were investigated prior to coating with Si-20Cr-20Fe and slurry composition modification for performance in a 1370 C ambient pressure slow cycle test. The best coating obtained was Si-20Cr-20Mn with an average life of 63 cycles, compared to 40 for Si-20Cr-20Fe on FS-85 (100 percent improvement in weight parity life). Edge beading extended the lives of Si-20Cr-20Fe-coated Cb-752 and FS-85 to 57 and 41 cycles respectively (50 and 20 percent improvements in weight parity life respectively). W, Al2O3 and ZrO2(CaO) surface modifications altered coating crack frequency and microstructure and increased life somewhat.

Laser surface modification of AZ31B Mg alloy for bio-wettability.

PubMed

Ho, Yee-Hsien; Vora, Hitesh D; Dahotre, Narendra B

2015-02-01

Magnesium alloys are the potential degradable materials for load-bearing implant application due to their comparable mechanical properties to human bone, excellent bioactivity, and in vivo non-toxicity. However, for a successful load-bearing implant, the surface of bio-implant must allow protein absorption and layer formation under physiological environment that can assist the cell/osteoblast growth. In this regard, surface wettability of bio-implant plays a key role to dictate the quantity of protein absorption. In light of this, the main objective of the present study was to produce favorable bio-wettability condition of AZ31B Mg alloy bio-implant surface via laser surface modification technique under various laser processing conditions. In the present efforts, the influence of laser surface modification on AZ31B Mg alloy surface on resultant bio-wettability was investigated via contact-angle measurements and the co-relationships among microstructure (grain size), surface roughness, surface energy, and surface chemical composition were established. In addition, the laser surface modification technique was simulated by computational (thermal) model to facilitate the prediction of temperature and its resultant cooling/solidification rates under various laser processing conditions for correlating with their corresponding composition and phase evolution. These predicted thermal properties were later used to correlate with the corresponding microstructure, chemical composition, and phase evolution via experimental analyses (X-ray diffractometer, scanning electron microscope, energy-dispersive spectroscopy). © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Heat treatment study 2

NASA Technical Reports Server (NTRS)

Workman, Gary L.

1990-01-01

The microstructural variations in nickel based superalloys that result from modifications in processing were examined. These superalloys include MAR-M246(HF) and PWA1480. Alternate heat treatments for equiaxed as-cast specimens were studied and a sample matrix of 42 variations in the heat treatments were processed, as well as different directional solidification parameters. Variation in temperature and times for both solution and aging were performed. Photomicrographs were made of the microstructure and volume fraction analysis of primary gamma-prime and aged gamma-prime precipitates were performed. The results of the heat treatment, cooling rate, and directional solidification experiments are discussed.

Influence of different modifications of a calcium phosphate bone cement on adhesion, proliferation, and osteogenic differentiation of human bone marrow stromal cells.

PubMed

Vater, Corina; Lode, Anja; Bernhardt, Anne; Reinstorf, Antje; Heinemann, Christiane; Gelinsky, Michael

2010-03-15

Collagen and noncollagenous proteins of the extracellular bone matrix are able to stimulate bone cell activities and bone healing. The modification of calcium phosphate bone cements used as temporary bone replacement materials with these proteins seems to be a promising approach to accelerate new bone formation. In this study, we investigated adhesion, proliferation, and osteogenic differentiation of human bone marrow stromal cells (hBMSC) on Biocement D/collagen composites which have been modified with osteocalcin and O-phospho-L-serine. Modification with osteocalcin was carried out by its addition to the cement precursor before setting as well as by functionalization of the cement samples after setting and sterilization. hBMSC were cultured on these samples for 28 days with and without osteogenic supplements. We found a positive impact especially of the phosphoserine-modifications but also of both osteocalcin-modifications on differentiation of hBMSC indicated by higher expression of the osteoblastic markers matrix metalloproteinase-13 and bone sialo protein II. For hBMSC cultured on phosphoserine-containing composites, an increased proliferation has been observed. However, in case of the osteocalcin-modified samples, only osteocalcin adsorbed after setting and sterilization of the cement samples was able to promote initial adhesion and proliferation of hBMSC. The addition of osteocalcin before setting results in a finer microstructure but the biological activity of osteocalcin might be impaired due to the sterilization process. Thus, our data indicate that the initial adhesion and proliferation of hBMSC is enhanced rather by the biological activity of osteocalcin than by the finer microstructure. (c) 2009 Wiley Periodicals, Inc.

NASA's activities in the conservation of strategic aerospace materials

NASA Technical Reports Server (NTRS)

Stephens, J. R.

1980-01-01

The United States imports 50-100 percent of certain metals critical to the aerospace industry, namely, cobalt, columbium, chromium, and tantalum. In an effort to reduce this dependence on foreign sources, NASA is planning a program called Conservation of Strategic Aerospace Materials (COSAM), which will provide technology minimizing strategic metal content in the components of aerospace structures such as aircraft engines. With a proposed starting date of October 1981, the program will consist of strategic element substitution, process technology development, and alternate materials research. NASA's two-fold pre-COSAM studies center on, first, substitution research involving nickel-base and cobalt-base superalloys (Waspaloy, Udimet-700, MAE-M247, Rene 150, HA-188) used in turbine disks, low-pressure blades, turbine blades, and combustors; and, second, alternate materials research devoted initially to investigating possible structural applications of the intermetallic alloys nickel aluminide and iron aluminide.

Synthesis of advanced aluminide intermetallic coatings by low-energy Al-ion radiation

NASA Astrophysics Data System (ADS)

Shen, Mingli; Gu, Yan; Zhao, Panpan; Zhu, Shenglong; Wang, Fuhui

2016-05-01

Metals that work at high temperatures (for instance, superalloys in gas-turbines) depend on thermally grown oxide (TGO, commonly alumina) to withstand corrosion attack. Nickel Aluminide (NiAl) as one superior alumina TGO former plays an important role in protective coatings for turbine blades in gas-turbine engines used for aircraft propulsion and power generation. Lowering TGO growth rate is essentially favored for offering sustainable protection, especially in thermal barrier coatings (TBC). However, it can only be achieved currently by a strategy of adding the third element (Pt or reactive elements) into NiAl during traditional diffusion- or deposition-based synthesis of the coating. Here we present a highly flexible Al-ion radiation-based synthesis of advanced NiAl coatings, achieving low TGO growth rate without relying on the third element addition. Our results expand the strategy for lowering TGO growth rate and demonstrate potentials for ion radiation in advancing materials synthesis.

Synthesis of advanced aluminide intermetallic coatings by low-energy Al-ion radiation

PubMed Central

Shen, Mingli; Gu, Yan; Zhao, Panpan; Zhu, Shenglong; Wang, Fuhui

2016-01-01

Metals that work at high temperatures (for instance, superalloys in gas-turbines) depend on thermally grown oxide (TGO, commonly alumina) to withstand corrosion attack. Nickel Aluminide (NiAl) as one superior alumina TGO former plays an important role in protective coatings for turbine blades in gas-turbine engines used for aircraft propulsion and power generation. Lowering TGO growth rate is essentially favored for offering sustainable protection, especially in thermal barrier coatings (TBC). However, it can only be achieved currently by a strategy of adding the third element (Pt or reactive elements) into NiAl during traditional diffusion- or deposition-based synthesis of the coating. Here we present a highly flexible Al-ion radiation-based synthesis of advanced NiAl coatings, achieving low TGO growth rate without relying on the third element addition. Our results expand the strategy for lowering TGO growth rate and demonstrate potentials for ion radiation in advancing materials synthesis. PMID:27194417

Titanium Aluminide Casting Technology Development

NASA Astrophysics Data System (ADS)

Bünck, Matthias; Stoyanov, Todor; Schievenbusch, Jan; Michels, Heiner; Gußfeld, Alexander

2017-12-01

Titanium aluminide alloys have been successfully introduced into civil aircraft engine technology in recent years, and a significant order volume increase is expected in the near future. Due to its beneficial buy-to-fly ratio, investment casting bears the highest potential for cost reduction of all competing production technologies for TiAl-LPTB. However, highest mechanical properties can be achieved by TiAl forging. In view of this, Access e.V. has developed technologies for the production of TiAl investment cast parts and TiAl die cast billets for forging purposes. While these parts meet the highest requirements, establishing series production and further optimizing resource and economic efficiency are present challenges. In order to meet these goals, Access has recently been certified according to aircraft standards, aiming at qualifying parts for production on technology readiness level 6. The present work gives an overview of the phases of development and certification.

Assessment of Fatigue Resistance of Aluminide Layers on MAR 247 Nickel Super Alloy with Full-Field Optical Strain Measurements

NASA Astrophysics Data System (ADS)

Kukla, D.; Brynk, T.; Pakieła, Z.

2017-08-01

This work presents the results of fatigue tests of MAR 247 alloy flat specimens with aluminides layers of 20 or 40 µm thickness obtained in CVD process. Fatigue test was conducted at amplitude equal to half of maximum load and ranging between 300 and 650 MPa (stress asymmetry ratio R = 0, frequency f = 20 Hz). Additionally, 4 of the tests, characterized by the highest amplitude, were accompanied with non-contact strain field measurements by means of electronic speckle pattern interferometry and digital image correlation. Results of these measurements allowed to localize the areas of deformation concentration identified as the damage points of the surface layer or advanced crack presence in core material. Identification and observation of the development of deformation in localization areas allowed to assess fatigue-related phenomena in both layer and substrate materials.

Development of Improved Iron-Aluminide Filter Tubes and Elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Judkins, R.R.; Sutton, T.G.; Miller, C.J.

2008-01-14

The purpose of this Cooperative Research and Development Agreement (CRADA) was to explore and develop advanced manufacturing techniques to fabricate sintered iron-aluminide intermetallic porous bodies used for gas filtration so as to reduce production costs while maintaining or improving performance in advanced coal gasification and combustion systems. The use of a power turbine fired with coal-derived synthesis gas requires some form of gas cleaning in order to protect turbine and downstream components from degradation by erosion, corrosion, and/or deposition. Hot-gas filtration is one form of cleaning that offers the ability to remove particles from the gases produced by gasification processesmore » without having to substantially cool and, possibly, reheat them before their introduction into the turbine. This technology depends critically on materials durability and reliability, which have been the subject of study for a number of years.« less

Synthesis of advanced aluminide intermetallic coatings by low-energy Al-ion radiation.

PubMed

Shen, Mingli; Gu, Yan; Zhao, Panpan; Zhu, Shenglong; Wang, Fuhui

2016-05-19

Metals that work at high temperatures (for instance, superalloys in gas-turbines) depend on thermally grown oxide (TGO, commonly alumina) to withstand corrosion attack. Nickel Aluminide (NiAl) as one superior alumina TGO former plays an important role in protective coatings for turbine blades in gas-turbine engines used for aircraft propulsion and power generation. Lowering TGO growth rate is essentially favored for offering sustainable protection, especially in thermal barrier coatings (TBC). However, it can only be achieved currently by a strategy of adding the third element (Pt or reactive elements) into NiAl during traditional diffusion- or deposition-based synthesis of the coating. Here we present a highly flexible Al-ion radiation-based synthesis of advanced NiAl coatings, achieving low TGO growth rate without relying on the third element addition. Our results expand the strategy for lowering TGO growth rate and demonstrate potentials for ion radiation in advancing materials synthesis.

Ni{sub 3}Al technology transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sikka, V.K.; Viswanathan, S.; Santella, M.L.

1997-04-01

Ductile Ni{sub 3}Al and Ni{sub 3}Al-based alloys have been identified for a range of applications. These applications require the use of material in a variety of product forms such as sheet, plate, bar, wire, tubing, piping, and castings. Although significant progress has been made in the melting, casting, and near-net-shape forming of nickel aluminides, some issues still remain. These include the need for: (1) high-strength castable composition for many applications that have been identified; (2) castability (mold type, fluidity, hot-shortness, porosity, etc.); (3) weld reparability of castings; and (4) workability of cast or powder metallurgy product to sheet, bar, andmore » wire. The four issues listed above can be {open_quotes}show stoppers{close_quotes} for the commercial application of nickel aluminides. This report describes the work completed to address some of these issues during FY 1996.« less

Microstructure and mechanical properties of heat-resistant 12% Cr ferritic-martensitic steel EK-181 after thermomechanical treatment

NASA Astrophysics Data System (ADS)

Polekhina, N. A.; Litovchenko, I. Yu.; Tyumentsev, A. N.; Astafurova, E. G.; Chernov, V. M.; Leontyeva-Smirnova, M. V.

2015-10-01

The effect of high-temperature thermomechanical treatment (TMT) with the deformation in the austenitic region on the features of microstructure, phase transformations and mechanical properties of low-activation 12% Cr ferritic-martensitic steel EK-181 is investigated. It is established, that directly after thermomechanical treatment (without tempering) the sizes and density of V(CN) particles are comparable with those after a traditional heat treatment (air quenching and tempering at 720°C, 3 h), where these particles are formed only during tempering. It causes the increasing of the yield strength of the steel up to ≈1450 MPa at room temperature and up to ≈430 MPa at the test temperature T = 650°C. The potential of microstructure modification by this treatment aimed at improving heat resistance of steel is discussed.

Modification of the Stress-Strain Curve for High-Strength Line Pipe Steel

NASA Astrophysics Data System (ADS)

Jonsson, Katherine

2013-01-01

This thesis presents work performed to improve the work hardening behaviour of an X80 microalloyed steel through various Interrupted Thermal Treatments (ITT). The aim of this work was to determine the relationships between thermal history, microstructure and mechanical properties through both qualitative and quantitative measures. Prior to the ITT experiments, a continuous cooling transformation (CCT) diagram was constructed under no-strain conditions to identify the transformation temperatures and products that are achievable in X80 steel. The thermal treatments were applied using a Gleeble thermal-mechanical simulator to generate a variety of microstructures in various fractions and morphologies. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate and quantify the microstructures in terms of phase fraction and grain size. The ITT experiments successfully generated microstructures comprised of ferrite, bainitic ferrite, martensite and martensite-austenite (M-A) without the addition of strain. The effect of cooling rates, interrupt temperature, re-heat temperature and hold times were investigated and the mechanical performance was correlated with the quantified microstructures. Although the ITT experiments did not improve the strength relative to a continuously cooled sample, the work hardening coefficient was increased as a result of the interrupted thermal treatments.

Drug loading optimization and extended drug delivery of corticoids from pHEMA based soft contact lenses hydrogels via chemical and microstructural modifications.

PubMed

García-Millán, Eva; Koprivnik, Sandra; Otero-Espinar, Francisco Javier

2015-06-20

This paper proposes an approach to improve drug loading capacity and release properties of poly(2-hydroxyethyl methacrylate) (p(HEMA)) soft contact lenses based on the optimization of the hydrogel composition and microstructural modifications using water during the polymerization process. P(HEMA) based soft contact lenses were prepared by thermal or photopolymerization of 2-hydroxyethyl methacrylate (HEMA) solutions containing ethylene glycol di-methacrylate as crosslinker and different proportions of N-vinyl-2-pyrrolidone (NVP) or methacrylic acid (MA) as co-monomers. Transmittance, water uptake, swelling, microstructure, drug absorption isotherms and in vitro release were characterized using triamcinolone acetonide (TA) as model drug. Best drug loading ratios were obtained with lenses containing the highest amount (200 mM) of MA. Incorporation of 40% V/V of water during the polymerization increases the hydrogel porosity giving a better drug loading capacity. In vitro TA release kinetics shows that MA hydrogels released the drug significantly faster than NVP-hydrogels. Drug release was found to be diffusion controlled and kinetics was shown to be reproducible after consecutive drug loading/release processes. Results of p(HEMA) based soft contact lenses copolymerized with ethylene glycol dimethacrylate (EGDMA) and different co-monomers could be a good alternative to optimize the loading and ocular drug delivery of this corticosteroid drug. Copyright © 2015. Published by Elsevier B.V.

Plasma Electrolytic Oxidation of Titanium Implant Surfaces: Microgroove-Structures Improve Cellular Adhesion and Viability.

PubMed

Hartjen, Philip; Hoffmann, Alexia; Henningsen, Anders; Barbeck, Mike; Kopp, Alexander; Kluwe, Lan; Precht, Clarissa; Quatela, Olivia; Gaudin, Robert; Heiland, Max; Friedrich, Reinhard E; Knipfer, Christian; Grubeanu, Daniel; Smeets, Ralf; Jung, Ole

2018-01-01

Plasma electrolytic oxidation (PEO) is an established electrochemical treatment technique that can be used for surface modifications of metal implants. In this study we to treated titanium implants with PEO, to examine the resulting microstructure and to characterize adhesion and viability of cells on the treated surfaces. Our aim was to identify an optimal surface-modification for titanium implants in order to improve soft-tissue integration. Three surface-variants were generated on titanium alloy Ti6Al4V by PEO-treatment. The elemental composition and the microstructures of the surfaces were characterized using energy dispersive X-ray spectroscopy, scanning electron microscopy and profilometry. In vitro cytocompatibility of the surfaces was assessed by seeding L929 fibroblasts onto them and measuring the adhesion, viability and cytotoxicity of cells by means of live/dead staining, XTT assay and LDH assay. Electron microscopy and profilometry revealed that the PEO-surface variants differed largely in microstructure/topography, porosity and roughness from the untreated control material as well as from one another. Roughness was generally increased after PEO-treatment. In vitro, PEO-treatment led to improved cellular adhesion and viability of cells accompanied by decreased cytotoxicity. PEO-treatment provides a promising strategy to improve the integration of titanium implants with surrounding tissues. Copyright© 2018, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.

AFWAL FY80 Technical Accomplishments Report.

DTIC Science & Technology

1981-12-01

through cooperative effort of the Materials and Certain compositions in the titanium aluminide Propulsion Laboratories. In addition to an extensive system...Bonded Structures Technology Transitioned .................................................. 43 Superplastically Formed and Diffusion Bonded Titanium ...Technology ................................................................................................. 75 First RSR Radial Wafer Blade Engine Test

The influence of chromium on structure and mechanical properties of B2 nickel aluminide alloys. Ph.D. Thesis - Florida Univ., 1991 Final Report

NASA Technical Reports Server (NTRS)

Cotton, James Dean

1992-01-01

Major obstacles to the use of NiAl-based alloys and composites are low ductility and toughness. These shortcomings result in part from a lack of sufficient slip systems to accommodate plastic deformation of polycrystalline material (von Mises Criterion). It has been reported that minor additions of chromium to polycrystalline NiAl cause the predominant slip system to shift from the usual. If true, then a major step toward increasing ductility in this compound may be realized. The purpose of the present study was to verify this phenomenon, characterize it with respect to chromium level and Ni to Al ratio, and correlate any change in slip system with microstructure and mechanical properties. Compression and tensile specimens were prepared from alloys containing 0 to 5 percent chromium and 45 to 55 percent aluminum. Following about one percent strain, transmission electron microscopy foils were produced and the slip systems determined using the g x b = 0 invisibility criterion. Contrary to previous results, chromium was found to have no effect on the preferred slip system of any of the alloys studied. Possible reasons for the inconsistency of the current results with previous work are considered. Composition-structure-property relationships are discerned for the alloys, and good correlation are demonstrated in terms of conventional strengthening models for metallic systems.

Laser Cladding of γ-TiAl Intermetallic Alloy on Titanium Alloy Substrates

NASA Astrophysics Data System (ADS)

Maliutina, Iuliia Nikolaevna; Si-Mohand, Hocine; Piolet, Romain; Missemer, Florent; Popelyukh, Albert Igorevich; Belousova, Natalya Sergeevna; Bertrand, Philippe

2016-01-01

The enhancement of titanium and titanium alloy's tribological properties is of major interest in many applications such as the aerospace and automotive industry. Therefore, the current research paper investigates the laser cladding of Ti48Al2Cr2Nb powder onto Ti6242 titanium alloy substrates. The work was carried out in two steps. First, the optimal deposition parameters were defined using the so-called "combined parameters," i.e., the specific energy E specific and powder density G. Thus, the results show that those combined parameters have a significant influence on the geometry, microstructure, and microhardness of titanium aluminide-formed tracks. Then, the formation of dense, homogeneous, and defect-free coatings based on optimal parameters has been investigated. Optical and scanning electron microscopy techniques as well as energy-dispersive spectroscopy and X-ray diffraction analyses have shown that a duplex structure consisting of γ-TiAl and α 2-Ti3Al phases was obtained in the coatings during laser cladding. Moreover, it was shown that produced coatings exhibit higher values of microhardness (477 ± 9 Hv0.3) and wear resistance (average friction coefficient is 0.31 and volume of worn material is 5 mm3 after 400 m) compared to those obtained with bare titanium alloy substrates (353 Hv0.3, average friction coefficient is 0.57 and a volume of worn material after 400 m is 35 mm3).

Evolution of the microstructure of unmodified and polymer modified asphalt binders with aging in an accelerated weathering tester.

PubMed

Menapace, Ilaria; Masad, Eyad

2016-09-01

This paper presents findings on the evolution of the surface microstructure of two asphalt binders, one unmodified and one polymer modified, directly exposed to aging agents with increasing durations. The aging is performed using an accelerated weathering tester, where ultraviolet radiation, oxygen and an increased temperature are applied to the asphalt binder surface. Ultraviolet and dark cycles, which simulated the succession of day and night, alternated during the aging process, and also the temperature varied, which corresponded to typical summer day and night temperatures registered in the state of Qatar. Direct aging of an exposed binder surface is more effective in showing microstructural modifications than previously applied protocols, which involved the heat treatment of binders previously aged with standardized methods. With the new protocol, any molecular rearrangements in the binder surface after aging induced by the heat treatment is prevented. Optical photos show the rippling and degradation of the binder surface due to aging. Microstructure images obtained by means of atomic force microscopy show gradual alteration of the surface due to aging. The original relatively flat microstructure was substituted with a profoundly different microstructure, which significantly protrudes from the surface, and is characterized by various shapes, such as rods, round structures and finally 'flower' or 'leaf' structures. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

Microstructural characterization and hardness properties of electric resistance welding titanium joints for dental applications.

PubMed

Ceschini, Lorella; Boromei, Iuri; Morri, Alessandro; Nardi, Diego; Sighinolfi, Gianluca; Degidi, Marco

2015-06-01

The electric resistance welding procedure is used to join a titanium bar with specific implant abutments in order to produce a framework directly in the oral cavity of the patient. This investigation studied the effects of the welding process on microstructure and hardness properties of commercially pure (CP2 and CP4) Ti components. Different welding powers and cooling procedures were applied to bars and abutments, normally used to produce the framework, in order to simulate the clinical intraoral welding procedure. The analyses highlighted that the joining process did not induce appreciable changes in the geometry of the abutments. However, because of unavoidable microstructural modifications in the welded zones, the hardness decreased to values lower than those of the unwelded CP2 and CP4 Ti grades, irrespective of the welding environments and parameters. © IMechE 2015.

Secondary-Phase Stochastics in Lithium-Ion Battery Electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mistry, Aashutosh N.; Smith, Kandler; Mukherjee, Partha P.

Lithium-ion battery electrodes exhibit complex interplay among multiple electrochemically coupled transport processes, which rely on the underlying functionality and relative arrangement of different constituent phases. The electrochemically inactive solid phases (e.g., conductive additive and binder, referred to as the secondary phase), while beneficial for improved electronic conductivity and mechanical integrity, may partially block the electrochemically active sites and introduce additional transport resistances in the pore (electrolyte) phase. In this work, the role of mesoscale interactions and inherent stochasticity in porous electrodes is elucidated in the context of short-range (interface) and long-range (transport) characteristics. The electrode microstructure significantly affects kinetically andmore » transport-limiting scenarios and thereby the cell performance. The secondary-phase morphology is also found to strongly influence the microstructure-transport-kinetics interactions. Apropos, strategies have been proposed for performance improvement via electrode microstructural modifications.« less

Secondary-Phase Stochastics in Lithium-Ion Battery Electrodes

DOE PAGES

Mistry, Aashutosh N.; Smith, Kandler; Mukherjee, Partha P.

2018-01-12

Lithium-ion battery electrodes exhibit complex interplay among multiple electrochemically coupled transport processes, which rely on the underlying functionality and relative arrangement of different constituent phases. The electrochemically inactive solid phases (e.g., conductive additive and binder, referred to as the secondary phase), while beneficial for improved electronic conductivity and mechanical integrity, may partially block the electrochemically active sites and introduce additional transport resistances in the pore (electrolyte) phase. In this work, the role of mesoscale interactions and inherent stochasticity in porous electrodes is elucidated in the context of short-range (interface) and long-range (transport) characteristics. The electrode microstructure significantly affects kinetically andmore » transport-limiting scenarios and thereby the cell performance. The secondary-phase morphology is also found to strongly influence the microstructure-transport-kinetics interactions. Apropos, strategies have been proposed for performance improvement via electrode microstructural modifications.« less

Water transport mechanism through open capillaries analyzed by direct surface modifications on biological surfaces

NASA Astrophysics Data System (ADS)

Ishii, Daisuke; Horiguchi, Hiroko; Hirai, Yuji; Yabu, Hiroshi; Matsuo, Yasutaka; Ijiro, Kuniharu; Tsujii, Kaoru; Shimozawa, Tateo; Hariyama, Takahiko; Shimomura, Masatsugu

2013-10-01

Some small animals only use water transport mechanisms passively driven by surface energies. However, little is known about passive water transport mechanisms because it is difficult to measure the wettability of microstructures in small areas and determine the chemistry of biological surfaces. Herein, we developed to directly analyse the structural effects of wettability of chemically modified biological surfaces by using a nanoliter volume water droplet and a hi-speed video system. The wharf roach Ligia exotica transports water only by using open capillaries in its legs containing hair- and paddle-like microstructures. The structural effects of legs chemically modified with a self-assembled monolayer were analysed, so that the wharf roach has a smart water transport system passively driven by differences of wettability between the microstructures. We anticipate that this passive water transport mechanism may inspire novel biomimetic fluid manipulations with or without a gravitational field.

Superhydrophobic surfaces fabricated by femtosecond laser with tunable water adhesion: from lotus leaf to rose petal.

PubMed

Long, Jiangyou; Fan, Peixun; Gong, Dingwei; Jiang, Dafa; Zhang, Hongjun; Li, Lin; Zhong, Minlin

2015-05-13

Superhydrophobic surfaces with tunable water adhesion have attracted much interest in fundamental research and practical applications. In this paper, we used a simple method to fabricate superhydrophobic surfaces with tunable water adhesion. Periodic microstructures with different topographies were fabricated on copper surface via femtosecond (fs) laser irradiation. The topography of these microstructures can be controlled by simply changing the scanning speed of the laser beam. After surface chemical modification, these as-prepared surfaces showed superhydrophobicity combined with different adhesion to water. Surfaces with deep microstructures showed self-cleaning properties with extremely low water adhesion, and the water adhesion increased when the surface microstructures became flat. The changes in surface water adhesion are attributed to the transition from Cassie state to Wenzel state. We also demonstrated that these superhydrophobic surfaces with different adhesion can be used for transferring small water droplets without any loss. We demonstrate that our approach provides a novel but simple way to tune the surface adhesion of superhydrophobic metallic surfaces for good potential applications in related areas.

Microstructure and fracture in SiC whisker reinforced 2124 aluminum composite

NASA Technical Reports Server (NTRS)

Nieh, T. G.; Raninen, R. A.; Chellman, D. J.

1985-01-01

The microstructures of extruded and hot-rolled 2124 Al-15 percent (by weight) SiC whisker composites have been investigated, experimentally. Among the specific factors studied were: the strength of the whisker-matrix interfaces; (2) the presence of oxides; (3) the presence of defective whiskers; (4) and the presence of distribution of intermetallic compounds, impurities in the SiC(w) powder, and microstructural inhomogeneities. Modifications in the microstructure of the SiC/AL composites due to hot rolling and extrusion are illustrated in a series of microphotographs. It was found that hot rolling along the axis of extrusion was associated with some types of whisker damage, while the whiskers still retain their original orientation. Hot-rolling perpendicular to the axis of extrusion, however, tended to rotate the whiskers and produced a nearly isotropic material. Whisker free zones were virtually eliminated or reduced in size by hot rolling. In situ Auger fractography of the composite showed that the interfacial bonding between the SiC and the Al matrix was good and that Al2O2 had no significant influence on the fracture mechanics of the composite.

Simulations of Precipitate Microstructure Evolution during Heat Treatment

NASA Astrophysics Data System (ADS)

Wu, Kaisheng; Sterner, Gustaf; Chen, Qing; Jou, Herng-Jeng; Jeppsson, Johan; Bratberg, Johan; Engström, Anders; Mason, Paul

Precipitation, a major solid state phase transformation during heat treatment processes, has for more than one century been intensively employed to improve the strength and toughness of various high performance alloys. Recently, sophisticated precipitation reaction models, in assistance with well-developed CALPHAD databases, provide an efficient and cost-effective way to tailor precipitate microstructures that maximize the strengthening effect via the optimization of alloy chemistries and heat treatment schedules. In this presentation, we focus on simulating precipitate microstructure evolution in Nickel-base superalloys under arbitrary heat treatment conditions. The newly-developed TC-PRISMA program has been used for these simulations, with models refined especially for non-isothermal conditions. The effect of different cooling profiles on the formation of multimodal microstructures has been thoroughly examined in order to understand the underlying thermodynamics and kinetics. Meanwhile, validations against several experimental results have been carried out. Practical issues that are critical to the accuracy and applicability of the current simulations, such as modifications that overcome mean-field approximations, compatibility between CALPHAD databases, selection of key parameters (particularly interfacial energy and nucleation site densities), etc., are also addressed.

Gums induced microstructure stability in Ca(II)-alginate beads containing lactase analyzed by SAXS.

PubMed

Traffano-Schiffo, Maria Victoria; Castro-Giraldez, Marta; Fito, Pedro J; Perullini, Mercedes; Santagapita, Patricio R

2018-01-01

Previous works show that the addition of trehalose and gums in β-galactosidase (lactase) Ca(II)-alginate encapsulation systems improved its intrinsic stability against freezing and dehydration processes in the pristine state. However, there is no available information on the evolution in microstructure due to the constraints imposed by the operational conditions. The aim of this research is to study the time course of microstructural changes of Ca(II)-alginate matrices driven by the presence of trehalose, arabic and guar gums as excipients and to discuss how these changes influence the diffusional transport (assessed by LF-NMR) and the enzymatic activity of the encapsulated lactase. The structural modifications at different scales were assessed by SAXS. The incorporation of gums as second excipients induces a significant stabilization in the microstructure not only at the rod scale, but also in the characteristic size and density of alginate dimers (basic units of construction of rods) and the degree of interconnection of rods at a larger scale, improving the performance in terms of lactase activity. Copyright © 2017 Elsevier Ltd. All rights reserved.

He implantation induced microstructure- and hardness-modification of the intermetallic γ-TiAl

NASA Astrophysics Data System (ADS)

Pouchon, Manuel A.; Chen, Jiachao; Hoffelner, Wolfgang

2009-05-01

TiAl is a well known high temperature material with good creep properties. It is investigated as a potential structural material for Generation IV high temperature gas cooled nuclear reactors. The tests are performed with the ABB-2 (Ti-rich TiAl with 2 at.% W) developed by ASEA Brown Boveri Ltd. (ABB). Thin samples are irradiated throughout with 24 MeV 4He2+ ions; the irradiated material is then investigated towards its microstructure and its hardness. The microstructure is studied by transmission electron microscopy and the hardness is investigated using a micro-hardness tester and a nano-indenter. Different effects can be identified. From room to moderate irradiation temperatures, the radiation induced hardening of the material slowly vanishes until the material completely recovers at about 943 K. Beyond this temperature, He-bubble formation seems to harden the material again, until beyond 1200 K a steep increase in hardening is detected. This effect can be correlated with bubbles being identified in the micrographs. The results are consistent and give strong indications to a microstructural development as a function of temperature.

MANTECH Project Book

DTIC Science & Technology

1991-01-01

degrade due to thermal cyclingmultiple repairs, and/or corrosion. Depending on the service history and alloy, reduced properties result from carbide U...subsystem 91 titanitun alloys 85 cleanliness gas turbine engines 85 titani •-n aluminide 81 tolerance control 92 tool breaqkage 95 tool fracture 95 tools

From atactic to isotactic CO/p-methylstyrene copolymer by proper modification of Pd(II) catalysts bearing achiral alpha-diimines.

PubMed

Binotti, Barbara; Carfagna, Carla; Zuccaccia, Cristiano; Macchioni, Alceo

2005-01-07

Cationic Pd(II) complexes modified with achiral C(2v)-symmetric alpha-diimine ligands allow preparation of atactic or isotactic stereoblock CO/p-methylstyrene copolymers; both catalyst activity and polyketone microstructure depend on the choice of alpha-diimine substituents and counterion.

A coating of silane modified silica nanoparticles on PET substrate film for inkjet printing

NASA Astrophysics Data System (ADS)

Wu, J.; Liu, L.; Jiang, B.; Hu, Z.; Wang, X. Q.; Huang, Y. D.; Lin, D. R.; Zhang, Q. H.

2012-04-01

The paper aims to design nanoporous coatings for inkjet printing and study its microstructure influence on the ink absorption. In the present work, two inkjet materials were prepared: one with unmodified nano-SiO2 (S_1), the other with silica coupling agent modified nano-SiO2 (S_2). The surface characteristic changing after modification was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM). Wetting with contact angles was determined by the dynamic contact angle analysis test (DCAT). Through measurements, the dispersion of modified nano-SiO2 particles in the coating was superior to the dispersion of unmodified nano-SiO2 particles, surface roughness value (Ra) of S_1 was significantly higher than that of S_2, dynamic contact angle of S_2 is smaller than that of S_1 and ink droplet absorption in S_2 was much faster than in S_1. These results also reveal that the modification method is effective and offers a potential way to fabricate inkjet material with the advantages of microstructure and ink absorption over traditional methods.

Using of material-technological modelling for designing production of closed die forgings

NASA Astrophysics Data System (ADS)

Ibrahim, K.; Vorel, I.; Jeníček, Š.; Káňa, J.; Aišman, D.; Kotěšovec, V.

2017-02-01

Production of forgings is a complex and demanding process which consists of a number of forging operations and, in many cases, includes post-forge heat treatment. An optimized manufacturing line is a prerequisite for obtaining prime-quality products which in turn are essential to profitable operation of a forging company. Problems may, however, arise from modifications to the manufacturing route due to changing customer needs. As a result, the production may have to be suspended temporarily to enable changeover and optimization. Using material-technological modelling, the required modifications can be tested and optimized under laboratory conditions outside the plant without disrupting the production. Thanks to material-technological modelling, the process parameters can be varied rapidly in response to changes in market requirements. Outcomes of the modelling runs include optimum parameters for the forging part’s manufacturing route, values of mechanical properties, and results of microstructure analysis. This article describes the use of material-technological modelling for exploring the impact of the amount of deformation and the rate of cooling of a particular forged part from the finish-forging temperature on its microstructure and related mechanical properties.

Corrosion Behavior of Heat-Treated AlSi10Mg Manufactured by Laser Powder Bed Fusion.

PubMed

Cabrini, Marina; Calignano, Flaviana; Fino, Paolo; Lorenzi, Sergio; Lorusso, Massimo; Manfredi, Diego; Testa, Cristian; Pastore, Tommaso

2018-06-21

This experimental work is aimed at studying the effect of microstructural modifications induced by post-processing heat treatments on the corrosion behavior of silicon-aluminum alloys produced by means of laser powder bed fusion (LPBF). The manufacturing technique leads to microstructures characterized by the presence of melt pools, which are quite different compared to casting alloys. In this study, the behavior of an AlSi10Mg alloy was evaluated by means of intergranular corrosion tests according to ISO 11846 standard on heat-treated samples ranging from 200 to 500 °C as well as on untreated samples. We found that temperatures above 200 °C reduced microhardness of the alloy, and different corrosion morphologies occurred due to the modification of both size and distribution of silicon precipitates. Selective penetrating attacks occurred at melt pool borders. The intergranular corrosion phenomena were less intense for as-produced specimens without heat treatments compared to the heat-treated specimens at 200 and 300 °C. General corrosion morphologies were noticed for specimens heat treated at temperatures exceeding 400 °C.

A Printing-Centric Approach to the Electrostatic Modification of Polymer/Clay Composites for use in 3D Direct-Ink Writing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rauzan, Brittany; Lehman, Sean; McCracken, Josell

Polymer/clay composite inks are exceptionally useful materials for fabrication processes based on 3D direct-ink writing, however, there remains an insufficient understanding of how their physiochemical dynamics impact printability. Using a model system, N-isopropylacrylamide/Laponite, the electrostatic interactions between Laponite platelets are modified to tune critical rheological properties in order to improve printability. Rheological measurements and X-ray scattering experiments are carried out to monitor the nano/micro-structural dynamics and complex physicochemical interactions of Laponite as it impacts complex modulus in the linear region, flow behavior, thixotropy, and yield stress of the composite ink. Modification of the electrostatic interactions between platelets reduces the yieldmore » stress of the material, while maintaining a complex microstructure that allows for sufficient recovery times upon removal of stress to form stable, and thus printable, filaments. A printing-centric approach is established based on a fundamental understanding of electrostatic inter-particle interactions, harnessing the innate microstructure of Laponite in 3D direct-ink writing of composites.« less

Development of Advanced Coatings for Laser Modifications Through Process and Materials Simulation

NASA Astrophysics Data System (ADS)

Martukanitz, R. P.; Babu, S. S.

2004-06-01

A simulation-based system is currently being constructed to aid in the development of advanced coating systems for laser cladding and surface alloying. The system employs loosely coupled material and process models that allow rapid determination of material compatibility over a wide range of processing conditions. The primary emphasis is on the development and identification of composite coatings for improved wear and corrosion resistance. The material model utilizes computational thermodynamics and kinetic analysis to establish phase stability and extent of diffusional reactions that may result from the thermal response of the material during virtual processing. The process model is used to develop accurate thermal histories associated with the laser surface modification process and provides critical input for the non-isothermal materials simulations. These techniques were utilized to design a laser surface modification experiment that utilized the addition of stainless steel alloy 431 and TiC produced using argon and argon and nitrogen shielding. The deposits representing alloy 431 and TiC powder produced in argon resulted in microstructures retaining some TiC particles and an increase in hardness when compared to deposits produced using only the 431 powder. Laser deposits representing alloy 431 and TiC powder produced with a mixture of argon and nitrogen shielding gas resulted in microstructures retaining some TiC particles, as well as fine precipitates of Ti(CN) formed during cooling and a further increase in hardness of the deposit.

Plasma electrolytic oxidation of Titanium Aluminides

NASA Astrophysics Data System (ADS)

Morgenstern, R.; Sieber, M.; Grund, T.; Lampke, T.; Wielage, B.

2016-03-01

Due to their outstanding specific mechanical and high-temperature properties, titanium aluminides exhibit a high potential for lightweight components exposed to high temperatures. However, their application is limited through their low wear resistance and the increasing high-temperature oxidation starting from about 750 °C. By the use of oxide ceramic coatings, these constraints can be set aside and the possible applications of titanium aluminides can be extended. The plasma electrolytic oxidation (PEO) represents a process for the generation of oxide ceramic conversion coatings with high thickness. The current work aims at the clarification of different electrolyte components’ influences on the oxide layer evolution on alloy TNM-B1 (Ti43.5Al4Nb1Mo0.1B) and the creation of compact and wear resistant coatings. Model experiments were applied using a ramp-wise increase of the anodic potential in order to show the influence of electrolyte components on the discharge initiation and the early stage of the oxide layer growth. The production of PEO layers with technically relevant thicknesses close to 100 μm was conducted in alkaline electrolytes with varying amounts of Na2SiO3·5H2O and K4P2O7 under symmetrically pulsed current conditions. Coating properties were evaluated with regard to morphology, chemical composition, hardness and wear resistance. The addition of phosphates and silicates leads to an increasing substrate passivation and the growth of compact oxide layers with higher thicknesses. Optimal electrolyte compositions for maximum coating hardness and thickness were identified by statistical analysis. Under these conditions, a homogeneous inner layer with low porosity can be achieved. The frictional wear behavior of the compact coating layer is superior to a hard anodized layer on aluminum.

The effect of aluminium on the creep behavior of titanium aluminide alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nandy, T.K.; Mishra, R.S.; Gogia, A.K.

Small increases in the Al content of Ti{sub 3}Al-Nb alloys are known to improve creep resistance at the expense of the room temperature ductility. Though considerable work has been done on the creep behavior of titanium aluminide alloys, a systematic investigation involving the role of Al on the creep of aluminides is lacking. In the present study the authors have therefore carried out a complete investigation on stress and temperature effects on two alloys with differing Al contents, Ti-24Al-15Nb and Ti-26Al-15Nb (nominal composition in at%) in order to understand the effect of Al in terms of power law creep behavior.more » The following conclusions are made: (1) A strong Al effect on the creep resistance of O phase alloys in the Ti-Al-Nb systems has been confirmed, through a study of stress and temperature effects on the creep behavior of the Ti-24Al-15Nb and the Ti-26Al-15Nb compositions. (2) It has been shown, however, that the small differences in Al do not affect either the activation energies for creep ({approximately}370 kJ/mole) or the creep mechanism (climb controlled creep with a stress exponent of 4). The activation energies and stress exponents are similar to that observed in single phase O alloys. (3) It is suggested that Al influences creep strength through an intrinsic effect on the pre-exponential term AD{sub o} in the power law creep equation. It is possible that this effect is related to a higher ordering energy of the O phase with increasing Al content.« less

Influence of Sc on microstructure and mechanical properties of Al-Si-Mg-Cu-Zr alloy

NASA Astrophysics Data System (ADS)

Li, Yukun; Du, Xiaodong; Zhang, Ya; Zhang, Zhen; Fu, Junwei; Zhou, Shi'ang; Wu, Yucheng

2018-02-01

In the present study, the effects of Mg, Cu, Sc and Zr combined additions on the microstructure and mechanical properties of hypoeutectic Al-Si cast alloy were systematically investigated. Characterization techniques such as optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), electron back-scatter diffraction (EBSD), atomic force microscopy (AFM), transmission electron microscope (TEM), Brinell hardness tester and universal testing machine were employed to analyze the microstructure and mechanical properties. The results showed that Sc served as modifier on the microstructure of Al-3Si-0.45Mg-0.45Cu-0.2Zr alloys, including modification of eutectic Si and grains. Extraordinarily, grain refinement was found to be related to the primary particles, which exhibited a close orientation to matrix. After T6 heat treatment, the grain structures were composed of nano-scaled secondary Al3(Sc, Zr) precipitates and spherical eutectic Si. Combined with T6 heat treatment, the highest hardness, yield strength, ultimate tensile strength and elongation were achieved in 0.56 wt.% Sc-modified alloy. Interestingly, the strength and ductility had a similar tendency. This paper demonstrated that combined additions of Mg, Cu, Sc and Zr could significantly improve the microstructure and performance of the hypoeutectic Al-Si cast alloy.

Investigation of the Use of Laser Shock Peening for Enhancing Fatigue and Stress Corrosion Cracking Resistance of Nuclear Energy Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasudevan, Vijay K.; Jackson, John; Teysseyre, Sebastien

The objective of this project, which includes close collaboration with scientists from INL and ANL, is to investigate and demonstrate the use of advanced mechanical surface treatments like laser shock peening (LSP) and ultrasonic nanocrystal surface modification (UNSM) and establish baseline parameters for enhancing the fatigue properties and SCC resistance of nuclear materials like nickel-based alloy 600 and 304 stainless steel. The research program includes the following key elements/tasks: 1) Procurement of Alloy 600 and 304 SS, heat treatment studies; 2) LSP and UNSM processing of base metal and welds/HAZ of alloys 600 and 304; (3) measurement and mapping ofmore » surface and sub-surface residual strains/stresses and microstructural changes as a function of process parameters using novel methods; (4) determination of thermal relaxation of residual stresses (macro and micro) and microstructure evolution with time at high temperatures typical of service conditions and modeling of the kinetics of relaxation; (5) evaluation of the effects of residual stress, near surface microstructure and temperature on SCC and fatigue resistance and associated microstructural mechanisms; and (6) studies of the effects of bulk and surface grain boundary engineering on improvements in the SCC resistance and associated microstructural and cracking mechanisms« less

Thermal Microstructural Stability of AZ31 Magnesium after Severe Plastic Deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Young, John P.; Askari, Hesam A.; Hovanski, Yuri

2015-03-01

Both equal channel angular pressing and friction stir processing have the ability to refine the grain size of twin roll cast AZ31 magnesium and potentially improve its superplastic properties. This work used isochronal and isothermal heat treatments to investigate the microstructural stability of twin roll cast, equal channel angular pressed and friction stir processed AZ31 magnesium. For both heat treatment conditions, it was found that the twin roll casted and equal channel angular pressed materials were more stable than the friction stir processed material. Calculations of the grain growth kinetics showed that severe plastic deformation processing decreased the activation energymore » for grain boundary motion with the equal channel angular pressed material having the greatest Q value of the severely plastically deformed materials and that increasing the tool travel speed of the friction stir processed material improved microstructural stability. The Hollomon-Jaffe parameter was found to be an accurate means of identifying the annealing conditions that will result in substantial grain growth and loss of potential superplastic properties in the severely plastically deformed materials. In addition, Humphreys’s model of cellular microstructural stability accurately predicted the relative microstructural stability of the severely plastically deformed materials and with some modification, closely predicted the maximum grain size ratio achieved by the severely plastically deformed materials.« less

Laser hardening techniques on steam turbine blade and application

NASA Astrophysics Data System (ADS)

Yao, Jianhua; Zhang, Qunli; Kong, Fanzhi; Ding, Qingming

Different laser surface hardening techniques, such as laser alloying and laser solution strengthening were adopted to perform modification treatment on the local region of inset edge for 2Cr13 and 17-4PH steam turbine blades to prolong the life of the blades. The microstructures, microhardness and anti-cavitation properties were investigated on the blades after laser treatment. The hardening mechanism and technique adaptability were researched. Large scale installation practices confirmed that the laser surface modification techniques are safe and reliable, which can improve the properties of blades greatly with advantages of high automation, high quality, little distortion and simple procedure.

Flower-Like CuO/ZnO Hybrid Hierarchical Nanostructures Grown on Copper Substrate: Glycothermal Synthesis, Characterization, Hydrophobic and Anticorrosion Properties

PubMed Central

Beshkar, Farshad; Khojasteh, Hossein; Salavati-Niasari, Masoud

2017-01-01

In this work we have demonstrated a facile formation of CuO nanostructures on copper substrates by the oxidation of copper foil in ethylene glycol (EG) at 80 °C. On immersing a prepared CuO film into a solution containing 0.1 g Zn(acac)2 in 20 mL EG for 8 h, ZnO flower-like microstructures composed of hierarchical three-dimensional (3D) aggregated nanoparticles and spherical architectures were spontaneously formed at 100 °C. The as-synthesized thin films and 3D microstructures were characterized using XRD, SEM, and EDS techniques. The effects of sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromide (CTAB), and polyethylene glycol (PEG) 6000 as surfactants and stabilizers on the morphology of the CuO and ZnO structures were discussed. Possible growth mechanisms for the controlled organization of primary building units into CuO nanostructures and 3D flower-like ZnO architectures were proposed. The hydrophobic property of the products was characterized by means of water contact angle measurement. After simple surface modification with stearic acid and PDMS, the resulting films showed hydrophobic and even superhydrophobic characteristics due to their special surface energy and nano-microstructure morphology. Importantly, stable superhydrophobicity with a contact angle of 153.5° was successfully observed for CuO-ZnO microflowers after modification with PDMS. The electrochemical impedance measurements proved that the anticorrosion efficiency for the CuO/ZnO/PDMS sample was about 99%. PMID:28773056

Flower-Like CuO/ZnO Hybrid Hierarchical Nanostructures Grown on Copper Substrate: Glycothermal Synthesis, Characterization, Hydrophobic and Anticorrosion Properties.

PubMed

Beshkar, Farshad; Khojasteh, Hossein; Salavati-Niasari, Masoud

2017-06-25

In this work we have demonstrated a facile formation of CuO nanostructures on copper substrates by the oxidation of copper foil in ethylene glycol (EG) at 80 °C. On immersing a prepared CuO film into a solution containing 0.1 g Zn(acac)₂ in 20 mL EG for 8 h, ZnO flower-like microstructures composed of hierarchical three-dimensional (3D) aggregated nanoparticles and spherical architectures were spontaneously formed at 100 °C. The as-synthesized thin films and 3D microstructures were characterized using XRD, SEM, and EDS techniques. The effects of sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromide (CTAB), and polyethylene glycol (PEG) 6000 as surfactants and stabilizers on the morphology of the CuO and ZnO structures were discussed. Possible growth mechanisms for the controlled organization of primary building units into CuO nanostructures and 3D flower-like ZnO architectures were proposed. The hydrophobic property of the products was characterized by means of water contact angle measurement. After simple surface modification with stearic acid and PDMS, the resulting films showed hydrophobic and even superhydrophobic characteristics due to their special surface energy and nano-microstructure morphology. Importantly, stable superhydrophobicity with a contact angle of 153.5° was successfully observed for CuO-ZnO microflowers after modification with PDMS. The electrochemical impedance measurements proved that the anticorrosion efficiency for the CuO/ZnO/PDMS sample was about 99%.

Graphene-Based Functional Architectures: Sheets Regulation and Macrostructure Construction toward Actuators and Power Generators.

PubMed

Cheng, Huhu; Huang, Yaxin; Shi, Gaoquan; Jiang, Lan; Qu, Liangti

2017-07-18

Graphene, with large delocalized π electron cloud on a two-dimensional (2D) atom-thin plane, possesses excellent carrier mobility, large surface area, high light transparency, high mechanical strength, and superior flexibility. However, the lack of intrinsic band gap, poor dispersibility, and weak reactivity of graphene hinder its application scope. Heteroatom-doping regulation and surface modification of graphene can effectively reconstruct the sp 2 bonded carbon atoms and tailor the surface chemistry and interfacial interaction, while microstructure mediation on graphene can induce the special chemical and physical properties because of the quantum confinement, edge effect, and unusual mass transport process. Based on these regulations on graphene, series of methods and techniques are developed to couple the promising characters of graphene into the macroscopic architectures for potential and practical applications. In this Account, we present our effort on graphene regulation from chemical modification to microstructure control, from the morphology-designed macroassemblies to their applications in functional systems excluding the energy-storage devices. We first introduce the chemically regulative graphene with incorporated heteroatoms into the honeycomb lattice, which could open the intrinsic band gap and provide many active sites. Then the surface modification of graphene with functional components will improve dispersibility, prevent aggregation, and introduce new functions. On the other hand, microstructure mediation on graphene sheets (e.g., 0D quantum dots, 1D nanoribbons, and 2D nanomeshes) is demonstrated to induce special chemical and physical properties. Benefiting from the effective regulation on graphene sheets, diverse methods including dimension-confined strategy, filtration assembly, and hydrothermal treatment have been developed to assemble individual graphene sheets to macroscopic graphene fibers, films, and frameworks. These rationally regulated graphene sheets and well-constructed assemblies present promising applications in energy-conversion materials and device systems focusing on actuators that can convert different energy forms (e.g., electric, chemical, photonic, thermal, etc.) to mechanical actuation and electrical generators that can directly transform environmental energy to electric power. These results reveal that graphene sheets with surface chemistry and microstructure regulations as well as their rationally designed assemblies provide a promising and abundant platform for development of diverse functional devices. We hope that this Account will promote further efforts toward fundamental research on graphene regulation and the wide applications of advanced designed assemblies in new types of energy-conversion materials/devices and beyond.

Benchmark Testing of the Largest Titanium Aluminide Sheet Subelement Conducted

NASA Technical Reports Server (NTRS)

Bartolotta, Paul A.; Krause, David L.

2000-01-01

To evaluate wrought titanium aluminide (gamma TiAl) as a viable candidate material for the High-Speed Civil Transport (HSCT) exhaust nozzle, an international team led by the NASA Glenn Research Center at Lewis Field successfully fabricated and tested the largest gamma TiAl sheet structure ever manufactured. The gamma TiAl sheet structure, a 56-percent subscale divergent flap subelement, was fabricated for benchmark testing in three-point bending. Overall, the subelement was 84-cm (33-in.) long by 13-cm (5-in.) wide by 8-cm (3-in.) deep. Incorporated into the subelement were features that might be used in the fabrication of a full-scale divergent flap. These features include the use of: (1) gamma TiAl shear clips to join together sections of corrugations, (2) multiple gamma TiAl face sheets, (3) double hot-formed gamma TiAl corrugations, and (4) brazed joints. The structural integrity of the gamma TiAl sheet subelement was evaluated by conducting a room-temperature three-point static bend test.

Technical and Economical Aspects of Current Thermal Barrier Coating Systems for Gas Turbine Engines by Thermal Spray and EBPVD: A Review

NASA Astrophysics Data System (ADS)

Feuerstein, Albert; Knapp, James; Taylor, Thomas; Ashary, Adil; Bolcavage, Ann; Hitchman, Neil

2008-06-01

The most advanced thermal barrier coating (TBC) systems for aircraft engine and power generation hot section components consist of electron beam physical vapor deposition (EBPVD) applied yttria-stabilized zirconia and platinum modified diffusion aluminide bond coating. Thermally sprayed ceramic and MCrAlY bond coatings, however, are still used extensively for combustors and power generation blades and vanes. This article highlights the key features of plasma spray and HVOF, diffusion aluminizing, and EBPVD coating processes. The coating characteristics of thermally sprayed MCrAlY bond coat as well as low density and dense vertically cracked (DVC) Zircoat TBC are described. Essential features of a typical EBPVD TBC coating system, consisting of a diffusion aluminide and a columnar TBC, are also presented. The major coating cost elements such as material, equipment and processing are explained for the different technologies, with a performance and cost comparison given for selected examples.

Component Activity Measurements in the Ti-Al-O System by Knudsen Cell Mass Spectrometry

NASA Technical Reports Server (NTRS)

Copland, Evan; Jacobson, Nathan S.

2003-01-01

Titanium-aluminides (containing (alpha)2-Ti3Al and gamma-TiAl intermetallic phases) have received continued research focus due to their potential as low-density materials for structural applications at intermediate temperatures. However their application above about 850C is hindered by poor oxidation resistance, characterized by the formation of a non-protective TiO2+Al2O3 scale and an oxygen-enriched subsurface zone. Consistent with this are measured titanium and aluminum activities in "oxygen-free" titanium-aluminides, which indicate Al2O3 is only stable for aluminum concentrations greater then 54 atom percent at 1373 K. However, the inability to form a protective Al2O3 scale is in apparent conflict with phase diagram studies, as experimental isothermal sections of the Ti-Al-O system show gamma-TiAl + alpha2-Ti3Al structures are in equilibrium only with Al2O3. The apparent resolution to this conflict lies in the inclusion of oxygen effects in the thermodynamic measurements

Oxidation, Creep And Fatigue Properties of Bare and Coated 31V alloy

DOE PAGES

Dryepondt, Sebastien N.; Jones, Samuel J.; Zhang, Ying; ...

2014-12-06

Increasing the efficiency of natural gas reciprocating engines will require materials with better mechanical and corrosion resistance at high temperatures. One solution to increase the lifetime of exhaust valves is to apply an aluminide coating to prevent corrosion assisted fatigue cracking, but the impact of the coating on the valve material mechanical properties needs to be assessed. Creep and high cycle fatigue (HCF) testing were conducted at 816°C on bare and slurry or pack-coated 31V alloy. After annealing according to the 31V standard heat treatment, the coated and bare creep specimens exhibited very similar creep rupture lives. The HCF behaviormore » of the pack-coated alloy was close to the behavior of the bar alloy, but fatigue lifetimes of slurry-coated 31V specimens had higher variability. Aluminide coatings have the potential to improve the valve performance at high temperature, but the coating deposition process needs to be tailored for the substrate standard heat treatment.« less

Influence of Heat Treatments on Microstructure and Magnetic Domains in Duplex Stainless Steel S31803

NASA Astrophysics Data System (ADS)

Dille, Jean; Pacheco, Clara Johanna; Camerini, Cesar Giron; Malet, Loic Charles; Nysten, Bernard; Pereira, Gabriela Ribeiro; De Almeida, Luiz Henrique; Alcoforado Rebello, João Marcos

2018-06-01

The influence of heat treatments on microstructure and magnetic domains in duplex stainless steel S31803 is studied using an innovative structural characterization protocol. Electron backscatter diffraction (EBSD) maps as well as magnetic force microscopy (MFM) images acquired on the same region of the sample, before and after heat treatment, are compared. The influence of heat treatments on the phase volumetric fractions is studied, and several structural modifications after heat treatment are highlighted. Three different mechanisms for the decomposition of ferrite into sigma phase and secondary austenite are observed during annealing at 800 °C. MFM analysis reveals that a variety of magnetic domain patterns can exist in one ferrite grain.

Shaping thin film growth and microstructure pathways via plasma and deposition energy: a detailed theoretical, computational and experimental analysis.

PubMed

Sahu, Bibhuti Bhusan; Han, Jeon Geon; Kersten, Holger

2017-02-15

Understanding the science and engineering of thin films using plasma assisted deposition methods with controlled growth and microstructure is a key issue in modern nanotechnology, impacting both fundamental research and technological applications. Different plasma parameters like electrons, ions, radical species and neutrals play a critical role in nucleation and growth and the corresponding film microstructure as well as plasma-induced surface chemistry. The film microstructure is also closely associated with deposition energy which is controlled by electrons, ions, radical species and activated neutrals. The integrated studies on the fundamental physical properties that govern the plasmas seek to determine their structure and modification capabilities under specific experimental conditions. There is a requirement for identification, determination, and quantification of the surface activity of the species in the plasma. Here, we report a detailed study of hydrogenated amorphous and crystalline silicon (c-Si:H) processes to investigate the evolution of plasma parameters using a theoretical model. The deposition processes undertaken using a plasma enhanced chemical vapor deposition method are characterized by a reactive mixture of hydrogen and silane. Later, various contributions of energy fluxes on the substrate are considered and modeled to investigate their role in the growth of the microstructure of the deposited film. Numerous plasma diagnostic tools are used to compare the experimental data with the theoretical results. The film growth and microstructure are evaluated in light of deposition energy flux under different operating conditions.

75 FR 24711 - Food and Drug Administration Modernization Act of 1997: Modifications to the List of Recognized...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-05

... newer version Indicators - Guidance for the Selection, Use and Interpretation of Results I. Tissue Engineering 15-6 15-16 ASTM F2450-09 Standard Guide for Assessing Withdrawn and replaced Microstructure of Polymeric Scaffolds for with newer version Use in Tissue Engineered Medical Products\\1\\ 15-9 15-17 ASTM...

Microstructure and Mechanical Properties of Additively Manufactured Parts with Staircase Feature

NASA Astrophysics Data System (ADS)

Keya, Tahmina

This thesis focuses on a part with staircase feature that is made of Inconel 718 and fabricated by SLM process. The objective of the study was to observe build height effect on the microstructure and mechanical properties of the part. Due to the nature of SLM, there is possibility of different microstructure and mechanical properties in different locations depending on the design of the part. The objective was to compare microstructure and mechanical properties from different location and four comparison groups were considered: 1. Effect of thermal cycle; 2. External and internal surfaces; 3. Build height effect and 4. Bottom surfaces. To achieve the goals of this research, standard metallurgical procedure has been performed to prepare samples. Etching was done to reveal the microstructure of SLM processed Inconel 718 parts. Young's modulus and hardness were measured using nanoindentation technique. FEM analysis was performed to simulate nanoindentation. The conclusions drawn from this research are: 1. The microstructure of front and side surface of SLM processed Inconel 718 consists of arc shaped cut ends of melt pools with intermetallic phase at the border of the melt pool; 2. On top surface, melted tracks and scanning patterns can be observed and the average width of melted tracks is 100-150 microm; 3. The microstructure looks similar at different build height; 4. Microstructure on the top of a stair is more defined and organized than the internal surface; 5. The mechanical properties are highest at the bottom. OM images revealed slight difference in microstructure in terms of build height for this specific part, but mechanical properties seem to be vary noticeably. This is something to be kept in mind while designing or determining build orientation. External and internal surfaces of a stair at the same height showed difference in both microstructure and mechanical properties. To minimize that effect and to make it more uniform, gradual elevation can be considered when suitable as far as design modification is concerned. Above all, this study reveals important information about the pattern of microstructure, thus heat transfer mechanism inside a part which is useful to understand the SLM process.

Department of Defense Program Solicitation 94; Small Business Technology Transfer (STTR) Program; Fiscal Year 1994.

DTIC Science & Technology

1994-01-01

advanced diesel engine components; high-temperature titanium aluminide and Al-Fe alloys for aircraft and missile engines; environmentally compliant...gun-chamber liners and KE penetrator stabilizer fins, tips, and leading edges; low cost, ceramic thermal barrier coatings for gas turbine blades and

Duplex aluminized coatings

NASA Technical Reports Server (NTRS)

Gedwill, M. A.; Grisaffe, S. J. (Inventor)

1975-01-01

The surface of a metallic base system is initially coated with a metallic alloy layer that is ductile and oxidation resistant. An aluminide coating is then applied to the metallic alloy layer. The chemistry of the metallic alloy layer is such that the oxidation resistance of the subsequently aluminized outermost layer is not seriously degraded.

Failure modes of microstructured fibers with sacrificial bonds made by instability-assisted 3D printing

NASA Astrophysics Data System (ADS)

Zou, Shibo; Therriault, Daniel; Gosselin, Frederick

A simple modification by increasing the deposition height on a commercially available 3D printer makes it a mechanical sewing machine due to the fluid mechanical instability. A variety of stitches-like patterns can be produced, similar to those by the Newtonian fluid mechanical sewing machine\\x9D, but with more interesting characteristics in the additional third dimension, which creates weakly fused bonds in some patterns. With these bonds, the fabricated fibers exhibit improved toughness in uniaxial tensile test. The toughening mechanism is found to be similar to the one in spider silk - the breaking of sacrificial bonds and the releasing of hidden length contribute significant dissipated energy to the system. However, the mechanical performance of these microstructured fibers is restricted by early fiber breakage as the number of sacrificial bonds increases. Here, we seek to understand the failure mechanisms of the microstructured fibers through tensile tests and finite element simulations. Static and dynamic failure are both found to cause early fiber breakage. These findings are helpful for the design optimization of microstructured fibers with high toughness and ductility, which can find potential use in impact protection and safety-critical applications.

Microstructure of the Sn-Cu{sub 6}Sn{sub 5} fibrous eutectic and its modification by segregation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drevet, B.; Camel, D.; Favier, J.J.

The influence of segregation due to thermal convection on the microstructure of Sn-Cu{sub 6}Sn{sub 5} fibrous eutectic alloys is studied in a Bridgman type configuration. The eutectic microstructure is characterized by means of image analysis, X-ray diffraction and scanning and transmission electron microscopy. In the absence of segregation, the eutectic is regular and its growth controlled by that of the Cu{sub 6}Sn{sub 5} fibers. The effect of interphases on eutectic spacing, through orientation relationships between fibers and matrix, is also evidenced. The influence of segregation can be summed up by the following effects. At first, in agreement with the Jacksonmore » and Hunt model, it leads to a variation of the eutectic spacing which results from a variation of the fiber volume fraction. Then, the spacing is much greater than the one obtained in the absence of segregation, due to a different tin growth plane and non-optimized fiber/matrix orientation relationships. Finally, the absence of steady state leads to a large dispersion of the spacing associated with a microstructural disorder.« less

Investigation of Microstructure and Mechanical Properties of ECAP-Processed AM Series Magnesium Alloy

NASA Astrophysics Data System (ADS)

Gopi, K. R.; Nayaka, H. Shivananda; Sahu, Sandeep

2016-09-01

Magnesium alloy Mg-Al-Mn (AM70) was processed by equal channel angular pressing (ECAP) at 275 °C for up to 4 passes in order to produce ultrafine-grained microstructure and improve its mechanical properties. ECAP-processed samples were characterized for microstructural analysis using optical microscopy, scanning electron microscopy, and transmission electron microscopy. Microstructural analysis showed that, with an increase in the number of ECAP passes, grains refined and grain size reduced from an average of 45 to 1 µm. Electron backscatter diffraction analysis showed the transition from low angle grain boundaries to high angle grain boundaries in ECAP 4 pass sample as compared to as-cast sample. The strength and hardness values an showed increasing trend for the initial 2 passes of ECAP processing and then started decreasing with further increase in the number of ECAP passes, even though the grain size continued to decrease in all the successive ECAP passes. However, the strength and hardness values still remained quite high when compared to the initial condition. This behavior was found to be correlated with texture modification in the material as a result of ECAP processing.

Sleep modifications in acute transient global amnesia.

PubMed

Della Marca, Giacomo; Mazza, Marianna; Losurdo, Anna; Testani, Elisa; Broccolini, Aldobrando; Frisullo, Giovanni; Marano, Giuseppe; Morosetti, Roberta; Pilato, Fabio; Profice, Paolo; Vollono, Catello; Di Lazzaro, Vincenzo

2013-09-15

Transient global amnesia (TGA) is a temporary memory loss characterized by an abrupt onset of antero-grade and retrograde amnesia, totally reversible. Since sleep plays a major role in memory consolidation, and in the storage of memory-related traces into the brain cortex, the aims of the present study were: (1) to evaluate changes in sleep macro-structure in TGA; (2) to assess modifications in sleep micro-structure in TGA, with particular reference to the arousal EEG and to cyclic alternating pattern (CAP); (3) to compare sleep parameters in TGA patients with a control group of patients with acute ischemic events ("minor stroke" or transient ischemic attack [TIA]) clinically and neuroradiologically "similar" to the TGA. TGA GROUP: 17 patients, (8 men and 9 women, 60.2 ± 12.5 years). Stroke or TIA (SoT) group: 17 patients hospitalized in the Stroke Unit for recent onset of minor stroke or TIA with hemispheric localization; healthy controls (HC) group: 17 healthy volunteers, matched for age and sex. Patients and controls underwent full-night polysomnography. In the multivariate analysis (conditions TGA, SoT, and HC) a significant effect of the condition was observed for sleep efficiency index, number of awakenings longer 1 min, REM latency, CAP time, and CAP rate. TGA and SoT differed only for CAP time and CAP rate, which were lower in the TGA group. Microstructural modification associated with tga could be consequent to: (1) hippocampal dysfunction and memory impairment; (2) impairment of arousal-related structures (in particular, cholinergic pathways); (3) emotional distress.

Maleic anhydride-g-low density polyethylene: Modification of LDPE molecular structure by γ-irradiation

NASA Astrophysics Data System (ADS)

Sheeja, Manaf, O.; Sujith, A.

2017-06-01

Polymer modification by radiation grafting of monomers onto polymers has received much attention recently. In the current study, γ-irradiation technique was used to achieve graft copolymerization of maleic anhydride (MA) onto low-density polyethylene (LDPE). To optimize, the process was performed at different γ-irradiation doses and MA concentration. The microstructure of grafted polymer film has been characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, field emission-scanning electron microscopy, and atomic force microscopy. The studies performed made possible the selection of experimental protocols adequate for the production of new copolymeric materials with high grafting yield.

Ceramics in Restorative and Prosthetic DENTISTRY1

NASA Astrophysics Data System (ADS)

Kelly, J. Robert

1997-08-01

This review is intended to provide the ceramic engineer with information about the history and current use of ceramics in dentistry, contemporary research topics, and potential research agenda. Background material includes intra-oral design considerations, descriptions of ceramic dental components, and the origin, composition, and microstructure of current dental ceramics. Attention is paid to efforts involving net-shape processing, machining as a forming method, and the analysis of clinical failure. A rationale is presented for the further development of all-ceramic restorative systems. Current research topics receiving attention include microstructure/processing/property relationships, clinical failure mechanisms and in vitro testing, wear damage and wear testing, surface treatments, and microstructural modifications. The status of the field is critically reviewed with an eye toward future work. Significant improvements seem possible in the clinical use of ceramics based on engineering solutions derived from the study of clinically failed restorations, on the incorporation of higher levels of "biomimicry" in new systems, and on the synergistic developments in dental cements and adhesive dentin bonding.

Manipulating Semicrystalline Polymers in Confinement.

PubMed

Shingne, Nitin; Geuss, Markus; Thurn-Albrecht, Thomas; Schmidt, Hans-Werner; Mijangos, Carmen; Steinhart, Martin; Martín, Jaime

2017-08-17

Because final properties of nanoscale polymeric structures are largely determined by the solid-state microstructure of the confined polymer, it is imperative not only to understand how the microstructure of polymers develops under nanoscale confinement but also to establish means to manipulate it. Here we present a series of processing strategies, adapted from methods used in bulk polymer processing, that allow us to control the solidification of polymer nanostructures. First, we show that supramolecular nucleating agents can be readily used to modify the crystallization kinetics of confined poly(vinylidene fluoride) (PVDF). In addition, we demonstrate that microstructural features that are not traditionally affected by nucleating agents, such as the orientation of crystals, can be tuned with the crystallization temperature applied. Interestingly, we also show that high crystallization temperatures and long annealing periods induce the formation of the γ modification of PVDF, hence enabling the simple production of ferro/piezoelectric nanostructures. We anticipate that the approaches presented here can open up a plethora of new possibilities for the processing of polymer-based nanostructures with tailored properties and functionalities.

Effect of pullulan on the water distribution, microstructure and textural properties of rice starch gels during cold storage.

PubMed

Chen, Long; Tian, Yaoqi; Tong, Qunyi; Zhang, Zipei; Jin, Zhengyu

2017-01-01

The effects of pullulan on the water distribution, microstructure and textural properties of rice starch gels during cold storage were investigated by low field-nuclear magnetic resonance (LF-NMR), scanning electron microscope (SEM), and texture profile analysis (TPA). The addition of pullulan reduced the transversal relaxation time of rice starch gels during cold storage. The microstructure of rice starch gel with 0.5% pullulan was denser and more uniform compared with that of rice starch without pullulan in each period of storage time. With regard to textural properties, 0.01% pullulan addition did not significantly change the texture of rice starch gels, while 0.5% pullulan addition appeared to reduce the hardness and retain the springiness of rice starch gels (P⩽0.05). The restriction effects of pullulan on water mobility and starch retrogradation were hypothesized to be mainly responsible for the water retention, gel structure maintenance, and modification of the textural attributes of rice starch gels. Copyright © 2016 Elsevier Ltd. All rights reserved.

Immunosensing by luminescence reduction in surface-modified microstructured SU-8

NASA Astrophysics Data System (ADS)

Eravuchira, Pinkie Jacob; Baranowska, Malgorzata; Eckstein, Chris; Díaz, Francesc; Llobet, Eduard; Marsal, Lluis F.; Ferré-Borrull, Josep

2017-01-01

SU-8, an epoxy based negative photoresist is extensively used as a structural material for the fabrication of microelectro-mechanical systems and in microelectronics technology. However, the possible applications of SU-8 for biosensing have not been explored much, mainly because of the photoluminescence SU-8 possesses in the near-UV and visible wavelength ranges which hinders fluorescent labelling of biorecognition events. In this study we demonstrate that photoluminescence of SU-8 can be employed itself as a sensing transduction parameter to produce a tool for immunosensing: the photoluminescence shows a systematic reduction upon modification of its surface chemistry, and in particular upon attachment of an antigen-antibody (aIgG-IgG) pair. We investigate the relation of the amount of reduction of photoluminescence on planar and microstructured surfaces, and we show that microstructuring leads to a higher reduction than a planar surface. Furthermore, we evaluated the dependence of photoluminescence reduction as a function of analyte concentration to prove that this magnitude can be applied to immunosensing.

Prediction of equibiaxial loading stress in collagen-based extracellular matrix using a three-dimensional unit cell model.

PubMed

Susilo, Monica E; Bell, Brett J; Roeder, Blayne A; Voytik-Harbin, Sherry L; Kokini, Klod; Nauman, Eric A

2013-03-01

Mechanical signals are important factors in determining cell fate. Therefore, insights as to how mechanical signals are transferred between the cell and its surrounding three-dimensional collagen fibril network will provide a basis for designing the optimum extracellular matrix (ECM) microenvironment for tissue regeneration. Previously we described a cellular solid model to predict fibril microstructure-mechanical relationships of reconstituted collagen matrices due to unidirectional loads (Acta Biomater 2010;6:1471-86). The model consisted of representative volume elements made up of an interconnected network of flexible struts. The present study extends this work by adapting the model to account for microstructural anisotropy of the collagen fibrils and a biaxial loading environment. The model was calibrated based on uniaxial tensile data and used to predict the equibiaxial tensile stress-stretch relationship. Modifications to the model significantly improved its predictive capacity for equibiaxial loading data. With a comparable fibril length (model 5.9-8μm, measured 7.5μm) and appropriate fibril anisotropy the anisotropic model provides a better representation of the collagen fibril microstructure. Such models are important tools for tissue engineering because they facilitate prediction of microstructure-mechanical relationships for collagen matrices over a wide range of microstructures and provide a framework for predicting cell-ECM interactions. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Rock-Fluid Interactions Under Stress: How Rock Microstructure Controls The Evolution of Porosity and Permeability

NASA Astrophysics Data System (ADS)

Vanorio, T.

2016-12-01

Monitoring chemo-mechanical processes geophysically — e.g., fluid disposal or storage, thermal and chemical stimulation of reservoirs, or natural fluids simply entering a new system in the subsurface— raises numerous concerns because of the likelihood of fluid-rock chemical interactions and our limited ability to decipher the geophysical signature of coupled processes. One of the missing links is coupling the evolution of porosity, permeability, and velocity of rocks together with reactive transport, since rocks deform and their microstructure evolves, as a result of chemical reactions under stress. This study describes recent advances in rock-physics experiments to understand the effects of dissolution-induced compaction on acoustic velocity, porosity, and permeability. Data observation includes time-lapse experiments and imaging tracking transport and elastic properties, the rock microstructure, and the pH and chemical composition of the fluid permeating the rock. Results show that the removal of high surface area, mineral phases such as microcrystalline calcite and clay appears to be mostly responsible for dissolution-induced compaction. Nevertheless, it is the original rock microstructure and its response to stress that ultimately defines how solution-transfer and rock compaction feed back upon each other. This work has a dual aim: understanding the mechanisms underlying permanent modifications to the rock microstructure and providing a richer set of experimental information to inform the formulation of new simulations and rock modeling.

Diffusion and phase transformation behavior in poly-synthetically-twinned (PST) titanium-aluminum/titanium diffusion couple

NASA Astrophysics Data System (ADS)

Pan, Ling

Motivated by the great potential applications of gamma titanium aluminide based alloys and the important effect of diffusion on the properties of gamma-TiAl/alpha2-Ti3Al two-phase lamellar structure, we conduct this thesis research to explore the microstructural evolution and interdiffusion behavior, and their correlations in multi-phase solid state diffusion couples made up of pure titanium and polysynthetically-twinned (PST) Ti-49.3 at.% Al "single" crystal, in the temperature range of 973--1173 K. The diffusion couples are prepared by high vacuum hot-pressing, with the diffusion direction parallel to the lamellar planes. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) are employed to observe the microstructure at various interfaces/interphases. A reaction zone (RZ) of polycrystalline alpha 2-Ti3Al phase forms along the PST Ti-Al/Ti bonding interface having a wavy interface with the PST crystal and exhibits deeper penetration in alpha2 lamellae, consisting of many fine alpha2 and secondary gamma laths, than in primary gamma lamellae. Direct measurement of the RZ thickness on SEM back-scattered electron images reveals a parabolic growth of the RZ, indicating a macroscopically diffusion-controlled growth. Concentration profiles from Ti, through the RZ, into the alpha2 lamellae of the PST crystal are measured by quantitative energy-dispersive x-ray spectroscopy (EDS) in a scanning transmission electron microscope (STEM). A plateau of composition adjacent to the RZ/(mixed alpha2 lath in PST) interface forms in the deeply penetrated RZ grains, implying a diffusion barrier crossing the interface and some extent of interface control in the RZ grain growth. The interdiffusion coefficient is evaluated both independent of composition and as a function of composition. No significant concentration dependence of the interdiffusion coefficients is observed using Boltzmann-Matano analysis. The temperature dependence of the interdiffusion coefficients obeys the Arrhenius relationship with a pre-exponential factor of D 0 = (7.56 +/- 7.14) x 10-5 m2/s and an activation enthalpy of Q = 255.6+8.9-8.3 kJ/mol = (2.65 +/- 0.09) eV/atom. The initial nucleation stage of the RZ grains plays an important role in the later microstructural evolution as does the local mass balance. The interfacial energy and the strain energy in the deeply penetrated RZ grains are possible reasons for the plateau.

Beneficial effects of a N-terminally modified GIP agonist on tissue-level bone material properties.

PubMed

Mabilleau, Guillaume; Mieczkowska, Aleksandra; Irwin, Nigel; Simon, Yannick; Audran, Maurice; Flatt, Peter R; Chappard, Daniel

2014-06-01

Bone remodeling is under complex regulation from nervous, hormonal and local signals, including gut hormones. Among the gut hormones, a role for the glucose-dependent insulinotropic polypeptide (GIP) has been suggested. However, the rapid degradation of GIP in the bloodstream by the ubiquitous enzyme dipeptidyl peptidase-4 (DPP-4) precludes therapeutic use. To circumvent this problem, a series of N-terminally modified GIP agonists have been developed, with N-AcGIP being the most promising. The aims of the present study were to investigate the effects of N-AcGIP on bone at the micro-level using trabecular and cortical microstructural morphology, and at the tissue-level in rats. Copenhagen rats were randomly assigned into control or N-AcGIP-treated groups and received daily injection for 4 weeks. Bone microstructural morphology was assessed by microCT and dynamic histomorphometry and tissue-level properties by nanoindentation, qBEI and infra-red microscopy. Four week treatment with N-AcGIP did not alter trabecular or cortical microstructural morphology. In addition, no significant modifications of mechanical response and properties at the tissue-level were observed in trabecular bone. However, significant augmentations in maximum load (12%), hardness (14%), indentation modulus (13%) and dissipated energy (16%) were demonstrated in cortical bone. These beneficial modifications of mechanical properties at the tissue-level were associated with increased mineralization (22%) and collagen maturity (13%) of the bone matrix. Taken together, the results support a beneficial role of GIP, and particularly stable analogs such as N-AcGIP, on tissue material properties of bone. Copyright © 2014 Elsevier Inc. All rights reserved.

Enhancing Reactivity in Structural Energetic Materials

NASA Astrophysics Data System (ADS)

Glumac, Nick

2017-06-01

In many structural energetic materials, only a small fraction of the metal oxidizes, and yet this provides a significant boost in the overall energy release of the system. Different methodologies to enhance this reactivity include alloying and geometric modifications of microstructure of the reactive material (RM). In this presentation, we present the results of several years of systematic study of both chemical (alloy) and mechanical (geometry) effects on reactivity for systems with typical charge to case mass ratios. Alloys of aluminum with magnesium and lithium are considered, as these are common alloys in aerospace applications. In terms of geometric modifications, we consider surface texturing, inclusion of dense additives, and inclusion of voids. In all modifications, a measurable influence on output is observed, and this influence is related to the fragment size distribution measured from the observed residue. Support from DTRA is gratefully acknowledged.

Single organic microtwist with tunable pitch.

PubMed

Chen, Hai-Bo; Zhou, Yan; Yin, Jie; Yan, Jing; Ma, Yuguo; Wang, Lei; Cao, Yong; Wang, Jian; Pei, Jian

2009-05-19

A facile synthesis of previously unknown, well-separated, uniform chiral microstructures from achiral pi-conjugated organic molecules was developed by simple solution process. Detailed characterization and formation mechanism were presented. By simple structure modification or temperature change, the pitch of the chiral structure can be fine tuned. Our result opens new possibilities for novel materials in which structure chirality is coupled to device performance.

CAEBAT Model Featured on American Chemical Society Journal Tenth

Science.gov Websites

University's School of Mechanical Engineering has yielded new insights for lithium-ion (Li-ion) battery corresponding article, "Secondary-Phase Stochastics in Lithium-Ion Battery Electrodes" detailing the microstructural modifications can greatly improve overall Li-ion battery performance. The value of this work is

Microstructural evidence of melting in crustal rocks (Invited)

NASA Astrophysics Data System (ADS)

Holness, M. B.; Cesare, B.; Sawyer, E. W.

2010-12-01

The signature of the former presence of melt on a microscopic scale is highly variable, subject to modification both during the melting event and during its subsequent history. Static pyrometamorphism results in melt films on grain boundaries between reactant phases. If a volume increase is involved, melting results in hydrofracture. On a longer timescale, as demonstrated by fragments of the crustal source in lava flows at El Hoyazo (SE Spain), melt occurs throughout the rock. These examples are highly unusual: the great majority of rocks that underwent melting cooled more slowly, permitting microstructural modification driven by a combination of textural equilibration, reaction and deformation. In the absence of deformation, and at constant temperature, melt-bearing rocks approach textural equilibrium, characterised by uniform grain size, smoothly curved grain boundaries and the establishment at all three-grain junctions of the equilibrium dihedral angle. The dihedral angle controls melt connectivity, with consequences for melt mobility and rock rheology. However, deformation is the rule rather than the exception in regional metamorphic terrains with profound effects on melt distribution. If deformation occurs predominantly by diffusive processes, textural equilibration can keep pace. At higher deformation rates melt is squeezed into planar pockets aligned parallel to the shearing direction or perpendicular to the extensional stress. Microstructures formed during solidification are controlled by cooling rate, H2O, and the size of the melt pockets. Large pockets solidify to look like igneous rocks. In small pores the supersaturation required for crystal growth is high and melt persist to lower temperatures, even being preserved as tiny glassy inclusions (“nanogranites”) in regional terranes. The pore size effect changes crystallization order, resulting in small, highly cuspate grains on grain boundaries with low dihedral angles. Crystallisation microstructures of poly-component liquids are highly dependent on diffusion rates, and therefore H2O content. Dry conditions result in diffusion-limited crystallisation to form intergrowths and symplectites (e.g. granophyre). The cooling rate must be slow in order to nucleate and grow individual grains from the melt. If the melt was primarily concentrated in thick films on grain boundaries this results in the “string of beads” texture. If there is sufficient water, and the rocks stay sufficiently hot, the microstructures will move towards a granular texture, driven by the reduction in interfacial energy. Highly cuspate pseudomorphs of melt at three-grain junctions will become rounded as the dihedral angle increases (generally towards the range 110-140°). Melt-related microstructures are more likely to be retained in dry rocks: in migmatite terranes in which melting was driven by infiltration of aqueous fluids and where melt extraction wasn’t pervasive, microstructures are likely to have been significantly modified by sub-solidus recrystallisation, especially likely if the rock underwent intense deformation on the retrograde path.

A Compendium of Scale Surface Microstructures: Ni(pt)al Coatings Oxidized at 1150 C for 2000 1-h Cycles

NASA Technical Reports Server (NTRS)

Smialek, James L.; Garg, Anita

2010-01-01

The surface structure of scales formed on Ni(Pt)Al coatings was characterized by SEM/EDS/BSE in plan view. Two nominally identical {100} samples of aluminide coated CMSX4 single crystal were oxidized at 1150 C for 2000 1-h cycles and were found to produce somewhat disparate behavior. One sample, with less propensity for coating grain boundary ridge deformation, presented primarily alpha-Al2O3 scale structures, with minimal weight loss and spallation. The original scale structure, still retained over most of the sample, consisted of the classic theta-alpha transformation-induced ridge network structure, with approx. 25 nm crystallographic steps and terraces indicative of surface rearrangement to low energy alumina planes. The scale grain boundary ridges were often decorated with a fine, uniform distribution of (Hf,Ti)O2 particles. Another sample, producing steady state weight losses, exhibited much interfacial spallation and a complex assortment of different structures. Broad areas of interfacial spalling, crystallographically-faceted (Ni,Co)(Al,Cr)2O4 spinel, with an alpha-Al2O3 base scale, were the dominant features. Other regions exhibited nodular spinel grains, with fine or (Ta,Ti)-rich (rutile) particles decorating or interspersed with the spinel. While these features were consistent with a coating that presented more deformation at extruded grain boundaries, the root cause of the different behavior between the duplicate samples could not be conclusively identified.

Surface modification of investment cast-316L implants: microstructure effects.

PubMed

El-Hadad, Shimaa; Khalifa, Waleed; Nofal, Adel

2015-03-01

Artificial femur stem of 316L stainless steel was fabricated by investment casting using vacuum induction melting. Different surface treatments: mechanical polishing, thermal oxidation and immersion in alkaline solution were applied. Thicker hydroxyapatite (HAP) layer was formed in the furnace-oxidized samples as compared to the mechanically polished ones. The alkaline treatment enhanced the precipitation of HAP on the samples. It was also observed that the HAP precipitation responded differently to the different phases of the microstructure. The austenite phase was observed to have more homogeneous and smoother layer of HAP. In addition, the growth of HAP was sometimes favored on the austenite phase rather than on ferrite phase. Copyright © 2014 Elsevier B.V. All rights reserved.

Chromium modified nickel-iron aluminide useful in sulfur bearing environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cathcart, J.V.; Liu, C.T.

1989-06-13

This patent describes a composition of matter consisting essentially of 18 to 19 at. % aluminum, 10 to 11.5 at. % iron, 6.5 to 8.0 at. % chromium, 0.4 to 0.8 at. % molybdenum, 0.1 to 0.3 at. % zirconium, 0.05 to 0.2 at. % boron and the balance nickel.

The free growth criterion for grain initiation in TiB 2 inoculated γ-titanium aluminide based alloys

NASA Astrophysics Data System (ADS)

Gosslar, D.; Günther, R.

2014-02-01

γ-titanium aluminide (γ-TiAl) based alloys enable for the design of light-weight and high-temperature resistant engine components. This work centers on a numerical study of the condition for grain initiation during solidification of TiB2 inoculated γ-TiAl based alloys. Grain initiation is treated according to the so-called free growth criterion. This means that the free growth barrier for grain initiation is determined by the maximum interfacial mean curvature between a nucleus and the melt. The strategy presented in this paper relies on iteratively increasing the volume of a nucleus, which partially wets a hexagonal TiB2 crystal, minimizing the interfacial energy and calculating the corresponding interfacial curvature. The hereby obtained maximum curvature yields a scaling relation between the size of TiB2 crystals and the free growth barrier. Comparison to a prototypical TiB2 crystal in an as cast γ-TiAl based alloy allowed then to predict the free growth barrier prevailing under experimental conditions. The validity of the free growth criterion is discussed by an interfacial energy criterion.

Fabrication and evaluation of enhanced diffusion bonded titanium honeycomb core sandwich panels with titanium aluminide face sheets

NASA Technical Reports Server (NTRS)

Hoffmann, E. K.; Bird, R. K.; Bales, T. T.

1989-01-01

A joining process was developed for fabricating lightweight, high temperature sandwich panels for aerospace applications using Ti-14Al-21Nb face sheets and Ti-3Al-2.5V honeycomb core. The process, termed Enhanced Diffusion Bonding (EDB), relies on the formation of a eutectic liquid through solid-state diffusion at elevated temperatures and isothermal solidification to produce joints in thin-gage titanium and titanium aluminide structural components. A technique employing a maskant on the honeycomb core was developed which permitted electroplating a controlled amount of EDB material only on the edges of the honeycomb core in order to minimize the structural weight and metallurgical interaction effects. Metallurgical analyses were conducted to determine the interaction effects between the EDB materials and the constituents of the sandwich structure following EDB processing. The initial mechanical evaluation was conducted with butt joint specimens tested at temperatures from 1400 - 1700 F. Further mechanical evaluation was conducted with EDB sandwich specimens using flatwise tension tests at temperatures from 70 - 1100 F and edgewise compression tests at ambient temperature.

Surface characterization of hydrogen charged and uncharged alpha-2 and gamma titanium aluminide alloys using AES and REELS

NASA Technical Reports Server (NTRS)

Shanabarger, M. R.

1990-01-01

The surfaces of selected uncharged and hydrogen charged alpha-2 and gamma titanium aluminide alloys with Nb additions were characterized by Auger electron (AES) and reflected electron energy loss (REELS) spectroscopy. The alloy surfaces were cleaned before analysis at room temperature by ion sputtering. The low energy (500 eV) ion sputtering process preferentially sputtered the surface concentration. The surface concentrations were determined by comparing AES data from the alloys with corresponding data from elemental references. No differences were observed in the Ti or Nb Auger spectra for the uncharged and hydrogen charged alloys, even though the alpha-2 alloy had 33.4 atomic percent dissolved hydrogen. Also, no differences were observed in the AES spectra when hydrogen was adsorbed from the gas phase. Bulk plasmon energy shifts were observed in all alloys. The energy shifts were induced either by dissolved hydrogen (alpha-2 alloy) or hydrogen adsorbed from the gas phase (alpha-2 and gamma alloys). The adsorption induced plasmon energy shifts were greatest for the gamma alloy and cp-Ti metal.

The Flexural Strength and Fracture Toughness of TC4-Based Laminated Composites Reinforced with Ti Aluminide and Carbide

PubMed Central

Fei, Yanhan; Ai, Taotao; Niu, Qunfei; Li, Wenhu; Yuan, Xinqiang; Jing, Ran; Dong, Hongfeng

2017-01-01

TiC–Ti–Al mixed powders and TC4 titanium alloy foils were overlapped layer-by-layer in the graphite die. The TC4-based laminated composite sheets reinforced by Ti aluminide and carbide were successfully fabricated via spark plasma sintering (SPS) at 1100 °C with a well-bonded interface. The composite layers were mainly composed of TiAl, Ti3Al, Ti2AlC, and Ti3AlC2 phases. The carbides particles distributed in the matrix played an important role in the deflection of cracks and the passivation of microcracks. TC4 titanium alloy layers had an obvious effect on the stress distribution during the loading process, and provided an energy dissipation mechanism, which could improve the mechanical properties of the laminated composite sheets obviously. When the theoretical amount of Ti2AlC was 20 wt %, the flexural strength and fracture toughness of the laminated composite sheets reached the maximum value in the arrester direction, which were 1428.79 MPa and 64.08 MPa·m1/2, respectively. PMID:29027949

The Flexural Strength and Fracture Toughness of TC4-Based Laminated Composites Reinforced with Ti Aluminide and Carbide.

PubMed

Fei, Yanhan; Ai, Taotao; Niu, Qunfei; Li, Wenhu; Yuan, Xinqiang; Jing, Ran; Dong, Hongfeng

2017-10-13

TiC-Ti-Al mixed powders and TC4 titanium alloy foils were overlapped layer-by-layer in the graphite die. The TC4-based laminated composite sheets reinforced by Ti aluminide and carbide were successfully fabricated via spark plasma sintering (SPS) at 1100 °C with a well-bonded interface. The composite layers were mainly composed of TiAl, Ti₃Al, Ti₂AlC, and Ti₃AlC₂ phases. The carbides particles distributed in the matrix played an important role in the deflection of cracks and the passivation of microcracks. TC4 titanium alloy layers had an obvious effect on the stress distribution during the loading process, and provided an energy dissipation mechanism, which could improve the mechanical properties of the laminated composite sheets obviously. When the theoretical amount of Ti₂AlC was 20 wt %, the flexural strength and fracture toughness of the laminated composite sheets reached the maximum value in the arrester direction, which were 1428.79 MPa and 64.08 MPa·m 1/2 , respectively.

Life prediction and constitutive models for engine hot section anisotropic materials program

NASA Technical Reports Server (NTRS)

Swanson, G. A.; Linask, I.; Nissley, D. M.; Norris, P. P.; Meyer, T. G.; Walker, K. P.

1986-01-01

This report presents the results of the first year of a program designed to develop life prediction and constitutive models for two coated single crystal alloys used in gas turbine airfoils. The two alloys are PWA 1480 and Alloy 185. The two oxidation resistant coatings are PWA 273, an aluminide coating, and PWA 286, an overlay NiCoCrAlY coating. To obtain constitutive and/or fatigue data, tests were conducted on coated and uncoated PWA 1480 specimens tensilely loaded in the 100 , 110 , 111 , and 123 directions. A literature survey of constitutive models was completed for both single crystal alloys and metallic coating materials; candidate models were selected. One constitutive model under consideration for single crystal alloys applies Walker's micromechanical viscoplastic formulation to all slip systems participating in the single crystal deformation. The constitutive models for the overlay coating correlate the viscoplastic data well. For the aluminide coating, a unique test method is under development. LCF and TMF tests are underway. The two coatings caused a significant drop in fatigue life, and each produced a much different failure mechanism.

In situ micro-compression testing of He2+ ion irradiated titanium aluminide

NASA Astrophysics Data System (ADS)

Wei, Tao; Xu, Alan; Zhu, Hanliang; Ionescu, Mihail; Bhattacharyya, Dhriti

2017-10-01

A titanium aluminide (TiAl) alloy 45XD has been irradiated by a He ion beam with an energy of 5 MeV on a tandem accelerator at the Australian Nuclear Science and Technology Organization (ANSTO). The total fluence of He ions was 5 × 1017 ion cm-2. A 17 μm uniform damage region from the material surface with a helium concentration of about 5000 appm was achieved by using an energy degrading wheel in front of the TiAl target. The micro-size test specimens from the damage layer were fabricated using a focused ion beam & scanning electron microscope (FIB-SEM) system. The in situ SEM micromechanical compressive testing was carried out inside an SEM and the results indicated irradiation embrittlement in the helium affected region. Electron back scatter diffraction (EBSD) analysis has been applied to reveal the orientation of the lamellae in the TiAl specimens, and used to understand the deformation processes in the sample. The irradiation damage of gallium ion beam from FIB on the surface of TiAl sample was also investigated.

Elevated Temperature Deformation of Fe-39.8Al and Fe-15.6Mn-39.4Al

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel

2004-01-01

The elevated temperature compressive properties of binary Fe-39.8 at % Al and Fe-15.6Mn-39.4Al have been measured between 1000 and 1300 K at strain rates between 10(exp 7) and 10(exp 3)/ s. Although the Mn addition to iron aluminide did not change the basic deformation characteristics, the Mn-modified alloy was slightly weaker. In the regime where deformation of FeAl occurs by a high stress exponent mechanism (n = 6), strength increases as the grain size decreases at least for diameters between approx. 200 and approx. 10 microns. Due to the limitation in the grain size-flow stress-temperature-strain rate database, the influence of further reductions of the grain size on strength is uncertain. Based on the appearance of subgrains in deformed iron aluminide, the comparison of grain diameters to expected subgrain sizes, and the grain size exponent and stress exponent calculated from deformation experiments, it is believed that grain size strengthening is the result of an artificial limitation on subgrain size as proposed by Sherby, Klundt and Miller.

Dart model for irradiation-induced swelling of dispersion fuel elements including aluminum-fuel interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rest, J.; Hofman, G.L.

1997-06-01

The Dispersion Analysis Research Tool (DART) contains models for fission-gas induced fuel swelling, interaction of fuel with the matrix aluminum, resultant reaction-product swelling, and calculation of the stress gradient within the fuel particle. The effects of an aluminide shell on fuel particle swelling are evaluated. Validation of the model is demonstrated by a comparison of DART calculations of fuel swelling of U{sub 3}SiAl-Al and U{sub 3}Si{sub 2}-Al for various dispersion fuel element designs with the data. DART results are compared with data for fuel swelling Of U{sub 3}SiAl-Al in plate, tube, and rod configurations as a function of fission density.more » Plate and tube calculations were performed at a constant fuel temperature of 373 K and 518 K, respectively. An irradiation temperature of 518 K results in a calculated aluminide layer thickness for the Russian tube that is in the center of the measured range (16 {mu}m). Rod calculations were performed with a temperature gradient across the rod characterized by surface and central temperatures of 373 K and 423 K, respectively. The effective yield stress of irradiated Al matrix material and the aluminide was determined by comparing the results of DART calculations with postirradiation immersion volume measurement of U{sub 3}SiAl plates. The values for the effective yield stress were used in all subsequent simulations. The lower calculated fuel swelling in the rod-type element is due to an assumed biaxial stress state. Fuel swelling in plates results in plate thickness increase only. Likewise, in tubes, only the wall thickness increases. Irradiation experiments have shown that plate-type dispersion fuel elements can develop blisters or pillows at high U-235 burnup when fuel compounds exhibiting breakaway swelling are used at moderate to high fuel volume fractions. DART-calculated interaction layer thickness and fuel swelling follows the trends of the observations. 3 refs., 2 figs.« less

Comprehensive study of the abrasive wear and slurry erosion behavior of an expanded system of high chromium cast iron and microstructural modification for enhanced wear resistance

NASA Astrophysics Data System (ADS)

Chung, Reinaldo Javier

High chromium cast irons (HCCIs) have been demonstrated to be an effective material for a wide range of applications in aggressive environments, where resistances to abrasion, erosion and erosion-corrosion are required. For instance, machinery and facilities used in mining and extraction in Alberta's oil sands suffer from erosion and erosion-corrosion caused by silica-containing slurries, which create challenges for the reliability and maintenance of slurry pumping systems as well as other processing and handling equipment. Considerable efforts have been made to determine and understand the relationship between microstructural features of the HCCIs and their wear performance, in order to guide the material selection and development for specific service conditions with optimal performance. The focus was previously put on a narrow group of compositions dictated by ASTM A532. However, with recent advances in casting technology, the HCCI compositional range can be significantly expanded, which potentially brings new alloys that can be superior to those which are currently employed. This work consists of three main aspects of study. The first one is the investigation of an expanded system of white irons with their composition ranging from 1 to 6 wt.% C and 5 to 45 wt.% Cr, covering 53 alloys. This work has generated wear and corrosion maps and established correlation between the performance and microstructural features for the alloys. The work was conducted in collaboration with the Materials Development Center of Weir Minerals in Australia, and the results have been collected in a database that is used by the company to guide materials selection for slurry pump components in Alberta oil sands and in other mining operations throughout the world. The second part consists of three case studies on effects of high chromium and high carbon, respectively, on the performance of the HCCIs. The third aspect is the development of an approach to enhance the wear resistance of HCCIs by microstructural modification through addition of strong carbide-forming elements to produce eutectic microstructures reinforced with in-situ formed foreign carbides. Very promising results have been obtained in lab, which demonstrates that the approach is feasible and effective in tailoring HCCIs for improved performance.

Effects of carbon and hafnium concentrations in wrought powder-metallurgy superalloys based on NASA 2B-11 alloy

NASA Technical Reports Server (NTRS)

Miner, R. V., Jr.

1976-01-01

A candidate alloy for advanced-temperature turbine engine disks, and four modifications of that alloy with various C and Hf concentrations were produced as cross-rolled disks from prealloyed powder that was hot isostatically compacted. The mechanical properties, microstructures, and phase relations of the alloys are discussed in terms of their C and Hf concentrations. A low-C and high-Hf modification of IIB-11 had the best balance of mechanical properties for service below about 750 C. Because of their finer grain sizes, none of the powder-metallurgy alloys produced had the high-temperature rupture strength of conventionally cast and wrought IIB-11.

Surface Modification of Micro-Alloyed High-Strength Low-Alloy Steel by Controlled TIG Arcing Process

NASA Astrophysics Data System (ADS)

Ghosh, P. K.; Kumar, Ravindra

2015-02-01

Surface modification of micro-alloyed HSLA steel plate has been carried out by autogenous conventional and pulse current tungsten inert gas arcing (TIGA) processes at different welding parameters while the energy input was kept constant. At a given energy input the influence of pulse parameters on the characteristics of surface modification has been studied in case of employing single and multi-run procedure. The role of pulse parameters has been studied by considering their summarized influence defined by a factor Φ. The variation in Φ and pulse frequency has been found to significantly affect the thermal behavior of fusion and accordingly the width and penetration of the modified region along with its microstructure, hardness and wear characteristics. It is found that pulsed TIGA is relatively more advantageous over the conventional TIGA process, as it leads to higher hardness, improved wear resistance, and a better control over surface characteristics.

Microstructure and Microhardness of 17-4PH Deposited with Co-based Alloy Hardfacing Coating

NASA Astrophysics Data System (ADS)

Deng, D. W.; Zhang, C. P.; Chen, R.; Xia, H. F.

Hardfacing is widely used to improve the performance of components exposed to severe service conditions. In this paper, the surface modification was evaluated for precipitation hardening martensitic stainless steel 17-4PH deposited with Co-based alloy stellite12 by the plasma-transferred arc welding (PTAW). The microstructure and microhardness of coating and heat affected zone(HAZ) of base metal were characterized by optical microscope (OM), scanning electron scanning microscope (SEM), X-ray diffractometer and hardness tester. The results show that the interface between weld metal and base metal is favorable without pore and crack, at the same time elements diffusion is observed in the fusion area. However, as the distance from the interface increases, HAZ comprises three different microstructural zones, namely, zones of coarse overheated structures, quenching martensite and martensite, ferrite. The microhardness decreases gradually from the HAZ near interface to the base metal, except the zone of coarse overheated structures. The microhardness of the coating improves a lot and fluctuates in a definitive range, and microstructural gradient is observed including the fusion area (the planar region and the bulky dendrite in a direction perpendicular to the weld interface), the transition zone (the dendrite in a multi-direction way) and the fine grain zone near the surface in the coating (fine equiaxial structure).

The influence of different processing stages on particle size, microstructure, and appearance of dark chocolate.

PubMed

Glicerina, Virginia; Balestra, Federica; Dalla Rosa, Marco; Bergenhstål, Bjorn; Tornberg, Eva; Romani, Santina

2014-07-01

The effect of different process stages on microstructural and visual properties of dark chocolate was studied. Samples were obtained at each phase of the manufacture process: mixing, prerefining, refining, conching, and tempering. A laser light diffraction technique and environmental scanning electron microscopy (ESEM) were used to study the particle size distribution (PSD) and to analyze modifications in the network structure. Moreover, colorimetric analyses (L*, h°, and C*) were performed on all samples. Each stage influenced in stronger way the microstructural characteristic of products and above all the PSD. Sauter diameter (D [3.2]) decreased from 5.44 μm of mixed chocolate sample to 3.83 μm, of the refined one. ESEM analysis also revealed wide variations in the network structure of samples during the process, with an increase of the aggregation and contact point between particles from mixing to refining stage. Samples obtained from the conching and tempering were characterized by small PS, and a less dense aggregate structure. From color results, samples with the finest particles, having larger specific surface area and the smallest diameter, appeared lighter and more saturated than those with coarse particles. Final quality of food dispersions is affected by network and particles characteristics. The deep knowledge of the influence of single processing stage on chocolate microstructural properties is useful in order to improve or modify final product characteristics. ESEM and laser diffraction are suitable techniques to study changes in chocolate microstructure. © 2014 Institute of Food Technologists®

Influence of pH Adjustment Parameter for Sol-Gel Modification on Structural, Microstructure, and Magnetic Properties of Nanocrystalline Strontium Ferrite

NASA Astrophysics Data System (ADS)

Azis, Raba'ah Syahidah; Sulaiman, Sakinah; Ibrahim, Idza Riati; Zakaria, Azmi; Hassan, Jumiah; Muda, Nor Nadhirah Che; Nazlan, Rodziah; Saiden, Norlaily M.; Fen, Yap Wing; Mustaffa, Muhammad Syazwan; Matori, Khamirul Amin

2018-05-01

Synthesis of nanocrystalline strontium ferrite (SrFe12O19) via sol-gel is sensitive to its modification parameters. Therefore, in this study, an attempt of regulating the pH as a sol-gel modification parameter during preparation of SrFe12O19 nanoparticles sintered at a low sintering temperature of 900 °C has been presented. The relationship of varying pH (pH 0 to 8) on structural, microstructures, and magnetic behaviors of SrFe12O19 nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning microscope (FESEM), and vibrating sample magnetometer (VSM). Varying the pH of precursor exhibited a strong effect on the sintered density, crystal structure and magnetic properties of the SrFe12O19 nanoparticles. As the pH is 0, the SrFe12O19 produced relatively largest density, saturation magnetization, M s, and coercivity, H c, at a low sintering temperature of 900 °C. The grain size of SrFe12O19 is obtained in the range of 73.6 to 133.3 nm. The porosity of the sample affected the density and the magnetic properties of the SrFe12O19 ferrite. It is suggested that the low-temperature sintered SrFe12O19 at pH 0 displayed M s of 44.19 emu/g and H c of 6403.6 Oe, possessing a significant potential for applying in low-temperature co-fired ceramic permanent magnet.

Multifunctional wall coating combining photocatalysis, self-cleaning and latent heat storage

NASA Astrophysics Data System (ADS)

Lucas, S. S.; Barroso de Aguiar, J. L.

2018-02-01

Mortars, one of the most common construction materials, have not received any substantial modification for many decades. This has changed in recent years; new compositions are now being developed, with new properties, using nano-additives, fibres and capsules. In this work, surfaces with new and innovative functionalities that promote energy savings and improve air quality have been developed and studied. Incorporation of phase change materials (PCM) and titanium dioxide (TiO2) nanoparticles in construction products is currently under study by different research groups. However, these studies only address their incorporation separately. Adding new additives into the mortar’s matrix can be complex—due to microstructural modifications that will influence both fresh and hardened state properties. Moving from a single additive to multiple additions, as in this study, increases the system’s complexity. Only with a good understanding of the microstructural properties, it is possible to add multiple additives (including nano and microparticles) to mortars, without damaging its final quality. This work demonstrates that a higher additive content is not always a guarantee of better results; lower additions can often provide a better compromise between performance and final mechanical properties. The results presented in this paper confirmed this and show that combining PCM microcapsules and TiO2 nanoparticles open a new path in the development of mortars with multiple functionalities. In this study, a new material with depolluting, self-cleaning and heat storage was created. For the development of new and innovative mortars, a proper balance of multiple additives, supported by the study of microstructural changes, can lead to an optimization of the compositions, ensuring that the mortar’s final properties are not affected.

Bulk undercooling

NASA Technical Reports Server (NTRS)

Kattamis, T. Z.

1984-01-01

Bulk undercooling methods and procedures will first be reviewed. Measurement of various parameters which are necessary to understand the solidification mechanism during and after recalescence will be discussed. During recalescence of levitated, glass-encased large droplets (5 to 8 mm diam) high speed temperature sensing devices coupled with a rapid response oscilloscope are now being used at MIT to measure local thermal behavior in hypoeutectic and eutectic binary Ni-Sn alloys. Dendrite tip velocities were measured by various investigators using thermal sensors or high speed cinematography. The confirmation of the validity of solidification models of bulk-undercooled melts is made difficult by the fineness of the final microstructure, the ultra-rapid evolution of the solidifying system which makes measurements very awkward, and the continuous modification of the microstructure which formed during recalescence because of precipitation, remelting and rapid coarsening.

Method for preparing ceramic composite

DOEpatents

Alexander, Kathleen B.; Tiegs, Terry N.; Becher, Paul F.; Waters, Shirley B.

1996-01-01

A process for preparing ceramic composite comprising blending TiC particulates, Al.sub.2 O.sub.3 particulates and nickle aluminide and consolidating the mixture at a temperature and pressure sufficient to produce a densified ceramic composite having fracture toughness equal to or greater than 7 MPa m.sup.1/2, a hardness equal to or greater than 18 GPa.

MANTECH Project Book, 1992

DTIC Science & Technology

1992-01-01

RUGATE FILTER PROCESS AND PRODUCTION ................ 111 MANUFACTURING SCIENCE FOR TITANIUM ALUMINIDE COMPOSITE ENGINE STRU CTURES...rejection and mission filters , anti-reflection coatings, and dichroic layers which can have demanding optical requirements. Rugate m coatings can be used to...SCIENCE RUGATE FILTER PROCESS AND PRODUCTION CONTRACT NUMBER: F33615-86-C-5059STATEMENT OF NEED Achieving the optical performance specifications for

Cracks growth behaviors of commercial pure titanium under nanosecond laser irradiation for formation of nanostructure-covered microstructures (with sub-5-μm)

NASA Astrophysics Data System (ADS)

Pan, A. F.; Wang, W. J.; Mei, X. S.; Zheng, B. X.; Yan, Z. X.

2016-11-01

This study reported on the formation of sub-5-μm microstructures covered on titanium by cracks growth under 10-ns laser radiation at the wavelength of 532 nm and its induced light modification for production of nanostructures. The electric field intensity and laser power density absorbed by commercial pure titanium were computed to investigate the self-trapping introduced by cracks and the effect of surface morphology on laser propagation characteristics. It is found that nanostructures can form at the surface with the curvature radius below 20 μm. Meanwhile, variable laser fluences were applied to explore the evolution of cracks on commercial pure titanium with or without melt as spot overlap number increased. Experimental study was first performed at the peak laser fluence of 1.063 J/cm2 to investigate the microstructures induced only by cracks growth. The results demonstrated that angular microstructures with size between 1.68 μm and 4.74 μm was obtained and no nanostructure covered. Then, at the peak laser fluence of 2.126 J/cm2, there were some nanostructures covered on the melt-induced curved microstructured surface. However, surface molten material submerged in the most of cracks at the spot overlap number of 744, where the old cracks disappeared. The results indicated that there was too much molten material and melting time at the peak laser fluence of 2.126 J/cm2, which was not suitable for obtainment of perfect micro-nano structures. On this basis, peak laser fluence was reduced down to 1.595 J/cm2 and the sharp sub-5 μm microstructures with nanostructures covered was obtained at spot overlap number of 3720.

Fabricating Superior NiAl Bronze Components through Wire Arc Additive Manufacturing.

PubMed

Ding, Donghong; Pan, Zengxi; van Duin, Stephen; Li, Huijun; Shen, Chen

2016-08-03

Cast nickel aluminum bronze (NAB) alloy is widely used for large engineering components in marine applications due to its excellent mechanical properties and corrosion resistance. Casting porosity, as well as coarse microstructure, however, are accompanied by a decrease in mechanical properties of cast NAB components. Although heat treatment, friction stir processing, and fusion welding were implemented to eliminate porosity, improve mechanical properties, and refine the microstructure of as-cast metal, their applications are limited to either surface modification or component repair. Instead of traditional casting techniques, this study focuses on developing NAB components using recently expanded wire arc additive manufacturing (WAAM). Consumable welding wire is melted and deposited layer-by-layer on substrates producing near-net shaped NAB components. Additively-manufactured NAB components without post-processing are fully dense, and exhibit fine microstructure, as well as comparable mechanical properties, to as-cast NAB alloy. The effects of heat input from the welding process and post-weld-heat-treatment (PWHT) are shown to give uniform NAB alloys with superior mechanical properties revealing potential marine applications of the WAAM technique in NAB production.

Strain rate effects on fracture behavior of Austempered Ductile Irons

NASA Astrophysics Data System (ADS)

Ruggiero, Andrew; Bonora, Nicola; Gentile, Domenico; Iannitti, Gianluca; Testa, Gabriel; Hörnqvist Colliander, Magnus; Masaggia, Stefano; Vettore, Federico

2017-06-01

Austempered Ductile Irons (ADIs), combining high strength, good ductility and low density, are candidates to be a suitable alternative to high-strength steels. Nevertheless, the concern about a low ductility under dynamic loads often leads designers to exclude cast irons for structural applications. However, results from dynamic tensile tests contradict this perception showing larger failure strain with respect to quasistatic data. The fracture behaviour of ADIs depends on damage mechanisms occurring in the spheroids of graphite, in the matrix and at their interface, with the matrix (ausferrite) consisting of acicular ferrite in carbon-enriched austenite. Here, a detailed microstructural analysis was performed on the ADI 1050-6 deformed under different conditions of strain rates, temperatures, and states of stress. Beside the smooth specimens used for uniaxial tensile tests, round notched bars to evaluate the ductility reduction with increasing stress triaxiality and tophat geometries to evaluate the propensity to shear localization and the associated microstructural alterations were tested. The aim of the work is to link the mechanical and fracture behavior of ADIs to the load condition through the microstructural modifications that occur for the corresponding deformation path.

Microstructural and techno-functional properties of cassava starch modified by ultrasound.

PubMed

Monroy, Yuliana; Rivero, Sandra; García, María A

2018-04-01

This work was focused on the correlation between the structural and techno-functional properties of ultrasound treated cassava starch for the preparation of tailor-made starch-based ingredients and derivatives. Furthermore, the effect of treatment time, sample conditioning and ultrasound amplitude was studied. Ultrasonic treatment of cassava starch induced structural disorganization and microstructural changes evidenced mainly in the morphological characteristics of the granules and in their degrees of crystallinity. These structural modifications were supported by ATR-FTIR and SEM and CSLM studies as well as DRX and thermal analysis. The selection of the processing conditions is critical due to the complete gelatinization of the starch was produced with the maximum amplitude tested and without temperature control. Rheological dynamical analysis indicated changes at the molecular level in starch granules due to the ultrasound treated, revealing the paste stability under refrigeration condition. PCA allow to establish the interrelationships between microstructural and techno-functional properties. In summary, different starch derivatives could be obtained by adjusting the ultrasound treatment conditions depending on their potential applications. Copyright © 2018 Elsevier B.V. All rights reserved.

Fabricating Superior NiAl Bronze Components through Wire Arc Additive Manufacturing

PubMed Central

Ding, Donghong; Pan, Zengxi; van Duin, Stephen; Li, Huijun; Shen, Chen

2016-01-01

Cast nickel aluminum bronze (NAB) alloy is widely used for large engineering components in marine applications due to its excellent mechanical properties and corrosion resistance. Casting porosity, as well as coarse microstructure, however, are accompanied by a decrease in mechanical properties of cast NAB components. Although heat treatment, friction stir processing, and fusion welding were implemented to eliminate porosity, improve mechanical properties, and refine the microstructure of as-cast metal, their applications are limited to either surface modification or component repair. Instead of traditional casting techniques, this study focuses on developing NAB components using recently expanded wire arc additive manufacturing (WAAM). Consumable welding wire is melted and deposited layer-by-layer on substrates producing near-net shaped NAB components. Additively-manufactured NAB components without post-processing are fully dense, and exhibit fine microstructure, as well as comparable mechanical properties, to as-cast NAB alloy. The effects of heat input from the welding process and post-weld-heat-treatment (PWHT) are shown to give uniform NAB alloys with superior mechanical properties revealing potential marine applications of the WAAM technique in NAB production. PMID:28773774

Novel microstructural growth in the surface of Inconel 625 by the addition of SiC under electron beam melting

NASA Astrophysics Data System (ADS)

Ahmad, M.; Ali, G.; Ahmed, Ejaz; Haq, M. A.; Akhter, J. I.

2011-06-01

Electron beam melting is being used to modify the microstructure of the surfaces of materials due to its ability to cause localized melting and supercooling of the melt. This article presents an experimental study on the surface modification of Ni-based superalloy (Inconel 625) reinforced with SiC ceramic particles under electron beam melting. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction techniques have been applied to characterize the resulted microstructure. The results revealed growth of novel structures like wire, rod, tubular, pyramid, bamboo and tweezers type morphologies in the modified surface. In addition to that fibrous like structure was also observed. Formation of thin carbon sheet has been found at the regions of decomposed SiC. Electron beam modified surface of Inconel 625 alloy has been hardened twice as compared to the as-received samples. Surface hardening effect may be attributed to both the formation of the novel structures as well as the introduction of Si and C atom in the lattice of Inconel 625 alloy.

Sleep Modifications in Acute Transient Global Amnesia

PubMed Central

Della Marca, Giacomo; Mazza, Marianna; Losurdo, Anna; Testani, Elisa; Broccolini, Aldobrando; Frisullo, Giovanni; Marano, Giuseppe; Morosetti, Roberta; Pilato, Fabio; Profice, Paolo; Vollono, Catello; Di Lazzaro, Vincenzo

2013-01-01

Study Objective: Transient global amnesia (TGA) is a temporary memory loss characterized by an abrupt onset of antero-grade and retrograde amnesia, totally reversible. Since sleep plays a major role in memory consolidation, and in the storage of memory-related traces into the brain cortex, the aims of the present study were: (1) to evaluate changes in sleep macro-structure in TGA; (2) to assess modifications in sleep micro-structure in TGA, with particular reference to the arousal EEG and to cyclic alternating pattern (CAP); (3) to compare sleep parameters in TGA patients with a control group of patients with acute ischemic events (“minor stroke” or transient ischemic attack [TIA]) clinically and neuroradiologically “similar” to the TGA. Methods: TGA group: 17 patients, (8 men and 9 women, 60.2 ± 12.5 years). Stroke or TIA (SoT) group: 17 patients hospitalized in the Stroke Unit for recent onset of minor stroke or TIA with hemispheric localization; healthy controls (HC) group: 17 healthy volunteers, matched for age and sex. Patients and controls underwent full-night polysomnography. Results: In the multivariate analysis (conditions TGA, SoT, and HC) a significant effect of the condition was observed for sleep efficiency index, number of awakenings longer 1 min, REM latency, CAP time, and CAP rate. TGA and SoT differed only for CAP time and CAP rate, which were lower in the TGA group. Conclusions: Microstructural modification associated with TGA could be consequent to: (1) hippocampal dysfunction and memory impairment; (2) impairment of arousal-related structures (in particular, cholinergic pathways); (3) emotional distress. Citation: Della Marca G; Mazza M; Losurdo A; Testani E; Broccolini A; Frisullo G; Marano G; Morosetti R; Pilato F; Profice P; Vollono C; Di Lazzaro V. Sleep modifications in acute transient global amnesia. J Clin Sleep Med 2013;9(9):921-927. PMID:23997704

Grain Refining and Microstructural Modification during Solidification.

DTIC Science & Technology

1983-10-01

was found to be insensitive to the iron concentration in the samples solidified in the levitated state but not in samples quenched from the liquid . The... liquid . The preliminary * results with niobium additions indicate that no appreciable grain refinement * is achieved when the samples are levitated in an...to the critical examination of the Cr-Ni phase diagram, by using high purity starting materials, and a containerless electromagnetic levitation

Food processing strategies to enhance phenolic compounds bioaccessibility and bioavailability in plant-based foods.

PubMed

Ribas-Agustí, Albert; Martín-Belloso, Olga; Soliva-Fortuny, Robert; Elez-Martínez, Pedro

2017-06-13

Phenolic compounds are important constituents of plant-based foods, as their presence is related to protective effects on health. To exert their biological activity, phenolic compounds must be released from the matrix during digestion in an absorbable form (bioaccessible) and finally absorbed and transferred to the bloodstream (bioavailable). Chemical structure and matrix interactions are some food-related factors that hamper phenolic compounds bioaccessibility and bioavailability, and that can be counteracted by food processing. It has been shown that food processing can induce chemical or physical modifications in food that enhance phenolic compounds bioaccessibility and bioavailability. These changes include: (i) chemical modifications into more bioaccessible and bioavailable forms; (ii) cleavage of covalent or hydrogen bonds or hydrophobic forces that attach phenolic compounds to matrix macromolecules; (iii) damaging microstructural barriers such as cell walls that impede the release from the matrix; and (iv) create microstructures that protect phenolic compounds until they are absorbed. Indeed, food processing can produce degradation of phenolic compounds, however, it is possible to counteract it by modulating the operating conditions in favor of increased bioaccessibility and bioavailability. This review compiles the current knowledge on the effects of processing on phenolic compounds bioaccessibility or bioavailability, while suggesting new guidelines in the search of optimal processing conditions as a step forward towards the design of healthier foods.

Orienting the Microstructure Evolution of Copper Phthalocyanine as an Anode Interlayer in Inverted Polymer Solar Cells for High Performance.

PubMed

Li, Zhiqi; Liu, Chunyu; Zhang, Xinyuan; Li, Shujun; Zhang, Xulin; Guo, Jiaxin; Guo, Wenbin; Zhang, Liu; Ruan, Shengping

2017-09-20

Recent advances in the interfacial modification of inverted-type polymer solar cells (PSCs) have resulted from controlling the surface energy of the cathode-modified layer (TiO 2 or ZnO) to enhance the short-circuit current (J sc ) or optimizing the contact morphology of the cathode (indium tin oxide or fluorine-doped tin oxide) and active layer to increase the fill factor. Herein, we report that the performance enhancement of PSCs is achieved by incorporating a donor macromolecule copper phthalocyanine (CuPc) as an anode modification layer. Using the approach based on orienting the microstructure evolution, uniformly dispersed island-shaped CuPc spot accumulations are built on the top of PTB7:PC 71 BM blend film, leading to an efficient spectral absorption and photogenerated exciton splitting. The best power conversion efficiency of PSCs is increased up to 9.726%. In addition to the enhanced light absorption, the tailored anode energy level alignment and optimized boundary morphology by incorporating the CuPc interlayer boost charge extraction efficiency and suppress the interfacial molecular recombination. These results demonstrate that surface morphology induction through molecular deposition is an effective method to improve the performance of PSCs, which reveals the potential implications of the interlayer between the organic active layer and the electrode buffer layer.

Influences of thermal environment on fish growth.

PubMed

Boltaña, Sebastián; Sanhueza, Nataly; Aguilar, Andrea; Gallardo-Escarate, Cristian; Arriagada, Gabriel; Valdes, Juan Antonio; Soto, Doris; Quiñones, Renato A

2017-09-01

Thermoregulation in ectothermic animals is influenced by the ability to effectively respond to thermal variations. While it is known that ectotherms are affected by thermal changes, it remains unknown whether physiological and/or metabolic traits are impacted by modifications to the thermal environment. Our research provides key evidence that fish ectotherms are highly influenced by thermal variability during development, which leads to important modifications at several metabolic levels (e.g., growth trajectories, microstructural alterations, muscle injuries, and molecular mechanisms). In Atlantic salmon ( Salmo salar ), a wide thermal range (Δ T 6.4°C) during development (posthatch larvae to juveniles) was associated with increases in key thermal performance measures for survival and growth trajectory. Other metabolic traits were also significantly influenced, such as size, muscle cellularity, and molecular growth regulators possibly affected by adaptive processes. In contrast, a restricted thermal range (Δ T 1.4°C) was detrimental to growth, survival, and cellular microstructure as muscle growth could not keep pace with increased metabolic demands. These findings provide a possible basic explanation for the effects of thermal environment during growth. In conclusion, our results highlight the key role of thermal range amplitude on survival and on interactions with major metabolism-regulating processes that have positive adaptive effects for organisms.

Unmanned Aerial Vehicles Roadmap 2000-2025

DTIC Science & Technology

2001-04-01

Develop and mature enabling materials technologies such as gamma titanium aluminides , refractory intermetallic alloys, ceramic matrix composites, higher...percent (see Figure 4.1.2-1). For UAV use, these goals may partially be met by deleting turbine blade containment rings and redundant controls, as well...and Barium Strontium Titanium (BST) used in uncooled LWIR detectors, and fabrication techniques of thin pixels will enable improved thermal

Method for preparing ceramic composite

DOEpatents

Alexander, K.B.; Tiegs, T.N.; Becher, P.F.; Waters, S.B.

1996-01-09

A process is disclosed for preparing ceramic composite comprising blending TiC particulates, Al{sub 2}O{sub 3} particulates and nickel aluminide and consolidating the mixture at a temperature and pressure sufficient to produce a densified ceramic composite having fracture toughness equal to or greater than 7 MPa m{sup 1/2}, a hardness equal to or greater than 18 GPa. 5 figs.

Hypersonic Technology Developments with EU Co-Funded Projects

DTIC Science & Technology

2010-09-01

metal or even high performance alloys . The hollow sphere technology allows high degrees of porosities, reproducible properties and fair process control...sandwich structure configuration will be investigated. Titanium alloys and Ti-aluminides exhibit excellent mechanical properties for applications where...cooling techniques, new alloys , improved thermodynamic cycles by increased pressure ratios and TIT, etc… As the Olympus 593 engine was based on the

Damage in gamma titanium aluminides due to small particle impacts

NASA Astrophysics Data System (ADS)

Stief, P. S.; Rubal, M. P.; Gray, G. T., III; Pereiras, J. M.

1998-10-01

Initiation of cracking due to small particle impacts on low ductility intermetallics is investigated experimentally and theoretically. The gamma titanium aluminide alloys of interest which are being considered for elevated temperature structural applications in aircraft engines exhibit tensile ductilities on the order of 1-2%. Cracking due to any source, including small particle impacts, is of concern given the rapid growth of cracks in fatigue. This investigation focuses on a model geometry which reproduces the rear face cracking that is induced by a small particle impinging on an air foil leading edge. Small steel spheres are projected onto thin plates at velocities ranging from 76 to 305 ms ; cracking is thereby induced on the rear surface of the plates. Through finite element analyses of the dynamic impact event and some analytical estimates, we examine the hypothesis that crack initiation due to small particle impacts can be correlated with material ductility and with the severity and spatial extent of the straining during the impact event. In addition, with the use of static indentation tests in which similar strain distributions are present, some insight is gained into the difference in ductility between high and low strain rates. 1998 Elsevier Science Ltd.

Thermomechanical Processing of Fe-6.9Al-2Cr-0.88C Steel: Intercritical Annealing Followed by Quench Tempering

NASA Astrophysics Data System (ADS)

Farahat, Ahmed Ismail Zaky; Mohamed, Masoud Ibrahim

2015-01-01

A hot forged Fe-0.88 pct C-6.9 pct Al steel was intercritically annealed at temperatures in the range of 1173 K to 1283 K (900 °C to 1010 °C), and subsequently tempered at 623 K (350 °C) to enhance the mechanical properties by microstructure modification. Room temperature compression tests were carried out to evaluate the influence of the intercritical annealing temperature on the mechanical properties. A substructure was present in the microstructure after each intercritical annealing treatment. The substructure was absent after annealing at 1263 K (990 °C) and higher temperatures. Over-aging occurred when the annealing temperature was increased to 1283 K (1010 °C). A remarkable increase in strength and ductility was achieved after annealing at 1263 K (990 °C).

Surface Modification by Friction Stir Processing of Low-Carbon Steel: Microstructure Investigation and Wear Performance

NASA Astrophysics Data System (ADS)

Sattari, Behnoosh; Shamanian, Morteza; Salimijazi, Farshid; Salehi, Mehdi

2018-02-01

A low-carbon steel sheet with a thickness of 5 mm was subjected to friction stir processing (FSP) by one to four different passes. The microstructures of different regions were characterized using the optical microscopy and electron backscatter diffraction. The Vickers micro-harness was measured at the distance of 200 μm below the processed surfaces. The influence of pass numbers (PNs) on wear resistance was studied in terms of coefficients of friction (CoFs), weight losses and wear rates. SEM topographies of the worn surfaces were also studied to evaluate the wear mechanisms. Microstructure observations showed that Widmänstatten ferrite plates were formed in stir zones (SZs) and heat affected zones. As PN increased, these grains were widened due to the increment of the carbon diffusivity and lengthened because of the high heat input and microstructure anisotropy. Besides, increasing the PN causes increasing of the hardness and wear resistance, simultaneously. Specifically, the wear rate in the SZ was reduced from 2.8 × 10-2 mm3 m-1 in base metal to 0.3 × 10-2 mm3 m-1 in sample which was subjected to 4 FSP passes. However, variation in PN had no considerable effect on CoFs. Oxidative wear mechanism was observed on the worn surface of the steel and the FSPed samples while more debris was formed by increasing the PNs.

Microstructural and surface modifications and hydroxyapatite coating of Ti-6Al-4V triply periodic minimal surface lattices fabricated by selective laser melting.

PubMed

Yan, Chunze; Hao, Liang; Hussein, Ahmed; Wei, Qingsong; Shi, Yusheng

2017-06-01

Ti-6Al-4V Gyroid triply periodic minimal surface (TPMS) lattices were manufactured by selective laser melting (SLM). The as-built Ti-6Al-4V lattices exhibit an out-of-equilibrium microstructure with very fine α' martensitic laths. When subjected to the heat treatment of 1050°C for 4h followed by furnace cooling, the lattices show a homogenous and equilibrium lamellar α+β microstructure with less dislocation and crystallographic defects compared with the as-built α' martensite. The as-built lattices present very rough strut surfaces bonded with plenty of partially melted metal particles. The sand blasting nearly removed all the bonded metal particles, but created many tiny cracks. The HCl etching eliminated these tiny cracks, and subsequent NaOH etching resulted in many small and shallow micro-pits and develops a sodium titanate hydrogel layer on the surfaces of the lattices. When soaked in simulated body fluid (SBF), the Ti-6Al-4V TPMS lattices were covered with a compact and homogeneous biomimetic hydroxyapatite (HA) layer. This work proposes a new method for making Ti-6Al-4V TPMS lattices with a homogenous and equilibrium microstructure and biomimetic HA coating, which show both tough and bioactive characteristics and can be promising materials usable as bone substitutes. Copyright © 2017 Elsevier B.V. All rights reserved.

Lanthanum doped strontium titanate - ceria anodes: deconvolution of impedance spectra and relationship with composition and microstructure

NASA Astrophysics Data System (ADS)

Burnat, Dariusz; Nasdaurk, Gunnar; Holzer, Lorenz; Kopecki, Michal; Heel, Andre

2018-05-01

Electrochemical performance of ceramic (Ni-free) SOFC anodes based on La0.2Sr0.7TiO3-δ (LST) and Gd0.1Ce0.9O1.95-δ (CGO) is thoroughly investigated. Microstructures and compositions are systematically varied around the percolation thresholds of both phases by modification of phase volume fractions, particle size distributions and firing temperature. Differential impedance spectroscopy was performed while varying gas composition, electrical potential and operating temperature, which allows determining four distinct electrode processes. Significant anode impedances are measured at low frequencies, which in contrast to the literature cannot be linked with gas concentration impedance. The dominant low frequency process (∼1 Hz) is attributed to the chemical capacitance. Combined EIS and microstructure investigations show that the chemical capacitance correlates inversely with the available surface area of CGO, indicating CGO surface reactions as the kinetic limitation for the dominant anode process and for the associated chemical capacitance. In anodes with a fine-grained microstructure this limitation is significantly smaller, which results in an impressive power output as high as 0.34 Wcm-2. The anodes show high redox stability by not only withstanding 30 isothermal redox cycles, but even improving the performance. Hence, compared to conventional Ni-cermet anodes the new LST-CGO material represents an interesting alternative with much improved redox-stability.

Effect of Adding Cerium on Microstructure and Morphology of Ce-Based Inclusions Formed in Low-Carbon Steel

PubMed Central

Adabavazeh, Z.; Hwang, W. S.; Su, Y. H.

2017-01-01

Intra-granular Acicular Ferrite (IAF), as one of the most well-known desirable microstructure of ferrite with a chaotic crystallographic orientation, can not only refine the microstructure and retard the propagation of cleavage crack but also provide excellent combination of strength and toughness in steel. The effect of adding cerium on microstructure and controlling proper cerium-based inclusions in order to improve properties in low-carbon commercial steel (SS400) were investigated. The type of inclusions can be controlled by changing S/O ratio and Ce content. Without Ce modification, MnS is a dominate inclusion. After adding Ce, the stable inclusion phases change from AlCeO3 to Ce2O2S. The optimum amount of cerium, 0.0235 wt.%, lead in proper grain refinement and formation of cerium oxide, oxy-sulfide and sulfide inclusions. Having a high amount of cerium results in increasing the number of inclusions significantly as a result it cannot be effective enough and the inclusions will act like barriers for others. It is found that the inclusions with a size of about 4∼7 μm can serve as heterogeneous nucleation sites for AF formation. Thermodynamic calculations have been applied to predict the inclusion formation in this molten steel as well, which show a good agreement with experimental one. PMID:28485376

[Surface modifications of titanium implant material with excimer laser for more effective osseointegration].

PubMed

Pelsoczi, Kovács István; Bereznai, Miklós; Tóth, Zsolt; Turzó, Kinga; Radnai, Márta; Bor, Zsolt; Fazekas, András

2004-12-01

The biointegration of dental and orthopaedic implants depends mainly on the morphology and physical-chemical properties of their surfaces. Accordingly, the development of the desired microstructure is a relevant requirement in the bulk manufacture. Besides the widely used sandblasting plus acid etching and plasma-spray coating techniques, the laser surface modification method offers a plausible alternative. In order to analyze the influence of the laser treatment, the surfaces of titanium samples were exposed to excimer laser irradiation. The aim of this study was to develop surfaces that provide optimal conditions for bone-implant contact, bone growth, formation and maintenance of gingival attachment. For this purpose, holes were ablated on the surface of samples by nanosecond (18 ns, ArF) and also sub-picosecond (0,5 ps, KrF) laser pulses. Using pulses of ns length, due to melt ejection, crown-like protrusions were formed at the border of the holes, which made them sensitive to mechanical effects. To avoid these undesirable crown-like structures ultrashort KrF excimer laser pulses were successfully applied. On the other hand, titanium samples were laser-polished in favour of formation and connection of healthy soft tissues. Irradiation by a series of nanosecond laser pulses resulted in an effective smoothening as detected by atomic force microscopy (AFM). By inhibiting plaque accumulation this favours formation of gingival attachment. X-ray photoelectron spectroscopy (XPS) studies showed that laser treatment, in addition to micro-structural and morphological modification, results in decreasing of surface contamination and thickening of the oxide layer. X-ray diffraction (XRD) analysis revealed that the original alpha-titanium crystalline structure of the laser-polished titanium surface was not altered by the irradiation.

Silane surface modification effects on the electromagnetic properties of phosphatized iron-based SMCs

NASA Astrophysics Data System (ADS)

Fan, Liang-Fang; Hsiang, Hsing-I.; Hung, Jia-Jing

2018-03-01

It is difficult to achieve homogeneous phosphatized iron powder dispersion in organic resins during the preparation of soft magnetic composites (SMCs). Inhomogeneous iron powder mixing in organic resins generally leads to the formation of micro-structural defects in SMCs and hence causes the magnetic properties to become worse. Phosphatized iron powder dispersion in organic resins can be improved by coating the phosphatized iron powder surfaces with a coupling agent. This study investigated the (3-aminopropyl) triethoxysilane (APTES) surface modification effects on the electromagnetic properties of phosphatized iron-based soft magnetic composites (SMCs). The results showed that the phosphatized iron powder surface can be modified using APTES to improve the phosphatized iron powder and epoxy resin compatibility and hence enhance phosphate iron powder epoxy mixing. The tensile strength, initial permeability, rated current under DC-bias superposition and magnetic loss in SMCs prepared using phosphatized iron powders can be effectively improved using APTES surface modification, which provides a promising candidate for power chip inductor applications.

Modification of the SERS spectrum of cyanide traces due to complex formation between cyanide and silver

NASA Astrophysics Data System (ADS)

Cao Dao, Tran; Kieu, Ngoc Minh; Quynh Ngan Luong, Truc; Cao, Tuan Anh; Hai Nguyen, Ngoc; Le, Van Vu

2018-06-01

It is well known that cyanide is an extremely toxic lethal poison with human death within minutes after exposure to only 300 ppm cyanide. On the other hand, cyanide is released into the environment (mainly through waste water) every day from various human activities. Therefore, rapid, sensitive and cost-effective cyanide trace detection is an urgent need. Surface-enhanced Raman scattering (SERS) is a method that meets these requirements. It should be noted, however, that in this technique SERS substrates, which are usually made of gold or silver, will be leached with aqueous cyanide by the formation of complexes between gold or silver with cyanide. This will cause the SERS spectrum of cyanide to be modified. When determining cyanide concentrations by SERS analysis, this spectral modification should be taken into account. This report presents the SERS spectral modification of aqueous cyanide traces (in ppm and lower concentration range) when the SERS substrates used are flower-like silver micro-structures.

Air Force Systems Command Research Planning Guide (Research Objectives).

DTIC Science & Technology

1987-07-15

potential for producing alloys with superior properties. Titanium and Iron Aluminides - Basic research to identify approaches leading to the formation...performance of ni’.kel, aluminumr,, and titanium alloys and ceramics are required to provide future Air Force weapon systems components with structural...seriously block full exploitat,on. Aluminum and Titanium Alloys - Three generic families of Pylie-,7 alloys are being investigated for both alloy

Chemical Vapor Synthesis of Niobium Aluminides

DTIC Science & Technology

1992-01-01

69 4.2.2 Deposition on Singly Supported Niobium Substrates ............ . . . ..... 72 4.3 DEPOSITION OF NbxSiy FROM H2, NbC15 , AND SICl4 ...direct CVD of NbxSiy from the hydrogen reduction of SiCl4 and NbCl5 is described by the overall reaction: xNbCl5 + ySiCl4 + (5x + 4y)/2 H2 - NbxSiy

Development of Iron Aluminides.

DTIC Science & Technology

1986-03-01

in the evolution of technology for the aerospace industry. This is particularly true for the gas turbine engine industry, where the requirements for...vulnerability of the U.S. gas turbine industry in terms of its heavy reliance upon non-domestic sources for much of its strategic metals requirements...superalloys used in gas turbine engines. The questionable future availability of chromium, for example, poses a potential serious threat to these applicacions

Corrosion-resistant fuel cladding allow for liquid metal fast breeder reactors

DOEpatents

Brehm, Jr., William F.; Colburn, Richard P.

1982-01-01

An aluminide coating for a fuel cladding tube for LMFBRs (liquid metal fast breeder reactors) such as those using liquid sodium as a heat transfer agent. The coating comprises a mixture of nickel-aluminum intermetallic phases and presents good corrosion resistance to liquid sodium at temperatures up to 700.degree. C. while additionally presenting a barrier to outward diffusion of .sup.54 Mn.

Insoluble coatings for Stirling engine heat pipe condenser surfaces

NASA Astrophysics Data System (ADS)

Dussinger, Peter M.

1993-09-01

The work done by Thermacore, Inc., Lancaster, Pennsylvania, for the Phase 1, 1992 SBIR National Aeronautics and Space Administration Contract, 'Insoluble Coatings for Stirling Engine Heat Pipe Condenser Surfaces' is described. The work was performed between January 1992 and July 1992. Stirling heat engines are being developed for electrical power generation use on manned and unmanned earth orbital and planetary missions. Dish Stirling solar systems and nuclear reactor Stirling systems are two of the most promising applications of the Stirling engine electrical power generation technology. The sources of thermal energy used to drive the Stirling engine typically are non-uniform in temperature and heat flux. Liquid metal heat pipe receivers are used as thermal transformers and isothermalizers to deliver the thermal energy at a uniform high temperature to the heat input section of the Stirling engine. The use of a heat pipe receiver greatly enhances system efficiency and potential life span. One issue that is raised during the design phase of heat pipe receivers is the potential solubility corrosion of the Stirling engine heat input section by the liquid metal working fluid. This Phase 1 effort initiated a program to evaluate and demonstrate coatings, applied to nickel based Stirling engine heater head materials, that are practically 'insoluble' in sodium, potassium, and NaK. This program initiated a study of nickel aluminide as a coating and developed and demonstrated a heat pipe test vehicle that can be used to test candidate materials and coatings. Nickel 200 and nickel aluminide coated Nickel 200 were tested for 1000 hours at 800 C at a condensation heat flux of 25 W/sq cm. Subsequent analyses of the samples showed no visible sign of solubility corrosion of either coated or uncoated samples. The analysis technique, photomicrographs at 200X, has a resolution of better than 2.5 microns (.0001 in). The results indicate that the heat pipe environment is not directly comparable to liquid metal pumped loop data, that nickel aluminide is still a leading candidate for solubility corrosion protection, and that longer duration tests are required to reach a definitive conclusion whether coatings are required at all. Should further testing be required, the test vehicle and analytical tools were developed.

Insoluble coatings for Stirling engine heat pipe condenser surfaces

NASA Technical Reports Server (NTRS)

Dussinger, Peter M.

1993-01-01

The work done by Thermacore, Inc., Lancaster, Pennsylvania, for the Phase 1, 1992 SBIR National Aeronautics and Space Administration Contract, 'Insoluble Coatings for Stirling Engine Heat Pipe Condenser Surfaces' is described. The work was performed between January 1992 and July 1992. Stirling heat engines are being developed for electrical power generation use on manned and unmanned earth orbital and planetary missions. Dish Stirling solar systems and nuclear reactor Stirling systems are two of the most promising applications of the Stirling engine electrical power generation technology. The sources of thermal energy used to drive the Stirling engine typically are non-uniform in temperature and heat flux. Liquid metal heat pipe receivers are used as thermal transformers and isothermalizers to deliver the thermal energy at a uniform high temperature to the heat input section of the Stirling engine. The use of a heat pipe receiver greatly enhances system efficiency and potential life span. One issue that is raised during the design phase of heat pipe receivers is the potential solubility corrosion of the Stirling engine heat input section by the liquid metal working fluid. This Phase 1 effort initiated a program to evaluate and demonstrate coatings, applied to nickel based Stirling engine heater head materials, that are practically 'insoluble' in sodium, potassium, and NaK. This program initiated a study of nickel aluminide as a coating and developed and demonstrated a heat pipe test vehicle that can be used to test candidate materials and coatings. Nickel 200 and nickel aluminide coated Nickel 200 were tested for 1000 hours at 800 C at a condensation heat flux of 25 W/sq cm. Subsequent analyses of the samples showed no visible sign of solubility corrosion of either coated or uncoated samples. The analysis technique, photomicrographs at 200X, has a resolution of better than 2.5 microns (.0001 in). The results indicate that the heat pipe environment is not directly comparable to liquid metal pumped loop data, that nickel aluminide is still a leading candidate for solubility corrosion protection, and that longer duration tests are required to reach a definitive conclusion whether coatings are required at all. Should further testing be required, the test vehicle and analytical tools were developed.

Melting of SiC powders preplaced duplex stainless steel using TIG welding

NASA Astrophysics Data System (ADS)

Maleque, M. A.; Afiq, M.

2018-01-01

TIG torch welding technique is a conventional melting technique for the cladding of metallic materials. Duplex stainless steels (DSS) show decrease in performance under aggressive environment which may lead to unanticipated failure due to poor surface properties. In this research, surface modification is done by using TIG torch method where silicon carbide (SiC) particles are fused into DSS substrate in order to form a new intermetallic compound at the surface. The effect of particle size, feed rate of SiC preplacement, energy input and shielding gas flow rate on surface topography, microstructure, microstructure and hardness are investigated. Deepest melt pool (1.237 mm) is produced via TIG torch with highest energy input of 1080 J/mm. Observations of surface topography shows rippling marks which confirms that re-solidification process has taken place. Melt microstructure consist of dendritic and globular carbides precipitate as well as partially melted silicon carbides (SiC) particles. Micro hardness recorded at value ranging from 316 HV0.5 to 1277 HV0.5 which shows increment from base hardness of 260 HV0.5kgf. The analyzed result showed that incorporation of silicon carbide particles via TIG Torch method increase the hardness of DSS.

Evolution of thermo-physical properties and annealing of fast neutron irradiated boron carbide

NASA Astrophysics Data System (ADS)

Gosset, Dominique; Kryger, Bernard; Bonal, Jean-Pierre; Verdeau, Caroline; Froment, Karine

2018-03-01

Boron carbide is widely used as a neutron absorber in most nuclear reactors, in particular in fast neutron ones. The irradiation leads to a large helium production (up to 1022/cm3) together with a strong decrease of the thermal conductivity. In this paper, we have performed thermal diffusivity measurements and X-ray diffraction analyses on boron carbide samples coming from control rods of the French Phenix LMFBR reactor. The burnups range from 1021 to 8.1021/cm3. We first confirm the strong decrease of the thermal conductivity at the low burnup, together with high microstructural modifications: swelling, large micro-strains, high defects density, and disordered-like material conductivity. We observe the microstructural parameters are highly anisotropic, with high micro-strains and flattened coherent diffracting domains along the (00l) direction of the hexagonal structure. Performing heat treatments up to high temperature (2200 °C) allows us to observe the material thermal conductivity and microstructure restoration. It then appears the thermal conductivity healing is correlated to the micro-strain relaxation. We then assume the defects responsible for most of the damage are the helium bubbles and the associated stress fields.

Surface modification of hydroturbine steel using friction stir processing

NASA Astrophysics Data System (ADS)

Grewal, H. S.; Arora, H. S.; Singh, H.; Agrawal, A.

2013-03-01

Friction stir processing (FSP) has proved to be a viable tool for enhancing the mechanical properties of materials, however, the major focus has been upon improving the bulk properties of light metals and their alloys. Hydroturbines are susceptible to damage owing to slurry and cavitation erosion. In this study, FSP of a commonly employed hydroturbine steel, 13Cr4Ni was undertaken. Microstructural characterization of the processed steel was conducted using optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and electron back scatter diffraction (EBSD) techniques. Mechanical characterization of the steel was undertaken in terms of microhardness and resistance to cavitation erosion (CE). FSP resulted in the refinement of the microstructure with reduction in grain size by a factor of 10. EBSD results confirmed the existence of submicron and ultrafine grained microstructure. The microhardness of the steel was found to enhance by 2.6 times after processing. The processed steel also showed 2.4 times higher resistance against cavitation erosion in comparison to unprocessed steel. The primary erosion mechanism for both the steels was identical in nature, with plastic deformation responsible for the loss of material.

Phase transformation in δ-Pu alloys at low temperature: An in situ microstructural characterization using X-ray diffraction

NASA Astrophysics Data System (ADS)

Ravat, B.; Platteau, C.; Texier, G.; Oudot, B.; Delaunay, F.

2009-09-01

In order to investigate the martensitic transformation, an isothermal hold at -130 °C for 48 h was performed on a highly homogenized PuGa alloy. The modifications of the microstructure were characterized in situ thanks to a specific tool. This device was developed at the CEA-Valduc to analyze the crystalline structure of plutonium alloys as a function of temperature and more especially at low temperature using X-ray diffraction. The analysis of the recorded diffraction patterns highlighted that the martensitic transformation for this alloy is the result of a direct δ → α' + δ phase transformation. Moreover, a significant Bragg's peaks broadening corresponding to the δ-phase was observed. A microstructural analysis was made to characterize anisotropic microstrain resulting from the stress induced by the unit cell volume difference between the δ and α' phases. The amount of α'-phase evolved was analyzed within the framework of the Avrami theory in order to characterize the nucleation process. The results suggested that the growth mechanism corresponded to a general mechanism where the nucleation sites were in the δ-grain edges and the α'-phase had a plate-like morphology.

Tailored Buckling Microlattices as Reusable Light-Weight Shock Absorbers.

PubMed

Frenzel, Tobias; Findeisen, Claudio; Kadic, Muamer; Gumbsch, Peter; Wegener, Martin

2016-07-01

Structures and materials absorbing mechanical (shock) energy commonly exploit either viscoelasticity or destructive modifications. Based on a class of uniaxial light-weight geometrically nonlinear mechanical microlattices and using buckling of inner elements, either a sequence of snap-ins followed by irreversible hysteretic - yet repeatable - self-recovery or multistability is achieved, enabling programmable behavior. Proof-of-principle experiments on three-dimensional polymer microstructures are presented. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Grain boundary modification to suppress lithium penetration through garnet-type solid electrolyte

NASA Astrophysics Data System (ADS)

Hongahally Basappa, Rajendra; Ito, Tomoko; Morimura, Takao; Bekarevich, Raman; Mitsuishi, Kazutaka; Yamada, Hirotoshi

2017-09-01

Garnet-type solid electrolytes are one of key materials to enable practical usage of lithium metal anode for high-energy-density batteries. However, it suffers from lithium growth in pellets on charging, which causes short circuit. In this study, grain boundaries of Li6.5La3Zr1.5Ta0.5O12 (LLZT) pellets are modified with Li2CO3 and LiOH to investigate the influence of the microstructure of grain boundaries on lithium growth and to study the mechanism of the lithium growth. In spite of similar properties (relative density of ca. 96% and total ionic conductivity of 7 × 10-4 S cm-1 at 25 °C), the obtained pellets exhibit different tolerance on the short circuit. The LLZT pellets prepared from LiOH-modified LLZT powders exhibit rather high critical current density of 0.6 mA cm-2, at which short circuit occurs. On the other hand, the LLZT pellets without grain boundary modification short-circuited at 0.15 mA cm-2. Microstructural analyses by means of SEM, STEM and EIS suggest that lithium grows through interconnected open voids, and reveal that surface layers such as Li2CO3 and LiOH are not only plug voids but also facilitate the sintering of LLZT to suppress the lithium growth. The results indicate a strategy towards short-circuit-free lithium metal batteries.

Electron-beam irradiation induced transformation of Cu2(OH)3NO3 nanoflakes into nanocrystalline CuO

NASA Astrophysics Data System (ADS)

Padhi, S. K.; Gottapu, S. N.; Krishna, M. Ghanashyam

2016-05-01

The transmission electron microscope electron-beam (TEM e-beam) as a material modification tool has been demonstrated. The material modification is realised in the high-resolution TEM mode (largest condenser aperture, 150 μm, and 200 nm spot size) at a 200 keV beam energy. The Cu2(OH)3NO3 (CHN) nanoflakes used in this study were microwave solution processed that were layered single crystals and radiation sensitive. The single domain CHN flakes disintegrate into a large number of individual CuO crystallites within a 90 s span of time. The sequential bright-field, dark-field, and selected area electron diffraction modes were employed to record the evolved morphology, microstructural changes, and structural transformation that validate CHN modification. High-resolution transmission electron microscopy imaging of e-beam irradiated regions unambiguously supports the growth of CuO nanoparticles (11.8(3.2) nm in diameter). This study demonstrates e-beam irradiation induced CHN depletion, subsequent nucleation and growth of nanocrystalline CuO regions well embedded in the parent burnt porous matrix which can be useful for miniaturized sensing applications. NaBH4 induced room temperature reduction of CHN to elemental Cu and its printability on paper was also demonstrated.The transmission electron microscope electron-beam (TEM e-beam) as a material modification tool has been demonstrated. The material modification is realised in the high-resolution TEM mode (largest condenser aperture, 150 μm, and 200 nm spot size) at a 200 keV beam energy. The Cu2(OH)3NO3 (CHN) nanoflakes used in this study were microwave solution processed that were layered single crystals and radiation sensitive. The single domain CHN flakes disintegrate into a large number of individual CuO crystallites within a 90 s span of time. The sequential bright-field, dark-field, and selected area electron diffraction modes were employed to record the evolved morphology, microstructural changes, and structural transformation that validate CHN modification. High-resolution transmission electron microscopy imaging of e-beam irradiated regions unambiguously supports the growth of CuO nanoparticles (11.8(3.2) nm in diameter). This study demonstrates e-beam irradiation induced CHN depletion, subsequent nucleation and growth of nanocrystalline CuO regions well embedded in the parent burnt porous matrix which can be useful for miniaturized sensing applications. NaBH4 induced room temperature reduction of CHN to elemental Cu and its printability on paper was also demonstrated. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02572b

Effects of Surface-Modified MgO Nanoparticles on Inclusion Characteristics and Microstructure in Carbon Structural Steel

NASA Astrophysics Data System (ADS)

Guo, Hao; Yang, Shufeng; Li, Jingshe; Zhao, Mengjing; Chen, Zhengyang; Zhang, Xueliang; Li, Jikang

2018-05-01

An innovative approach involving chemical modification of the surface of MgO nanoparticles (NPs) for steelmaking and application of NPs to carbon structural steel has been investigated. The results show that the inclusions in the test steels were completely converted to MgAl2O4 spinel or MnS complex inclusions. The mean inclusion size decreased with increasing NP content from 0.01% to 0.03%, but increased at 0.05% because of NP aggregation. Addition of NPs increased the amount of intragranular ferrite and prevented polygonal ferrite formation, thereby enhancing the impact toughness. Impact tests showed that the dimple fractures in steel with 0.05% NP content were deeper than those in the other samples because the MgAl2O4 inclusions were larger. The surface-modified MgO NPs had a major effect on the inclusion characteristics and microstructure of carbon structural steel.

Phase development in a U-7 wt.% Mo vs. Al-7 wt.% Ge diffusion couple

NASA Astrophysics Data System (ADS)

Perez, E.; Keiser, D. D.; Sohn, Y. H.

2013-10-01

Fuel development for the Reduced Enrichment for Research and Test Reactors (RERTR) program has demonstrated that U-Mo alloys in contact with Al develop interaction regions with phases that have poor irradiation behavior. The addition of Si to the Al has been considered with positive results. In this study, compositional modification is considered by replacing Si with Ge to determine the effect on the phase development in the system. The microstructural and phase development of a diffusion couple of U-7 wt.% Mo in contact with Al-7 wt.% Ge was examined by transmission electron microscopy, scanning electron microscopy and energy dispersive spectroscopy. The interdiffusion zone developed a microstructure that included the cubic-UGe3 phase and amorphous phases. The UGe3 phase was observed with and without Mo and Al solid solution developing a (U,Mo)(Al,Ge)3 phase.

One - step nanosecond laser microstructuring, sulfur hyperdoping, and annealing of silicon surfaces in liquid carbondisulfide

NASA Astrophysics Data System (ADS)

Van Luong, Nguyen; Danilov, P. A.; Ionin, A. A.; Khmel'nitskii, P. A.; Kudryashov, S. I.; Mel'nik, N. N.; Saraeva, I. N.; Смirnov, H. A.; Rudenko, A. A.; Zayarny, D. A.

2017-09-01

We perform a single-shot IR nanosecond laser processing of commercial silicon wafers in ambient air and under a 2 mm thick carbon disulfide liquid layer. We characterize the surface spots modified in the liquid ambient and the spots ablated under the same conditions in air in terms of its surface topography, chemical composition, band-structure modification, and crystalline structure by means of SEM and EDX microscopy, as well as of FT-IR and Raman spectroscopy. These studies indicate that single-step microstructuring and deep (up to 2-3% on the surface) hyperdoping of the crystalline silicon in its submicron surface layer, preserving via pulsed laser annealing its crystallinity and providing high (103 - 104 cm-1) spectrally at near- and mid-IR absorption coefficients, can be obtained in this novel approach, which is very promising for thin - film silicon photovoltaic devices

BaTiO3-based piezoelectrics: Fundamentals, current status, and perspectives

NASA Astrophysics Data System (ADS)

Acosta, M.; Novak, N.; Rojas, V.; Patel, S.; Vaish, R.; Koruza, J.; Rossetti, G. A.; Rödel, J.

2017-12-01

We present a critical review that encompasses the fundamentals and state-of-the-art knowledge of barium titanate-based piezoelectrics. First, the essential crystallography, thermodynamic relations, and concepts necessary to understand piezoelectricity and ferroelectricity in barium titanate are discussed. Strategies to optimize piezoelectric properties through microstructure control and chemical modification are also introduced. Thereafter, we systematically review the synthesis, microstructure, and phase diagrams of barium titanate-based piezoelectrics and provide a detailed compilation of their functional and mechanical properties. The most salient materials treated include the (Ba,Ca)(Zr,Ti)O3, (Ba,Ca)(Sn,Ti)O3, and (Ba,Ca)(Hf,Ti)O3 solid solution systems. The technological relevance of barium titanate-based piezoelectrics is also discussed and some potential market indicators are outlined. Finally, perspectives on productive lines of future research and promising areas for the applications of these materials are presented.

Microstructure and calorimetric behavior of laser welded open cell foams in CuZnAl shape memory alloy

NASA Astrophysics Data System (ADS)

Biffi, Carlo Alberto; Previtali, Barbara; Tuissi, Ausonio

Cellular shape memory alloys (SMAs) are very promising smart materials able to combine functional properties of the material with lightness, stiffness, and damping capacity of the cellular structure. Their processing with low modification of the material properties remains an open question. In this work, the laser weldability of CuZnAl SMA in the form of open cell foams was studied. The cellular structure was proved to be successfully welded in lap joint configuration by using a thin plate of the same alloy. Softening was seen in the welded bead in all the investigated ranges of process speed as well as a double stage heat affected zone was identified due to different microstructures; the martensitic transformation was shifted to higher temperatures and the corresponding peaks were sharper with respect to the base material due to the rapid solidification of the material. Anyways, no compositional variations were detected in the joints.

Laser surface modification of 316 L stainless steel with bioactive hydroxyapatite.

PubMed

Balla, Vamsi Krishna; Das, Mitun; Bose, Sreyashree; Ram, G D Janaki; Manna, Indranil

2013-12-01

Laser-engineered net shaping (LENS™), a commercial additive manufacturing process, was used to modify the surfaces of 316 L stainless steel with bioactive hydroxyapatite (HAP). The modified surfaces were characterized in terms of their microstructure, hardness and apatite forming ability. The results showed that with increase in laser energy input from 32 J/mm(2) to 59 J/mm(2) the thickness of the modified surface increased from 222±12 μm to 355±6 μm, while the average surface hardness decreased marginally from 403±18 HV0.3 to 372±8 HV0.3. Microstructural studies showed that the modified surface consisted of austenite dendrites with HAP and some reaction products primarily occurring in the inter-dendritic regions. Finally, the surface-modified 316 L samples immersed in simulated body fluids showed significantly higher apatite precipitation compared to unmodified 316 L samples. © 2013.

Modification of Lightweight Aggregates' Microstructure by Used Motor Oil Addition.

PubMed

Franus, Małgorzata; Jozefaciuk, Grzegorz; Bandura, Lidia; Lamorski, Krzysztof; Hajnos, Mieczysław; Franus, Wojciech

2016-10-18

An admixture of lightweight aggregate substrates (beidellitic clay containing 10 wt % of natural clinoptilolite or Na-P1 zeolite) with used motor oil (1 wt %-8 wt %) caused marked changes in the aggregates' microstructure, measured by a combination of mercury porosimetry (MIP), microtomography (MT), and scanning electron microscopy. Maximum porosity was produced at low (1%-2%) oil concentrations and it dropped at higher concentrations, opposite to the aggregates' bulk density. Average pore radii, measured by MIP, decreased with an increasing oil concentration, whereas larger (MT) pore sizes tended to increase. Fractal dimension, derived from MIP data, changed similarly to the MIP pore radius, while that derived from MT remained unaltered. Solid phase density, measured by helium pycnometry, initially dropped slightly and then increased with the amount of oil added, which was most probably connected to changes in the formation of extremely small closed pores that were not available for He atoms.

Novel pre-alloyed powder processing of modified alnico 8: Correlation of microstructure and magnetic properties

DOE PAGES

Anderson, I. E.; Kassen, A. G.; White, E. M. H.; ...

2015-04-13

Progress is reviewed on development of an improved near-final bulk magnet fabrication process for alnico 8, as a non-rare earth permanent magnet with promise for sufficient energy density and coercivity for electric drive motors. This study showed that alnico bulk magnets in near-final shape can be made by simple compression molding from spherical high purity gas atomized pre-alloyed powder. Dwell time at peak sintering temperature (1250°C) greatly affected grain size of the resulting magnet alloys. This microstructure transformation was demonstrated to be useful for gaining partially aligned magnetic properties and boosting energy product. Furthermore, while a route to increased coercivitymore » was not identified by these experiments, manufacturability of bulk alnico magnet alloys in near-final shapes was demonstrated, permitting further processing and alloy modification experiments that can target higher coercivity and better control of grain anisotropy during grain growth.« less

Multi-scale Modeling of Radiation Damage: Large Scale Data Analysis

NASA Astrophysics Data System (ADS)

Warrier, M.; Bhardwaj, U.; Bukkuru, S.

2016-10-01

Modification of materials in nuclear reactors due to neutron irradiation is a multiscale problem. These neutrons pass through materials creating several energetic primary knock-on atoms (PKA) which cause localized collision cascades creating damage tracks, defects (interstitials and vacancies) and defect clusters depending on the energy of the PKA. These defects diffuse and recombine throughout the whole duration of operation of the reactor, thereby changing the micro-structure of the material and its properties. It is therefore desirable to develop predictive computational tools to simulate the micro-structural changes of irradiated materials. In this paper we describe how statistical averages of the collision cascades from thousands of MD simulations are used to provide inputs to Kinetic Monte Carlo (KMC) simulations which can handle larger sizes, more defects and longer time durations. Use of unsupervised learning and graph optimization in handling and analyzing large scale MD data will be highlighted.

Modification of Lightweight Aggregates’ Microstructure by Used Motor Oil Addition

PubMed Central

Franus, Małgorzata; Jozefaciuk, Grzegorz; Bandura, Lidia; Lamorski, Krzysztof; Hajnos, Mieczysław; Franus, Wojciech

2016-01-01

An admixture of lightweight aggregate substrates (beidellitic clay containing 10 wt % of natural clinoptilolite or Na-P1 zeolite) with used motor oil (1 wt %–8 wt %) caused marked changes in the aggregates’ microstructure, measured by a combination of mercury porosimetry (MIP), microtomography (MT), and scanning electron microscopy. Maximum porosity was produced at low (1%–2%) oil concentrations and it dropped at higher concentrations, opposite to the aggregates’ bulk density. Average pore radii, measured by MIP, decreased with an increasing oil concentration, whereas larger (MT) pore sizes tended to increase. Fractal dimension, derived from MIP data, changed similarly to the MIP pore radius, while that derived from MT remained unaltered. Solid phase density, measured by helium pycnometry, initially dropped slightly and then increased with the amount of oil added, which was most probably connected to changes in the formation of extremely small closed pores that were not available for He atoms. PMID:28773964

Water diffusion to assess meat microstructure.

PubMed

Laghi, Luca; Venturi, Luca; Dellarosa, Nicolò; Petracci, Massimiliano

2017-12-01

In the quest for setting up rapid methods to evaluate water retention ability of meat microstructures, time domain nuclear magnetic resonance (TD-NMR) has gained a prominent role, due to the possibility to observe water located outside the myofibrils, easily lost upon storage or cooking. Diffusion weighted signals could be used to monitor the shape and dimension of the pores in which water is confined, thus boosting the information offered by TD-NMR. The work outlines a parsimonious model to describe relative abundance and diffusion coefficient of intra and extra myofibrillar water populations, exchange rate between them, diameter of the myofibrillar cells. To test our model, we registered diffusion and T 2 weighted NMR signals at 20MHz on fresh meat from pectoralis major muscle of 100days old female turkey. We then purposely altered water distribution and myofibrils shape by means of freezing. The model predicted nicely the consequences of the imposed modifications. Copyright © 2016. Published by Elsevier Ltd.

Next Generation Thermal Barrier Coatings for the Gas Turbine Industry

NASA Astrophysics Data System (ADS)

Curry, Nicholas; Markocsan, Nicolaie; Li, Xin-Hai; Tricoire, Aurélien; Dorfman, Mitch

2011-01-01

The aim of this study is to develop the next generation of production ready air plasma sprayed thermal barrier coating with a low conductivity and long lifetime. A number of coating architectures were produced using commercially available plasma spray guns. Modifications were made to powder chemistry, including high purity powders, dysprosia stabilized zirconia powders, and powders containing porosity formers. Agglomerated & sintered and homogenized oven spheroidized powder morphologies were used to attain beneficial microstructures. Dual layer coatings were produced using the two powders. Laser flash technique was used to evaluate the thermal conductivity of the coating systems from room temperature to 1200 °C. Tests were performed on as-sprayed samples and samples were heat treated for 100 h at 1150 °C. Thermal conductivity results were correlated to the coating microstructure using image analysis of porosity and cracks. The results show the influence of beneficial porosity on reducing the thermal conductivity of the produced coatings.

Laser surface alloying on aluminum and its alloys: A review

NASA Astrophysics Data System (ADS)

Chi, Yiming; Gu, Guochao; Yu, Huijun; Chen, Chuanzhong

2018-01-01

Aluminum and its alloys have been widely used in aerospace, automotive and transportation industries owing to their excellent properties such as high specific strength, good ductility and light weight. Surface modification is of crucial importance to the surface properties of aluminum and its alloys since high coefficient of friction, wear characteristics and low hardness have limited their long term performance. Laser surface alloying is one of the most effective methods of producing proper microstructure by means of non-equilibrium solidification which results from rapid heating and cooling. In this paper, the influence of different processing parameters, such as laser power and scanning velocity is discussed. The developments of various material systems including ceramics, metals or alloys, and metal matrix composites (MMCs) are reviewed. The microstructure, hardness, wear properties and other behaviors of laser treated layer are analyzed. Besides, the existing problems during laser surface treatment and the corresponding solutions are elucidated and the future developments are predicted.

Multifunctional zirconium nitride/copper multilayer coatings on medical grade 316L SS and titanium substrates for biomedical applications.

PubMed

Kumar, D Dinesh; Kaliaraj, Gobi Saravanan

2018-01-01

Protecting from wear and corrosion of many medical devices in the biomedical field is an existing scientific challenge. Surface modification with multilayer ZrN/Cu coating was deposited on medical grade stainless steel (SS) and titanium substrates to enhance their surface properties. Structural results revealed that the ZrN/Cu coatings are highly crystalline and uniform microstructure on both the substrates. Dry and wet tribological measurements of the coated titanium substrate exhibit enhanced wear resistance and low friction coefficient due to the improved microstructure. Similarly, the corrosion resistance was exceptionally improved on titanium substrates, resulting from the high inertness of coating to the SBF electrolyte solution. Antibacterial activity and epifluorescence results signify the effective killing of pathogens by means of ion release killing as well as contact killing mechanisms. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of Thermal and Chemical Treatment on the Microstructural, Mechanical and Machining Performance of W319 Al-Si-Cu Cast Alloy Engine Blocks and Directionally Solidified Machinability Test Blocks

NASA Astrophysics Data System (ADS)

Szablewski, Daniel

The research presented in this work is focused on making a link between casting microstructural, mechanical and machining properties for 319 Al-Si sand cast components. In order to achieve this, a unique Machinability Test Block (MTB) is designed to simulate the Nemak V6 Al-Si engine block solidification behavior. This MTB is then utilized to cast structures with in-situ nano-alumina particle master alloy additions that are Mg based, as well as independent in-situ Mg additions, and Sr additions to the MTB. The Universal Metallurgical Simulator and Analyzer (UMSA) Technology Platform is utilized for characterization of each cast structure at different Secondary Dendrite Arm Spacing (SDAS) levels. The rapid quench method and Jominy testing is used to assess the capability of the nano-alumina master alloy to modify the microstructure at different SDAS levels. Mechanical property assessment of the MTB is done at different SDAS levels on cast structures with master alloy additions described above. Weibull and Quality Index statistical analysis tools are then utilized to assess the mechanical properties. The MTB is also used to study single pass high speed face milling and bi-metallic cutting operations where the Al-Si hypoeutectic structure is combined with hypereutectoid Al-Si liners and cast iron cylinder liners. These studies are utilized to aid the implementation of Al-Si liners into the Nemak V6 engine block and bi-metallic cutting of the head decks. Machining behavior is also quantified for the investigated microstructures, and the Silicon Modification Level (SiML) is utilized for microstructural analysis as it relates to the machining behavior.

Biometric, microstructural, and high-resolution trace element studies in Crassostrea gigas of Cantabria (Bay of Biscay, Spain): Anthropogenic and seasonal influences

NASA Astrophysics Data System (ADS)

Higuera-Ruiz, R.; Elorza, J.

2009-04-01

Living Crassostrea gigas oysters of different ages and sizes were collected in three estuaries of Cantabria (Bay of Biscay, Spain): San Vicente de la Barquera Estuary, Santander Bay, and Marismas de Santoña Estuary. The main objective was to determine different shell responses to variable environmental parameters. A shell morphological study, based on three biometric indices, indicates that oysters of Santander Bay have two significant shell anomalies: abnormal thickening of the right valve and loss of vital cavity volume. These shell abnormalities are related with the presence in these waters of the chemical tributyltin. In the other two estuaries, the oysters show no detectable anomalies. Four shell microstructures have been distinguished: Regular Simple Prismatic, Regular Foliated, cone-Complex Cross Foliated, and Chalk. In Santander Bay oysters, the Chalk forms a "root-type" framework, whereas in the other two estuaries it forms a more compact microstructure. It is proposed that exposure to tributyltin has produced this modification. High-spatial-resolution geochemical transects have been carried out on the Regular Foliated microstructure in the umbo region in order to evaluate the distribution of Mg, Sr, and Na. The elements analysed exhibit clear cyclic variations in San Vicente de la Barquera Estuary and Marismas de Santoña Estuary oysters, related with seasonal periods, and characterised by broad maxima during months in which the waters are warmer and have higher salinity. These patterns are buffered in Santander Bay oysters. Our results demonstrate that biometric, microstructural, and high-resolution trace element studies in oyster shells can provide information about contaminants and seasonal variations in the estuarine environment.

Direct generation of superhydrophobic microstructures in metals by UV laser sources in the nanosecond regime

NASA Astrophysics Data System (ADS)

Ocaña, Jose L.; Jagdheesh, R.; García-Ballesteros, J. J.

2016-02-01

The current availability of new advanced fiber and DPSS lasers with characteristic pulse lengths ranging from ns to fs has provided a unique frame in which the development of laser-generated microstructures has been made possible for very diverse kinds of materials and applications. At the same time, the development of the appropriate laser-processing workstations granting the appropriate precision and repeatability of the respective laser interaction processes in line with the characteristic dimension features required in the microstructured samples has definitively consolidated laser surface microstructuring as a reference domain, nowadays, unavoidable for the design and manufacturing of current use microsystem: MEMSs, fluidic devices, advanced sensors, biomedical devices and instruments, etc., are all among the most well-known developments of the micromanufacturing technology. Completing the broad spectrum of applications developed mostly involving the generation of geometrical features on a subtrate with specific functional purposes, a relatively new, emerging class of laser-microstructuring techniques is finding an important niche of application in the generation of physically structured surfaces (particularly of metallic materials) with specific contact, friction, and wear functionalities, for whose generation the concourse of different types of laser sources is being found as an appropriate tool. In this paper, the application of laser sources with emission in the UV and at ns time regime to the surface structuration of metal surfaces (specifically Al) for the modification of their wettability properties is described as an attractive application basis for the generation of self-cleaning properties of extended functional surfaces. Flat aluminum sheets of thickness 100 μm were laser machined with ultraviolet laser pulses of 30 ns with different laser parameters to optimize the process parameters. The samples produced at the optimum conditions with respect to contact angle measurement were subjected to microstructure and chemical analysis. The wetting properties were evaluated by static contact angle measurements on the laser-patterned surface. The laser-patterned microstructures exhibited superhydrophobicity with a maximum contact angle of 180° for the droplet volumes in the range of 8-12 μl.

Inorganic Composite Materials in Japan: Status and Trends

DTIC Science & Technology

1989-11-01

is planned with have already done some preliminary work) more sayby engineers and scientists and less on titanium and aluminide matrix compos- by...structural reliability of continued research in elevated tempera- the components. ture fiber and ceramic matrix composites. F=aMoving Blade (FRP...Forming Kawasaki 11eavy Ind with regard to these program target goals ONRFE M7 6 for carbon (CF), SiC, and boron filaments in isotropic titanium

International Conference on Superplasticity and Superplastic Forming

DTIC Science & Technology

1988-08-09

aluminides and other intermetallic compounds, as well as certain metal matrix composites. The applications of SPF parts continues to increase both in...aerospace and non-aerospace areas. Titanium continues to be the primary material processed for aerospace, although the development in Al SPF is accelerating...Electrical Technology of SCMI Superplastic Forming of Ti-Alloy Turbine Blade Paper 28 WANG CHENG and LUO YING-SHE, Xiangtan University Nc~’ Advance

Manufacturing Methods and Technology Project Summary Reports

DTIC Science & Technology

1982-12-01

aluminide was used to eliminate adhesive failures. A doctor blade and expandable ring segment were selected as the tooling to apply the 0.010 inch...contractual effort is to develop manu- facturing technology for the production of integrally bladed impellers using titanium pre-alloyed powder and...Projectiles in Modernized Plants 1-16 METALS Abstracts ME-1 Projects 176 7046, 17T 7046 and 177 7046 - Precision Cast Titanium Compressor Casing ME

The Aging of Engines: An Operator’s Perspective

DTIC Science & Technology

2000-10-01

internal HCF failures of blades . Erosion of compressor gas path 2-3 components can be minimized through the use of inlet aluminide intermetallic...fatigue problems in the dovetails durability in accelerated burner rig tests [2,35]. areas of titanium alloy fan and compressor blades . Shot peening in...Criticality Analysis replacement of durability-critical components, such as FOD Foreign object damage blades and vanes. The need to balance risk and escalating

Coating-Substrate Systems for Thermomechanically Durable Turbine Airfoils

DTIC Science & Technology

2015-06-30

vapor phase NiA ! aluminide and NiAI(Cr.Zr) coated Rene N5 samples cycled at 1093°C with Ae, = 0.35%. PtAI VPA NiAI(Cr,Zr) EQ Y-Y’ 10000.0... 505 (2001). 2. T.M. Pollock and S. Tin, AIAA J. Propulsion and Power, 22, 2, (2006), pp. 361 - 374. 3. A.G. Evans, D.R. Clarke and C.G. Lev

Development of Iron Aluminides

DTIC Science & Technology

1987-05-01

in aircraft turbine engines as altIErnatives to high chromium steels and nickel-base alloys. The pirogram was divided into three tasks. A process and...RSR) and the determination of their potential for use in aircraft turbine engines as alternative. to high chromium steels and nickel-base alloys. The...intermediated temperatures. Any alloys must also exhibit adequate corrosion resistance in a gas turbine environment if they are to replace existing alloys. A

Wedlable nickel aluminide alloy

DOEpatents

Santella, Michael L.; Sikka, Vinod K.

2002-11-19

A Ni.sub.3 Al alloy with improved weldability is described. It contains about 6-12 wt % Al, about 6-12 wt % Cr, about 0-3 wt % Mo, about 1.5-6 wt % Zr, about 0-0.02 wt % B and at least one of about 0-0.15 wt % C, about 0-0.20 wt % Si, about 0-0.01 wt % S and about 0-0.30 wt % Fe with the balance being Ni.

Corrosion Behavior of Candidate Materials Used for Urea Hydrolysis Equipment in Coal-Fired Selective Catalytic Reduction Units

NASA Astrophysics Data System (ADS)

Lu, Jintao; Yang, Zhen; Zhang, Bo; Huang, Jinyang; Xu, Hongjie

2018-05-01

Corrosion tests were performed in the laboratory in order to assess the corrosion resistance of candidate materials used in urea hydrolysis equipment. The materials to be evaluated were exposed at 145 °C for 1000 h. Alloys 316L, 316L Mod., HR3C, Inconel 718, and TC4 were evaluated. Additionally, aluminide and chromate coatings applied to a 316L substrate were examined. After exposure, the mass changes in the test samples were measured by a discontinuous weighing method, and the morphologies, compositions, and phases of the corrosion products were analyzed using scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. Results indicated that continuous pitting and dissolution corrosion were the main failure modes for 316L stainless steel. 316L Mod. and HR3C alloy showed better corrosion resistance than 316L due to their relatively high Cr contents, but HR3C exhibited a strong tendency toward intergranular corrosion. Inconel 718, TC4, and aluminide and chromate coating samples showed similar corrosion processes: only depositions formed by hydrothermal reactions were observed. Based on these results, a possible corrosion process in the urea hydrolysis environment was discussed for these candidate materials and questions to be clarified were proposed.

The Effects Of Micro Arc Oxidation Of Gamma Titanium Aluminide Surfaces On Osteoblast Adhesion And Differentiation

PubMed Central

Santiago-Medina, Pricilla; Sundaram, Paul A.; Diffoot-Carlo, Nanette

2014-01-01

The adhesion and proliferation of human fetal osteoblasts, hFOB 1.19, on micro arc oxidized (MAO) gamma titanium aluminide (γTiAl) surfaces were examined in vitro. Cells were seeded on MAO treated γTiAl disks and incubated for 3 days at 33.5°C and subsequently for 7 days at 39.5°C. Samples were then analyzed by Scanning Electron Microscopy (SEM) and the Alkaline Phosphatase Assay (ALP) to evaluate cell adhesion and differentiation, respectively. Similar Ti-6Al-4V alloy samples were used for comparison. Untreated γTiAl and Ti-6Al-4V disks, to study the effect of micro arc oxidation and glass coverslips as cell growth controls were also incubated concurrently. The ALP Assay results, at 10 days post seeding, showed significant differences in cell differentiation, with p values < 0.05 between MAO γTiAl and MAO Ti-6Al-4V with respect to the corresponding untreated alloys. While SEM images showed that hFOB 1.19 cells adhered and proliferated on all MAO and untreated surfaces, as well as on glass coverslips at 10 days post seeding, cell differentiation, determined by the ALP assay, was significantly higher for the MAO alloys. PMID:24577944

Status of reduced enrichment programs for research reactors in Japan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanda, Keiji; Nishihara, Hedeaki; Shirai, Eiji

1997-08-01

The reduced enrichment programs for the JRR-2, JRR-3, JRR-4 and JMTR of Japan Atomic Energy Research Institute (JAERI), and the KUR of Kyoto University Research Reactor Institute (KURRI) have been partially completed and are mostly still in progress under the Joint Study Programs with Argonne National Laboratory (ANL). The JMTR and JRR-2 have been already converted to use MEU aluminide fuels in 1986 and 1987, respectively. The operation of the upgraded JRR-3(JRR-3M) has started in March 1990 with the LEU aluminide fuels. Since May 1992, the two elements have been inserted in the KUR. The safety review application for themore » full core conversion to use LEU silicide in the JMTR was approved in February 1992 and the conversion has been done in January 1994. The Japanese Government approved a cancellation of the KUHFR Project in February 1991, and in April 1994 the U.S. Government gave an approval to utilize HEU in the KUR instead of the KUHFR. Therefore, the KUR will be operated with HEU fuel until 2001. Since March 1994, Kyoto University is continuing negotiation with UKAEA Dounreay on spent fuel reprocessing and blending down of recovered uranium, in addition to that with USDOE.« less

Halo Formation During Solidification of Refractory Metal Aluminide Ternary Systems

NASA Astrophysics Data System (ADS)

D'Souza, N.; Feitosa, L. M.; West, G. D.; Dong, H. B.

2018-02-01

The evolution of eutectic morphologies following primary solidification has been studied in the refractory metal aluminide (Ta-Al-Fe, Nb-Al-Co, and Nb-Al-Fe) ternary systems. The undercooling accompanying solid growth, as related to the extended solute solubility in the primary and secondary phases can be used to account for the evolution of phase morphologies during ternary eutectic solidification. For small undercooling, the conditions of interfacial equilibrium remain valid, while in the case of significant undercooling when nucleation constraints occur, there is a departure from equilibrium leading to unexpected phases. In Ta-Al-Fe, an extended solubility of Fe in σ was observed, which was consistent with the formation of a halo of μ phase on primary σ. In Nb-Al-Co, a halo of C14 is formed on primary CoAl, but very limited vice versa. However, in the absence of a solidus projection it was not possible to definitively determine the extended solute solubility in the primary phase. In Nb-Al-Fe when nucleation constraints arise, the inability to initiate coupled growth of NbAl3 + C14 leads to the occurrence of a two-phase halo of C14 + Nb2Al, indicating a large undercooling and departure from equilibrium.

Interdiffusion behaviors of iron aluminide coatings on China low activation martensitic steel

NASA Astrophysics Data System (ADS)

Zhu, X. X.; Yang, H. G.; Yuan, X. M.; Zhao, W. W.; Zhan, Q.

2014-12-01

The iron aluminide coating on China Low Activation Martensitic (CLAM) steel was prepared by pack cementation and subsequent heat treatment. A surface Fe2Al5 layer was formed on CLAM substrate by pack cementation process with Fe2Al5 donor powder and NH4Cl activator. Diffusion heat treatment was performed in order to allow the phase transformation from Fe2Al5 to a phase with lower aluminum content. Morphology and composition of the coatings were characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), glow discharge optical emission spectroscopy (GDOES) and X-ray diffraction (XRD). There is a need to study the interdiffusion behaviors in these Al containing systems, as a basis for controlling the formation and subsequent degradation of the coating. In this paper, a predictive model was developed to describe the phase transformation of Fe2Al5 as a function of processing parameters. The Wagner's equation was used to calculate the interdiffusion coefficients based on the analysis of the Al concentration profiles. The results showed that the interdiffusion coefficients in the FeAl and α-Fe(Al) phase strongly depends on Al content and showed a maximum at about 28 at.% Al.

Effects of silver and group II fluoride solid lubricant additions to plasma-sprayed chromium carbide coatings for foil gas bearings to 650 C

NASA Technical Reports Server (NTRS)

Wagner, R. C.; Sliney, Harold E.

1986-01-01

A new self-lubricating coating composition of nickel aluminide-bonded chromium carbide formulated with silver and Group II fluorides was developed in a research program on high temperature solid lubricants. One of the proposed applications for this new coating composition is as a wide temperature spectrum solid lubricant for complaint foil gas bearings. Friction and wear properties were obtained using a foil gas bearing start-stop apparatus at temperatures from 25 to 650 C. The journals were Inconel 748. Some were coated with the plasma sprayed experimental coating, others with unmodified nickel aluminide/chromium carbide as a baseline for comparison. The additional components were provided to assist in achieving low friction over the temperature range of interest. Uncoated, preoxidized Inconel X-750 foil bearings were operated against these surfaces. The foils were subjected to repeated start/stop cycles under a 14-kPa (2-Psi) bearing unit loading. Sliding contact occurred during lift-off and coastdown at surface velocities less than 6 m/s (3000 rPm). Testing continued until 9000 start/stop cycles were accumulated or until a rise in starting torque indicated the journal/bearing had failed. Comparison in coating performance as well as discussions of their properties and methods of application are given.

Chemical contrast in STM imaging of transition metal aluminides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duguet, T.; Thiel, Patricia A.

2012-08-01

The present manuscript reviews recent scanning tunnelling microscopy (STM) studies of transition metal (TM) aluminide surfaces. It provides a general perspective on the contrast between Al atoms and TM atoms in STM imaging. A general trend is the much stronger bias dependence of TM atoms, or TM-rich regions of the surface. This dependence can be attenuated by the local chemical arrangements and environments. Al atoms can show a stronger bias dependence when their chemical environment, such as their immediate subsurface, is populated with TM. All this is well explained in light of combined results of STM and both theoretical andmore » experimental electronic and crystallographic structure determinations. Since STM probes the Fermi surface, the electronic structure in the vicinity of the Fermi level (EF) is essential for understanding contrast and bias dependence. Hence, partial density of states provides information about the TM d band position and width, s–p–d hybridization or interactions, or charge transfer between constituent elements. In addition, recent developments in STM image simulations are very interesting for elucidating chemical contrast at Al–TM alloy surfaces, and allow direct atomic identification, when the surface does not show too much disorder. Overall, we show that chemically-specific imaging is often possible at these surfaces.« less

Effects of silver and group 2 fluorides addition to plasma sprayed chromium carbide high temperature solid lubricant for foil gas bearing to 650 deg C

NASA Technical Reports Server (NTRS)

Wagner, R. C.; Sliney, H. E.

1984-01-01

A new self-lubricating coating composition of nickel aluminide-bonded chromium carbide formulated with silver and Group II fluorides was developed in a research program on high temperature solid lubricants. One of the proposed applications for this new coating composition is as a wide temperature spectrum solid lubricant for complaint foil gas bearings. Friction and wear properties were obtained using a foil gas bearing start/stop apparatus at temperatures from 25 to 650 C. The journals were Inconel 718. Some were coated with the plasma sprayed experimental coating, others with unmodified nickel aluminide/chromium carbide as a baseline for comparison. The addtitional components were provided to assist in achieving low friction over the temperature range of interest. Uncoated, preoxidized Inconel X-750 foil bearings were operated against these surfaces. The foils were subjected to repeated start/stop cycles under a 14-kPa (2-psi) bearing unit loading. Sliding contact occurred during lift-off and coastdown at surface velocities less than 6 m/s (3000 rpm). Testing continued until 9000 start/stop cycles were accumulated or until a rise in starting torque indicated the journal/bearing had failed. Comparison in coating performance as well as discussions of their properties and methods of application are given.

Microstructured Optical Fiber-based Biosensors: Reversible and Nanoliter-Scale Measurement of Zinc Ions.

PubMed

Heng, Sabrina; McDevitt, Christopher A; Kostecki, Roman; Morey, Jacqueline R; Eijkelkamp, Bart A; Ebendorff-Heidepriem, Heike; Monro, Tanya M; Abell, Andrew D

2016-05-25

Sensing platforms that allow rapid and efficient detection of metal ions would have applications in disease diagnosis and study, as well as environmental sensing. Here, we report the first microstructured optical fiber-based biosensor for the reversible and nanoliter-scale measurement of metal ions. Specifically, a photoswitchable spiropyran Zn(2+) sensor is incorporated within the microenvironment of a liposome attached to microstructured optical fibers (exposed-core and suspended-core microstructured optical fibers). Both fiber-based platforms retains high selectivity of ion binding associated with a small molecule sensor, while also allowing nanoliter volume sampling and on/off switching. We have demonstrated that multiple measurements can be made on a single sample without the need to change the sensor. The ability of the new sensing platform to sense Zn(2+) in pleural lavage and nasopharynx of mice was compared to that of established ion sensing methodologies such as inductively coupled plasma mass spectrometry (ICP-MS) and a commercially available fluorophore (Fluozin-3), where the optical-fiber-based sensor provides a significant advantage in that it allows the use of nanoliter (nL) sampling when compared to ICP-MS (mL) and FluoZin-3 (μL). This work paves the way to a generic approach for developing surface-based ion sensors using a range of sensor molecules, which can be attached to a surface without the need for its chemical modification and presents an opportunity for the development of new and highly specific ion sensors for real time sensing applications.

Microstructure and high-temperature oxidation resistance of TiN/Ti3Al intermetallic matrix composite coatings on Ti6Al4V alloy surface by laser cladding

NASA Astrophysics Data System (ADS)

Zhang, Xiaowei; Liu, Hongxi; Wang, Chuanqi; Zeng, Weihua; Jiang, Yehua

2010-11-01

A high-temperature oxidation resistant TiN embedded in Ti3Al intermetallic matrix composite coating was fabricated on titanium alloy Ti6Al4V surface by 6kW transverse-flow CO2 laser apparatus. The composition, morphology and microstructure of the laser clad TiN/Ti3Al intermetallic matrix composite coating were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to evaluate the high-temperature oxidation resistance of the composite coatings and the titanium alloy substrate, isothermal oxidation test was performed in a conventional high-temperature resistance furnace at 600°C and 800°C respectively. The result shows that the laser clad intermetallic composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like, and dendrites), and uniformly distributed in the Ti3Al matrix. It indicates that a physical and chemical reaction between the Ti powder and AlN powder occurred completely under the laser irradiation. In addition, the microhardness of the TiN/Ti3Al intermetallic matrix composite coating is 844HV0.2, 3.4 times higher than that of the titanium alloy substrate. The high-temperature oxidation resistance test reveals that TiN/Ti3Al intermetallic matrix composite coating results in the better modification of high-temperature oxidation behavior than the titanium substrate. The excellent high-temperature oxidation resistance of the laser cladding layer is attributed to the formation of the reinforced phase TiN and Al2O3, TiO2 hybrid oxide. Therefore, the laser cladding TiN/Ti3Al intermetallic matrix composite coating is anticipated to be a promising oxidation resistance surface modification technique for Ti6Al4V alloy.

Directional solidification of Al2-Cu-Al and Al3-Ni-Al eutectics during TEXUS rocket flight

NASA Technical Reports Server (NTRS)

Favier, J. J.; Degoer, J.

1984-01-01

One lamellar eutectic sample and one fiber-like eutectic sample were solidified directionally during the TEXUS-6 rocket flight. The microstructures and the results of the thermal analysis, obtained from the temperatures recorded on the cartridge skin, are compared. No appreciable modifications of the regularity of the eutectic structures were observed by passing from 1 g to 0.0001 g in these experiments. No steady state growth conditions were achieved in these experiments.

Results of the technical exchange agreement between NASA and DuPont on the containerless drop tube solidification of NiAl3

NASA Technical Reports Server (NTRS)

Ethridge, E. C.; Curreri, P. A.; Kelly, M.

1984-01-01

The final results of the Drop Tube Solidification of NiAl3 are presented. Problems associated with the utilization of a dripper furnace in the drop tube are discussed and the modification of experimental procedures required to achieve results are described. Sample microstructures of drop tube samples are compared with other samples. The dendrite arm spacings of drop tube samples are correlated with the rapid cooling rates.

Preliminary studies concerning Hadfield steel behavior during laser beam welding in pulsating regime

NASA Astrophysics Data System (ADS)

David, Ion; Şerban, Viorel-Aurel

2007-08-01

This work proposes to analyze the behavior of austenitic manganese - Hadfield steel during laser beam welding in continuous regime. In order to limit the number of experiments, a 2 4 type factorial experiment was used, with 16 assays, after a frequently used program matrix for these situations. Fusion lines at different service regimes, as well as head to head welds were performed. Microhardness measurements and microstructure modifications that appear as an effect of laser irradiation are also analyzed.

Surface modification and electrochemical properties of activated carbons for supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Yang, Dan; Qiu, Wenmei; Xu, Jingcai; Han, Yanbing; Jin, Hongxiao; Jin, Dingfeng; Peng, Xiaoling; Hong, Bo; Li, Ji; Ge, Hongliang; Wang, Xinqing

2015-12-01

Modifications with different acids (HNO3, H2SO4, HCl and HF, respectively) were introduced to treat the activated carbons (ACs) surface. The microstructures and surface chemical properties were discussed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), ASAP, Raman spectra and Fourier transform infrared (FTIR) spectra. The ACs electrode-based supercapacitors were assembled with 6 mol ṡ L-1 KOH electrolyte. The electrochemical properties were studied by galvanostatic charge-discharge and cyclic voltammetry. The results indicated that although the BET surface area of modified ACs decreased, the functional groups were introduced and the ash contents were reduced on the surface of ACs, receiving larger specific capacitance to initial AC. The specific capacitance of ACs modified with HCl, H2SO4, HF and HNO3 increased by 31.4%, 23%, 21% and 11.6%, respectively.

Influence of Low-Frequency Vibration and Modification on Solidification and Mechanical Properties of Al-Si Casting Alloy.

PubMed

Selivorstov, Vadim; Dotsenko, Yuri; Borodianskiy, Konstantin

2017-05-20

One of the major aims of the modern materials foundry industry is the achievement of advanced mechanical properties of metals, especially of light non-ferrous alloys such as aluminum. Usually an alloying process is applied to obtain the required properties of aluminum alloys. However, the presented work describes an alternative approach through the application of vibration treatment, modification by ultrafine powder and a combination of these two methods. Microstructural studies followed by image analysis revealed the refinement of α-Al grains with an increase in the Si network area around them. As evidence, the improvement of the mechanical properties of Al casting alloy was detected. It was found that the alloys subjected to the vibration treatment displayed an increase in tensile and yield strengths by 20% and 10%, respectively.

Reduction of Surface Roughness by Means of Laser Processing over Additive Manufacturing Metal Parts.

PubMed

Alfieri, Vittorio; Argenio, Paolo; Caiazzo, Fabrizia; Sergi, Vincenzo

2016-12-31

Optimization of processing parameters and exposure strategies is usually performed in additive manufacturing to set up the process; nevertheless, standards for roughness may not be evenly matched on a single complex part, since surface features depend on the building direction of the part. This paper aims to evaluate post processing treating via laser surface modification by means of scanning optics and beam wobbling to process metal parts resulting from selective laser melting of stainless steel in order to improve surface topography. The results are discussed in terms of roughness, geometry of the fusion zone in the cross-section, microstructural modification, and microhardness so as to assess the effects of laser post processing. The benefits of beam wobbling over linear scanning processing are shown, as heat effects in the base metal are proven to be lower.

Influence of Low-Frequency Vibration and Modification on Solidification and Mechanical Properties of Al-Si Casting Alloy

PubMed Central

Selivorstov, Vadim; Dotsenko, Yuri; Borodianskiy, Konstantin

2017-01-01

One of the major aims of the modern materials foundry industry is the achievement of advanced mechanical properties of metals, especially of light non-ferrous alloys such as aluminum. Usually an alloying process is applied to obtain the required properties of aluminum alloys. However, the presented work describes an alternative approach through the application of vibration treatment, modification by ultrafine powder and a combination of these two methods. Microstructural studies followed by image analysis revealed the refinement of α-Al grains with an increase in the Si network area around them. As evidence, the improvement of the mechanical properties of Al casting alloy was detected. It was found that the alloys subjected to the vibration treatment displayed an increase in tensile and yield strengths by 20% and 10%, respectively. PMID:28772922

Specific physical and chemical properties of two modifications of poly(N-vinylcaprolcatam)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chihacheva, I. P.; Timaeva, O. I.; Kuz’micheva, G. M., E-mail: galina-kuzmicheva@list.ru

2016-05-15

Two modifications of poly(N-vinylcaprolactam)—PVCL25 and PVCL40 (drying of a PVCL solution at 25 and 40°C, respectively)—as powdered films and their solutions were systematically investigated for the first time. Powders were studied by X-ray diffraction, IR spectroscopy, scanning electron microscopy, low-temperature krypton adsorption, and differential scanning calorimetry. Solutions were studied by smallangle X-ray scattering and dynamic light scattering. It was demonstrated that powders of PVCL25 and PVCL40 differ in the characteristics of the sub- and microstructure and in the water content and the solutions differ in the particle size. The relationships between the characteristics of the systems in the solid andmore » liquid state and between the hydrodynamic diameter of PVCL particles in solution and their coagulation time were found.« less

Reduction of Surface Roughness by Means of Laser Processing over Additive Manufacturing Metal Parts

PubMed Central

Alfieri, Vittorio; Argenio, Paolo; Caiazzo, Fabrizia; Sergi, Vincenzo

2016-01-01

Optimization of processing parameters and exposure strategies is usually performed in additive manufacturing to set up the process; nevertheless, standards for roughness may not be evenly matched on a single complex part, since surface features depend on the building direction of the part. This paper aims to evaluate post processing treating via laser surface modification by means of scanning optics and beam wobbling to process metal parts resulting from selective laser melting of stainless steel in order to improve surface topography. The results are discussed in terms of roughness, geometry of the fusion zone in the cross-section, microstructural modification, and microhardness so as to assess the effects of laser post processing. The benefits of beam wobbling over linear scanning processing are shown, as heat effects in the base metal are proven to be lower. PMID:28772380

Textural evidence of the significance of compaction in the formation of adcumulates in the Skaergaard intrusion, East Greenland

NASA Astrophysics Data System (ADS)

Vukmanovic, Zoja; Holness, Marian; Mariani, Elisabetta

2017-04-01

It has been argued that the upwards decrease in incompatible element concentration in the Skaergaard Layered Series is due to an upwards increasing significance of compaction driven by gravitational loading. The suggested mechanisms for compaction are dislocation creep and dissolution-reprecipitation creep. Localised elongate zones of strong modal banding in the upper part of the Layered Series, known as trough bands, have also been interpreted as the result of localised recrystallization during compaction. In this study we examine the microstructures of Skaergaard gabbros to determine whether their fabrics (foliations and lineations) preserve a record of compaction. The most common microstructures formed by dislocation creep are low angle boundaries and, as a result of ongoing recovery processes, new grains. The (010)[001] slip system in plagioclase is commonly observed to be a "soft" orientation, creating a crystallographic preferred orientation (CPO) defined by the alignment of (010) planes, with [001] parallel to lineation. Previous work on dissolution-reprecipitation creep, shows a CPO with (010) planes aligned parallel to the principal compressive stress, and preferential mineral growth on (010) planes to form an SPO defined by grains elongated perpendicular to (010). In the Skaergaard Layered Series, the shape of cumulus plagioclase grains (as viewed in thin section) changes systematically up through the stratigraphy from highly tabular to equant. Foliations, defined both by a plagioclase SPO (with tabular grains aligned horizontally) and an associated CPO ((010) parallel to foliation), are strongest lower in the stratigraphy and reduce in strength upwards. Evidence for crystal plasticity is limited to bending of some plagioclase crystals and small numbers of low angle boundaries in all phases. There are no signs of recovery associated with dislocation creep. Compositional zoning is present on all plagioclase growth faces in the lower part of the stratigraphy, inconsistent with preferential dissolution-reprecipitation during compression. There are no fabrics or microstructures that can be attributed to solution-reprecipitation, and evidence for only minor microstructural modification by dislocation creep throughout the entire stratigraphy. The trough bands are characterised by strong lineation of elongate grains, an almost complete absence of microstructures caused by deformation, and euhedral plagioclase grains with concentric compositional zoning. These observations rule out recrystallization driven by compaction, and support the hypothesis that the modal banding in the trough bands is a result of grain sorting by magmatic flow. Our observations suggest that the Skaergaard fabrics throughout the Layered Series, are primary and formed at or close to the magma-mush interface as a consequence of particle re-arrangement by magmatic current, with only minor deformation-related fabric modification deeper in the mush. The Skaergaard adcumulates cannot therefore be attributed to compaction.

FY98 Aero Propulsion & Power Technology Area Plan.

DTIC Science & Technology

1997-11-01

controlled area turbine nozzle (HPT & LPT) - second quarter FY98 a Fabrication/test of gamma titanium aluminide exhaust flap/liner - third quarter...both a commercial business jet and an unmanned air vehicle (Dark Star). - "Super-cooled" turbine blade designs permit 3000 F higher gas temperature for...increased thrust, or 30% reduction in blade cooling air for reduced fuel consumption, or two-to four- fold increase in turbine blade life - all at a

Electrospark Deposition for Depot- and Field-Level Component Repair and Replacement of Hard Chromium Plating

DTIC Science & Technology

2008-02-01

with an ASAP proprietary process. Corrosion applications frequently are addressed with iron- aluminide and nickel alloys such as Inconel 625 alloy...IN625) and Hastelloy C-22. Wear applications commonly treated with ESD include cutting edges of chipper knives, saw teeth, and mower blades ; wear...Applications for ESD repair include components of steel, stainless steel, nickel- and cobalt-based superalloys, aluminum, Monel, titanium , and magnesium

Aerospace Plane Technology, Research and Development Efforts in Europe

DTIC Science & Technology

1991-07-25

to conventional titanium alloys. Moreover, ti- aluminide has one-half the weight of the material previously used at these high temperatures. Real Gas...for the engine’s blades , turbine blisk (a turbine disk with integral blades ), Page 44 GAO/NSIAID-91-194 Aerospace Plane Technology Chapter 3 European...X-30 fuselage section from silicon carbide-reinforced titanium and manufactured an X-30 fuel tank from a graphite-polyamide composite. Although

K-Rb Laser Pump Lamp

DTIC Science & Technology

1975-11-01

for K-Rb Lamps With Xenon and Argon Figure 25 Specimen for Protective Coating Evaluation 65 Figure 26 Specimen Coated With Fused Tin- Aluminide After...through hot titanium and copper purifiers to maia.in low levels (a few ppm) of oxygen, nitrogen and water vapor. The box also contains an integral...case with titanium , zirconium, thorium, and other common reactive metals. 15 - -’-- .--󈨑CP>4 -_ A thin strip of uranium is inserted into the fill

Structural Property Effects for Platinum Modified Aluminide Coatings.

DTIC Science & Technology

1986-09-01

change from a low energy fracture to a high energy one occurs is called the DBTT. Transition temperatures are exhibited by body centered cubic and...tdapcrature as a result of residual ~:n~~.’ estresses unless the sample had been plastically deformed. Use ofpl~stic ..... .:,.as jilwed exam-ination of a...34 Fracture Properties of Superalloys," Superalloys Source Book, American Society for Metals, 1984. 11. American Society for Metals, Metals Handbook, Desk

Transformation temperatures of martensite in beta phase nickel aluminide

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Hehemann, R. F.

1972-01-01

Resistivity and thermal arrest measurements determined that the compositional dependence of Ms (martensite state) temperatures for NiAl martensite was linear between 60 and 69 atomic percent nickel, with Ms = 124 Ni - 7410 K. Resistivity and surface relief experiments indicated the presence of thermoelastic martensite for selected alloys. Some aspects of the transformation were studied by hot stage microscopy and related to the behavior observed for alloys exhibiting the shape-memory effect.

Thermomechanical fatigue behavior of SiC/Ti-24Al-11Nb in air and argon environments

NASA Technical Reports Server (NTRS)

Bartolotta, Paul A.; Verrilli, Michael J.

1992-01-01

A series of tension-tension, load-controlled thermomechanical fatigue (TMF) tests were conducted on a titanium aluminide composite in both laboratory air and a flowing argon environment. Results from these tests show that the environment plays an increasingly important role as applied stress levels are decreased. Differences in damage mechanisms between the two environments were observed which corresponds to observed variations in TMF lives.

Iron aluminide knife and method thereof

DOEpatents

Sikka, Vinod K.

1997-01-01

Fabricating an article of manufacture having a Fe.sub.3 Al-based alloy cutting edge. The fabrication comprises the steps of casting an Fe.sub.3 Al-based alloy, extruding into rectangular cross section, rolling into a sheet at 800.degree. C. for a period of time followed by rolling at 650.degree. C., cutting the rolled sheet into an article having an edge, and grinding the edge of the article to form a cutting edge.

Virtual Design and Testing of Materials: A Multiscale Approach

DTIC Science & Technology

2006-06-30

Impurities in Aluminum and Their Effect on Mechanical Properties ", Phys. Rev. B 65, 064102 (2002). 21. G. Lu, V. Bulatov, and N. Kioussis, "Dislocation...materials: atomistic and continuum models with application to titanium - aluminides ", Phil. Mag. A 82, 2397-2417 (2002). 31. V.S. Deshpande, A. Needleman and...be used to test, and suggest design strategies for, new advanced structured materials. IS. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: Unclassified

Transformation temperatures of martensite in beta-phase nickel aluminide.

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Hehemann, R. F.

1973-01-01

Resistivity and thermal arrest measurements determined that the compositional dependence of M sub s temperatures for NiAl martensite was linear between 60 and 69 at. % Ni, with M sub s = (124 Ni - 7410)K. Resistivity and surface relief experiments for selected alloys indicated the presence of thermoelastic martensite. Some aspects of the transformation were studied by hot-stage microscopy and related to the behavior observed for alloys exhibiting the shape-memory effect.

Mechanical Response of Titanium Aluminide (TiAl3)

DTIC Science & Technology

2010-06-01

of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display...17. LIMITATION OF ABSTRACT Same as Report (SAR) 18. NUMBER OF PAGES 22 19a. NAME OF RESPONSIBLE PERSON a . REPORT unclassified b. ABSTRACT...should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of

Alteration layer formation of Ca- and Zn-oxide bearing alkali borosilicate glasses for immobilisation of UK high level waste: A vapour hydration study

NASA Astrophysics Data System (ADS)

Cassingham, N. J.; Corkhill, C. L.; Stennett, M. C.; Hand, R. J.; Hyatt, N. C.

2016-10-01

The UK high level nuclear waste glass modified with CaO/ZnO was investigated using the vapour phase hydration test, performed at 200 °C, with the aim of understanding the impact of the modification on the chemical composition and microstructure of the alteration layer. Experiments were undertaken on non-modified and CaO/ZnO-modified base glass, with or without 25 wt% of simulant Magnox waste calcine. The modification resulted in a dramatic reduction in gel layer thickness and also a reduction in the reaction rate, from 3.4 ± 0.3 g m-2 d-1 without CaO/ZnO modification to 0.9 ± 0.1 g m-2 d-1 with CaO/ZnO. The precipitated phase assemblage for the CaO/ZnO-modified compositions was identified as hydrated Ca- and Zn-bearing silicate phases, which were absent from the non-modified counterpart. These results are in agreement with other recent studies showing the beneficial effects of ZnO additions on glass durability.

Fabrication of robust hydrogel coatings on polydimethylsiloxane substrates using micropillar anchor structures with chemical surface modification.

PubMed

Zhang, Hongbin; Bian, Chao; Jackson, John K; Khademolhosseini, Farzad; Burt, Helen M; Chiao, Mu

2014-06-25

A durable hydrophilic and protein-resistant surface of polydimethylsiloxane (PDMS) based devices is desirable in many biomedical applications such as implantable and microfluidic devices. This paper describes a stable antifouling hydrogel coating on PDMS surfaces. The coating method combines chemical modification and surface microstructure fabrication of PDMS substrates. Three-(trimethoxysilyl)propyl methacrylates containing C═C groups were used to modify PDMS surfaces with micropillar array structures fabricated by a replica molding method. The micropillar structures increase the surface area of PDMS surfaces, which facilitates secure bonding with a hydrogel coating compared to flat PMDS surfaces. The adhesion properties of the hydrogel coating on PDMS substrates were characterized using bending, stretching and water immersion tests. Long-term hydrophilic stability (maintaining a contact angle of 55° for a month) and a low protein adsorption property (35 ng/cm(2) of adsorbed BSA-FITC) of the hydrogel coated PDMS were demonstrated. This coating method is suitable for PDMS modification with most crosslinkable polymers containing C═C groups, which can be useful for improving the anti-biofouling performance of PDMS-based biomedical microdevices.

Evaluation of modified titanium surfaces physical and chemical characteristics

NASA Astrophysics Data System (ADS)

Lukaszewska-Kuska, Magdalena; Leda, Bartosz; Gajdus, Przemyslaw; Hedzelek, Wieslaw

2017-11-01

Development of dental implantology is focused, among other things, on devising active surface of the implant, conditioning acceleration of the implant's integration with the bone. Increased roughness, characteristic for group of implants with developed surface, altered topography and chemically modified implant's surface determines increased implants stability. In this study four different titanium surfaces modifications: turned (TS); aluminium oxide-blasted (Al2O3); resorbable material blasted (RBM); sandblast and then etched with a mixture of acids (SAE), were evaluated in terms of surfaces topography and chemical composition prior to in vivo analysis. Topography analysis revealed two groups: one with smooth, anisotropic, undeveloped TS surface and the second group with remaining surfaces presenting rough, isotropic, developed surfaces with added during blasting procedure aluminium for Al2O3 and calcium and phosphorus for RBM. Physical and chemical modifications of titanium surface change its microstructure (typical for SAE) and increase its roughness (highest for Al2O3-blasted and RBM surfaces). The introduced modifications develop titanium surface - 10 times for SAE surfaces, 16 times for Al2O3-blasted surfaces, and 20 times for RBM surfaces.

On the Effect of Nb on the Microstructure and Properties of Next Generation Polycrystalline Powder Metallurgy Ni-Based Superalloys

NASA Astrophysics Data System (ADS)

Christofidou, Katerina A.; Hardy, Mark C.; Li, Hang-Yue; Argyrakis, Christos; Kitaguchi, Hiroto; Jones, Nicholas G.; Mignanelli, Paul M.; Wilson, Alison S.; Messé, Olivier M. D. M.; Pickering, Ed J.; Gilbert, Robert J.; Rae, Cathie M. F.; Yu, Suyang; Evans, Alex; Child, Daniel; Bowen, Paul; Stone, Howard J.

2018-05-01

The effect of Nb on the properties and microstructure of two novel powder metallurgy (P/M) Ni-based superalloys was evaluated, and the results critically compared with the Rolls-Royce alloy RR1000. The Nb-containing alloy was found to exhibit improved tensile and creep properties as well as superior oxidation resistance compared with both RR1000 and the Nb-free variant tested. The beneficial effect of Nb on the tensile and creep properties was due to the microstructures obtained following the post-solution heat treatments, which led to a higher γ' volume fraction and a finer tertiary γ' distribution. In addition, an increase in the anti-phase-boundary energy of the γ' phase is also expected with the addition of Nb, further contributing to the strength of the material. However, these modifications in the γ' distribution detrimentally affect the dwell fatigue crack-growth behavior of the material, although this behavior can be improved through modified heat treatments. The oxidation resistance of the Nb-containing alloy was also enhanced as Nb is believed to accelerate the formation of a defect-free Cr2O3 scale. Overall, both developmental alloys, with and without the addition of Nb, were found to exhibit superior properties than RR1000.

Microstructure and Tensile Properties of Friction Stir Processed Mg–Sn–Zn Alloy

PubMed Central

Chen, Xiaoyang; Dai, Qiao; Li, Xingcheng; Lu, Yalin; Zhang, Yang

2018-01-01

In this study, as-cast Mg–6Sn–2Zn (wt.%) alloy was subjected to friction stir processing (FSP) and the microstructure and tensile properties of FSP Mg–6Sn–2Zn samples were investigated. It was found that, in the stir zone (SZ) of FSP Mg–6Sn–2Zn samples, α-Mg grains were significantly refined via dynamic recrystallization (DRX) and the Mg2Sn phase was broken and partially dissolved. The microstructure in SZ was nonuniform and DRXed grains in the SZ-up regions were coarser than those in the SZ-down regions. Coarse broken Mg2Sn particles were observed in the SZ-up regions, while only fine Mg2Sn particles were observed in the SZ-down regions. Strong {0001} basal texture developed in the SZ regions of Mg–6Sn–2Zn samples after FSP. The increase of travel speed had little effect on the texture of different SZ regions. The ductility of FSP Mg–6Sn–2Zn samples was obviously improved, while the improvement in strength was negligible when compared to the as-cast sample. The tensile properties of FSP Mg–6Sn–2Zn samples were influenced by grain refinement, texture modification, and the breaking up and dissolution of the Mg2Sn phase. PMID:29690590

Electrochemical corrosion behavior, microstructure and magnetic properties of sintered Nd-Fe-B permanent magnet doped by CuZn5 powders

NASA Astrophysics Data System (ADS)

Liu, W. Q.; Wang, Z.; Sun, C.; Yue, M.; Liu, Y. Q.; Zhang, D. T.; Zhang, J. X.

2014-05-01

Nd-Fe-B permanent magnets with a small amount of CuZn5 powders doping were prepared by conventional sintered method. The effects of CuZn5 contents on magnetic properties and microstructure, electrochemical corrosion resistance of sintered Nd-Fe-B magnets were systematically studied. The results show that the magnetic properties of magnets do not have a significant variation by CuZn5 powders doping; the coercivity of magnets rises gradually, while the remanence of the magnets decreases a little with increasing of the CuZn5 amount. The CuZn5 doped magnets have more positive corrosion potential, Ecorr, and much lower corrosion current density, icorr, than the magnets without CuZn5 doping, indicating CuZn5 doping could improve the corrosion resistance. Both Zn and Cu enrich mainly into the Nd-rich phase, fully improve the wettability between the Nd-rich phase and the Nd2Fe14B phase, and repair the defects of the main phase, so the coercivity of magnets doped with CuZn5 powders rises. Such microstructure modification effectively restrains the aggressive inter-granular corrosion. As a result, the CuZn5 doped magnet possesses excellent corrosion resistance in NaCl electrolyte.

Microstructure and Tensile Properties of Friction Stir Processed Mg⁻Sn⁻Zn Alloy.

PubMed

Chen, Xiaoyang; Dai, Qiao; Li, Xingcheng; Lu, Yalin; Zhang, Yang

2018-04-23

In this study, as-cast Mg⁻6Sn⁻2Zn (wt.%) alloy was subjected to friction stir processing (FSP) and the microstructure and tensile properties of FSP Mg⁻6Sn⁻2Zn samples were investigated. It was found that, in the stir zone (SZ) of FSP Mg⁻6Sn⁻2Zn samples, α-Mg grains were significantly refined via dynamic recrystallization (DRX) and the Mg₂Sn phase was broken and partially dissolved. The microstructure in SZ was nonuniform and DRXed grains in the SZ-up regions were coarser than those in the SZ-down regions. Coarse broken Mg₂Sn particles were observed in the SZ-up regions, while only fine Mg₂Sn particles were observed in the SZ-down regions. Strong {0001} basal texture developed in the SZ regions of Mg⁻6Sn⁻2Zn samples after FSP. The increase of travel speed had little effect on the texture of different SZ regions. The ductility of FSP Mg⁻6Sn⁻2Zn samples was obviously improved, while the improvement in strength was negligible when compared to the as-cast sample. The tensile properties of FSP Mg⁻6Sn⁻2Zn samples were influenced by grain refinement, texture modification, and the breaking up and dissolution of the Mg₂Sn phase.

A bioactive coating with submicron-sized titania crystallites fabricated by induction heating of titanium after tensile deformations.

PubMed

Li, Ning-Bo; Xu, Wen-Hua; Xiao, Gui-Yong; Zhao, Jun-Han; Lu, Yu-Peng

2017-11-01

Thermal oxidation technology was widely investigated as one of effective surface modification method for improving the bioactivity and biocompatibility of titanium and its alloys. In this work, the induction heat oxidization method, a fast, efficient, economical and environmental protective technology, was applied to prepare the submicron-morphological oxide coating with variable rutile TiO 2 equiaxed crystallites on the surface of pure Ti substrates after cold-drawing with 10-20% deformations. The results showed the plastic-deformed Ti cylinders recrystallized during induction heating treatment (IHT) for 10-20s which resulted in evolution of microstructures as well as slight improvement of microhardness. The surface characteristics of TiO 2 crystallites in oxidation layers were determined by the microstructural evolutions of Ti substrate in terms of the nucleation and growth of TiO 2 crystallites. Specially, the oxidized surface with 50-75nm roughness and more uniform and finer equiaxed oxide grains remarkablely improved the apatite deposition after bioactive evaluation in 1.5 × SBF for 7 days. This work provided a potential method to create controlled bioactive oxide coatings with submicro-/nano-scaled TiO 2 crystallites on titanium substrate in terms of the role of metallographic microstructure in the formation process of titanium oxides. Copyright © 2017 Elsevier Ltd. All rights reserved.

Combination of experimental and numerical methods for mechanical characterization of Al-Si alloys

NASA Astrophysics Data System (ADS)

Kruglova, A.; Roland, M.; Diebels, S.; Mücklich, F.

2017-10-01

In general, mechanical properties of Al-Si alloys strongly depend on the morphology and arrangement of microconstituents, such as primary aluminium dendrites, silicon particles, etc. Therefore, a detailed characterization of morphological and mechanical properties of the alloys is necessary to better understand the relations between the underlined properties and to tailor the material’s microstructure to the specific application needs. The mechanical characterization usually implies numerical simulations and mechanical tests, which allow to investigate the influence of different microstructural aspects on different scales. In this study, the uniaxial tension and compression tests have been carried out on Al-Si alloys having different microstructures. The mechanical behavior of the alloys has been interpreted with respect to the morphology of the microconstituents and has been correlated with the results of numerical simulations. The advantages and limitations of the experimental and numerical methods have been disclosed and the importance of combining both techniques for the interpretation of the mechanical behavior of Al-Si alloys has been shown. Thereby, it has been suggested that the density of Si particles and the size of Al dendrites are more important for the strengthening of the alloys than the size-shape features of the eutectic Si induced by the modification.

Modelling of the mechanical behaviour of the single-crystal turbine alloy CMSX-4 during thermomechanical loading

NASA Astrophysics Data System (ADS)

Schubert, F.; Fleury, G.; Steinhaus, T.

2000-11-01

Turbine blades in gas turbine engines are subjected during operation to triaxial stress fields. For the description of the deformation behaviour of anisotropic single-crystal blades, constitutive equations are required which take account of modifications to the deformation processes caused by evolution of the γ/γ' microstructure during service (γ' rafting). A microstructure-dependent, orthotropic Hills potential, whose anisotropy coefficients are connected to the edge length of γ' particles, has been applied. The shape of γ' particles remains cubic below exposures at 700 °C. At high temperatures (above 850 °C) the γ' particles coalesce to rafts, and the viscoplastic response of the superalloy is continuously modified. This reduces the creep resistance of <001> orientated specimen. After tensile loading of the <001>-orientated specimens at 1000 °C, the rafting of γ' in the (100) plane was observed as expected, whereas the <111> specimens did not reveal γ' rafting. Torsionally loaded specimens exhibited rafting only in the near <100>-orientated surface regions of the specimen. The deformation in the <111> tensile and <001> torsion specimens occurred by octahedral slip of dislocations and not by cubic slip, as expected from theoretical considerations. Rafting did not occur in the <111>-orientated specimens. This anisotropy change is simulated successfully by the microstructure-dependent model.

Effect of a weak transverse magnetic field on the microstructure in directionally solidified peritectic alloys

PubMed Central

Li, Xi; Lu, Zhenyuan; Fautrelle, Yves; Gagnoud, Annie; Moreau, Rene; Ren, Zhongming

2016-01-01

Effect of a weak transverse magnetic field on the microstructures in directionally solidified Fe-Ni and Pb-Bi peritectic alloys has been investigated experimentally. The results indicate that the magnetic field can induce the formation of banded and island-like structures and refine the primary phase in peritectic alloys. The above results are enhanced with increasing magnetic field. Furthermore, electron probe micro analyzer (EPMA) analysis reveals that the magnetic field increases the Ni solute content on one side and enhances the solid solubility in the primary phase in the Fe-Ni alloy. The thermoelectric (TE) power difference at the liquid/solid interface of the Pb-Bi peritectic alloy is measured in situ, and the results show that a TE power difference exists at the liquid/solid interface. 3 D numerical simulations for the TE magnetic convection in the liquid are performed, and the results show that a unidirectional TE magnetic convection forms in the liquid near the liquid/solid interface during directional solidification under a transverse magnetic field and that the amplitude of the TE magnetic convection at different scales is different. The TE magnetic convections on the macroscopic interface and the cell/dendrite scales are responsible for the modification of microstructures during directional solidification under a magnetic field. PMID:27886265

Gradient Nanostructured Tantalum by Thermal-Mechanical Ultrasonic Impact Energy.

PubMed

Chae, Jong-Min; Lee, Keun-Oh; Amanov, Auezhan

2018-03-20

Microstructural evolution and wear performance of Tantalum (Ta) treated by ultrasonic nanocrystalline surface modification (UNSM) at 25 and 1000 °C were reported. The UNSM treatment modified a surface along with subsurface layer with a thickness in the range of 20 to 150 µm, which depends on the UNSM treatment temperature, via the surface severe plastic deformation (S²PD) method. The cross-sectional microstructure of the specimens was observed by electron backscattered diffraction (EBSD) in order to confirm the microstructural alteration in terms of effective depth and refined grain size. The surface hardness measurement results, including depth profile, revealed that the hardness of the UNSM-treated specimens at both temperatures was increased in comparison with those of the untreated ones. The increase in UNSM treatment temperature led to a further increase in hardness. Moreover, both the UNSM-treated specimens with an increased hardness resulted in a higher resistance to wear in comparison with those of the untreated ones under dry conditions. The increase in hardness and induced compressive residual stress that depend on the formation of severe plastically deformed layer with the refined nano-grains are responsible for the enhancement in wear resistance. The findings of this study may be implemented in response to various industries that are related to strength improvement and wear enhancement issues of Ta.

Gradient Nanostructured Tantalum by Thermal-Mechanical Ultrasonic Impact Energy

PubMed Central

Chae, Jong-Min; Lee, Keun-Oh; Amanov, Auezhan

2018-01-01

Microstructural evolution and wear performance of Tantalum (Ta) treated by ultrasonic nanocrystalline surface modification (UNSM) at 25 and 1000 °C were reported. The UNSM treatment modified a surface along with subsurface layer with a thickness in the range of 20 to 150 µm, which depends on the UNSM treatment temperature, via the surface severe plastic deformation (S2PD) method. The cross-sectional microstructure of the specimens was observed by electron backscattered diffraction (EBSD) in order to confirm the microstructural alteration in terms of effective depth and refined grain size. The surface hardness measurement results, including depth profile, revealed that the hardness of the UNSM-treated specimens at both temperatures was increased in comparison with those of the untreated ones. The increase in UNSM treatment temperature led to a further increase in hardness. Moreover, both the UNSM-treated specimens with an increased hardness resulted in a higher resistance to wear in comparison with those of the untreated ones under dry conditions. The increase in hardness and induced compressive residual stress that depend on the formation of severe plastically deformed layer with the refined nano-grains are responsible for the enhancement in wear resistance. The findings of this study may be implemented in response to various industries that are related to strength improvement and wear enhancement issues of Ta. PMID:29558402

Simulated Fission Gas Behavior in Silicide Fuel at LWR Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, Yinbin; Mo, Kun; Yacout, Abdellatif

As a promising candidate for the accident tolerant fuel (ATF) used in light water reactors (LWRs), the fuel performance of uranium silicide (U 3Si 2) at LWR conditions needs to be well-understood. However, existing experimental post-irradiation examination (PIE) data are limited to the research reactor conditions, which involve lower fuel temperature compared to LWR conditions. This lack of appropriate experimental data significantly affects the development of fuel performance codes that can precisely predict the microstructure evolution and property degradation at LWR conditions, and therefore evaluate the qualification of U 3Si 2 as an AFT for LWRs. Considering the high cost,more » long timescale, and restrictive access of the in-pile irradiation experiments, this study aims to utilize ion irradiation to simulate the inpile behavior of the U 3Si 2 fuel. Both in situ TEM ion irradiation and ex situ high-energy ATLAS ion irradiation experiments were employed to simulate different types of microstructure modifications in U 3Si 2. Multiple PIE techniques were used or will be used to quantitatively analyze the microstructure evolution induced by ion irradiation so as to provide valuable reference for the development of fuel performance code prior to the availability of the in-pile irradiation data.« less

Microstructural Variations Across a Dissimilar 316L Austenitic: 9Cr Reduced Activation Ferritic Martensitic Steel Weld Joint

NASA Astrophysics Data System (ADS)

Thomas Paul, V.; Karthikeyan, T.; Dasgupta, Arup; Sudha, C.; Hajra, R. N.; Albert, S. K.; Saroja, S.; Jayakumar, T.

2016-03-01

This paper discuss the microstructural variations across a dissimilar weld joint between SS316 and 9Cr-RAFM steel and its modifications on post weld heat treatments (PWHT). Detailed characterization showed a mixed microstructure of austenite and martensite in the weld which is in agreement with the phases predicted using Schaeffler diagram based on composition measurements. The presence of very low volume fraction of δ-ferrite in SS316L has been identified employing state of the art electron back-scattered diffraction technique. PWHT of the ferritic steel did not reduce the hardness in the weld metal. Thermal exposure at 973 K (700 °C) showed a progressive reduction in hardness of weld joint with duration of treatment except in austenitic base metal. However, diffusion annealing at 1073 K (800 °C) for 100 hours resulted in an unexpected increase in hardness of weld metal, which is a manifestation of the dilution effects and enrichment of Ni on the transformation characteristics of the weld zone. Migration of carbon from ferritic steel aided the precipitation of fine carbides in the austenitic base metal on annealing at 973 K (700 °C); but enhanced diffusion at 1073 K (880 °C) resulted in coarsening of carbides and thereby reduction of hardness.

Microstructural analysis of laser weld fusion zone in Haynes 282 superalloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osoba, L.O.; Ding, R.G.; Ojo, O.A., E-mail: ojo@cc.umanitoba.ca

Analytical electron microscopy and spectroscopy analyses of the fusion zone (FZ) microstructure in autogenous laser beam welded Haynes 282 (HY 282) superalloy were performed. The micro-segregation patterns observed in the FZ indicate that Co, Cr and Al exhibited a nearly uniform distribution between the dendrite core and interdendritic regions while Ti and Mo were rejected into the interdendritic liquid during the weld solidification. Transmission electron diffraction analysis and energy dispersive X-ray microanalysis revealed the second phase particles formed along the FZ interdendritic region to be Ti-Mo rich MC-type carbide particles. Weld FZ solidification cracking, which is sometimes associated with themore » formation of {gamma}-{gamma}' eutectic in {gamma}' precipitation strengthened nickel-base superalloys, was not observed in the HY 282 superalloy. Modified primary solidification path due to carbon addition in the newly developed superalloy is used to explain preclusion of weld FZ solidification cracking in the material. - Highlights: Black-Right-Pointing-Pointer A newly developed superalloy was welded by CO{sub 2} laser beam joining technique. Black-Right-Pointing-Pointer Electron microscopy characterization of the weld microstructure was performed. Black-Right-Pointing-Pointer Identified interdendritic microconstituents consist of MC-type carbides. Black-Right-Pointing-Pointer Modification of primary solidification path is used to explain cracking resistance.« less

Physical modification of palm kernel meal improved available carbohydrate, physicochemical properties and in vitro digestibility in economic freshwater fish.

PubMed

Thongprajukaew, Karun; Yawang, Pinya; Dudae, Lateepah; Bilanglod, Husna; Dumrongrittamatt, Terdtoon; Tantikitti, Chutima; Kovitvadhi, Uthaiwan

2013-12-01

Unavailable carbohydrates are an important limiting factor for utilization of palm kernel meal (PKM) as aquafeed ingredients. The aim of this study was to improve available carbohydrate from PKM. Different physical modifications including water soaking, microwave irradiation, gamma irradiation and electron beam, were investigated in relation to chemical composition, physicochemical properties and in vitro carbohydrate digestibility using digestive enzymes from economic freshwater fish. Modified methods had significant (P < 0.05) effects on chemical composition by decreasing crude fiber and increasing available carbohydrates. Improvements in physicochemical properties of PKM, such as water solubility, microstructure, relative crystallinity and lignocellulosic spectra, were mainly achieved by soaking and microwave irradiation. Carbohydrate digestibility varied among the physical modifications tested (P < 0.05) and three fish species had different abilities to digest PKM. Soaking was the appropriate modification for increasing carbohydrate digestion specifically in Nile tilapia (Oreochromis niloticus), whereas either soaking or microwave irradiation was effective for striped snakehead (Channa striata). For walking catfish (Clarias batrachus), carbohydrate digestibility was similar among raw, soaked and microwave-irradiated PKM. These findings suggest that soaking and microwave irradiation could be practical methods for altering appropriate physicochemical properties of PKM as well as increasing carbohydrate digestibility in select economic freshwater fish. © 2013 Society of Chemical Industry.

Characterization of Microstructure and Texture of 13Cr4Ni Martensitic Stainless Steel Weld Before and After Tempering =

NASA Astrophysics Data System (ADS)

Mokhtabad Amrei, Mohsen

13Cr4Ni martensitic stainless steels are known for their outstanding performances in the hydroelectric industry, where they are mainly used in the construction of turbine components. Considering the size and geometry of turbine runners and blades, multi-pass welding procedures are commonly used in the fabrication and repair of such turbines. The final microstructure and mechanical properties of the weld are sensitive to the welding process parameters and thermal history. In the case of 13Cr4Ni steel, the thermal cycles imposed by the multi-pass welding operation have significant effects on the complex weld microstructure. Additionally, post-weld heat treatments are commonly used to reduce weld heterogeneity and improve the material's mechanical properties by tempering the microstructure and by forming a "room-temperature-stable austenite." In the first phase of this research, the microstructures and crystallographic textures of aswelded single-pass and double-pass welds were studied as a basis to studying the more complex multi-pass weld microstructure. This study found that the maximum hardness is obtained in high temperature heat affected zone inside the base metal. In particular, the results showed that the heat cycle exposed by the second pass increases the hardness of the previous pass because it produces a finer martensite microstructure. In areas of heat affected zone, a tempering effect is reported from 3 up to 6 millimeters far from the fusion line. Finding austenite phase in these areas are matter of interest and it can be indicative of the microstructure complexity of multi-pass welds. In the second phase of research, the microstructure of multi-pass welds was found to be more heterogeneous than that of single- and double-pass welds. Any individual pass in a multi-pass weld consists of several regions formed by adjacent weld passes heat cycle. Results showed that former austenite grains modification occurred in areas close to the subsequent weld passes. Furthermore, low angle interface laths were observed inside martensite sub-blocks over different regions. The hardness profile of a multi-pass weld was explained by the overlaying heat effects of surrounding passes. In some regions, a tempered matrix was observed, while in other regions a double-quenched microstructure was found. The final aspect of this study focused on the effects of post-weld heat treatments on reformed austenite and carbide formations, and evolution of hardness. The effects of tempering duration and temperature on microstructure were investigated. The study found that nanometer-sized carbides form at martensite lath interfaces and sub-block boundaries. Additionally, it was determined that for any holding duration, the maximum austenite percentage is achievable by tempering at 610 °C. Similarly, the maximum softening was reported for tempering at 610 °C, for any given holding period.

Experimental Study on Modification of Concrete with Asphalt Admixture

NASA Astrophysics Data System (ADS)

Bołtryk, Michał; Małaszkiewicz, Dorota; Pawluczuk, Edyta

2017-10-01

Durability of engineering structures made of cement concrete with high compressive strength is a very vital issue, especially when they are exposed to different aggressive environments and dynamic loads. Concrete resistance to weathering actions and chemical attack can be improved by combined chemical and mechanical modification of concrete microstructure. Asphalt admixture in the form of asphalt paste (AP) was used for chemical modification of cement composite microstructure. Concrete structure was formed using special technology of compaction. A stand for vibro-vibropressing with regulated vibrator force and pressing force was developed. The following properties of the modified concrete were tested: compressive strength, water absorption, freeze-thaw resistance, scaling resistance in the presence of de-icing agents, chloride migration, resistance to CO2 and corrosion in aggressive solutions. Corrosion resistance was tested alternately in 1.8% solutions of NH4Cl, MgSO4, (NH2)2CO and CaCl2, which were altered every 7 days; the experiment lasted 9.5 months. Optimum compaction parameters in semi-industrial conditions were determined: ratio between piston stress (Qp ) and external top vibrator force (Po ) in the range 0.4÷-0.5 external top vibrator force 4 kN. High strength concretes with compressive strength fcm = 60÷70 MPa, very low water absorption (<1%) and high resistance to aggressive environments were obtained in this study. AP content was reduced from 10% (previous investigations) to 2-4% of cement mass thanks to the special compaction method. Excellent chloride ion penetration resistance and carbonation resistance of concrete containing AP admixture is due to the asphalt barrier formed in pores of cement hydrates against dioxide and chloride ions. Concrete specimens containing AP 4% c.m. and consolidated by vibro-vibropressing method proved to be practically resistant to highly corrosive environment. Vibro-vibropressing compaction technology of concrete modified with AP can be applied in prefabrication plants to produce elements for road, bridge and hydraulic engineering constructions.