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1

Reactions of hydrogen with V-Cr-Ti alloys  

NASA Astrophysics Data System (ADS)

The interest in vanadium alloys for use as a first-wall material in fusion reactor applications has led to a study to determine the effects of hydrogen on the mechanical properties of certain V-Cr-Ti alloys. Hydrogen uptake by the alloys is a function of temperature and pressure. In the absence of increases in oxygen concentration, additions of up to 400 wpm hydrogen to V-4Cr-4Ti did not result in any significant embrittlement. However, when hydrogen approached 500 wppm, rapid embrittlement occurred at 325C that was suggested to result from formation of a hydride phase upon cooling. When oxygen was added as well, either during or prior to hydrogen exposure, synergistic effects depending on grain size occurred that led to significant embrittlement by 35-130 wppm hydrogen. Because of its synergism with hydrogen and ubiquitous presence in most environments, oxygen pick-up remains as one of the major concerns for use of V-Cr-Ti alloys in fusion reactor applications.

DiStefano, J. R.; De Van, J. H.; Rhrig, D. H.; Chitwood, L. D.

2

Oxidation and microstrucure of V-Cr-Ti alloys exposed to oxygen-containing environments  

SciTech Connect

The objectives of this task are to (a) evaluate the oxygen uptake of several V-Cr-Ti alloys as a function of temperature and oxygen partial pressure in the exposure environment, (b) examine the microstructural characteristics of oxide scales and oxygen trapped at the grain boundaries in the substrate alloys, and (c) evaluate the influence of alloy composition on oxygen uptake and develop correlation(s) between alloy composition, exposure environment, and temperature.

Natesan, K. [Argonne National Lab., IL (United States); Uz, M. [Lafayette College, Easton, PA (United States); Ulie, T.

1997-08-01

3

Development of techniques for welding V Cr Ti alloys  

NASA Astrophysics Data System (ADS)

Welding vanadium alloys is complicated by interstitial impurity introduction and redistribution at elevated temperatures. Gas tungsten arc (GTA) welding, which will probably be required for the fabrication of large tokamak structures, must be done in a glove box environment. Welds were evaluated by Charpy testing. GTA welds could be made with a ductile to brittle transition temperature (DBTT) of 50C with a post-weld heat treatment (PWHT) or by using a heated Ti getter system on the glove box to reduce interstitial contamination. Titanium-O,N,C precipitates in the fusion zone were found to transform to a more oxygen-rich phase during a PWHT of 950C/2 h. Hydrogen was found to promote cleavage cracking following welding in cases where the atmosphere was contaminated. Grain size and microstructure also affected weld embrittlement.

Grossbeck, M. L.; King, J. F.; Alexander, D. J.; Rice, P. M.; Goodwin, G. M.

1998-10-01

4

Performance of V?Cr?Ti alloys in a hydrogen environment  

NASA Astrophysics Data System (ADS)

A systematic study is underway at Argonne National Laboratory to evaluate the mechanical properties of several V-Cr-Ti alloys after exposure to environments containing hydrogen at various partial pressures (pH 2). The goal is to correlate the chemistry of the exposure environment with hydrogen uptake by the samples and with the resulting influence on microstructures and tensile properties of the alloys. Other variables examined are specimen cooling rate and synergistic effects, if any, of oxygen and hydrogen on tensile behavior of the alloys. Experiments were conducted to evaluate the effect of pH 2 in the range of 310 -6 and 1 Torr on tensile properties of two V-Cr-Ti alloys. Up to pH 2 of 0.05 Torr, negligible effect of H was observed on either maximum engineering stress or uniform and total elongation. However, uniform and total elongation decreased substantially when the alloys were exposed at 500C to 1.0 Torr of H 2 pressure. Preliminary data from sequential exposures of the materials to low-pO 2 and several low-pH 2 environments did not reveal adverse effects on the maximum engineering stress or on uniform and total elongation when the alloy contained ?2000 wppm O and 16 wppm H. Furthermore, tests in H 2-exposed specimens, initially annealed at various temperatures, showed that grain-size variation by a factor of ?2 had little or no effect on tensile properties. Also, specimen cooling rate had a small effect, if any, on the tensile properties of the alloy.

Natesan, K.; Soppet, W. K.

2000-12-01

5

Assessment of the radiation-induced loss of ductility in V-Cr-Ti alloys  

SciTech Connect

Alloys based on the V-Cr-Ti system are attractive candidates for structural applications in fusion systems because of their low activation properties, high thermal stress factor (high thermal conductivity, moderate strength, and low coefficient of thermal expansion), and their good compatibility with liquid lithium. The U.S. program has defined a V-4Cr-4Ti (wt %) alloy as a leading candidate alloy based upon evidence from laboratory-scale (30 kg) heats covering the approximate composition range 0-8 wt % Ti and 5 to 15 wt % Cr. A review of the effects of neutron displacement damage, helium, and hydrogen generation on mechanical behavior, and of compatibility with lithium, water, and helium environments was presented at the ICFRM-5 conference at Clearwater in 1991. The results of subsequent optimization studies, focusing on the effects of fast reactor irradiation on tensile and impact properties of a range of alloys, were presented at the ICFRM-6 conference at Stresa in 1993. The primary conclusion of this work was that the V-4Cr-4Ti alloy composition possessed a near-optimal combination of physical and mechanical properties for fusion structural applications. Subsequently, a production-scale (500 kg) heat of V-4Cr-4Ti (Heat No. 832665) was procured from Teledyne Wah-Chang, together with several 15 kg heats of alloys with small variations in Cr and Ti. Further testing has been carried out on these alloys, including neutron irradiation experiments to study swelling and mechanical property changes. This paper discusses ductility measurements from some of these tests which are in disagreement with earlier work.

Rowcliffe, A.F.; Zinkle, S.J. [Oak Ridge National Lab., TN (United States)

1997-04-01

6

Effects of oxygen and hydrogen at low pressure on the mechanical properties of V?Cr?Ti alloys*1  

NASA Astrophysics Data System (ADS)

Exposure of V-Cr-Ti alloys to low oxygen partial pressures at high temperature results in oxygen absorption and internal oxidation. Characterization of a V-4Cr-4Ti alloy after oxidation at 500C revealed a microstructure with ultrafine oxide precipitates in the matrix and along grain boundaries. Heat treatment at 950C following oxidation resulted in large TiO x precipitates in the matrix and grain boundaries. Tensile ductility was reduced by exposure to low-pressure oxygen under the temperature and pressure conditions. However, heat treatment at 950C following oxidation was generally effective in recovering ductility irrespective of initial annealing treatment or grain size. Without increases in oxygen, >500 wppm hydrogen was required to cause significant decreases in tensile elongation. When oxygen was added either during or prior to hydrogen exposure, significant embrittlement occurred with 100 wppm hydrogen. Because of this synergism with hydrogen, oxygen pick-up remains a major concern for V-Cr-Ti alloys in fusion reactor applications.

DiStefano, J. R.; Pint, B. A.; DeVan, J. H.; Rhrig, H. D.; Chitwood, L. D.

2000-12-01

7

Tensile properties of V-Cr-Ti alloys after exposure in oxygen-containing environments  

SciTech Connect

A systematic study was conducted to evaluate the oxidation kinetics of V-4Cr-4Ti (44 alloy) and V-5Cr-5Ti alloys (55 alloy) and to establish the role of oxygen ingress on the tensile behavior of the alloys at room temperature and at 500 C. The oxidation rate of the 44 alloy is slightly higher than that of the 55 alloy. The oxidation process followed parabolic kinetics. Maximum engineering stress for 55 alloy increased with an increase in oxidation time at 500 C. The maximum stress values for 55 alloy were higher at room temperature than ta 500 C for the same oxidation treatment. Maximum engineering stresses for 44 alloy were substantially lower than those for 55 alloy in the same oxidation {approx}500 h exposure in air at 500 C; the same values were 4.8 and 6.1%, respectively, at 500 C after {approx}2060 h oxidation in air at 500 C. Maximum engineering stress for 44 alloy at room temperature was 421.6--440.6 MPa after {approx}250 h exposure at 500 C in environments with a pO{sub 2} range of 1 {times} 10{sup {minus}6} to 760 torr. The corresponding uniform and total elongation values were 11--14.4% and 14.5--21.7%, respectively. Measurements of crack depths in various specimens showed that depth is independent of pO{sub 2} in the preexposure environment and was of 70--95 {micro}m after 250--275 h exposure at 500 C.

Natesan, K.; Soppet, W.K. [Argonne National Lab., IL (United States)

1998-03-01

8

Procurement of V-Cr-Ti alloys to study minor variations on V-4Cr-4Ti  

SciTech Connect

The alloys V-6Cr-3Ti, V-4Cr-4Ti-Si, V-6Cr-6Ti, and V-3Cr-3Ti, were prepared by Teledyne Wah Chang Albany Corp. in 1994. Plate and sheet ranging from 0.76 mm to 6.25 mm with residual material being left in 12--20 mm thick bar were fabricated. Although the heats were prepared on a pilot plant scale using different equipment, an effort was made to keep the processing as close to Wah Chang Heat 832665, the reference fusion heat of V-4Cr-4Ti, as possible.

Grossbeck, M.L. [Oak Ridge National Lab., TN (United States)

1998-03-01

9

Mechanical properties of, and phase transformation in, V-Cr-Ti-O solid solutions  

SciTech Connect

Incorporation of O in the surface of V-Ti-Cr alloys has been investigated in controlled environments at 550-750{degrees}C. and tests were performed to determine the physical properties of V-Cr-Ti-O solid solutions. The amount of O in the alloys has been determined by weight-change measurements. Microhardness was used to determine O depth profiles in the alloys. X-ray, diffraction indicated a phase transformation from body-centered-cubic (bcc) to tetragonal in the highly stressed lattice because of O incorporation. Cr depletion was observed near alloy grain boundaries, based on back-scattered-electron images and electron-energy-dispersive spectra. Elastic modulus and Vickers hardness also increased in O-enriched V-Cr-Ti alloys. Hardening in the alloys results from O atoms on face-centered interstitial sites in the bcc sublattice and the formation of very fine coherent oxide particles. O or N diffusion occurs via the interstitial sublattice of the bcc V-base alloys and is accompanied by the formation of homogeneous oxide or nitride phases via internal oxidation or nitridation. The O,N-enriched surface region exhibited the extraordinarily high Vickers hardness of -18 GPa (1800 kg/mm{sup 2}). A value typical of oxides, nitrides, or carbides, or obtainable by ion-beam irradiation of metals.

Park, J.H.; Kuppermann, D.; Park, E.T.

1995-11-01

10

Effects of substitutions M on the formation, structure and magnetic properties of Sm 2Fe 15M 2C 2 (M = V, Cr, Ti, Nb, Zr, Mn and Mo) compounds  

Microsoft Academic Search

The effects of substitutions M on the formation, structure and magnetic properties of Sm2Fe15M2C2 (M = V, Cr, Ti, Nb, Zr, Mn and Mo) compounds have been systematically studied using XRD, magnetic and Mssbauer measurements. It has been found that V, Cr, Ti, Nb and Zr can help to form the 2 : 17 carbides, with a certain amount of

Zhongmin Chen; G. C. Hadjipanayis; M. Daniel; M. Digas; A. Moukarika; V. Papaefthymiou

1998-01-01

11

Effects of substitutions M on the formation, structure and magnetic properties of Sm2Fe15M2C2 (M = V, Cr, Ti, Nb, Zr, Mn and Mo) compounds  

Microsoft Academic Search

The effects of substitutions M on the formation, structure and magnetic properties of Sm2Fe15M2C2 (M = V, Cr, Ti, Nb, Zr, Mn and Mo) compounds have been systematically studied using XRD, magnetic and Mssbauer measurements. It has been found that V, Cr, Ti, Nb and Zr can help to form the 2 : 17 carbides, with a certain amount of

M. Daniel; M. Digas; A. Moukarika; V. Papaefthymiou; Z. Chen; G. C. Hadjipanayis

1998-01-01

12

Recycling of vanadium alloys in fusion reactors  

NASA Astrophysics Data System (ADS)

The feasibility of reprocessing a vanadium alloy after its use as a structural material in a fusion reactor, in order to enable its subsequent hands-on recycling within the nuclear industry, has been determined. For less neutron-exposed components, clearance of materials has also been considered. A conceptual model for the radiochemical processing of the alloy has been developed and tested experimentally. Using di-2-ethyl-hexyl-phosphoric acid it is possible to purify the components of the V-Cr-Ti alloy after its exposure in a fusion reactor down to the required level of activation product concentrations.

Bartenev, S. A.; Ciampichetti, A.; Firsin, N. G.; Forrest, R. A.; Kolbasov, B. N.; Kvasnitskij, I. B.; Romanov, P. V.; Romanovskij, V. N.; Zucchetti, M.

2007-08-01

13

Corrosion wear fracture of new ? type biomedical titanium alloys  

Microsoft Academic Search

Metallic materials such as stainless steel, CoCr alloy, pure titanium and titanium alloys have been used for surgical implant materials. The ?+? type titanium alloy such as Ti-6Al-4V ELI has been most widely used as an implant material for artificial hip joint and dental implant because of its high strength and excellent corrosion resistance. Toxicity of alloying elements in conventional

Mitsuo Niinomi; Daisuke Kuroda; Kei-ichi Fukunaga; Masahiko Morinaga; Yoshihisa Kato; Toshiaki Yashiro; Akihiro Suzuki

1999-01-01

14

The influence of hydrogen on tensile properties of V-base alloys developed in China  

NASA Astrophysics Data System (ADS)

Several V-Cr-Ti-Al-Si alloys were studied with respect to their mechanical performances after exposure to hydrogen environments. The alloys were developed in China by using a melting process in a magnetic floating furnace. Most of the alloys had a high oxygen concentration from 700 to 1100 wppm since the forging and hot rolling were performed in air at elevated temperature. The results showed a synergistic effect of oxygen and hydrogen. The ductility loss correlated largely with the hydrogen concentration up to 113 wppm. Both V4Ti and V4TiSi showed a relatively higher resistance to hydrogen embrittlement in comparison with other alloys such as V4Cr4Ti and V4Ti3Al.

Chen, Jiming; Xu, Zengyu; Yang, Lin

2002-12-01

15

Electrochemical behavior of Alloy 22 and friction type rock bolt  

NASA Astrophysics Data System (ADS)

Alloy 22 (Ni-22Cr-13Mo-3Fe-3W) is a candidate alloy for the outer shell of spent nuclear materials storage containers in the Yucca Mountain High Level Nuclear Waste Repository because of its excellent corrosion resistance. The nuclear waste container is cylindrical in shape and the end caps are welded. Typically, Alloy 22 retains the high temperature single phase cubic structure near room temperature, but topologically close packed (TCP) phases such as mu, P, sigma etc. and Cr rich carbides can form during thermal aging and welding. Rock bolts that are used for reinforcing subsurface tunnels are generally made of carbon or low alloy steels; these are being used in the nuclear repository tunnel. The corrosion behavior of these rock bolts have not been systematically evaluated under the environmental conditions of the repository. The ground waters at the Yucca Mountain (YM) repository permeate through the pores of the rock mass, and have propensity to corrode the rock bolts and waste package container. The environmental (aerated and deaerated) conditions influence the rate of corrosion in these material; these have not been systematically evaluated yet under the repository environment. In this study, the corrosion behavior of Alloy 22 and a friction type rock bolts was investigated as a function of temperature and concentration in complex multi-ionic electrolytes. Simulated electrolyte of YM ground water found in the repository environment was made in different concentrations (1X, 10X, and 100X). The interaction of simulated electrolytes in aerated and deaerated condition with Alloy 22 and low alloy steel of friction type rock bolt (split tapered cylinder type commercial design) has been investigated. Polarization resistance method was used to measure the corrosion rates. We found that the corrosion rate of Alloy 22 was higher in the deaerated electrolyte as compared to the aerated. The presence of oxygen in the electrolyte during aeration is conducive to formation of passive films that inhibits the corrosion process. The temperature dependency of the corrosion rate was affected by aeration and deaeration of the electrolytes. Another study related to corrosion behavior of weld Alloy 22 was undertaken to understand electrochemical behavior of welded structures. Corrosion studies were carried out in more aggressive electrolyte (0.1M HCl at 66C) after solution annealing at 1121C for 1 hr. In the as-welded structure a dendritic microstructure was observed in the weld region. However, after solution annealing these dendrites are not observed; suggesting homogenization of the grains. Three different specimens were made out from a welded Alloy 22 plates with large welded surface; weld interface, half weld and base metal away from the weld and heat affected zone, and corrosion rates of all these samples were measured. The results showed that the corrosion resistance of the solution annealed was higher in all three specimens than those of as-welded specimens. Corrosion rates of friction type set rock bolts (split set) were measured at 25C, 45C, 65C and 90C using 1X, 10X and 100X concentration of electrolyte both in aerated and deaerated conditions. The corrosion rates of rock bolts in 1X and 10X electrolyte showed ranged from 30 to 200mum/yr for deaerated and 150 to 1600 mum/yr for aerated. In summary, we have investigated the electrochemical behavior of the Alloy 22 and steels that have significance to the YM nuclear repository. The effects of temperature, type of electrolyte, condition of the alloys on the corrosion rates are reported.

Rahman, Md Sazzadur

16

A PROPOSED MECHANISM FOR THE STRENGTHENING OF SAP-TYPE ALLOYS  

Microsoft Academic Search

Wrought materials produced from sintered and extruded flake metal ; powders (SAP-type alloys) containing a finely dispersed stable second phase ; possess enhanced elevated temperature properties. Based upon an extension of the ; results found in investigating the creep properties of the MD 2100 aluminum SAP-; type alloy, it is proposed that the extrusion process causes motion of the grain

Ansell

1958-01-01

17

Microstructure and phase identification in type 304 stainless steel-zirconium alloys  

NASA Astrophysics Data System (ADS)

Stainless steel-zirconium alloys have been developed at Argonne National Laboratory to contain radioactive metal isotopes isolated from spent nuclear fuel. This article discusses the various phases that are formed in as-cast alloys of type 304 stainless steel and zirconium that contain up to 92 wt pct Zr. Microstructural characterization was performed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), and crystal structure information was obtained by X-ray diffraction. Type 304SS-Zr alloys with 5 and 10 wt pct Zr have a three-phase microstructureaustenite, ferrite, and the Laves intermetallic, Zr(Fe,Cr,Ni)2+x. whereas alloys with 15, 20, and 30 wt pct Zr contain only two phasesferrite and Zr(Fe,Cr,Ni)2+x. Alloys with 45 to 67 wt pct Zr contain a mixture of Zr(Fe,Cr,Ni)2+x and Zr2(Ni,Fe), whereas alloys with 83 and 92 wt pct Zr contain three phases?-Zr, Zr2(Ni,Fe), and Zr(Fe,Cr,Ni)2+x. Fe3Zr-type and Zr3Fe-type phases were not observed in the type 304SS-Zr alloys. The changes in alloy microstructure with zirconium content have been correlated to the Fe-Zr binary phase diagram.

Abraham, Daniel P.; McDeavitt, Sean M.; Park, Jangyul

1996-08-01

18

Development and testing of vanadium alloys for fusion applications  

NASA Astrophysics Data System (ADS)

Vanadium-base alloys are promising candidate materials for application in fusion reactor first-wall and blanket structure because of several important advantages, i.e., inherently low irradiation-induced activity, good mechanical properties, good compatibility with lithium, high thermal conductivity, and good resistance to irradiation-induced swelling and damage. To screen candidate alloys and develop an optimized vanadium-base alloy, extensive investigations of physical and mechanical properties of various V?Ti, V?Cr?Ti, and V?Ti?Si alloys have been conducted before and after irradiation in lithium environment in fast fission reactors. From these investigations, a V?4Cr?4Ti alloy containing 500-1000 wppm Si and < 1000 wppm O + N + C has been identified as the most promising alloy, and more comprehensive testing on the performance of this alloy is being conducted for fusion-relevant conditions. Major results of the comprehensive work to develop the optimal alloy and test the irradiation performance are presented in this paper. The reference alloy V?4Cr?4Ti exhibited the most attractive combination of the mechanical and physical properties that are prerequisite for first-wall and blanket structures, i.e., good thermal creep behavior, good tensile strength and ductility, high impact energy, excellent resistance to swelling, and very low ductile-brittle transition temperature before and after irradiation. The alloy was highly resistant to irradiation-induced embrittlement in Li at 420-600C, and the effects of dynamically charged helium on swelling and mechanical properties were insignificant. However, several important issues remain unresolved, e.g., welding, low-temperature irradiation properties, helium effect at high dose and high helium concentration, irradiation creep, and irradiation performance in air or helium environment. Initial results of investigation of some of these issues are also given.

Chung, H. M.; Loomis, B. A.; Smith, D. L.

1996-12-01

19

Electron diffraction identification of structure types of martensite in Cu-Zn-Al alloys.  

PubMed

Electron diffraction technique for identifying structure types of martensite in beta-Hume-Rothery alloys is described. It includes determination of the stacking sequence of the martensite of the basal planes, differentiation of the long-range ordering in martensite inherited from its parent phase (A2 type disordered; B2 type ordered; and D03, or Heusler, type ordered), and distinguishing between normal-type and modified-type martensite. In addition to the 18R1-type martensite, 12R, 6R, and 2H martensites were found in quenched Cu-Zn-Al alloys using this technique. PMID:3505596

Wang, R H; Zhao, Y C; Gui, J A

1987-12-01

20

Corrosion behavior of dental alloys in various types of electrolyzed water.  

PubMed

The corrosion behavior of dental alloys was examined in electrolyzed strong acid water, weak acid water and neutral water using a 7-day immersion test. The precious metal alloys, gold alloy. Au-Ag-Pd alloy and silver alloy showed the greatest surface color change and dissolution of constituents in the strong acid water and the smallest in the neutral water. The release of Au from gold alloy was especially marked in the strong acid water. Co-Cr alloy showed greater corrosion and tarnish resistance in the strong acid water rather than in the weak acid water and the neutral water. X-ray microanalysis revealed that the corrosion products on the precious metal alloys were silver chloride crystals and the thin brown products on Co-Cr alloy were cobalt and chromium oxides. Ti was sound in all three types of electrolyzed water. The neutral water appeared the least corrosive to metals among the three types showing equivalent bactericidal activity. PMID:15005226

Dong, Hongwei; Nagamatsu, Yuki; Chen, Ker-Kong; Tajima, Kiyoshi; Kakigawa, Hiroshi; Shi, Sizhen; Kozono, Yoshio

2003-12-01

21

Evaluation of tensile properties of 5052 type aluminum-magnesium alloy at warm temperatures  

Microsoft Academic Search

Purpose: The purpose of the paper is to evaluate the tensile properties of 5052 type aluminum-manganese alloy in warm temperatures. Design\\/methodology\\/approach: In this research, uniaxial tensile deformation behavior of 5052-H32 type aluminum magnesium alloy was studied range between room to 300C and in the strain rate range of 0.0083-0.16 s-1. Findings: It was observed that the uniaxial tensile elongation of

F. Ozturk; S. Toros; S. Kilic

22

Effect of irradiation damage and helium on swelling and structure of vanadium-base alloys*1  

NASA Astrophysics Data System (ADS)

Swelling behavior and microstructural evolution of V-Ti, V-Cr-Ti, and V-Ti-Si alloys were investigated after irradiation at 420-600C up to 114 dpa. The alloys exhibited swelling maxima between 30 and 80 dpa and swelling decreased on irradiation to higher dpa. This is in contrast to the monotonically increasing swelling of binary alloys that contain Fe, Ni, Cr, Mo, and Si. Precipitation of dense Ti 5Si 3 promotes good resistance to swelling of the Ti-containing alloys, and it was concluded that Ti of > 3 wt% and 400-1000 wppm Si are necessary to effectively suppress swelling. Swelling was minimal in V-4Cr-4Ti, identified as the most promising alloy based on good mechanical properties and superior resistance to irradiation embrittlement. V-20Ti doped with B exhibited somewhat higher swelling because of He generation. Lithium atoms, generated from transmutation of 10B, formed ?-LiV 2O 5 precipitates and did not seem to produce undesirable effects on mechanical properties.

Chung, H. M.; Loomis, B. A.; Smith, D. L.

1994-09-01

23

P and n-type microcrystalline semiconductor alloy material including band gap widening elements, devices utilizing same  

DOEpatents

An n-type microcrystalline semiconductor alloy material including a band gap widening element; a method of fabricating p-type microcrystalline semiconductor alloy material including a band gap widening element; and electronic and photovoltaic devices incorporating said n-type and p-type materials.

Guha, Subhendu (Troy, MI); Ovshinsky, Stanford R. (Bloomfield Hills, MI)

1988-10-04

24

Thermoelectric properties of some p-type half-Heusler alloys  

Microsoft Academic Search

We have synthesized a series of multi-component p-type half Heusler alloys by simultaneously substituting suitable elements at different crystallographic sites. Both electrical and thermal transport properties of these alloys are studied up to 1000K to evaluate their thermoelectric potential. At 300K, typical thermopower(S) and resistivity(rho) values are around 80 muV\\/K and 1mphi-cm respectively. Due to heavy substitution\\/doping, (rho)-T behavior

V. Ponnambalam; T. M. Tritt; Meng Zhu; S. J. Poon

2006-01-01

25

Magnetic transformation of Ni 2 AlMn heusler-type shape memory alloys  

Microsoft Academic Search

It has recently been reported that the movement of twin (or variant) boundaries, induced by a magnetic field during the martensitic transformation, affects the magnetic properties and shape change in the ferromagnetic NiGaMn shape memory (SM) alloys. These observations suggest that the NiGaMn SM alloys with an L2 (NiGaMn: Heusler) structure have the potential for use as a new type

F. Gejima; Y. Sutou; R. Kainuma; K. Ishida

1999-01-01

26

Strain glass transition in a multifunctional ?-type Ti alloy  

NASA Astrophysics Data System (ADS)

Recently, a class of multifunctional Ti alloys called GUM metals attracts tremendous attentions for their superior mechanical behaviors (high strength, high ductility and superelasticity) and novel physical properties (Invar effect, Elinvar effect and low modulus). The Invar and Elinvar effects are known to originate from structural or magnetic transitions, but none of these transitions were found in the GUM metals. This challenges our fundamental understanding of their physical properties. In this study, we show that the typical GUM metal Ti-23Nb-0.7Ta-2Zr-1.2O (at%) alloy undergoes a strain glass transition, where martensitic nano-domains are frozen gradually over a broad temperature range by random point defects. These nano-domains develop strong texture after cold rolling, which causes the lattice elongation in the rolling direction associated with the transition upon cooling and leads to its Invar effect. Moreover, its Elinvar effect and low modulus can also be explained by the nano-domain structure of strain glass.

Wang, Yu; Gao, Jinghui; Wu, Haijun; Yang, Sen; Ding, Xiangdong; Wang, Dong; Ren, Xiaobing; Wang, Yunzhi; Song, Xiaoping; Gao, Jianrong

2014-02-01

27

Strain glass transition in a multifunctional ?-type Ti alloy.  

PubMed

Recently, a class of multifunctional Ti alloys called GUM metals attracts tremendous attentions for their superior mechanical behaviors (high strength, high ductility and superelasticity) and novel physical properties (Invar effect, Elinvar effect and low modulus). The Invar and Elinvar effects are known to originate from structural or magnetic transitions, but none of these transitions were found in the GUM metals. This challenges our fundamental understanding of their physical properties. In this study, we show that the typical GUM metal Ti-23Nb-0.7Ta-2Zr-1.2O (at%) alloy undergoes a strain glass transition, where martensitic nano-domains are frozen gradually over a broad temperature range by random point defects. These nano-domains develop strong texture after cold rolling, which causes the lattice elongation in the rolling direction associated with the transition upon cooling and leads to its Invar effect. Moreover, its Elinvar effect and low modulus can also be explained by the nano-domain structure of strain glass. PMID:24500779

Wang, Yu; Gao, Jinghui; Wu, Haijun; Yang, Sen; Ding, Xiangdong; Wang, Dong; Ren, Xiaobing; Wang, Yunzhi; Song, Xiaoping; Gao, Jianrong

2014-01-01

28

Magnetic transformation of Ni{sub 2}AlMn Heusler-type shape memory alloys  

SciTech Connect

It has recently been reported that the movement of twin (or variant) boundaries, induced by a magnetic field during the martensitic transformation, affects the magnetic properties and shape change in the ferromagnetic NiGaMn shape memory (SM) alloys. These observations suggest that the NiGaMn SM alloys with an L2{sub 1} (Ni{sub 2}GaMn: Heusler) structure have the potential for use as a new type of smart materials whose SM properties can be controlled not only by temperature and stress, but also by a magnetic field. Very recently, the present authors have detected that in the alloys with compositions near the stoichiometric Ni{sub 2}AlMn, the ferromagnetic L2{sub 1} phase appears on low-temperature aging and it transforms martensitically from B2 to 2M. This suggests that the NiAlMn Heusler alloys could also exhibit unique magnetic and SM properties similar to those of the NiGaMn alloys. It is the purpose of this article to report the results of investigations on the magnetic properties of the NiAlMn Heusler alloys.

Gejima, F.; Sutou, Y.; Kainuma, R.; Ishida, K.

1999-10-01

29

NixCd1-xO: Semiconducting alloys with extreme type III band offsets  

NASA Astrophysics Data System (ADS)

We have synthesized alloys of NiO and CdO that exhibit an extreme type III band offset and have studied the structural, electrical, and optical properties of NixCd1-xO over the entire composition range. The alloys are rocksalt structured and exhibit a monotonic shift of the (220) diffraction peak to higher 2? angles with increasing Ni concentration. The electron mobility and electron concentration decrease with increasing x, and samples become insulating for Ni content x > 0.44. This decrease in n-type conductivity is consistent with the movement of the conduction band minimum from below to above the Fermi stabilization energy with increasing Ni content. The optical absorption edge of the alloys can be tuned continuously from CdO to NiO. The intrinsic gap of the alloys was calculated with the electrical and optical measurements and accounting for Burstein-Moss carrier filling and carrier-induced bandgap renormalization effects. We observe an uncommon composition dependence of the intrinsic bandgap on the alloy composition. The effect is tentatively attributed to an interaction between extended states of the conduction band and localized d-states of Ni.

Francis, Christopher A.; Detert, Douglas M.; Chen, Guibin; Dubon, Oscar D.; Yu, Kin M.; Walukiewicz, Wladek

2015-01-01

30

Effects of Alloying Additions on Corrosion and Passivation Behaviors of Type 304 Stainless Steel  

Microsoft Academic Search

The effects of copper, silicon, molybdenum, and nitrogen as alloying elements on the microstructure and corrosion behavior of type 304 (UNS S30400) austenitic stainless steel (SS) in deaerated dilute acidic chloride solutions at 30 C and 60 C was investigated using potentiodynamic, scanning electron microscopy, and energy dispersive X-ray analysis techniques. The addition of 2% Cu decreased the corrosion and

A. A. Hermas; K. A. Ogura; T. A. Adachi; S. A. Takagi

1995-01-01

31

Influence of the internal stresses relaxation on magnetic properties of Finemet-type amorphous alloy  

NASA Astrophysics Data System (ADS)

Joint action of low-temperature annealing followed by low-temperature treatment in liquid nitrogen on the magnetic properties of a Finemet-type amorphous alloy has been studied for the first time. Physical model of the processes is proposed, which agrees with experimental data and establishes generalities and distinction between structural relaxation and low-temperature ? T-effect.

Zaichenko, S.; Roth, S.; Glezer, A.

2003-03-01

32

Alloying effect of Ni and Cr on irradiated microstructural evolution of type 304 stainless steels  

NASA Astrophysics Data System (ADS)

Life extension of the existing nuclear power plants imposes significant challenges to core structural materials that suffer increased fluences. This paper presents the microstructural evolution of a type 304 stainless steel and its variants alloyed with extra Ni and Cr under neutron irradiation at 320 C for up to 10.2 dpa. Similar to the reported data of type 304 variants, a large amount of Frank loops, ultrafine G-phase/M23C6 particles, and limited amount of cavities were observed in the irradiated samples. The irradiation promoted the growth of pre-existing M23C6 at grain boundaries and resulted in some phase transformation to CrC in the alloy with both extra Ni and Cr. A new type of ultrafine precipitates, possibly (Ti,Cr)N, was observed in all the samples, and its amount was increased by the irradiation. Additionally, ?-ferrite was observed in the type 304 steel but not in the Ni or Ni + Cr alloyed variants. The effect of Ni and Cr alloying on the microstructural evolution is discussed.

Tan, L.; Busby, J. T.

2013-11-01

33

A NOTE ON REGULARITY FOR DISCRETE ALLOY-TYPE MARTIN TAUTENHAHN AND IVAN VESELIC  

E-print Network

on the random potential. In this informal note we discuss wheather the discrete alloy-type potential of random variables {V (x)}xZd , and > 0 controles the strength of the disorder. In the "original" Anderson point spectrum in the case of sufficiently large disorder. This phenomena was first proven by Fr

34

Alloy scattering in p-type Al(x)Ga(1-x)As  

NASA Astrophysics Data System (ADS)

The hole mobility of Be-doped Al(x)Ga(1-x)As, for x = 0-1, is analyzed both theoretically and experimentally. Allow scattering is very important, and in fact reduces the hole mobility from 150 to less than 90 sq cm/V s at x = 0.5. The main parameter in the alloy scattering formulation, the alloy potential, is found to be about 0.5 eV for p-type Al(x)Ga(1-x)As.

Look, D. C.; Lorance, D. K.; Sizelove, J. R.; Stutz, C. E.; Evans, K. R.; Whitson, D. W.

1992-01-01

35

Double Antiferromagnetism in Heusler-Type Alloys Fe2+xV1-xSi  

Microsoft Academic Search

Measurements of transport and magnetic properties, 57Fe-Mssbauer spectroscopy and 51V-NMR were performed for a Heusler-type alloy series Fe2+xV1-xSi (0.00<=q x<=q 0.08). In Fe2VSi (x=0.00), which had been reported to be an antiferromagnetic metal with the Nel temperature TN1=123 K, another antiferromagnetic transition was found at 34 K (TN2). The Nel temperature TN1 was found for the alloys with x less

Hiroko Matsuda; Keizo Endo; Masahumi Tokiyama; Hiroshi Shinmen; Yoshihiko Takano; Shinnichi Masubuchi; Kiyoshi Ooiwa; Hiroyuki Mitamura; Juichiro Arai; Tsuneaki Goto

2006-01-01

36

Tensile impact properties of vanadium-base alloys irradiated at <430{degree}C.  

SciTech Connect

Tensile and impact properties were investigated at <430 C on V-Cr-Ti, V-Ti-Si, and V-Ti alloys after irradiation to {approx}2-46 dpa at 205-430 C in lithium or helium in the Fast Flux Test Facility (FFTF), High Flux Isotope Reactor (HFIR), Experimental Breeder Reactor II (EBR-II), and Advanced Test Reactor (ATR). A 500-kg heat of V-4Cr-4Ti exhibited high ductile-brittle transition temperature and minimal uniform elongation as a result of irradiation-induced loss of work-hardening capability. Work-hardening capabilities of 30- and 100-kg heats of V-4Cr-4Ti varied significantly with irradiation conditions, although the 30-kg heat exhibited excellent impact properties after irradiation at {approx}390-430 C. The origin of the significant variations in the work-hardening capability of V-4Cr-4Ti is not understood, although fabrication variables, annealing history, and contamination from the irradiation environment are believed to play important roles. A 15-kg heat of V-3Ti-1Si exhibited good work-hardening capability and excellent impact properties after irradiation at {approx}390-430 C. Helium atoms, either charged dynamically or produced via transmutation of boron in the alloys, promote work-hardening capability in V-4Cr-4Ti and V-3Ti-1Si.

Chung, H. M.

1998-05-18

37

Surface treatment for inhibition of corrosion and hydrogen penetration of type 718 alloy  

SciTech Connect

Polarization and permeation experiments showed that a monolayer coverage of lead (Pb) effectively inhibited the hydrogen (H) evolution reaction and H penetration through type 718 (UNS N07718) alloy. Observed inhibition effects were a result of the kinetic limitations of the H discharge reaction and suppression of H absorption on the deposited monolayer. H evolution reaction and H permeation rates were reduced by [approximately]67% and 70%, respectively.

Popov, B.N.; Zheng, G.; White, R.E. (Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemical Engineering)

1994-08-01

38

Creep behavior of the heusler type structure alloy Ni 2 AlTi  

Microsoft Academic Search

A specific method for improving the high temperature creep strength of ?-NiAl by a ternary addition giving rise to an additional\\u000a degree of order is examined. The ternary alloy thus formed has theA\\u000a 2BC or Heusler type structure, and the present study is devoted to the creep behavior of polycrystalline Ni2AlTi of stoichiometric composition. Possible slip modes are predicted on

P. R. Strutt; R. S. Polvani; J. C. Ingram

1976-01-01

39

Low-temperature electrical transport in Heusler-type Fe2V (AlSi) alloys  

Microsoft Academic Search

The temperature variation of the electrical resistivity rho and the Seebeck coefficient S of Heusler-type Fe2VAl1-xSix (0<=x<=1) alloys has been investigated. We have shown that the transport parameters are very sensitive to doping. For the x = 0 sample, high values of rho and negative temperature coefficient of resistivity (TCR) have been observed. As the Si concentration increases, rho decreases

M. Vasundhara; V. Srinivas; V. V. Rao

2005-01-01

40

Alloy  

NASA Astrophysics Data System (ADS)

The Mg98.5Gd1Zn0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 C and 400 C). The microstructure of extruded materials was characterized by ?-Mg grains, and Mg3Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 ?m in the extruded ingot, down to 1.6 ?m for powders extruded at 623 K (350 C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.

Cabeza, Sandra; Garcs, Gerardo; Prez, Pablo; Adeva, Paloma

2014-07-01

41

Electroplating of thin films of bismuth onto type 4340 steel and alloy 718 to prevent hydrogen embrittlement  

SciTech Connect

Polarization and permeation experiments showed that a thin layer of electroplated bismuth (1 {mu}m to 2 {mu}m) inhibited the evolution and penetration of hydrogen through nickel-chromium alloy 718 (UNS N07718) and type 4340 (UNS G43400) steel. Inhibition effects were due to the kinetic limitations of the hydrogen discharge reaction and to the suppression of hydrogen adsorption on the deposited layers. The hydrogen evolution reactions on alloy 718 and type 4340 steel were inhibited by 28% and 85%, respectively. The hydrogen permeation rates through these alloys were reduced by 76% and 65%, respectively.

Popov, B.N.; Zheng, G.; White, R.E. [Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemical Engineering

1995-06-01

42

Fatigue properties of a metastable beta-type titanium alloy with reversible phase transformation.  

PubMed

Due to recent concern about allergic and toxic effects of Ni ions released from TiNi alloy into human body, much attention has been focused on the development of new Ni-free, metastable beta-type biomedical titanium alloys with a reversible phase transformation between the beta phase and the alpha'' martensite. This study investigates the effect of the stress-induced alpha'' martensite on the mechanical and fatigue properties of Ti-24Nb-4Zr-7.6Sn (wt.%) alloy. The results show that the as-forged alloy has a low dynamic Young's modulus of 55GPa and a recoverable tensile strain of approximately 3%. Compared with Ti-6Al-4V ELI, the studied alloy has quite a high low-cycle fatigue strength because of the effective suppression of microplastic deformation by the reversible martensitic transformation. Due to the low critical stress required to induce the martensitic transformation, it has low fatigue endurance comparable to that of Ti-6Al-4V ELI. Cold rolling produces a beta+alpha'' two-phase microstructure that is characterized by regions of nano-size beta grains interspersed with coarse grains containing alpha'' martensite plates. Cold rolling increases fatigue endurance by approximately 50% while decreasing the Young's modulus to 49GPa along the rolling direction but increasing it to 68GPa along the transverse direction. Due to the effective suppression of the brittle isothermal omega phase, balanced properties of high strength, low Young's modulus and good ductility can be achieved through ageing treatment at intermediate temperature. PMID:18006397

Li, S J; Cui, T C; Hao, Y L; Yang, R

2008-03-01

43

Osteoblast cell behavior on the new beta-type Ti-25Ta-25Nb alloy.  

PubMed

Among metallic materials used as bone substitutes, ? titanium alloys gain an increasing importance because of their low modulus, high corrosion resistance and good biocompatibility. In this work, an investigation of the in vitro cytocompatibility of a recently new developed ?-type Ti-25Ta-25Nb alloy was carried out by evaluating the behavior of human osteoblasts. The metallic Ti-6Al-4V biomaterial, which is one of representative ?+? type titanium alloys for biomedical applications, and Tissue Culture Polystyrene (TCPS), were also investigated as reference Ti-based material and control substrate, respectively. Both metallic surfaces were analyzed by X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy. The cellular response was quantified by assessments of viability, cell attachment and spreading, cell morphology, production and extracellular organization of fibronectin and cell proliferation. Polished surfaces from both materials having an equiaxed grain microstructure and nanometre scale surface roughness elicited an essentially identical osteoblast response in terms of all analyzed cellular parameters. Thus, on both surfaces the cells displayed high survival rates, good cell adhesion and spreading, a dense and randomly dispersed fibronectin matrix and increasing cell proliferation rates over the incubation time. Furhermore, the enhanced biological performance of Ti-25Ta-25Nb was highly supported by the results obtained in comparison with TCPS. These findings, together with previously shown superelastic behavior, low Young's modulus and high corrosion resistance, recommend Ti-25Ta-25Nb as good candidate for applications in bone implantology. PMID:24364960

Cimpean, Anisoara; Mitran, Valentina; Ciofrangeanu, Cristina M; Galateanu, Bianca; Bertrand, Emmanuel; Gordin, Doina-Margareta; Iordachescu, Dana; Gloriant, Thierry

2012-08-01

44

On the Understanding of Aluminum Grain Refinement by Al-Ti-B Type Master Alloys  

NASA Astrophysics Data System (ADS)

Al-Ti-B type master alloys have been widely used in the grain refinement of aluminum since 1940s. The introduction of Al3Ti and TiB2(AlB2) particles reduces the grain sizes down to about 200 micrometer level and makes aluminum alloys castable. However, the mechanism for the grain refinement is still not clear, though it is believed that TiB2 particles in the presence of Al3Ti nucleate ?-Al grains during solidification. This paper presents our finding on the formation of (Ti,Al)B2 solid solution, which leads to a proposed theory on grain refinement by Al-Ti-B type master alloys that upon addition into aluminum melt stable TiB2 particles react with aluminum slowly and release titanium into the melt. The titanium thus released in combination with titanium in the melt through dissolution of Al3Ti particles maintains a dynamic titanium-rich layer on the surface of (Ti,Al)B2. This layer offers a low crystal mismatch with ?-Al and promotes the nucleation of aluminum grains.

Wang, Xiaoming; Liu, Zhiwei; Dai, Wei; Han, Qingyou

2014-11-01

45

Enhanced thermoelectric figure-of-merit in spark plasma sintered nanostructured n-type SiGe alloys  

NASA Astrophysics Data System (ADS)

We report a significant enhancement in the thermoelectric figure-of-merit of phosphorous doped nanostructured n-type Si80Ge20 alloys, which were synthesized employing high energy ball milling followed by rapid-heating using spark plasma sintering. The rapid-heating rates, used in spark plasma sintering, allow the achievement of near-theoretical density in the sintered alloys, while retaining the nanostructural features introduced by ball-milling. The nanostructured alloys display a low thermal conductivity (2.3 W/mK) and a high value of Seebeck coefficient (-290 ?V/K) resulting in a significant enhancement in ZT to about 1.5 at 900 C, which is so far the highest reported value for n-type Si80Ge20 alloys.

Bathula, Sivaiah; Jayasimhadri, M.; Singh, Nidhi; Srivastava, A. K.; Pulikkotil, Jiji; Dhar, Ajay; Budhani, R. C.

2012-11-01

46

Structure fragmentation in Fe-based alloys by means of cyclic martensitic transformations of different types  

PubMed Central

The effect of martensite transformations of different types on the misorientation of austenite crystalline lattice, which characterizes the degree of structure fragmentation, was investigated for Fe-Ni and Fe-Mn alloys. As a result of multiple face-centered cubic (f.c.c.)-body-centered cubic (b.c.c.)-f.c.c. transformations, an austenite single-crystalline specimen is transformed in a polycrystalline one due to progressive fragmentation. It was shown that the degree of fragmentation depends on the magnitude of volume change and the density of dislocations generated on martensitic transformations. PMID:24565160

2014-01-01

47

Study on Defects in H+ion Implanted B2 type Fe-Al Alloy using Slow Positron Beam  

NASA Astrophysics Data System (ADS)

Fe48-at.%Al alloy were implanted with 50 keV H+ ions to the fluence of 31016 and 11018/cm2 at room temperature. Positron annihilation Doppler broadening and lifetime measurements for these alloys have been carried out using slow positron beam apparatus with an energy range of 0.2 to 30.2 keV. The positron annihilation S-parameter decreased by H+ ion irradiation. Also the positron lifetimes for hydrogen deposited region in the alloy decreased by the irradiation. These results show that implanted H atoms were trapped by vacancy type defects.

Komagata, S.; Kawasuso, A.; Yabuuchi, A.; Maekawa, M.; Batchulun, C.; Yasuda, K.; Ishigami, R.; Kume, K.; Iwase, A.; Hori, F.

48

Predominant factor determining wear properties of ?-type and (?+?)-type titanium alloys in metal-to-metal contact for biomedical applications.  

PubMed

The predominant factor determining the wear properties of a new titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ) and a conventional titanium alloy, Ti-6Al-4V extra-low interstitial (Ti64) was investigated for TNTZ and Ti64 combinations in metal-to-metal contacting bio-implant applications. The worn surfaces, wear debris, and subsurface damages were analyzed using a scanning electron microscopy combined with energy-dispersive spectroscopy and electron-back scattered diffraction analysis. The volume loss of TNTZ is found to be larger than that of Ti64, regardless of the mating material. The wear track of TNTZ exhibits the galled regions and severe plastic deformation with large flake-like debris, indicative of delamination wear, which strongly suggests the occurrence of adhesive wear. Whereas, the wear track of Ti64 have a large number of regular grooves and microcuttings with cutting chip-like wear debris and microfragmentation of fine oxide debris, indicative of abrasive wear combined with oxidative wear. This difference in the wear type is caused by severe and mild subsurface deformations of TNTZ and Ti64, respectively. The lower resistance to plastic shearing for TNTZ compared to that of Ti64 induces delamination, resulting in a higher wear rate. PMID:25460417

Lee, Yoon-Seok; Niinomi, Mitsuo; Nakai, Masaaki; Narita, Kengo; Cho, Ken

2015-01-01

49

Double Antiferromagnetism in Heusler-Type Alloys Fe2+xV1-xSi  

NASA Astrophysics Data System (ADS)

Measurements of transport and magnetic properties, 57Fe-Mssbauer spectroscopy and 51V-NMR were performed for a Heusler-type alloy series Fe2+xV1-xSi (0.00?q x?q 0.08). In Fe2VSi (x=0.00), which had been reported to be an antiferromagnetic metal with the Nel temperature TN1=123 K, another antiferromagnetic transition was found at 34 K (TN2). The Nel temperature TN1 was found for the alloys with x less than 0.08: it decreased monotonically with increasing x. The new antiferromagnetic transition temperature TN2 was also found for x=0.02 at 64 K. The characteristic hysteresis observed in the magnetization curve below TN2 was macroscopic evidence for the occurrence of another antiferromagnetic ordering. The presence of two types of magnetic transition at 40 and 120 K for Fe2VSi was confirmed microscopically by Mssbauer spectroscopy. The Mssbauer and NMR measurements showed the presence of slight Fe/V antisite disorder, which plays an important part in the magnetic order below TN2. The magnetic structure of Fe2VSi was discussed and the idea of double antiferromagnetism was proposed.

Matsuda, Hiroko; Endo, Keizo; Tokiyama, Masahumi; Shinmen, Hiroshi; Takano, Yoshihiko; Masubuchi, Shinnichi; Ooiwa, Kiyoshi; Mitamura, Hiroyuki; Arai, Juichiro; Goto, Tsuneaki

2006-09-01

50

A new type of Cu-Al-Ta shape memory alloy with high martensitic transformation temperature  

NASA Astrophysics Data System (ADS)

In this study, a new type of Cu-Al-Ta (Cu86Al12Ta2 wt%) shape memory alloy with high martensitic transformation temperature is explored. The microstructure, reversible martensitic transformation and shape memory properties are investigated by means of optical microscopy, back-scattered electron, electron probe microanalysis, x-ray diffraction, differential scanning calorimetry and tensile tests. It is proposed that Cu86Al12Ta2 alloy consists of a mixture of primarily {\\beta }_{1}^{\\prime} martensite and a little {\\gamma }_{1}^{\\prime} martensite and some different precipitates. The tiny thin-striped Ta2(Al,Cu)3 precipitate is predominant in the as-quenched condition, whereas the particle-shaped Cu(Al, Ta) precipitate is dominant after hot-rolling. Additionally, the dendritic-shaped ?1(Cu9Al4) phase begins to appear after hot-rolling, but it disappears when the sample is re-quenched. All studied samples have reversible martensitic transformation temperatures higher than 450? C. The results show that two-step martensitic transformation behavior is observed for Cu86Al12Ta2 alloy in all three different conditions due to the transformations between ({\\beta }_{1}^{\\prime}+{\\gamma }_{1}^{\\prime}) martensites and the austenite parent phase. The results further show that the recovery ratios are almost 100% when the pre-strains are ?2.5%, then they gradually decrease with further increase of the pre-strains. The shape memory effects clearly increase as a result of increase of the pre-strains, up to a maximum value of 3.2%.

Wang, C. P.; Su, Y.; Y Yang, S.; Shi, Z.; Liu, X. J.

2014-02-01

51

Low-temperature electrical transport in Heusler-type Fe2V (AlSi) alloys  

NASA Astrophysics Data System (ADS)

The temperature variation of the electrical resistivity ? and the Seebeck coefficient S of Heusler-type Fe2VAl1-xSix (0<=x<=1) alloys has been investigated. We have shown that the transport parameters are very sensitive to doping. For the x = 0 sample, high values of ? and negative temperature coefficient of resistivity (TCR) have been observed. As the Si concentration increases, ? decreases and the TCR changes its sign, while S shows significant changes in magnitude as well as sign when Al is replaced with Si. These changes appear to be reminiscent of a metal to semiconductor transition. It has been shown that the conventional transport theories proposed for intermetallic alloys or semiconductors cannot explain the transport behaviour in the whole temperature range of the present study. Low-temperature resistivity data of x = 0-0.02 samples could be described with a gapless semiconductor model. The strong composition dependence of S and ? is attributed to the sharp variations in electronic density of states at the Fermi energy. It is also shown that by optimum doping one can achieve very large values of power factor (P). The estimated power factor at room temperature is observed to be highest (2.23 10-3 W mK-2) for x = 0.06 and comparable to that of conventional thermoelectric material. At lower temperatures P is found to be even higher than that of conventional thermoelectric material.

Vasundhara, M.; Srinivas, V.; Rao, V. V.

2005-09-01

52

Adhesive strength of medical polymer on anodic oxide nanostructures fabricated on biomedical ?-type titanium alloy.  

PubMed

Anodic oxide nanostructures (nanopores and nanotubes) were fabricated on a biomedical ?-type titanium alloy, Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), by anodization in order to improve the adhesive strength of a medical polymer, segmented polyurethane (SPU), to TNTZ. TNTZ was anodized in 1.0M H3PO4 solution with 0.5 mass% NaF using a direct-current power supply at a voltage of 20V. A nanoporous structure is formed on TNTZ in the first stage of anodization, and the formation of a nanotube structure occurs subsequently beneath the nanoporous structure. The nanostructures formed on TNTZ by anodization for less than 3,600s exhibit higher adhesive strengths than those formed at longer anodization times. The adhesive strength of the SPU coating on the nanoporous structure formed on top of TNTZ by anodization for 1,200s improves by 144% compared to that of the SPU coating on as-polished TNTZ with a mirror surface. The adhesive strength of the SPU coating on the nanotube structure formed on TNTZ by anodization for 3,600s increases by 50%. These improvements in the adhesive strength of SPU are the result of an anchor effect introduced by the nanostructures formed by anodization. Fracture occurs at the interface of the nanoporous structure and the SPU coating layer. In contrast, in the case that SPU coating has been performed on the nanotube structure, fracture occurs inside the nanotubes. PMID:24433910

Hieda, Junko; Niinomi, Mitsuo; Nakai, Masaaki; Cho, Ken; Mohri, Tomoyoshi; Hanawa, Takao

2014-03-01

53

Linear augmented Slater-type-orbital study of Au-5d-transition-metal alloying  

NASA Astrophysics Data System (ADS)

We have used density-functional theory with an augmented Slater-type-orbital basis to calculate the heat of formation and crystal structure for the 5d-transition-metal-gold alloys AuLu through AuPt. The crystal structures considered were CsCl, CuAuI, ?-CuTi, MoSi2, Au2Nb3, Cu3Au, Cr3Si, and AlB2, though not all structures were calculated for each compound. There are no experimental values for the heats but our results are consistent with known phase diagrams. In several instances we find suppression of a phase at 50%-50% by another off 50%-50%. We have also calculated the charge transfer using Mulliken and Wigner-Seitz sphere counts. These do not follow electronegativity trends but are consistent with calculated initial-state core-level shifts and Mssbauer isomer shifts (obtained from the calculated contact density).

Watson, R. E.; Davenport, J. W.; Weinert, M.

1987-01-01

54

In vitro bio-functional performances of the novel superelastic beta-type Ti-23Nb-0.7Ta-2Zr-0.5N alloy  

E-print Network

for medical applications such as joint replacements, bone screws and plates, dental implants and surgical that of natural bone to leaching cytotoxic metallic ions. Beta ()-type titanium alloys with low elastic modulus and enhance bone remodeling. In this work, a new -type Ti-23Nb-0.7Ta- 2Zr-0.5N alloy with a Young's modulus

Paris-Sud XI, Université de

55

Corrosion of high Ni-Cr alloys and Type 304L stainless steel in HNO/sub 3/-HF  

SciTech Connect

Nineteen alloys were evaluated as possible materials of construction for steam heating coils, the dissolver vessel, and the off-gas system of proposed facilities to process thorium and uranium fuels. Commercially available alloys were found that are satisfactory for all applications. With thorium fuel, which requires HNO/sub 3/-HF for dissolution, the best alloy for service at 130/sup 0/C when complexing agents for fluoride are used is Inconel 690; with no complexing agents at 130/sup 0/C, Inconel 671 is best. At 95/sup 0/C, six other alloys tested would be adequate: Haynes 25, Ferralium, Inconel 625, Type 304L stainless steel, Incoloy 825, and Haynes 20 (in order of decreasing preference); based on composition, six untested alloys would also be adequate. The ions most effective in reducing fluoride corrosion were the complexing agents Zr/sup 4 +/ and Th/sup 4 +/; Al/sup 3 +/ was less effective. With uranium fuel, modestly priced Type 304L stainless steel is adequate. Corrosion will be most severe in HNO/sub 3/-HF used occasionally for flushing and in solutions of HNO/sub 3/ and corrosion products (ferric and dichromate ions). HF corrosion can be minimized by complexing the fluoride ion and by passivation of the steel with strong nitric acid. Corrosion caused by corrosion products can be minimized by operating at lower temperatures.

Ondrejcin, R.S.; McLaughlin, B.D.

1980-04-01

56

Synthesis of NiCoMnX (X = In, Al) Heusler-type Magnetic Shape Memory Alloy Thin Films  

E-print Network

applications, such as miniaturized actuators, small scale propulsion devices, and micro-electro-mechanical systems (MEMS). This thesis focuses on the synthesis of NiCoMnX (X=In, Al) Heusler-type magnetic shape memory alloy thin films via physical vapor...

Rios, Steven Eli

2014-08-13

57

A method for interface shape control during Bridgman type crystal growth of HgCdTe alloys  

NASA Technical Reports Server (NTRS)

A method is described for interface shape control of Hg(1-x)Cd(x)Te alloys during Bridgman-type crystal growth. The authors have used this method for several years to obtain the flat or convex interface shapes required for simultaneously reducing radial compositional variations and crystal defects. The method turns to advantage the thick-walled, fused-silica ampules required for growing these alloys. A proper combination of furnace geometry (two isothermal zones separated by a thin barrier), upper- and lower-zone temperatures, and growth rate is required. Examples of results are reported.

Szofran, F. R.; Lehoczky, S. L.

1984-01-01

58

Microstructure of 18R-type long period ordered structure phase in Mg 97Y 2Zn 1 alloy  

Microsoft Academic Search

The microstructure of the 18R-type long period stacking ordered (LPSO) phase in Mg97Y2Zn1 alloy was investigated by the first principles calculation. The arrangement rule of Zn and Y atoms in the LPSO structure is determined theoretically. The calculation results reveal that the additive atoms are firstly located in the fault layers at the two ends of the 18R-type LPSO structure,

Ping-ying TANG; Meng-meng WU; Bi-yu TANG; Ji-wei WANG; Li-ming PENG; Wen-jiang DING

2011-01-01

59

Synthesis of Zr-based perovskite-type alloy phosphors by polymerized complex method  

NASA Astrophysics Data System (ADS)

To demonstrate the fabrication of inorganic electroluminescent (EL) devices using perovskite-type oxide phosphors by electrophoretic deposition (EPD), AZrO3:RE (A = Ca, Sr, Ba; RE = Eu, Tb) were synthesized by the polymerized complex method. AZrO3:Eu showed orange or red emissions and AZrO3:Tb showed blue-green or green emissions depending on their crystal structures. The emission intensity was found to be enhanced by introducing strains to the host matrices by Mg codoping or alloying. Inorganic EL devices prepared by EPD using BaZrO3:Eu and SrZrO3:Eu as the phosphor layers showed orange and blue emissions that were observable under room light, respectively, which is the first observation of EL emission from the devices prepared by EPD to the best of our knowledge. The combination of perovskite-type oxide phosphors and EPD was found to be a promising way to fabricate inorganic EL devices.

Komagata, Hiroki; Kato, Riku; Kato, Ariyuki

2014-02-01

60

Valence Band Structure of Highly Efficient p-type Thermoelectric PbTe-PbS Alloys  

SciTech Connect

New experimental evidence is given relevant to the temperature-dependence of valence band structure of PbTe and PbTe1-xSx alloys (0.04 x 0.12), and its effect on the thermoelectric figure of merit zT. The x = 0.08 sample has zT ~ 1.55 at 773K. The magnetic field dependence of the high-temperature Hall resistivity of heavily p-type (> 1019 cm-3) Na-doped PbTe1-xSx reveals the presence of high-mobility electrons. This put in question prior analyses of the Hall coefficient and the conclusion that PbTe would be an indirect gap semiconductor at temperatures where its zT is optimal. Possible origins for these electrons are discussed: they can be induced by photoconductivity, or by the topology of the Fermi surface when the L and -bands merge. Negative values for the low-temperature thermopower are also observed. Our data show that PbTe continues to be a direct gap semiconductor at temperatures where the zT and S2 of p-type PbTe are optimal e.g. 700-900K. The previously suggested temperature induced rapid rise in energy of the heavy hole LVB relative to the light hole UVB is not supported by the experimental data.

Jaworski, C. M. [Ohio State University; Nielsen, Mechele [Ohio State University; Wang, Hsin [ORNL; Girard, Steven N. [Northwestern University, Evanston; Cai, Wei [ORNL; Porter, Wallace D [ORNL; Kanatzidis, Mercouri G. [Northwestern University, Evanston; Heremans, J. P. [Ohio State University

2013-01-01

61

Short-range order types in binary alloys: A reflection of coherent phase stability  

SciTech Connect

The short-range order (SRO) present in disordered solid solutions is classified according to three characteristic system-dependent energies: (1) formation enthalpies of ordered compounds, (2) enthalpies of mixing of disordered alloys, and (3) the energy of coherent phase separation, (the composition-weighted energy of the constituents each constrained to maintain a common lattice constant along an A/B interface). These energies are all compared against a common reference, the energy of incoherent phase separation (the composition-weighted energy of the constituents each at their own equilibrium volumes). Unlike long-range order (LRO), short-range order is determined by energetic competition between phases at a fixed composition, and hence only coherent phase-separated states are of relevance for SRO. The authors find five distinct SRO types, and show examples of each of these five types, including Cu-Au, Al-Mg, GaP-InP, Ni-Au, and Cu-Ag. The SRO is calculated from first-principles using the mixed-space cluster expansion approach combined with Monte Carlo simulations. Additionally, they examine the effect of inclusion of coherency strain in the calculation of SRO, and specifically examine the appropriate functional form for accurate SRO calculations.

W. Wolverton; V. Ozolins; Alex Zunger

1999-11-23

62

Preferential orientation and thermoelectric properties of n-type Bi2Te2.85Se0.15 alloys by mechanical alloying and equal channel angular extrusion  

NASA Astrophysics Data System (ADS)

Starting from elemental bismuth, tellurium and selenium powders, n-type Bi2Te2.85Se0.15 solid solution with a fine microstructure was prepared by mechanical alloying and equal channel angular extrusion (ECAE) in the present work. The effect of extrusion temperature on the microstructure and thermoelectric properties of the as-ECAEed samples was investigated. A preferentially oriented microstructure with the basal planes (0 0 l) in the parallel direction to extrusion was formed, and the orientation factors F of the (0 0 l) planes of the 703 K and 753 K ECAEed Bi2Te2.85Se0.15 alloys were 0.26 and 0.28, respectively. The electrical resistivity and the Seebeck coefficient decreased, and the thermal conductivity increased with increasing extrusion temperature. The electrical and thermal transmission performances were strongly affected by the preferentially oriented microstructure and the preferential orientation improved the thermoelectric properties of the ECAEed Bi2Te2.85Se0.15 alloys in the parallel direction to extrusion. The maximum dimensionless figure of merit was obtained when extruded at 753 K at a testing temperature of 343 K, ZT = 0.66.

Fan, X. A.; Yang, J. Y.; Zhu, W.; Bao, S. Q.; Duan, X. K.; Xiao, C. J.; Li, K.

2007-09-01

63

Precipitation of an intermetallic phase with Pt{sub 2}Mo-type structure in alloy 625  

SciTech Connect

The microstructure of Alloy 625, which has undergone prolonged ({approximately}70,000 hours) service at temperatures close to but less than 600 C, has been characterized by transmission electron microscopy. The precipitation of an intermetallic phase Ni{sub 2}(Cr, Mo) with Pt{sub 2}Mo-type structure has been observed in addition to that of the {gamma}{double_prime} phase. Six variants of Ni{sub 2} (Cr, Mo) precipitates have been found to occur in the austenite grains. These particles exhibit a snowflake-like morphology and are uniformly distributed in the matrix. They have been found to dissolve when the alloy is subjected to short heat treatments at 700 C. The occurrence of the Ni{sub 2}(Cr, Mo) phase has been discussed by taking the alloy chemistry into consideration. Apart from the intermetallic phases, the precipitation of a M{sub 6}C-type carbide phase within the matrix and the formation of near continuous films, comprising discrete M{sub 6}C/M{sub 23}C{sub 6} carbide particles, at the austenite grain boundaries have been noticed in the alloy after prolonged service.

Sundararaman, M.; Kumar, L.; Prasad, G.E.; Mukhopadhyay, P.; Banerjee, S. [Bhabha Atomic Research Centre, Mumbai (India). Materials Science Div.

1999-01-01

64

17.2: Ab initio models of dispenser B-type, scandate, and alloy cathode surfaces  

Microsoft Academic Search

The work function (?) and operating stability of dispenser, scandate, and alloy cathodes are investigated with ab initio quantum mechanical modeling. Low ?, thermodynamically stable, and steady state surface configurations are identified, while the ability of alloy surfaces to improve emission is presented.

V. Vlahos; D. Morgan; J. H. Booske

2010-01-01

65

Density functional study of elastic and vibrational properties of the Heusler-type alloys Fe2VAl and Fe2VGa  

E-print Network

Density functional study of elastic and vibrational properties of the Heusler-type alloys Fe2VAl-dispersion relations of the Heusler-type alloys Fe2VAl and Fe2VGa are computed using density functional and density.15.Nc, 62.20.de, 63.20.dk, 76.80. y I. INTRODUCTION The Heusler-type intermetallic compounds Fe2VAl

Svane, Axel Torstein

66

Relationship between Magnetocrystalline Anisotropy and Orbital Magnetic Moment in L10-Type Ordered and Disordered Alloys  

NASA Astrophysics Data System (ADS)

The magnetocrystalline anisotropy energy and orbital magnetic moment in L10-type transition metal alloys such as FePt, FePd, FeNi, CoPt, CoPd, and MnAl are evaluated while continuously varying the degree of order. The electronic structure with spin--orbit interaction is calculated by employing the tight-binding linear muffin-tin orbital method based on the local spin-density approximation. To control the degree of order, we consider a substitutional disorder and then adopt the coherent potential approximation. The magnetocrystalline anisotropy energy ? E is roughly proportional to the power of the long-range order parameter S, i.e., ? E \\propto Sn (n 1.6{--}2.4). We also discuss the relationship between the magnetocrystalline anisotropy energy and the orbital magnetic moment. In the same compositional system with different degrees of order, the difference between the orbital magnetic moment in the magnetic easy axis and that in the hard one is proportional to ? E. However, the coefficient corresponding to the effective spin--orbit coupling is inconsistent with the intrinsic one in some cases.

Kota, Yohei; Sakuma, Akimasa

2012-08-01

67

Ultrasonic detection of laminar-type defects in iridium alloy blanks  

SciTech Connect

Encapsulated isotopic heat sources for use in generating electrical power for space applications require flight-quality hardware material. Iridium is the chosen material for such applications, and Oak Ridge National Laboratory has been the prime supplier of iridium alloy forming blanks 52 mm in diameter by 0.66 mm thick (1.0 by 0.026 in.). Prior to the work reported here, these blanks were ultrasonically examined by using 0.9-mm-diam (0.035-in.) simulated flaw standards. However, as a result of this effort, the sensitivity of our ultrasonic pulse-echo test system has been increased. The improved ultrasonic test system permits blank inspection at the 0.5-mm-diam (0.020-in.) simulated flaw detection level. This test system was successfully demonstrated on the initial blanks provided via an improved processing route (consumable arc-melting, extruding, and rolling). The equipment modification and/or selection and the specific focused search unit immersion technique developed to provide this capability are described. The improved flaw detection capability also provides data maps of a common type of defect in iridium (delaminations).

Cook, K.V.; Cunningham, R.A. Jr.; Simpson, W.A. Jr.; McClung, R.W.

1986-07-01

68

Influence of substrate metal alloy type on the properties of hydroxyapatite coatings deposited using a novel ambient temperature deposition technique.  

PubMed

Hydroxyapatite (HA) coatings are applied widely to enhance the level of osteointegration onto orthopedic implants. Atmospheric plasma spray (APS) is typically used for the deposition of these coatings; however, HA crystalline changes regularly occur during this high-thermal process. This article reports on the evaluation of a novel low-temperature (<47C) HA deposition technique, called CoBlast, for the application of crystalline HA coatings. To-date, reports on the CoBlast technique have been limited to titanium alloy substrates. This study addresses the suitability of the CoBlast technique for the deposition of HA coatings on a number of alternative metal alloys utilized in the fabrication of orthopedic devices. In addition to titanium grade 5, both cobalt chromium and stainless steel 316 were investigated. In this study, HA coatings were deposited using both the CoBlast and the plasma sprayed techniques, and the resultant HA coating and substrate properties were evaluated and compared. The CoBlast-deposited HA coatings were found to present similar surface morphologies, interfacial properties, and composition irrespective of the substrate alloy type. Coating thickness however displayed some variation with the substrate alloy, ranging from 2.0 to 3.0??m. This perhaps is associated with the electronegativity of the metal alloys. The APS-treated samples exhibited evidence of both coating, and significantly, substrate phase alterations for two metal alloys; titanium grade 5 and cobalt chrome. Conversely, the CoBlast-processed samples exhibited no phase changes in the substrates after depositions. The APS alterations were attributed to the brief, but high-intensity temperatures experienced during processing. PMID:23589437

Barry, J N; Cowley, A; McNally, P J; Dowling, D P

2014-03-01

69

Structures and magnetism of two types of c(2x2)-Mn/Pd(001) surface alloys  

SciTech Connect

Mn/Pd(001) surface alloy was investigated by a tensor low-energy electron diffraction (LEED) analysis. After deposition of Mn on Pd(001) at room temperature, the surface was annealed at 570-620 K, which produced two types of c(2x2) surface alloys, according to the Mn coverage. At a low-Mn coverage, we obtained a Pd-capped c(2x2) surface, in which the first layer was composed of a (1x1)-Pd layer, and the second layer was a c(2x2)-MnPd mixed layer [{alpha}-c(2x2)]. The deposition of greater amounts of Mn followed by annealing resulted in another c(2x2) surface, in which Mn atoms existed in the substitutional sites of the first and third layers [{beta}-c(2x2)]. The first layer consisted of a c(2x2)-MnPd mixed layer, the second layer was a (1x1)-Pd layer, and the third layer was another c(2x2)-MnPd mixed layer. The structure of the {beta}-c(2x2) surface qualitatively agreed with the one previously investigated by LEED. These two types of surface alloys, {alpha}-c(2x2) and {beta}-c(2x2), may be considered as being precursors to the formation of the bulk MnPd{sub 3} alloy. We also investigated the magnetic properties of the {alpha}-c(2x2) and {beta}-c(2x2) surfaces by using surface magneto-optic Kerr effect (MOKE) and self-consistent, total-energy calculations. The MOKE measurements for both surface alloys show no hysterisis loop, even at 10 K. The total-energy calculation shows that Mn atoms have a local-spin moment of 3.9-4.1 {mu}{sub B} and that they are antiferromagnetically ordered in the ground state.

Tsuboi, N.; Okuyama, H.; Aruga, T. [Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)

2005-05-15

70

Improvement in fatigue characteristics of newly developed beta type titanium alloy for biomedical applications by thermo-mechanical treatments  

Microsoft Academic Search

Tensile and plain fatigue properties of ? type titanium alloy, Ti29Nb13Ta4.6Zr, which underwent various thermo-mechanical treatments, were investigated in order to judge its potential for biomedical applications.Microstructures of Ti29Nb13Ta4.6Zr (TNTZ) aged directly at 723 K for 259.2 ks after cold rolling and TNTZ aged at 723 K for 259.2 ks after solution treatment are composed of precipitated ? phase in

Toshikazu Akahori; Mitsuo Niinomi; Hisao Fukui; Michiharu Ogawa; Hiroyuki Toda

2005-01-01

71

Two different types of age-hardening behaviors in commercial dental gold alloys.  

PubMed

Age-hardening behavior during continuous heating in commercial dental casting gold alloys was investigated by means of electrical resistivity measurements, hardness tests and X-ray diffraction. Two distinguishable behaviors were detected. It is considered that the difference was attributed to the amount of platinum, and the atomic ratio of gold and copper in each alloy. The phase transformations during continuous heating progressed into two steps (stages I and II). Increase of the platinum addition in gold-based alloys retards the rate of the reaction and decreases remarkably the amount of stage I. PMID:17546416

Hisatsune, Kunihiro; Shiraishi, Takanobu; Takuma, Yasuko; Tanaka, Yasuhiro; Luciano, Rhodora H

2007-04-01

72

Determination of damage functions for the pitting of AISI type 403 blade alloy and ASTM A470/471 disk alloy  

NASA Astrophysics Data System (ADS)

The prediction of pitting accumulation on turbine blades and disks is of particular importance to predict localized corrosion damages in low pressure (LP) steam turbines. Damage Function Analysis (DFA) and Deterministic Extreme Value Statistics (DEVS) have been employed to predict the pitting damage on AISI Type 403 stainless steel (SS) blade alloy and ASTM A470/471 disk steel in simulated LP steam turbine environments within the phase transition zone. The passivity properties of Type 403 SS and A470/471 steel in the passive regions, including defect type, defect concentration in the barrier film, barrier film thickness, and the steady-state current density, agree with the predictions of the Point Defect Model (PDM) for an n-type semiconductor. Optimization of the PDM based impedance model on the experimental electrochemical impedance data has yielded a set of parameter values that can be used to predict the barrier film growth on Type 403 SS in deaerated borate buffer solution ( pH = 8.2) at ambient temperature. Experimental relationships between the breakdown potential and chloride activity, pH, temperature, and potential scan rate have demonstrated the applicability of the PDM for describing passivity breakdown on Type 403 SS and A470/471 steel. The obtained parameter values were used to calculate the breakdown potential, induction time, and their distributions, via the PDM, which represents the first quantitative characterization of the passivity breakdown behavior on Type 403 SS. Pitting damage functions for Type 403 SS have been experimentally determined for the first time. However, low pit density on A470/471 steel led to insufficient pit numbers on the 1.27 cm2 surface for the effective determination of damage functions. DEVS has been demonstrated by predicting the average maximum pit depth for 750 hours from short-term (24 hours and 240 hours) maximum pit depth data on Type 403 SS in deaerated buffer solution with 0.10 M NaCl at an applied potential of 0.090 VSCE and on A470/471 steel in the solution with 0.028 M NaCl at 0.058 VSCE. To the author's knowledge, the work reported in this dissertation represents the first instance in which DEVS has been used to predict the accumulation of pitting damage on LP steam turbine alloys, thereby heralding a new era in the prediction of corrosion damage in these systems.

Zhang, Yancheng

73

Method of fabricating n-type and p-type microcrystalline semiconductor alloy material including band gap widening elements  

DOEpatents

A method of fabricating doped microcrystalline semiconductor alloy material which includes a band gap widening element through a glow discharge deposition process by subjecting a precursor mixture which includes a diluent gas to an a.c. glow discharge in the absence of a magnetic field of sufficient strength to induce electron cyclotron resonance.

Guha, Subhendu (Troy, MI); Ovshinsky, Stanford R. (Bloomfield Hills, MI)

1990-02-02

74

[New type titan alloy with shape memory for use in dental implantology].  

PubMed

The paper summarizes the results of in vitro and in vivo studies that have proved biocompatibility and medical safety of Ta and Ti-Nb-Ta-bases alloys. According to some in vitro data Ti-Nb-Ta-based alloy possesses certain advantages when comparing to Ta-based. In particular, it contributes to elevation of viability of cellular elements and to definite increase of their adhesive potential. PMID:23528392

Grigor'ian, A S; Filonov, M R; Arkhipov, A V; Selezneva, I I; Zhukova, Iu S

2013-01-01

75

Modeling the behavior of a type-319 aluminum alloy during quenching  

NASA Astrophysics Data System (ADS)

Desired weight savings in automobiles has led to an increase in the use of cast aluminum parts in engine applications. To achieve the strength required in these applications, parts must be heat treated prior to service. This heat treatment involves a severe quench that can cause large thermal gradients, leading to undesirable residual stresses and strains. The ability to predict accurately residual stress and strain development during the quench would allow the design of aluminum engine parts with increased fatigue resistance and higher geometric tolerances. In this work, the behavior of a type-319 cast aluminum alloy (W319) is studied, from the equilibrium solid-solution state, to the end of the quench. A mechanical threshold stress model is used to predict the onset of plastic deformation in quenched parts due to effects of temperature and strain rate. The evolution of this mechanical threshold follows a Voce Law formulation. Parameters of the model are derived from rapid, uniaxial tension tests conducted on samples cast in green sand. The model is used in a one-dimensional, semi-analytical solution to predict the deformation and residual stress of side-quenched aluminum beams of uniform cross section. The model is also applied in full three-dimensional form to predict the behavior of beams of a non-uniform cross section. Model results are compared to results of quenching experiments performed on cast aluminum beams, including both transient deformation measurements and residual stress measurements obtained by a layer-removal technique. It is found that residual stress is predicted reasonably well by the model and that the model converges acceptably quickly to a solution when applied in a three-dimensional finite-element analysis. Transient and residual deformation are found to be more difficult to predict than residual stress.

Newman, Matthew Lloyd

76

Magnetic behavior of rapidly solidified Pr-Co alloys with the TbCu7-type structure  

NASA Astrophysics Data System (ADS)

Rapid solidification has been utilized to produce a series of Pr-Co alloys between the Pr2Co17 and PrCo5 stoichiometries. In this system, PrCo5 has easy axis magnetization while Pr2Co17 has easy-plane magnetization. Alloys of the form (PrxCo1-x)94Ti3C3 with x ranging from 0.105 corresponding to the Pr2Co17 compound to x=0.167 corresponding to the PrCo5 compound were produced by melt spinning at a tangential wheel speed of 40 m/s. The rapid solidification and alloying additions were found to suppress the formation of the Pr2Co17 ordered phase, leading to the formation of the disordered TbCu7-type structure over a range of Pr/Co ratios. Hysteresis loops were characterized by a smooth demagnetization curve reflective of single-phase demagnetization. Heat treatment at 800 C led to the formation of the Pr2Co17 and PrCo5 phases, and the presence of the soft magnetic Pr2Co17 phase drastically decreased the coercivity. The soft magnetic behavior was consistent with in-plane magnetization of the Pr2Co17 structure that formed during heat treatment. However, the relatively high coercivity observed in the as-solidified alloys with the disordered TbCu7-type structure suggests that dumbbell disorder may create easy axis magnetization, and changes in saturation magnetization also imply that dumbbell configuration is important to the magnetic properties.

Kostogorova, J.; Shield, J. E.

2006-04-01

77

Age Hardening Kinetics in 7xxx Type (Al-Mg-Zn) Alloys  

SciTech Connect

Age hardening in industrial 7xxx alloys at the temperature 100 deg. and 150 deg. C up to 144 hrs, after solid solution treatments at 450 deg. and 550 deg. C, has been followed by measurements of Vickers hardness, scanning and transmission electron microscopy. The influence of silicon on phase and kinetic of age hardening zones and precipitates has been studied. High iron and silicon content increase the number of primary particle in the alloy. Size distribution of {eta}'-precipitates has been determined.

Vevecka-Priftaj, A. [Department of Physic, Polytechnic University of Tirana, Sheshi 'Nene Tereza', N.4, Tirana (Albania); Lamani, E. [Department of Production and Menagement, Polytechnic University of Tirana (Albania); Fjerdingen, J. [Vitec AS, Akervegen2, 7650 Verdal (Norway); Langsrud, Y. [Hydro Aluminum Structures, Raufoss, P.O.Box 15, N-2831 Raufoss (Norway); Gjoennes, J. [Center for Materials Science, University of Oslo, Gaustadalleen 21, N-0349, Oslo (Norway); Hansen, V. [Faculty of Science and Technology, University of Stavanger, N-403, Stavanger (Norway)

2007-04-23

78

The effect of solidification rate on the growth of small fatigue cracks in a cast 319-type aluminum alloy  

NASA Astrophysics Data System (ADS)

A study was conducted to investigate the effect of solidification rate on the growth behavior of small fatigue cracks in a 319-type aluminum alloy, a common Al-Si-Cu alloy used in automotive castings. Fatigue specimens were taken from cast material that underwent a hot isostatic pressing (HIP) process in order to eliminate shrinkage pores and to facilitate the observation of surface-initiated cracks by replication. Naturally initiated surface cracks ranging in length from 17 m to 2 mm were measured using a replication technique. Growth rates of the small cracks were calculated as a function of the elastic stress-intensity-factor range (? K). Long-crack growth-rate data (10 mm?length?25 mm) were obtained from compact-tension (CT) specimens, and comparison to the small-crack data indicates the existence of a significant small-crack effect in this alloy. The solidification rate is shown to have a significant influence on small-crack growth behavior, with faster solidification rates resulting in slower growth rates at equivalent ? K levels. A stress-level effect is also observed for both solidification rates, with faster growth rates occurring at higher applied-stress amplitudes at a given ? K. A crack-growth relation proposed by Nisitani and others is modified to give reasonable correlation of small-crack growth data to different solidification rates and stress levels.

Caton, M. J.; Jones, J. Wayne; Boileau, J. M.; Allison, J. E.

1999-12-01

79

Thermoelectric properties of fine-grained FeVSb half-Heusler alloys tuned to p-type by substituting vanadium with titanium  

SciTech Connect

Fine-grained Ti-doped FeVSb half-Heusler alloys were synthesized by combining mechanical alloying and spark plasma sintering and their thermoelectric properties were investigated with an emphasis on the influences of Ti doping and phase purity. It was found that substituting V with Ti can change the electrical transport behavior from n-type to p-type due to one less valence electron of Ti than V, and the sample with nominal composition FeV{sub 0.8}Ti{sub 0.4}Sb exhibits the largest Seebeck coefficient and the maximum power factor. By optimizing the sintering temperature and applying annealing treatment, the power factor is significantly improved and the thermal conductivity is reduced simultaneously, resulting in a ZT value of 0.43 at 500 Degree-Sign C, which is relatively high as for p-type half-Heusler alloys containing earth-abundant elements. - Graphical abstract: Fine-grained Ti-doped FeVSb alloys were prepared by the MA-SPS method. The maximum ZT value reaches 0.43 at 500 Degree-Sign C, which is relatively high for p-type half-Heusler alloys. Highlights: Black-Right-Pointing-Pointer Ti-doped FeVSb half-Heusler alloys were synthesized by combining MA and SPS. Black-Right-Pointing-Pointer Substituting V with Ti changes the electrical behavior from n-type to p-type. Black-Right-Pointing-Pointer Thermoelectric properties are improved by optimizing sintering temperature. Black-Right-Pointing-Pointer Thermoelectric properties are further improved by applying annealing treatment. Black-Right-Pointing-Pointer A high ZT value of 0.43 is obtained at 500 Degree-Sign C for p-type Ti-doped FeVSb alloys.

Zou, Minmin [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)] [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Li, Jing-Feng, E-mail: jingfeng@mail.tsinghua.edu.cn [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)] [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Kita, Takuji [Advanced Material Engineering Division, Vehicle Engineering Group, Higashifuji Technical Center, Toyota Motor Corporation, 1200, Mishuku, Susono, Shizuoka 410-1193 (Japan)] [Advanced Material Engineering Division, Vehicle Engineering Group, Higashifuji Technical Center, Toyota Motor Corporation, 1200, Mishuku, Susono, Shizuoka 410-1193 (Japan)

2013-02-15

80

Effect of alloy type and surface conditioning on roughness and bond strength of metal brackets.  

PubMed

The effect of 5 different surface conditioning methods on bonding of metal brackets to cast dental alloys was examined. The surface conditioning methods were fine (30-microm) or rough (125-microm) diamond bur, sandblasting (50-microm or 110-microm aluminum oxide [Al2O3]), and silica coating (30-microm silica). Fifty disc-shaped specimens of 5 different alloys (gold-silver, palladium-silver, nickel-chromium, cobalt-chromium, and titanium) were ground with 1200-grit silicone carbide abrasive and polished before being reused for each conditioning method. Polished surfaces were used as negative controls. After measuring surface roughness (RZ), metal brackets were bonded to the conditioned alloys with a self-curing resin composite. Specimens were thermocycled (5000 times, 5 degrees-55 degrees C, 30 seconds), and shear bond tests were performed. Significantly higher (P<.001) surface roughnesses were observed with use of the rough diamond bur (RZ approximately 33 microm), 110-microm Al2O3 (RZ approximately 14 microm), and fine diamond bur (RZ approximately 10 microm), compared with the controls (RZ approximately 1 microm). Silica coating (RZ approximately 4 microm) and 50-microm Al2O3 (RZ approximately 4 microm) demonstrated no significant difference (P>.001) in roughness when compared with the controls. The control group showed no resistance to shear forces (0 MPa). Bond values were greater (19 MPa) when silica coating was used, compared with 50-microm Al2O3 (7 MPa) and 110-microm Al2O3 (8 MPa) for all alloys tested. However, interaction between alloys and conditioning methods exhibited significant differences (P<.0001). PMID:14718878

Nergiz, Ibrahim; Schmage, Petra; Herrmann, Wolfram; Ozcan, Mutlu

2004-01-01

81

Porosity structure and mechanical properties of vitalium-type alloy for implants  

Microsoft Academic Search

Results of porosity investigations performed on a CoCrMo alloy for implants, produced using powder metallurgy methods, are presented. Nonetched polished surfaces of as-sintered, rotary cold-repressed, and heat-treated material, respectively, were examined. Both, the face and axial section surfaces of cylindrical specimens were tested. Porosity assessment was accompanied by mechanical tests. It was demonstrated on the basis of the results obtained

Leszek Wojnar; Jan R. D?browski; Zbigniew Oksiuta

2001-01-01

82

Invar and Elinvar type amorphous Fe-Cr-B alloys with high corrosion resistance  

NASA Technical Reports Server (NTRS)

Amorphous (Fe(1-x)Cr(x))85B15 alloys (x = 0 to 0.15) were prepared from the melts by rapid quenching using a single roller techinque, and their Invar and Elinvar characteristics and corrosion resistance were investigated. With an increase in chromium content the Curie temperature and the saturation magnetic moment per iron atom decreased monotonically, while the crystallization temperature incresed gradually. The thermal expansion coefficient alpha around room temperature became slightly larger with increasing chromium content. Nevertheless, these amorphous alloys exhibited excellent Invar characteristics below the Curie temperature. The value of Young's modulus increased remarkably in a relatively low magnetic field and then saturated at a field of about 80 kA/m, showing a large delta E effect. Its value as well as a longitudinal linear magnetostriction became smaller with an increase in chromium content. The temperature coefficient of Young's modulus changed from postive to negative, and the temperature range showing the Elinvar characteristics became narrower with chromium content. The temperature coefficient of delay time determined from the values of alpha and e was very small. The corrosion resistance of these alloys was extremely improved by chromium addition.

Kikuci, M.; Fukamichi, K.; Masumoto, T.

1987-01-01

83

Crevice Repassivation Potential of Alloy 22 in High-Nitrate Dust Deliquescence Type Environments  

SciTech Connect

The nitrate ion (NO{sub 3}{sup -}) is an inhibitor for crevice corrosion of Alloy 22 (N06022) in chloride (Cl{sup -}) aqueous solutions. Naturally formed electrolytes may contain both chloride and nitrate ions. The higher the ratio R = [NO{sub 3}{sup -}]/[Cl{sup -}] in the solution the stronger the inhibition of crevice corrosion. Atmospheric desert dust contains both chloride and nitrate salts, generally based on sodium (Na{sup +}) and potassium (K{sup +}). Some of these salts may deliquescence at relatively low humidity at temperatures on the order of 150 C and higher. The resulting deliquescent brines are highly concentrated and especially rich in nitrate. Electrochemical tests have been performed to explore the anodic behavior of Alloy 22 in high chloride high nitrate electrolytes at temperatures as high as 150 C at ambient atmospheres. Naturally formed brines at temperatures higher than 120 C do not induce crevice corrosion in Alloy 22 because they contain high levels of nitrate. The inhibitive effect of nitrate on crevice corrosion is still active for temperatures higher than 100 C.

Lian, T; Gdowski, G E; Hailey, P D; Rebak, R B

2007-02-08

84

The structural, electronic and dynamic properties of the L12- type Co3Ti alloy  

NASA Astrophysics Data System (ADS)

The structural, electronic and dynamic properties of the cubic Co3Ti alloy in L12 structure have been investigated using a pseudopotential plane wave (PP-PW) method within the generalized gradient approximation proposed by Perdew-Burke-Ernzerhof (GGA-PBE). The structural properties, including the lattice constant, the bulk modulus and its pressure derivative agree reasonably with the previous results. The density of state (DOS), projected density of state (PDOS) and electronic band structure are also reported. The DOS shows that Co3Ti alloy has a metallic character since the energy bands cross the Fermi level. The density of states at Fermi level mainly comes from the Co-3d states. Phonon dispersion curves and their corresponding total densities of states were obtained using a linear response in the framework of the density functional perturbation theory. All computed phonon frequencies are no imaginer and thus, Co3Ti alloy is dynamically stable. The zone center phonon modes have been founded to be 9.307, 9.626 and 13.891 THz for Co3Ti.

Arikan, Nihat; zduran, Mustafa

2014-10-01

85

Effect of Sn Doping on the Thermoelectric Properties of n-type Bi2(Te,Se)3 Alloys  

NASA Astrophysics Data System (ADS)

In the present work, 0.01-0.05wt.% Sn-doped Bi2(Te0.9Se0.1)3 alloys were prepared by mechanical deformation followed by hot pressing, and their thermoelectric properties were studied. We observed that the Sn element is a very effective dopant as an acceptor to control the carrier concentration in the n-type Bi2(Te0.9Se0.1)3 alloys to optimize their thermoelectric property. The n-type carrier concentration can be controlled from 4.2 1019/cm3 to 2.4 1019/cm3 by 0.05wt.% Sn-doping. While the Seebeck coefficient and the electrical resistivity are both increased with doping, the power factor remains the same. Therefore, we found that the thermoelectric figure-of-merit becomes maximized at 0.75 when the thermal conductivity has a minimum value for the 0.03wt.% Sn-doped sample.

Lee, Jae-Uk; Lee, Deuk-Hee; Kwon, Beomjin; Hyun, Dow-Bin; Nahm, Sahn; Baek, Seung-Hyub; Kim, Jin-Sang

2015-01-01

86

Thermoelectric properties of fine-grained FeVSb half-Heusler alloys tuned to p-type by substituting vanadium with titanium  

NASA Astrophysics Data System (ADS)

Fine-grained Ti-doped FeVSb half-Heusler alloys were synthesized by combining mechanical alloying and spark plasma sintering and their thermoelectric properties were investigated with an emphasis on the influences of Ti doping and phase purity. It was found that substituting V with Ti can change the electrical transport behavior from n-type to p-type due to one less valence electron of Ti than V, and the sample with nominal composition FeV0.8Ti0.4Sb exhibits the largest Seebeck coefficient and the maximum power factor. By optimizing the sintering temperature and applying annealing treatment, the power factor is significantly improved and the thermal conductivity is reduced simultaneously, resulting in a ZT value of 0.43 at 500 C, which is relatively high as for p-type half-Heusler alloys containing earth-abundant elements.

Zou, Minmin; Li, Jing-Feng; Kita, Takuji

2013-02-01

87

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)

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.

Deadmore, D. L.

1974-01-01

88

Irradiation Performance of U-Mo Alloy Based Monolithic Plate-Type Fuel Design Selection  

SciTech Connect

A down-selection process has been applied to the U-Mo fuel alloy based monolithic plate fuel design, supported by irradiation testing of small fuel plates containing various design parameters. The irradiation testing provided data on fuel performance issues such as swelling, fuel-cladding interaction (interdiffusion), blister formation at elevated temperatures, and fuel/cladding bond quality and effectiveness. U-10Mo (wt%) was selected as the fuel alloy of choice, accepting a somewhat lower uranium density for the benefits of phase stability. U-7Mo could be used, with a barrier, where the trade-off for uranium density is critical to nuclear performance. A zirconium foil barrier between fuel and cladding was chosen to provide a predictable, well-bonded, fuel-cladding interface, allowing little or no fuel-cladding interaction. The fuel plate testing conducted to inform this selection was based on the use of U-10Mo foils fabricated by hot co-rolling with a Zr foil. The foils were subsequently bonded to Al-6061 cladding by hot isostatic pressing or friction stir bonding.

A. B. Robinson; G. S. Chang; D. D. Keiser, Jr.; D. M. Wachs; D. L. Porter

2009-08-01

89

SEM, EDS, EPMA-WDS and EBSD characterization of carbides in HP type heat resistant alloys  

SciTech Connect

The microstructure of centrifugally cast heat resistant alloys of the HP-series (Fe-35Ni-25Cr-0.4C, wt.%) contains several minor phases, like carbides (M{sub 7}C{sub 3}, M{sub 23}C{sub 6} and MC). Several alloys are characterized by means of scanning electron microscopy in back-scattered electron imaging and energy dispersive spectroscopy, of electron probe micro-analysis by X-ray wavelength dispersive spectroscopy, and of electron back-scattered diffraction. On the one hand, scanning electron microscopy imaging in the back-scattered mode, associated with energy dispersive spectroscopy analysis and electron back-scattered diffraction, can lead to the identification of all phases, but with a lack of accuracy in certain cases. On the other hand, electron probe micro-analysis by X-ray wavelength dispersive spectroscopy alone can always provide a strict identification of all phases, with additional precise information on phase composition, including for light elements, which is important in the case of carbides.

Laigo, J. [Universite de Nantes, Nantes Atlantique Universites, Polytech'Nantes, LGMPA, Rue Christian Pauc, BP 50609, F-44306 Nantes Cedex 3 (France); Air Liquide, Centre de Recherche Claude-Delorme, 1, chemin de la Porte des Loges, 78354 Jouy-en-Josas (France); Christien, F.; Le Gall, R. [Universite de Nantes, Nantes Atlantique Universites, Polytech'Nantes, LGMPA, Rue Christian Pauc, BP 50609, F-44306 Nantes Cedex 3 (France); Tancret, F. [Universite de Nantes, Nantes Atlantique Universites, Polytech'Nantes, LGMPA, Rue Christian Pauc, BP 50609, F-44306 Nantes Cedex 3 (France)], E-mail: franck.tancret@univ-nantes.fr; Furtado, J. [Air Liquide, Centre de Recherche Claude-Delorme, 1, chemin de la Porte des Loges, 78354 Jouy-en-Josas (France)

2008-11-15

90

Electrochemical corrosion and modeling studies of types 7075 and 2219 aluminum alloys in a nitric acid + ferric sulfate deoxidizer solution  

NASA Astrophysics Data System (ADS)

The corrosion behavior of types 7075-T73 and 2219-T852 high strength aluminum alloys have been investigated in a HNO3 + Fe2(SO 4)3 solution. The materials are characterized in the time domain using the electrochemical noise resistance parameter (Rn) and in the frequency-domain using the spectral noise impedance parameter ( Rsn). The Rsn parameter is derived from an equivalent electrical circuit model that represents the corrosion test cell schematic used in the present study. These calculated parameters are correlated to each other, and to corresponding scanning electron microscopy (SEM) examinations of the corroded surfaces. In addition, energy dispersive spectroscopy (EDS) spectra are used in conjunction with SEM exams for particle mapping and identification. These constituent particles are characterized with respect to their size and composition and their effect on the localized corrosion mechanisms taking place. Pitting mechanisms are identified as 'circumferential' where the particles appeared noble with respect to the aluminum matrix and by 'selective dissolution' where they are anodic to the aluminum matrix. The electrochemical data are found to be in good agreement with the surface examinations. Specifically, the electrochemical parameters Rn and Rsn were consistent in predicting the corrosion resistance of 7075-T73 to be lower than for the 2219-T852 alloy. Other characteristic features used in understanding the corrosion mechanisms include the open circuit potential (OCP) and coupling-current time records.

Savas, Terence P.

91

Investigation of early cellsurface interactions of human mesenchymal stem cells on nanopatterned ?-type titaniumniobium alloy surfaces  

PubMed Central

Multi-potent adult mesenchymal stem cells (MSCs) derived from bone marrow have therapeutic potential for bone diseases and regenerative medicine. However, an intrinsic heterogeneity in their phenotype, which in turn results in various differentiation potentials, makes it difficult to predict the response of these cells. The aim of this study is to investigate initial cellsurface interactions of human MSCs on modified titanium alloys. Gold nanoparticles deposited on ?-type Ti40Nb alloys by block copolymer micelle nanolithography served as nanotopographical cues as well as specific binding sites for the immobilization of thiolated peptides present in several extracellular matrix proteins. MSC heterogeneity persists on polished and nanopatterned Ti40Nb samples. However, cell heterogeneity and donor variability decreased upon functionalization of the gold nanoparticles with cyclic RGD peptides. In particular, the number of large cells significantly decreased after 24 h owing to the arrangement of cell anchorage sites, rather than peptide specificity. However, the size and number of integrin-mediated adhesion clusters increased in the presence of the integrin-binding peptide (cRGDfK) compared with the control peptide (cRADfK). These results suggest that the use of integrin ligands in defined patterns could improve MSC-material interactions, not only by regulating cell adhesion locally, but also by reducing population heterogeneity. PMID:24501674

Medda, Rebecca; Helth, Arne; Herre, Patrick; Pohl, Darius; Rellinghaus, Bernd; Perschmann, Nadine; Neubauer, Stefanie; Kessler, Horst; Oswald, Steffen; Eckert, Jrgen; Spatz, Joachim P.; Gebert, Annett; Cavalcanti-Adam, Elisabetta A.

2014-01-01

92

Investigation of early cell-surface interactions of human mesenchymal stem cells on nanopatterned ?-type titanium-niobium alloy surfaces.  

PubMed

Multi-potent adult mesenchymal stem cells (MSCs) derived from bone marrow have therapeutic potential for bone diseases and regenerative medicine. However, an intrinsic heterogeneity in their phenotype, which in turn results in various differentiation potentials, makes it difficult to predict the response of these cells. The aim of this study is to investigate initial cell-surface interactions of human MSCs on modified titanium alloys. Gold nanoparticles deposited on ?-type Ti-40Nb alloys by block copolymer micelle nanolithography served as nanotopographical cues as well as specific binding sites for the immobilization of thiolated peptides present in several extracellular matrix proteins. MSC heterogeneity persists on polished and nanopatterned Ti-40Nb samples. However, cell heterogeneity and donor variability decreased upon functionalization of the gold nanoparticles with cyclic RGD peptides. In particular, the number of large cells significantly decreased after 24 h owing to the arrangement of cell anchorage sites, rather than peptide specificity. However, the size and number of integrin-mediated adhesion clusters increased in the presence of the integrin-binding peptide (cRGDfK) compared with the control peptide (cRADfK). These results suggest that the use of integrin ligands in defined patterns could improve MSC-material interactions, not only by regulating cell adhesion locally, but also by reducing population heterogeneity. PMID:24501674

Medda, Rebecca; Helth, Arne; Herre, Patrick; Pohl, Darius; Rellinghaus, Bernd; Perschmann, Nadine; Neubauer, Stefanie; Kessler, Horst; Oswald, Steffen; Eckert, Jrgen; Spatz, Joachim P; Gebert, Annett; Cavalcanti-Adam, Elisabetta A

2014-02-01

93

Field ion microscopy of cascades of atomic displacements in metals and alloys after various types of irradiation  

NASA Astrophysics Data System (ADS)

Experimental results on atomic-spatial investigation of radiative defect formation in surface layers of materials, initiated by neutron bombardment (of Pt, E > 0.1 MeV) and ion implantation (in Cu3Au: E = 40 keV, F = 1016 ion/m2, j = 10-3 A/cm2), are considered. Quantitative estimates are obtained for the size, shape, and volume fraction of cascades of atomic displacements formed under various types of irradiation in the surface layers of the materials. It is shown that the average size of radiation clusters after irradiation of platinum to a fast neutron fluence of 6.7 1022 m-2 ( E > 0.1 MeV) is about 3.8 nm. The experimentally established average size of a radiation cluster (disordered zone) in the alloy after ion bombardment is 4 4 1.5 nm.

Ivchenko, V. A.

2014-09-01

94

Microstructure and thermoelectric properties of bulk and porous n-type silicon-germanium alloy prepared by HUP  

NASA Astrophysics Data System (ADS)

The optimization of powders preparation and consolidation process leads to the achievement of a high thermoelectric figure of merit (ZT=1.25 at 800C) in an n-type silicon-germanium (SiGe) alloy hot pressed at low heating rate. It has been experimentally observed that HUP compacting conditions can preserve nanostructuring. We also investigated the effect of porosity on the thermoelectric properties. Porous samples have enhanced Seebeck coefficients and low thermal conductivity. However, the figure of merit of the bulk specimen remains better than the porous samples due to a significant degradation of electrical conductivity. Working on grain boundaries engineering to enhance charge carriers mobility seems to be a promising way in addition to limiting nanograin growth with a densification process control.

Kallel, A.; Roux, G.; Derycke, T.; Martin, C. L.; Marinova, M.; Cayron, C.

2012-06-01

95

Induced magnetic moment on Co below T c in the ferromagnetic Heusler-type alloys Co 2MnX (X=Si, Ge and Sn)  

NASA Astrophysics Data System (ADS)

The paper gives the results of magnetic susceptibility measurements on pure and Fe doped Co 2MnX type Heusler alloys From the observed difference in the paramagnetic and the ferromagnetic moments (? p

Ido, H.

1986-02-01

96

Induced magnetic moment on Co below Tc in the ferromagnetic Heusler-type alloys Co2MnX (X=Si, Ge and Sn)  

Microsoft Academic Search

The paper gives the results of magnetic susceptibility measurements on pure and Fe doped Co2MnX type Heusler alloys From the observed difference in the paramagnetic and the ferromagnetic moments (mup

H. Ido

1986-01-01

97

NDE detectability of fatigue-type cracks in high-strength alloys: NDI reliability assessments  

NASA Technical Reports Server (NTRS)

This program was conducted to generate quantitative flaw detection capability data for the nondestructive evaluation (NDE) techniques typically practiced by aerospace contractors. Inconel 718 and Haynes 188 alloy test specimens containing fatigue flaws with a wide distribution of sizes were used to assess the flaw detection capabilities at a number of contractor and government facilities. During this program 85 inspection sequences were completed presenting a total of 20,994 fatigue cracks to 53 different inspectors. The inspection sequences completed included 78 liquid penetrant, 4 eddy current, and 3 ultrasonic evaluations. The results of the assessment inspections are presented and discussed. In generating the flaw detection capability data base, procedures for data collection, data analysis, and specimen care and maintenance were developed, demonstrated, and validated. The data collection procedures and methods that evolved during this program for the measurement of flaw detection capabilities and the effects of inspection variables on performance are discussed. The Inconel 718 and Haynes 188 test specimens that were used in conducting this program and the NDE assessment procedures that were demonstrated, provide NASA with the capability to accurately assess the flaw detection capabilities of specific inspection procedures being applied or proposed for use on current and future fracture control hardware program.

Christner, Brent K.; Long, Donald L.; Rummel, Ward D.

1988-01-01

98

Corrosion performance of mechanically fastened aluminum/steel joints: Influence of fastener type and aluminum alloy  

SciTech Connect

This paper discusses the corrosion test results for aluminum to steel lap-shear joints fabricated from three aluminum alloys using four different mechanical fasteners. The evaluations included exposure to alternate immersion (AI) and 100% relative humidity (RH) corrosion tests after phosphating and applying a 25 {micro}m E-Coat (i.e., electrolytic coating) to the completed assembly. Lap-shear test results showed that specimens fabricated using self-piercing rivets and solid rivets exhibited strengthening after 30--60 days exposure to AI or RH testing, which was subsequently followed by a decrease in tensile strength as aluminum base metal deterioration began to control the mechanical properties. Metallographic examination suggested the strengthening effect resulted from corrosion product buildup which produced compressive stresses on the joint members. The data indicated that stainless steel fasteners do not limit the corrosion performance of mechanically fastened aluminum to steel joints fabricated from bare sheets which are primed after assembly. The data also indicated that utilization of sealants in mechanically fastened aluminum/steel joints significantly improve corrosion performance of aluminum/steel joints.

Gunkel, R.W.; Moran, J.P. [Aluminum Co. of America, Alcoa Center, PA (United States). Alcoa Technical Center

1995-11-01

99

Crystal structure of the mirror symmetry 10H-type long-period stacking order phase in MgYZn alloy  

Microsoft Academic Search

The crystal structure of the 10H-type long-period stacking order structure in MgYZn alloy was investigated by first-principle calculations. The calculated results show that the accurate positions and distinctive arrangement of Zn and Y atoms in the most stable 10H-type LPSO phase exhibit mirror symmetry with respect to the atomic layer C6, which agrees well with the experimental observations. Theoretical calculations

Jian-Xiong Yi; Bi-Yu Tang; Ping Chen; Dong-Lin Li; Li-Ming Peng; Wen-Jiang Ding

2011-01-01

100

Microstructure and electronic characteristics of the 6H-type ABACAB LPSO structure in Mg 97Zn 1Y 2 alloy  

Microsoft Academic Search

Microstructure and electronic characteristics of the 6H-type ABACAB LPSO structure in Mg97Zn1Y2 alloy are investigated by means of first-principles calculation within the generalized gradient approximation. The accurate positions of the solid solution atoms Y and Zn together with the arrangement rules are determined theoretically and the lattice distortion of the 6H-type ABACAB structure is also discussed in comparison with the

Ping Chen; Dong-Lin Li; Jian-Xiong Yi; Bi-Yu Tang; Li-Ming Peng; Wen-Jiang Ding

2009-01-01

101

Low-cycle fatigue of Type 347 stainless steel and Hastelloy alloy X in hydrogen gas and in air at elevated temperatures  

NASA Technical Reports Server (NTRS)

An investigation was conducted to assess the low-cycle fatigue resistance of two alloys, Type 347 stainless steel and Hastelloy Alloy X, that were under consideration for use in nuclear-powered rocket vehicles. Constant-amplitude, strain-controlled fatigue tests were conducted under compressive strain cycling at a constant strain rate of 0.001/sec and at total axial strain ranges of 1.5, 3.0, and 5.0 %, in both laboratory-air and low-pressure hydrogen-gas environments at temperatures from 538 to 871 C. Specimens were obtained from three heats of Type 347 stainless steel bar and two heats of Hastelloy Alloy X. The tensile properties of each heat were determined at 21, 538, 649, and 760 C. The continuous cycling fatigue resistance was determined for each heat at temperatures of 538, 760, and 871 C. The Type 347 stainless steel exhibited equal or superior fatigue resistance to the Hastelloy Alloy X at all conditions of this study.

Jaske, C. E.; Rice, R. C.; Buchheit, R. D.; Roach, D. B.; Porfilio, T. L.

1976-01-01

102

Corrosion of a Type 304 stainless steel and a molybdenum-base TZM alloy in refluxing mercury with a small amount of potassium  

NASA Astrophysics Data System (ADS)

Corrosion of a Type 304 stainless steel and a molybdenum-base TZM alloy (Mo-0.5Ti-0.08Zr-0.025C-0.025 oxygen) in refluxing mercury with and without about 0.004 mol fraction of potassium in mercury has been examined using small capsules made of the steel and the alloy at 600 and 700 C to recognize the corrosion mechanisms. The wall of the austenitic 304 stainless steel capsule was severely corroded due to selective dissolution of nickel and chromium, leading to a ferritic layer which is more stable than the austenitic phase. The corrosion products were deposited near the vapor-liquid interface of the mercury. In contrast, the TZM alloy showed no noticeable changes except for carburization of the surface after heating for 2000 h, probably due to the low solubility of molybdenum in mercury.

Suzuki, Tadashi; Mutoh, Isao

1991-09-01

103

Cluster packing geometry for Al-based F-type icosahedral alloys  

E-print Network

This paper presents a new highly stable periodic approximant to the Al-based F-type icosahedral quasicrystals, i-Al-Pd-TM (TM=transition metals). The structure of this intermetallic Al-Pd-Cr-Fe compound is determined ab initio using single-crystal X-ray diffraction, where the space group is identified to be Pa-3 and the lattice constant 40.5 angstrom. The structure is well described as a dense packing of clusters of two kinds, which are known in the literature as the pseudo-Mackay type and the Bergman type clusters. The clusters are centered at the vertices of a canonical cell tiling, in which the parity of each vertex determines the kind of the associated cluster. Adjacent clusters can be markedly interpenetrated, while the structure requires no glue atoms to fill in the gaps between the clusters. It is shown that the crystal can be designated as a 2x2x2 superstructure of the ordinary cubic 3/2 rational approximant. The superlattice ordering is shown to be of a different kind from the P-type superlattice ordering previously reported in i-Al-Pd-Mn. The present results will greatly improve the understanding of atomic structures of F-type icosahedral quasicrystals and their approximants.

Nobuhisa Fujita; Hikari Takano; Akiji Yamamoto; An-Pang Tsai

2013-01-29

104

Effects of neutron irradiation on the mechanical properties of a 5154-0 type aluminium alloy  

SciTech Connect

A large number of Al 5154-0 tensile test specimens were irradiated in a core position facility of the High Flux Reactor in Petten, the Netherlands. They were withdrawn from the irradiation rig in seven batches with successively higher accumulated neutron fluences. The highest fluences achieved were 5.7 x 10/sup 26/ n/m/sup 2/ (E < 0.414 eV) and 6.0 x 10/sup 26/ n/m/sup 2/ (E > 0.1 MeV), which leads to a mean thermal-to-fast flux ratio of 0.95. The irradiation temperature was 360 K +- 10 K. After each withdrawal the material's tensile properties were determined at 293 K, 323 K and 373 K with a calculated strain rate epsilon = 1.65 x 10/sup -4//s. At the higher fluences the ductility figures appear to drop with increasing test temperature. Irradiation to a fluence level of 6 x 10/sup 26/ n/m/sup 2/ causes the 0.2% flow stress to increase from approx. 100 MPa to approx. 520 MPa and the uniform elongation to drop from more than 20% to less than 1% at the 323 K test temperature. The results of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and light microscopy (LM) confirm that the behavior of Al 5154-0 conforms to the general model for Al-Mg solid solution alloys obtained from the ORNL experiences with Al 5052-0. The objective of the irradiation program was to monitor the state of embrittlement that was expected to develop in the HFR core box material. The experimental results are representative for the PSF wall of the core box only. Because of the much higher thermal-to-fast neutron flux ratios prevailing in the other three walls, the test data are not directly applicable to these walls. By working out the implications of the basic model, however, it can be shown qualitatively that the ductility in the other walls will not be significantly better than in the PSF wall.

Lijbrink, E.; van Grol, H.J.; Dekker, F.; van Witzenburg, W.

1982-01-01

105

STRESS-CORROSION CRACKING OF TYPE 347 STAINLESS STEEL AND OTHER ALLOYS IN HIGH TEMPERATURE WATER  

Microsoft Academic Search

An extensive study was conducted on the susceptibility of Type 347 ; stainless steel to stress-corrosion cracking in high temperature water over wide ; ranges of chloride concentration, temperature, oxygen concentration, and pH. No ; cracking was observed at a chloride concentration of 5 ppm, but cracks were ; observed at 10 ppm and higher at temperatures of 100 deg

P. D. Neumann; J. C. Griess

1963-01-01

106

Germanium- and tellurium-doped GaAs for non-alloyed {ital p}-type and {ital n}-type ohmic contacts  

SciTech Connect

Epitaxial ohmic contacts to GaAs were grown by liquid phase epitaxy. Heavily Ge-doped GaAs was grown to prepare ohmic contacts to {ital p}-GaAs while Te was used for the {ital n}-type contacts. Hall measurements were carried out for the samples grown from melts in which the mole fraction of Ge was varied between 1.55 atomic % and 52.2 atomic %, while the Te mole fractions varied between 0.03% and 0.5%. Specific contact resistance, {ital r}{sub {ital c}}, as low as {ital r}{sub {ital cp}}=2.9{times}10{sup {minus}6} ohm-cm{sup 2} for Ge doping of {ital p}=({ital N}{sub {ital a}}{minus}{ital N}{sub {ital d}})=6.0{times}10{sup 19} holes/cm{sup 3} was measured for {ital p}-contacts and {ital r}{sub {ital cn}}=9.6{times}10{sup {minus}5} ohm-cm{sup 2 }was measured for Te doping of {ital n}=({ital N}{sub {ital d}}{minus}{ital N}{sub {ital a}})=8.9{times}10{sup 18} electrons/cm{sup 3 }for GaAs metallized with non-alloyed contacts of Ti/Al. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Park, J.; Barnes, P.A. [Department of Physics, Auburn University, Alabama 36849-5311 (United States)] [Department of Physics, Auburn University, Alabama 36849-5311 (United States); Lovejoy, M.L. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States)

1995-08-14

107

Mechanical properties and cytocompatibility of oxygen-modified ?-type Ti-Cr alloys for spinal fixation devices.  

PubMed

In this study, various amounts of oxygen were added to Ti-10Cr (mass%) alloys. It is expected that a large changeable Young's modulus, caused by a deformation-induced ?-phase transformation, can be achieved in Ti-10Cr-O alloys by the appropriate oxygen addition. This "changeable Young's modulus" property can satisfy the otherwise conflicting requirements for use in spinal implant rods: high and low moduli are preferred by surgeons and patients, respectively. The influence of oxygen on the microstructures and mechanical properties of the alloys was examined, as well as the bending springback and cytocompatibility of the optimized alloy. Among the Ti-10Cr-O alloys, Ti-10Cr-0.2O (mass%) alloy shows the largest changeable Young's modulus following cold rolling for a constant reduction ratio. This is the result of two competing factors: increased apparent ?-lattice stability and decreased amounts of athermal ? phase, both of which are caused by oxygen addition. The most favorable balance of these factors for the deformation-induced ?-phase transformation occurred at an oxygen concentration of 0.2mass%. Ti-10Cr-0.2O alloy not only exhibits high tensile strength and acceptable elongation, but also possesses a good combination of high bending strength, acceptable bending springback and great cytocompatibility. Therefore, Ti-10Cr-0.2O alloy is a potential material for use in spinal fixture devices. PMID:25449914

Liu, Huihong; Niinomi, Mitsuo; Nakai, Masaaki; Cho, Ken; Narita, Kengo; ?en, Mustafa; Shiku, Hitoshi; Matsue, Tomokazu

2015-01-15

108

Effect of Ternary Alloying Elements Addition on the Order-Disorder Transformation Temperatures of B2-Type Ordered Fe-Al-X Intermetallics  

NASA Astrophysics Data System (ADS)

The effect of alloying element additions on B2?A2 order-disorder phase transformation temperatures of B2-type ordered Fe0.5(Al1- n X n )0.5 intermetallics (X = Cr, Ni, Mo, Ta, Mn, Ti, and W) that readily form single-phase solid solution for X = 1 at. pct were investigated experimentally. It was shown that the type of the ternary substitutional alloying elements have a profound effect on the variation of order-disorder transition temperature of Fe0.5(Al1- n X n )0.5 alloys. Based on the magnitude of partial ordering energies of the Al-X and Fe-X atomic pairs, predicted normalized transition temperatures, ? T/ T o , were verified experimentally. Besides the normalized transition temperature, the relative partial ordering energy (RPOE) parameter, ?, was also defined to estimate the extent of variation in B2?A2 order-disorder phase transformation temperatures upon ternary alloying additions. The RPOE parameter, ?, takes into account both the effects of magnitude of partial ordering energies of Al-X and Fe-X atomic pairs and also the lattice site occupation preferences of X element atoms over B2-type ordered Fe-Al sublattices. The alloying elements, which are preferentially distributed Fe sublattice sites, ? > 0, and owing to ? >> 1, are more effective in increasing order-disorder transformation temperature in Fe-Al (B2) intermetallics. On the contrary, alloying elements having ? < 1 tend to decrease the transition temperature slightly relative to the binary FeAl intermetallic. The experimentally determined B2?A2 order-disorder transition temperatures are in good qualitative or semiquantitative agreement with theoretical predictions for all X ternary alloying elements. Accordingly, the present experimental results confirm the validity of the theoretical model and calculations proposed in our previous study on the B2?A2 order-disorder transition temperatures of single-phase Fe0.5(Al1- n X n )0.5 intermetallics.

Yildirim, Mehmet; Vedat Akdeniz, M.; Mekhrabov, Amdulla O.

2012-06-01

109

Alloyed Mn-Cu-In-S nanocrystals: a new type of diluted magnetic semiconductor quantum dots.  

PubMed

A new type of Mn-Cu-In-S diluted magnetic semiconductor quantum dots was synthesized and reported for the first time. The quantum dots, with no highly toxic elements, not only show the same classic diluted magnetic behavior as Mn-doped CdSe, but also exhibit tunable luminescent properties in a relatively large window from 542 to 648nm. An absolute photoluminescence quantum yield up to 20% was obtained after the shell growth of ZnS. This kind of magnetic/luminescent bi-functional Mn-Cu-In-S/ZnS core/shell quantum dot might serve as promising nanoprobes for use in dual-mode optical and magnetic resonance imaging techniques. PMID:22652831

Liu, Qinghui; Deng, Ruiping; Ji, Xiangling; Pan, Daocheng

2012-06-29

110

Effect of Y and Zn substitution on elastic properties of 6H-type ABCBCB LPSO structure in Mg 97Zn 1Y 2 alloy  

Microsoft Academic Search

Theoretical investigations of the effect of Y and Zn atom substitution on elastic properties of 6H-type ABCBCB LPSO structure in Mg97Zn1Y2 alloy have been performed from density function theory. Elastic properties, including elastic constants and elastic modulus were investigated, and the influence of Y and Zn substitution were discussed in detail. Elastic anisotropies were analyzed by several methods, and the

Ping-Ying Tang; Bi-Yu Tang; Li-Ming Peng; Wen-Jiang Ding

111

Improvement in Fatigue Strength of Biomedical beta-type Ti-Nb-Ta-Zr Alloy While Maintaining Low Young's Modulus Through Optimizing omega-Phase Precipitation  

Microsoft Academic Search

The improvement in fatigue strength, with maintenance of a low Young's modulus, in a biomedical beta-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), by thermomechanical treatment was investigated. A short aging time at an omega-phase-forming temperature combined with severe cold rolling was employed. A fine omega phase is observed in TNTZ subjected to this thermomechanical treatment. Because the rolling texture of beta phase

Masaaki Nakai; Mitsuo Niinomi; Takahiro Oneda

2011-01-01

112

A Probabilistic Model of Fatigue Strength Controlled by Porosity Population in a 319-Type Cast Aluminum Alloy: Part II. Monte-Carlo Simulation  

NASA Astrophysics Data System (ADS)

In Part I, the fatigue strength of a cast 319-type aluminum alloy at 108 cycles was evaluated using an ultrasonic testing system, and a simple probabilistic model was developed to establish the relationship between the porosity population and the resultant fatigue strength of the alloy. In Part II, a detailed analysis and comprehensive simulation based on this model were performed to examine the effects of casting porosity characteristics on fatigue strength in cast aluminum alloys. The results predict that, when fatigue life is controlled by porosity population, the mean and standard deviation of the fatigue strength decrease with increasing mean pore size, pore size standard deviation, and porosity number density in the castings. In addition, the specimen size and shape are predicted to influence the fatigue strength by affecting the number of pores and the probability of intersection of pores with the specimen surface within the stressed volume. In general, a large specimen volume containing a large number of pores (>1000) or surface over volume ratio in the range of 5.0 to 6.0 can lead to a decrease in fatigue strength up to 10 pct, as compared with the counterparts. The applicability of the model to a cast W319-T7 aluminum alloy is demonstrated.

Yi, J. Z.; Zhu, X.; Jones, J. W.; Allison, J. E.

2007-05-01

113

Deep drawability of type 5083 aluminiummagnesium alloy sheet under various conditions of temperature and forming speed  

Microsoft Academic Search

The effects of forming speed and temperature on the deep drawability were investigated for a fine-grain AlMg alloy (5083-O) sheet by performing cylindrical deep drawing tests at various forming speeds (0.2500mmmin?1) at die temperatures of 293453K (the die was heated, whilst the punch was water-cooled during the tests). In order to examine the mechanical properties of this AlMg alloy sheet,

Tetsuo Naka; Fusahito Yoshida

1999-01-01

114

Formation of the DO22-type superlattice during long-range ordering to Ni4Mo in a Ni-Mo alloy  

SciTech Connect

Khachaturyan (1973, 1974) has shown that many structures including a DO22-type superlattice can form during long-range ordering to Ni4Mo and Ni3Mo. The present investigation has the objective to show, that, in agreement with the statistical thermodynamic model used by Khachaturyan, a DO22 superlattice forms as an intermediate phase during long-range ordering to Ni4Mo. The structural transitions which occur during long-range ordering to Ni4Mo in a Ni-Mo alloy were studied. It was found that a DO22-type superlattice forms as an intermediate metastable phase. 28 references.

Tawancy, H.M.

1984-04-01

115

Subtyping in alloy  

E-print Network

A type system for the Alloy modelling language is described that supports subtypes and allows overloading of relation names. No special syntactic features needed to be added to the language to support the type system; there ...

Torlak, Emina, 1979-

2004-01-01

116

A Probabilistic Model of Fatigue Strength Controlled by Porosity Population in a 319-Type Cast Aluminum Alloy: Part I. Model Development  

NASA Astrophysics Data System (ADS)

The very high-cycle fatigue behavior of a 319-type cast aluminum alloy was investigated using ultrasonic fatigue instrumentation operating at 20 kHz. An endurance limit was demonstrated in the lifetime regime beyond 107 cycles. Accordingly, the fatigue strength at 108 cycles was determined using the staircase test method. Large pores at or close to the specimen surface or in the specimen interior were responsible for crack initiation in all specimens, and the staircase results were associated with both size and location of the initiating pores through a critical stress intensity factor for fatigue crack growth. Based on the experimental observations, a probabilistic model was developed to establish the relationship between the porosity population and the fatigue strength of the alloy. Good agreement was obtained between the modeling results and experiments.

Zhu, X.; Yi, J. Z.; Jones, J. W.; Allison, J. E.

2007-05-01

117

A comparative study on improved Arrhenius-type and artificial neural network models to predict high-temperature flow behaviors in 20MnNiMo alloy.  

PubMed

The stress-strain data of 20MnNiMo alloy were collected from a series of hot compressions on Gleeble-1500 thermal-mechanical simulator in the temperature range of 1173 ? 1473 K and strain rate range of 0.01 ? 10 s(-1). Based on the experimental data, the improved Arrhenius-type constitutive model and the artificial neural network (ANN) model were established to predict the high temperature flow stress of as-cast 20MnNiMo alloy. The accuracy and reliability of the improved Arrhenius-type model and the trained ANN model were further evaluated in terms of the correlation coefficient (R), the average absolute relative error (AARE), and the relative error (?). For the former, R and AARE were found to be 0.9954 and 5.26%, respectively, while, for the latter, 0.9997 and 1.02%, respectively. The relative errors (?) of the improved Arrhenius-type model and the ANN model were, respectively, in the range of -39.99% ? 35.05% and -3.77% ? 16.74%. As for the former, only 16.3% of the test data set possesses ?-values within 1%, while, as for the latter, more than 79% possesses. The results indicate that the ANN model presents a higher predictable ability than the improved Arrhenius-type constitutive model. PMID:24688358

Quan, Guo-zheng; Yu, Chun-tang; Liu, Ying-ying; Xia, Yu-feng

2014-01-01

118

Properties of the quaternary half-metal-type Heusler alloy CoMn{sub 1-x}FeSi  

Microsoft Academic Search

This paper reports on the bulk properties of the quaternary Heusler alloy CoMn{sub 1-x}FeSi with the Fe concentration x=0,1\\/2,1. All samples, which were prepared by arc melting, exhibit L2 long-range order over the complete range of Fe concentration. The structural and magnetic properties of the CoMn{sub 1-x}FeSi Heusler alloys were investigated by means of x-ray diffraction, high- and low-temperature magnetometry,

Benjamin Balke; Gerhard H. Fecher; Hem C. Kandpal; Claudia Felser; Keisuke Kobayashi; Eiji Ikenaga; Jung-Jin Kim; Shigenori Ueda

2006-01-01

119

Properties of the quaternary half-metal-type Heusler alloy Co2Mn1-xFexSi  

Microsoft Academic Search

This paper reports on the bulk properties of the quaternary Heusler alloy Co2Mn1-xFexSi with the Fe concentration x=0,1\\/2,1 . All samples, which were prepared by arc melting, exhibit L21 long-range order over the complete range of Fe concentration. The structural and magnetic properties of the Co2Mn1-xFexSi Heusler alloys were investigated by means of x-ray diffraction, high- and low-temperature magnetometry, Mssbauer

Benjamin Balke; Gerhard H. Fecher; Hem C. Kandpal; Claudia Felser; Keisuke Kobayashi; Eiji Ikenaga; Jung-Jin Kim; Shigenori Ueda

2006-01-01

120

Function of cobalt in the new type rare-earth Mg-based hydrogen storage electrode alloys  

Microsoft Academic Search

The role of cobalt on the structural and electrochemical properties of the La0.7Mg0.3Ni3.4?xMn0.1Cox (x=01.15) hydrogen storage alloys were investigated systematically. XRD and Rietveld analyses show that all alloys consist mainly of the (La,Mg)Ni3 phase and the LaNi5 phase. PC isotherms illustrate that the equilibrium pressure for hydrogen decreases monotonically with increasing x. Electrochemical studies indicate that the maximum discharge capacity

H. G. Pan; Y. F. Liu; M. X. Gao; R. Li; Y. Q. Lei

2005-01-01

121

Amorphous metal alloy  

DOEpatents

Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

Wang, R.; Merz, M.D.

1980-04-09

122

The effect of disorder on electronic and magnetic properties of quaternary Heusler alloy CoFeMnSi with LiMgPbSb-type structure  

NASA Astrophysics Data System (ADS)

Thin films based on Heusler alloy often lost their theoretical predicted ultra-high spin polarization owing to the appearance of disorder. Using the first-principles calculations within density functional theory (DFT), we investigate the effect of disorder including antisite and swap on electronic and magnetic properties of quaternary Heusler alloy CoFeMnSi with LiMgPbSb-type structure. Twelve kinds of antisites and six kinds of swap disorders are proposed and studied comprehensively. In our calculations, Co(Fe)-, Mn(Fe)-, Si(Mn)-antisite and Co-Fe swap disorders are most favorable due to their lowest formation energies. Moreover, the positive binding energies of Co-Fe, Co-Si, Fe-Si and Mn-Si swap disorders with respect to their corresponding antisite disorders indicate that these complex swap disorders are more stable compared with their corresponding isolated antisite disorders. The investigations on density of states (DOS) show that the spin down energy gap of disordered structures suffers contraction and their DOS entirely move towards lower zone. Besides, the 100% spin polarization is maintained in all structures with antisite and swap disorders except for those with Co(Mn)-, Co(Si)-antisite and Co-Mn, Co-Si swap disorders. Therefore, the half-metallicity of quaternary Heusler alloy CoFeMnSi is quite robust against interfering effects such as Si(Mn), Co(Fe) and Co-Fe disorders most possibly formed in the growth.

Feng, Yu; Chen, Hong; Yuan, Hongkuan; Zhou, Ying; Chen, Xiaorui

2015-03-01

123

Effects of micro- and nano-scale wave-like structures on fatigue strength of a beta-type titanium alloy developed as a biomaterial.  

PubMed

Some newly developed ?-type titanium alloys for biomedical applications exhibit distinctive heterogeneous structures. The formation mechanisms for these structures have not been completely revealed; however, understanding these mechanisms could lead to improving their properties. In this study, the heterogeneous structures of a Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), which is a candidate for next-generation metallic biomaterials, were analyzed. Furthermore, the effects of such heterogeneous structures on the mechanical strength of this alloy, including fatigue strength, were revealed by comparing its strength to that of homogenous TNTZ. The heterogeneous structures were characterized micro-, submicro- and nano-scale wave-like structures. The formation mechanisms of these wave-like structures are found to be different from each other even though their morphologies are similar. It is revealed that the micro-, submicro- and nano-scale wave-like structures are caused by elemental segregation, crystal distortion related to kink band and phase separation into ? and ?', respectively. However, these structures have no significant effect on both tensile properties and fatigue strength comparison with homogeneous structure in this study. PMID:24184863

Narita, Kengo; Niinomi, Mitsuo; Nakai, Masaaki

2014-01-01

124

Stability of Fe-based alloys with structure type C6Cr23 M. Widom and M. Mihalkovic  

E-print Network

glass-formability. We carry out first-principles total energy calculations of enthalpy of formation their enthalpies of formation. This study identified crystalline structures based on the C6Cr23 prototype of an alloy energy from the tie-surface joining pure elements is known as its enthalpy of formation

Widom, Michael

125

Development and Validation of Capabilities to Measure Thermal Properties of Layered Monolithic U-Mo Alloy Plate-Type Fuel  

NASA Astrophysics Data System (ADS)

The uranium-molybdenum (U-Mo) alloy in a monolithic form has been proposed as one fuel design capable of converting some of the world's highest power research reactors from the use of high enriched uranium to low enriched uranium. One aspect of the fuel development and qualification process is to demonstrate appropriate understanding of the thermal-conductivity behavior of the fuel system as a function of temperature and expected irradiation conditions. The purpose of this paper is to verify functionality of equipment installed in hot cells for eventual measurements on irradiated uranium-molybdenum (U-Mo) monolithic fuel specimens, refine procedures to operate the equipment, and validate models to extract the desired thermal properties. The results presented here demonstrate the adequacy of the equipment, procedures, and models that have been developed for this purpose based on measurements conducted on surrogate depleted uranium-molybdenum (DU-Mo) alloy samples containing a Zr diffusion barrier and clad in aluminum alloy 6061 (AA6061). The results are in excellent agreement with thermal property data reported in the literature for similar U-Mo alloys as a function of temperature.

Burkes, Douglas E.; Casella, Andrew M.; Buck, Edgar C.; Casella, Amanda J.; Edwards, Matthew K.; MacFarlan, Paul J.; Pool, Karl N.; Smith, Frances N.; Steen, Franciska H.

2014-07-01

126

Correlation between Mechanical Behavior and Actuator-type Performance of Ni-Ti-Pd High-temperature Shape Memory Alloys  

NASA Technical Reports Server (NTRS)

High-temperature shape memory alloys in the NiTiPd system are being investigated as lower cost alternatives to NiTiPt alloys for use in compact solid-state actuators for the aerospace, automotive, and power generation industries. A range of ternary NiTiPd alloys containing 15 to 46 at.% Pd has been processed and actuator mimicking tests (thermal cycling under load) were used to measure transformation temperatures, work behavior, and dimensional stability. With increasing Pd content, the work output of the material decreased, while the amount of permanent strain resulting from each load-biased thermal cycle increased. Monotonic isothermal tension testing of the high-temperature austenite and low temperature martensite phases was used to partially explain these behaviors, where a mismatch in yield strength between the austenite and martensite phases was observed at high Pd levels. Moreover, to further understand the source of the permanent strain at lower Pd levels, strain recovery tests were conducted to determine the onset of plastic deformation in the martensite phase. Consequently, the work behavior and dimensional stability during thermal cycling under load of the various NiTiPd alloys is discussed in relation to the deformation behavior of the materials as revealed by the strain recovery and monotonic tension tests.

Bigelow, Glen S.; Padula, Santo A., II; Garg, Anita; Noebe, Ronald D.

2007-01-01

127

Thermoelectric properties of the Heusler-type Fe{sub 2}VTa{sub x}Al{sub 1?x} alloys  

SciTech Connect

This study focuses on the thermoelectric properties of the Heusler-type Fe{sub 2}VTa{sub x}Al{sub 1?x} alloys (0?x?0.12). By means of Rietveld analyses on synchrotron X-ray diffraction patterns, it is shown that the Ta atoms enter sites occupied by V atoms in the stoichiometric Fe{sub 2}VAl alloy, while the ejected V atoms are transferred to the vacant Al sites. This Ta substitution leads to an improvement of the n-type thermoelectric properties owing to two mechanisms. On the one hand, the atoms position in the structure leads to an off-stoichiometric effect such as already observed in V-rich Fe{sub 2}V{sub 1+y}Al{sub 1?y} compounds: the Seebeck coefficient is increased towards negative absolute values and the electrical resistivity is decreased, with a large shift of their peak temperature towards higher temperature. The maximum power factor is 6.5??10{sup ?3} W/mK{sup 2} for x?=?0.05 at 340?K. On the other hand, the heavy element Ta substitution combined with this off-stoichiometric effect leads to a large decrease of the thermal conductivity, owing to an increase of the scattering events. Consequently, the dimensionless figure of merit is seen to reach higher values than for the Fe{sub 2}V{sub 1+y}Al{sub 1?y} alloys, i.e., 0.210.22 around 400500?K for x?=?0.05 and 500?K for x?=?0.08.

Renard, Krystel, E-mail: renard.krystel@nitech.ac.jp; Mori, Arinori; Yamada, Yuichiro; Tanaka, Suguru; Nishino, Yoichi [Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Miyazaki, Hidetoshi [Center for Fostering Young and Innovative Researchers, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

2014-01-21

128

Alloying of aluminum-beryllium alloys  

NASA Astrophysics Data System (ADS)

The existing phase diagrams of Al-Be- X alloys, where X is an alloying element, are analyzed. Element X is noted to poorly dissolve in both aluminum and beryllium. It is shown that the absence of intermetallic compounds in the Al-Be system affects the phase equilibria in an Al-Be- X system. Possible phase equilibria involving phases based on aluminum, beryllium, and intermetallic compounds are proposed, and the types of strengthening of Al-Be alloys by an addition of a third element are classified.

Molchanova, L. V.; Ilyushin, V. N.

2013-01-01

129

Thermoelectric Properties and n- to p-Type Conversion of Co-Doped ZrNiSn-Based Half-Heusler Alloys  

NASA Astrophysics Data System (ADS)

Half-Heulser thermoelectric materials ZrNi1- y Co y Sn ( y = 0, 0.02, 0.04, 0.08, 0.12) were prepared by a time-efficient levitation melting and spark plasma sintering procedure. X-ray diffraction analysis and electron probe microanalysis showed that single-phase half-Heusler compounds without compositional segregation have been obtained. The effects of Co doping on the electrical conductivity, Seebeck coefficient, and thermal conductivity of ZrNiSn-based half-Heusler alloys have been investigated from 300 K to 900 K. The Seebeck coefficient displayed a change from negative to positive values above nominal Co doping content of y = 0.02, indicating a transition in the conduction behavior from n-type to p-type. The maximum dimensionless figure of merit ZT of undoped ZrNiSn sample reached 0.5 at 870 K.

Xie, Han-Hui; Yu, Cui; He, Bin; Zhu, Tie-Jun; Zhao, Xin-Bing

2012-06-01

130

Magnetic properties and origin of the half-metallicity of Ti2MnZ (Z=Al, Ga, In, Si, Ge, Sn) Heusler alloys with the Hg2CuTi-type structure  

NASA Astrophysics Data System (ADS)

Using the first-principles calculations within density functional theory, we investigate the magnetic properties and electronic structures of the Ti2MnZ (Z=Al, Ga, In, Si, Ge, Sn) alloys with the Hg2CuTi-type structure. The Ti2MnZ (Z=Al, Ga, In, Si, Ge, Sn) are found to be half-metallic ferrimagnets. The total magnetic moments (t) of the Ti2MnZ alloys are calculated to be 0 for Z=Al, Ga, In and 1 for Z=Si, Ge, Sn, linearly scaled with the total number of valence electrons (Zt) by t=Zt-18. The origin of the band gap for these half-metallic alloys is well understood. We expect our results to trigger further experimental interest in these alloys.

Fang, Qing-Long; Zhang, Jian-Min; Xu, Ke-Wei

2014-01-01

131

Suppression effect of oxygen on the ? to ? transformation in a ?-type Ti alloy: insights from first-principles  

NASA Astrophysics Data System (ADS)

Oxygen has long been known to retard the formation of the hexagonal ? phase in body-centered-cubic ?-Ti based alloys, but a quantum mechanical evaluation of the thermodynamics associated with the ? to ? transformation remains unexplored. Our first-principles density functional theory calculations on a model Ti3Nb alloy containing 2 at% O reveal that O prefers an octahedral interstitial in both the ? and ? phases and increases the ? energy relative to ? (0.19 eV/O), thus making the ? phase thermodynamically less favorable. Interestingly, we find that O atoms in ? can be categorized into two sets which have a strikingly distinct effect. The O atoms in collapsing {1?1?1} planes increase the energy barrier (29 meV/atom) in the ? to ? transformation remarkably; whereas the O atoms in the uncollapsing {1?1?1} planes exert a much smaller retarding effect (5 meV/atom). This is because the former set of O atoms has to pass through high-lying intermediate tetragonal sites. The suppression effect of O can be understood with electronic structure analyses.

Niu, J. G.; Ping, D. H.; Ohno, T.; Geng, W. T.

2014-01-01

132

Microstructural studies on Alloy 693  

NASA Astrophysics Data System (ADS)

Superalloy 693, is a newly identified high-temperature corrosion resistant alloy. Present study focuses on microstructure and mechanical properties of the alloy prepared by double vacuum melting route. In general, the alloy contains ordered Ni3Al precipitates distributed within austenitic matrix. M6C primary carbide, M23C6 type secondary carbide and NbC particles are also found to be present. Heat treatment of the alloy at 1373 K for 30 min followed by water quenching (WQ) brings about a microstructure that is free from secondary carbides and Ni3Al type precipitates but contains primary carbides. Tensile property of Alloy 693 materials was measured with as received and solution annealed (1323 K, 60 min, WQ) and (1373 K, 30 min, WQ) conditions. Yield strength, ultimate tensile strength (UTS) and hardness of the alloy are found to drop with annealing. It is noted that in annealed condition, considerable cold working of the alloy can be performed.

Halder, R.; Dutta, R. S.; Sengupta, P.; Samajdar, I.; Dey, G. K.

2014-10-01

133

Microstructural and Orientation Dependence of the Plastic Deformation Behavior in ?-type Ti-15Mo-5Zr-3Al Alloy Single Crystals  

NASA Astrophysics Data System (ADS)

The plastic deformation behavior of a ?-type Ti-15Mo-5Zr-3Al alloy with a body-centered cubic (bcc) structure, which is a promising material for biomedical applications, was investigated. The orientation dependence of the plastic deformation behavior was examined by using a single crystal. In addition, changes in the mechanical properties depending on the microstructure were examined. The ? single phase was maintained even after short-time annealing below 673 K (400 C). Thus, the variations in the mechanical properties were small. However, an ellipsoidal ? phase and a lath-like ? phase were precipitated in long-time annealing at 573 K (300 C) and 673 K (400 C), leading to large increases in the yield stress. For the deformation behavior, a dislocation with a Burgers vector parallel to left< {111} rightrangle was observed irrespective of the heat-treatment conditions and loading orientations. However, the observed slip plane changed considerably depending on the loading axis, and the yield stress exhibited a strong orientation dependence because of the dislocation core structure effect in the bcc-structured crystals. The physical properties of Mo, which is the main constituent atom in the current alloy, may strongly affect the dislocation core structure and induce the characteristic orientation dependence of the plastic behavior.

Lee, Sang-Hoon; Hagihara, Koji; Nakano, Takayoshi

2012-05-01

134

Extrusion die geometry effects on the energy absorbing properties and deformation response of 6063-type Al-Mg-Si aluminum alloy  

NASA Astrophysics Data System (ADS)

The response of 6063-type Al-Mg-Si alloy to deformation via extrusion was studied using tool steel dies with 15, 30, 45, 60 and 75 entry angles. Compressive loads were subjected to each sample using the AVERY DENISON machine, adapted to supply a compressive load on the punch. The ability of the extrudate to absorb energy before fracture was calculated by integrating numerically the polynomial relationship between the compressive stress and sample strains. Strain rate was calculated for each specimen and the deformation zone length was mathematically derived from the die geometry to decipher its influence on both lateral and axial deformations. Results showed that extruding with a 15 die was the fastest as a result of the low flow stress encountered. Outstanding compressive strength, plastic deformation, strain rate and energy absorbing capacity were observed for the alloy extruded with a 75 die angle. Increase in die angles led to a decrease in deformation zone length and samples deformed more in the axial direction than in the lateral except for the 45o die which showed the opposite; the sample also showed the least ductility.

Gbenebor, O. P.; Fayomi, O. S. I.; Popoola, A. P. I.; Inegbenebor, A. O.; Oyawale, F.

135

In vivo corrosion, tumor outcome, and microarray gene expression for two types of muscle-implanted tungsten alloys  

SciTech Connect

Tungsten alloys are composed of tungsten microparticles embedded in a solid matrix of transition metals such as nickel, cobalt, or iron. To understand the toxicology of these alloys, male F344 rats were intramuscularly implanted with pellets of tungsten/nickel/cobalt, tungsten/nickel/iron, or pure tungsten, with tantalum pellets as a negative control. Between 6 and 12 months, aggressive rhabdomyosarcomas formed around tungsten/nickel/cobalt pellets, while those of tungsten/nickel/iron or pure tungsten did not cause cancers. Electron microscopy showed a progressive corrosion of the matrix phase of tungsten/nickel/cobalt pellets over 6 months, accompanied by high urinary concentrations of nickel and cobalt. In contrast, non-carcinogenic tungsten/nickel/iron pellets were minimally corroded and urinary metals were low; these pellets having developed a surface oxide layer in vivo that may have restricted the mobilization of carcinogenic nickel. Microarray analysis of tumors revealed large changes in gene expression compared with normal muscle, with biological processes involving the cell cycle significantly up?regulated and those involved with muscle development and differentiation significantly down?regulated. Top KEGG pathways disrupted were adherens junction, p53 signaling, and the cell cycle. Chromosomal enrichment analysis of genes showed a highly significant impact at cytoband 7q22 (chromosome 7) which included mouse double minute (MDM2) and cyclin?dependant kinase (CDK4) as well as other genes associated with human sarcomas. In conclusion, the tumorigenic potential of implanted tungsten alloys is related to mobilization of carcinogenic metals nickel and cobalt from corroding pellets, while gene expression changes in the consequent tumors are similar to radiation induced animal sarcomas as well as sporadic human sarcomas. -- Highlights: ? Tungsten/nickel/cobalt, tungsten/nickel/iron, and pure tungsten were studied. ? Male Fischer rats implanted with pellets in gastrocnemius muscle of each hind leg. ? Aggressive rhabdomyosarcomas developed from tungsten/nickel/cobalt pellets only. ? Microarray gene expression analysis was carried out on selected tumors. ? Pellet degradation, urinary metal concentration, and sarcoma were correlated.

Schuster, B.E. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, B434 Mulberry Road, Aberdeen Proving Ground, MD 21005-5609 (United States)] [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, B434 Mulberry Road, Aberdeen Proving Ground, MD 21005-5609 (United States); Roszell, L.E. [U.S. Army Institute of Public Health, 5158 Blackhawk Road, Aberdeen Proving Ground, MD 21010?5403 (United States)] [U.S. Army Institute of Public Health, 5158 Blackhawk Road, Aberdeen Proving Ground, MD 21010?5403 (United States); Murr, L.E.; Ramirez, D.A. [Department of Metallurgical and Materials Engineering, University of Texas, El Paso, TX 79968 (United States)] [Department of Metallurgical and Materials Engineering, University of Texas, El Paso, TX 79968 (United States); Demaree, J.D. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, B434 Mulberry Road, Aberdeen Proving Ground, MD 21005-5609 (United States)] [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, B434 Mulberry Road, Aberdeen Proving Ground, MD 21005-5609 (United States); Klotz, B.R. [Dynamic Science Inc., Aberdeen Proving Ground, MD 21005?5609 (United States)] [Dynamic Science Inc., Aberdeen Proving Ground, MD 21005?5609 (United States); Rosencrance, A.B.; Dennis, W.E. [U.S. Army Center for Environmental Health Research, Department of Chemistry, Ft. Detrick, MD 21702?5010 (United States)] [U.S. Army Center for Environmental Health Research, Department of Chemistry, Ft. Detrick, MD 21702?5010 (United States); Bao, W. [SAS Institute, Inc. SAS Campus Drive, Cary, NC 27513 (United States)] [SAS Institute, Inc. SAS Campus Drive, Cary, NC 27513 (United States); Perkins, E.J. [U.S. Army Engineer Research and Development Center, 3909 Hall Ferry Road, Vicksburg MS 39180 (United States)] [U.S. Army Engineer Research and Development Center, 3909 Hall Ferry Road, Vicksburg MS 39180 (United States); Dillman, J.F. [U.S. Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Aberdeen Proving Ground, MD 21010?5400 (United States)] [U.S. Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Aberdeen Proving Ground, MD 21010?5400 (United States); Bannon, D.I., E-mail: desmond.bannon@us.army.mil [U.S. Army Institute of Public Health, 5158 Blackhawk Road, Aberdeen Proving Ground, MD 21010?5403 (United States)

2012-11-15

136

Combinatorial sputtering in planetary type systems for alloy libraries with perpendicular gradients of layer thickness and composition realised by a timing approach  

NASA Astrophysics Data System (ADS)

We present a combinatorial sputtering technique to fabricate alloy thin films with orthogonal gradients of thickness and stoichiometry in a planetary type sputtering system. Using this approach we prepared a library of planar Nb Josephson junctions with a magnetic compound layer made from Si and Fe on one wafer. The independent investigation of thickness and composition changes of the FeSi layer allows the identification of transition regions where the phase difference of the superconducting order parameter across the barrier changes from 0 to . A mapping technique which allows to identify the different coupling regimes depending on material properties might facilitate the fabrication of junctions with tailored critical current, damping and normal resistance parameters for applications.

Ruppelt, N.; Vavra, O.; Sickinger, H.; Goldobin, E.; Koelle, D.; Kleiner, R.; Kohlstedt, H.

2014-07-01

137

Improving the structure, magnetic properties and thermal stability of rapidly quenched TbCu7-type SmCo6.4Si0.3Zr0.3 alloy by carbon addition  

NASA Astrophysics Data System (ADS)

The effects of carbon addition on the structure and magnetic properties of rapidly quenched TbCu7-type SmCo6.4Si0.3Zr0.3 alloy have been investigated. The alloys with a small amount of C addition (x?0.2) showed single Sm(Co,M)7 phase, while ZrC phase appeared in the alloys with x=0.3 and 0.4. With the increase of C content, the grain size decreased from approximately 850 nm for x=0.1 to approximately 300 nm for x=0.4. The coercivity Hc and maximum magnetic energy product (BH)max increased with the C content from x=0 to 0.2 and then decreased with excessive C addition. The optimal magnetic properties of Hc=1577 kA/m, Jr=0.53 T and (BH)max=52.1 kJ/m3 were achieved for SmCo6.4Si0.3Zr0.3C0.2 alloy with a grain size of 600-700 nm, which is close to the single domain size of TbCu7-type Sm(Co,Zr)7 alloy. Furthermore, C addition also improved the thermal stability by reducing the absolute values of temperature coefficients of remanence and coercivity.

Feng, D. Y.; Liu, Z. W.; Zheng, Z. G.; Zeng, D. C.; Zhang, G. Q.

2014-08-01

138

Design and fabrication of a locomotive mechanism for capsule-type endoscopes using shape memory alloys (SMAs)  

Microsoft Academic Search

Endoscopes are medical devices to diagnose various kinds of diseases throughout the whole gastrointestinal tracks. Generally, they are divided into conventional push-type endoscopes and more recently developed wireless capsule-type endoscopes. The conventional endoscopes cannot reach the small intestines and generate pain and discomfort to patients due to the stiffness of their body. Such disadvantages do not exist in wireless capsule-type

Byungkyu Kim; Sunghak Lee; Jong Heong Park; Jong-Oh Park

2005-01-01

139

Osmium isotope systematics of Os-rich alloys and Ru-Os sulfides from oceanic mantle: evidence from Proterozoic and Paleozoic ophiolite-type complexes  

NASA Astrophysics Data System (ADS)

This study presents a substantial data set of Os-isotope compositions of Os-rich alloys and Ru-Os sulfides from deep portions of ophiolite sections from oceanic mantle. These are represented by samples from different in age ophiolite-type massifs (i.e., Neoproterozoic Kunar in Northern Taimyr, Russia, and Hochgrossen in Eastern Alps, Austria, Paleozoic Verkh-Neivinsk in Middle Urals, Russia, and Shetland in northern Scotland). The investigation employed a number of analytical techniques, including electron microprobe analysis, ID ICP-MS after high pressure acid digestion, and laser ablation attached to multiple collector-inductively coupled plasma mass-spectrometry (LA MC-ICP-MS). Two distinct platinum-group mineral (PGM) assemblages have been recognized at the Shetland and Verkh-Neivinsk localities: a 'primary' euhedral PGM assemblage, which occur as inclusions in chromite, and a modified 'secondary' subeuhedral to anhedral PGM assemblage observed in cracks filled by chlorite or serpentine, interstitially to chromite grains [1]. A 'primary' PGM assemblage at Shetland is represented by solitary grains of laurite or iridian osmium and composite grains of laurite + osmian iridium iridian osmium that display well defined phase boundaries between two or three distinct PGMs. A 'primary' PGM assemblage at Verkh-Neivinsk is represented by Ru-Os-Ir alloy grains that frequently mantled by 'secondary' Ru-Os sulfide and/or Ru-Os sulfarsenide overgrowths. The osmium isotope results identify (1) a restricted range of 'unradiogenic' 187Os/188Os values for coexisting laurite and Os-rich alloy pairs that form 'primary' PGM assemblages at Hochgrossen and Shetland (0.11860-0.11866 and 0.12473-0.12488, respectively); (2) similar 'unradiogenic' 187Os/188Os values for both 'primary' and 'secondary' PGM assemblages at Shetland (with mean 187Os/188Os 0.12419 and 0.12464, respectively) and Verkh-Neivinsk (with distinct mean 187Os/188Os values), and (3) a wide scatter of subchondritic 187Os/188Os values for 'primary' PGM assemblages at Kunar (i.e., 187Os/188Os 0.11848-0.11239), Verkh-Neivinsk (0.11619-0.12565), and Hochgrossen (0.11860-0.12450). The whole-rock Os-isotope budget of chromitite at Shetland (0.12400.0006) is largely controlled by laurite-dominant assemblages. In this case, the 'secondary' PGM assemblage inherited the 'unradiogenic' Os-isotope signature of the 'primary' PGMs. No evidence for other source contributions during later thermal events has been observed here. However, the wide range of subchondritic 187Os/188Os values has been found in the 'primary' PGM assemblages (e.g., laurite and Os-rich alloys) from the ophiolite-type complexes worldwide [2 and references cited therein]. This wide range would be consistent with a model, in which a prolonged history of melting events of parent ultramafic source rocks took place in the mantle. This variability is in agreement with the conclusion that the Os-isotope system of PGMs records multiple events during the chemical differentiation history of the mantle [3] and could have been controlled by deep-geodynamic processes [4]. On the other hand, the observed Os-isotope heterogeneity may be also attributed to the presence of subcontinental lithospheric mantle (SCLM), characterized by highly unradiogenic 187Os/188Os values (i.e.,

Badanina, Inna Yu.; Malitch, Kreshimir N.; Belousova, Elena A.; Lord, Richard A.; Meisel, Thomas C.; Murzin, Valery V.; Pearson, Norman J.

2014-05-01

140

Structural and transport properties in alloyed Ti/Al Ohmic contacts formed on p-type Al-implanted 4H-SiC annealed at high temperature  

NASA Astrophysics Data System (ADS)

In this paper, the transport properties of alloyed Ti/Al Ohmic contacts formed on p-type Al-implanted silicon carbide (4H-SiC) were studied. The morphology of p-type implanted 4H-SiC was controlled using a capping layer during post-implantation activation annealing at 1700 C. The different morphological conditions do not affect the macroscopic electrical properties of the implanted SiC (such as the sheet resistance or the mobility). On the other hand, the improved morphology of implanted SiC allows us to achieve a flatter Ti/Al surface and a lower specific contact resistance. The temperature dependence of the specific resistance of the contacts was studied to obtain physical insights into the carrier transport mechanism at the metal/SiC interface. The fit comparing several models shows that thermionic field emission is the dominant transport mechanism through the metal/SiC interface, and that a reduction in the barrier height from 0.51 to 0.46 eV is associated with the improvement of the Ohmic properties. Transmission electron microscopy analysis showed the presence of a laterally inhomogeneous microstructure of the metal/SiC interface. The reduction in the barrier height could be correlated with the different microstructures of the interfacial region.

Frazzetto, A.; Giannazzo, F.; Lo Nigro, R.; Raineri, V.; Roccaforte, F.

2011-06-01

141

Influence of Fluidized Bed Quenching on the Mechanical Properties and Quality Index of T6 Tempered B319.2-Type Aluminum Alloys  

NASA Astrophysics Data System (ADS)

The current study aimed to investigate the effect of fluidized sand bed (FB) quenching on the mechanical performance of B319.2 aluminum cast alloys. Traditional water and conventional hot air (CF) quenching media were used to establish a relevant comparison with FB quenching. Quality charts were generated using two models of quality indices to support the selection of material conditions on the basis of the proposed quality indices. The use of an FB for the direct quenching-aging treatment of B319.2 casting alloys yields greater UTS and YS values compared to conventional furnace quenched alloys. The strength values of T6 tempered B319 alloys are greater when quenched in water compared with those quenched in an FB or CF. For the same aging conditions (170C/4h), the fluidized bed quenched-aged 319 alloys show nearly the same or better strength values than those quenched in water and then aged in a CF or an FB. Based on the quality charts developed for alloys subjected to different quenching media, higher quality index values are obtained by conventional furnace quenched-aged T6-tempered B319 alloys. The modification factor has the most significant effect on the quality results of the alloys investigated, for all heat treatment cycles, as compared to other metallurgical parameters. The results of alloys subjected to multi-temperature aging cycles reveal that the optimum strength properties of B319.2 alloys, however, is obtained by applying multi-temperature aging cycles such as, for example, 240 C/2 h followed by 170 C/8 h, rather than T6 aging treatments. The regression models indicate that the mean quality values of B319 alloys are highly quench sensitive due to the formation of a larger percent of clusters in Al-Si-Cu-Mg alloys. These clusters act as heterogeneous nucleation sites for precipitation and enhance the aging process.

Ragab, Kh. A.; Samuel, A. M.; Al-Ahmari, A. M. A.; Samuel, F. H.; Doty, H. W.

2013-11-01

142

Amorphous metal alloy and composite  

DOEpatents

Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

Wang, Rong (Richland, WA); Merz, Martin D. (Richland, WA)

1985-01-01

143

Microstructure and vacancy-type defects of high-pressure torsion deformed Al-3 wt%Cu alloy  

NASA Astrophysics Data System (ADS)

The influence of high-pressure torsion (HPT) on the microstructure and free-volume type defects of supersaturated Al-3 wt%Cu was studied. By means of HPT, grain refinement down to sizes of 100 nm could be achieved. Positron annihilation spectroscopy was applied for the characterization of deformation-induced defects and of vacancy-solute interaction. The chemical sensitive method of two-dimensional Doppler broadening spectroscopy reveals predominantly deformation-induced defects. In comparison to undeformed supersaturated Al-3 wt%Cu, the fraction of Cu-decorated free-volume type defects is strongly reduced and Al2Cu-precipitates with equilibrium structure occur rather than metastable semi-coherent Al-Cu precipitates. These precipitates stabilize the nanocrystalline structure and give rise to a rather different aging behaviour compared to the undeformed state.

Parz, Peter; Faller, Michael; Pippan, Reinhard; Reingruber, Herbert; Puff, Werner; Wrschum, Roland

2012-11-01

144

Improvement in Fatigue Strength of Biomedical ?-type Ti-Nb-Ta-Zr Alloy While Maintaining Low Young's Modulus Through Optimizing ?-Phase Precipitation  

NASA Astrophysics Data System (ADS)

The improvement in fatigue strength, with maintenance of a low Young's modulus, in a biomedical ?-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), by thermomechanical treatment was investigated. A short aging time at an ?-phase-forming temperature combined with severe cold rolling was employed. A fine ? phase is observed in TNTZ subjected to this thermomechanical treatment. Because the rolling texture of ? phase is formed by cold rolling, such as the ? phase may be preferentially oriented to a direction that is effective for inhibiting the increase in Young's modulus. The samples aged at 573 K (300 C) for 3.6 ks and 10.8 ks after cold rolling exhibit a good balance between a high tensile strength and low Young's modulus. In the case of the sample aged for 3.6 ks, the tensile strength is improved, although the fatigue strength is not improved significantly. Both the tensile strength and the fatigue strength of the sample aged for 10.8 ks are improved. This fatigue strength is the highest among the TNTZ samples used in the current and in previous studies with Young's moduli less than 80 GPa.

Nakai, Masaaki; Niinomi, Mitsuo; Oneda, Takahiro

2012-01-01

145

Structural, magnetic and electronic state characterization of L1 0-type ordered FeNi alloy extracted from a natural meteorite.  

PubMed

To understand the hard magnetism of L10-type ordered FeNi alloy, we extracted the L10-FeNi phase from a natural meteorite, and evaluated its fundamental solid-state properties: sample composition, magnetic hysteresis, crystal structure and electronic structure. We executed multidirectional analyses using scanning electron microscopy with an electron probe micro-analyzer (SEM-EPMA), a superconducting quantum interference device (SQUID), x-ray diffraction (XRD) and magnetic circular dichroism (MCD). As a result, we found that the composition was Fe: 50.47 1.98 at.%, Ni: 49.60 1.49 at.%, and an obvious superlattice peak is confirmed. The estimated degree of order was 0.608, with lattice constants a = b = 3.582 and c = 3.607 . The obtained coercivity was more than 500 Oe. MCD analysis using the K absorption edge suggests that the magnetic anisotropy could originate from the orbital magnetic moment of 3d electrons in Fe; this result is consistent with that in a previous report obtained with synthetic L10-FeNi. PMID:24469025

Kotsugi, M; Maruyama, H; Ishimatsu, N; Kawamura, N; Suzuki, M; Mizumaki, M; Osaka, K; Matsumoto, T; Ohkochi, T; Ohtsuki, T

2014-02-12

146

Characterization of Newly Developed Semisolid Stir Joining Method for Cast Cu Base Alloy (Cu-Al-Si-Fe) and Effect of Stirrer Type on Uniformity of Microstructure  

NASA Astrophysics Data System (ADS)

In this research, the semisolid stir joining method was used to overcome the problem of hot cracking in welding aluminum and silicon bronzes. Moreover, the effects of grooved and cylindrical tools on the microstructure and mechanical properties of samples were examined. After welding specimens, mechanical tests were carried out to find differences between the cast and welded samples. Optical microscopy and scanning electron microscopy were used to study microstructure. X-ray diffraction was used to investigate compounds formed during casting and welding. The solidus and liquidus temperatures of the alloy were measured by differential scanning calorimetry. In this study, the temperature of the work pieces was raised to 1203 K (930 C) that is in the semisolid region, and the weld seams were stirred by two different types of tools at the speed of 1600 rpm. Macro and micro-structural analyses show uniformity in the phase distribution for specimens welded by cylindrical tool. Desirable and uniform mechanical properties obtained when the cylindrical tool was used.

Ferasat, Keyvan; Aashuri, Hossein; Kokabi, Amir Hossein; Nikzad, Siamak; Shafizadeh, Mahdi

2015-02-01

147

Synthesis and structure determination of a new series of hydrogen storage alloys; RMg 2Ni 9 (R=La, Ce, Pr, Nd, Sm and Gd) built from MgNi 2 Laves-type layers alternating with AB 5 layers  

Microsoft Academic Search

A number of new ternary magnesium based alloys, RMg2Ni9 (where R=La, Ce, Pr, Nd, Sm and Gd), have been synthesized by reacting a mixture of MgNi2 with RNi5 intermetallic compounds or by direct combination of the elements in the atomic ratio R:Mg:Ni=1:2:9. The crystal structure, determined by Guinier-Hgg X-ray powder diffraction, is related to the hexagonal PuNi3 type. All interatomic

K. Kadir; T. Sakai; I. Uehara

1997-01-01

148

Influence of Aging Parameters on the Tensile Properties and Quality Index of Al-9 Pct Si-1.8 Pct Cu-0.5 Pct Mg 354-Type Casting Alloys  

NASA Astrophysics Data System (ADS)

The current study was carried out with a view to investigating the influence of age-hardening parameters, aging temperature and time, on the tensile properties and quality indices of a high-strength Al-9 pct Si casting alloy, namely, 354-Al-9 pct Si-1.8 pct Cu-0.5 pct Mg. Quality charts were used as an evaluation tool for selecting the optimum conditions to be applied, in practice, in order to develop high strength and optimum quality in 354 casting alloy. Aging at a low temperature of 428 K (155 C) was observed to produce the greatest strength and optimum quality in the 354-type castings compared to aging at higher temperatures. The peak strength observed for 354 alloy may be attained after shorter aging times on the condition that the aging temperature is increased. The aging times required for reaching peak strength in 354 alloys are 72 hours, 40 hours, 8 hours, 1 hour, and 15 minutes at aging temperatures of 428 K, 443 K, 468 K, 493 K, and 518 K (155 C, 170 C, 195 C, 220 C, and 245 C), respectively. Aging treatment at higher temperatures is accompanied by a reduction in the tensile properties and quality index values of the castings; however, it also introduces the possibility of a significant economical strategy for minimizing the time and the cost of this same treatment. Aging treatment at a lower temperature of 428 K (155 C) produces fine and dense precipitates displaying smaller interparticle spacing, while at higher aging temperatures, such as 518 K (245 C), the precipitates are coarser in size, less dense, and more widely dispersed. The quality charts developed in the course of the current research facilitate the interpretation and evaluation of the tensile properties of the 354 alloy. Such charts provide a logical evaluation tool, from the metallurgical point of view, for an accurate prediction of the influence of aging parameters studied on the properties of the alloys. Depending on the required level of tensile properties and based on the quality charts developed, it is possible to make a rigorous selection as to the most suitable aging parameters to be applied to the 354 alloy so as to obtain the best possible cost-effective compromise between alloy strength and quality.

Ammar, H. R.; Samuel, A. M.; Samuel, F. H.; Simielli, E.; Sigworth, G. K.; Lin, J. C.

2012-01-01

149

Synthesis and Characterization of p Type Pb 0.5 Sn 0.5 Te Thermoelectric Power Generation Elements by Mechanical Alloying  

Microsoft Academic Search

A mechanical alloying (MA) process to transform elemental powders into solid Pb0.5Sn0.5Te with thermoelectric functionality comparable to melt-alloyed material is described. The room-temperature doping level and\\u000a mobility as well as temperature-dependent electrical conductivity, Seebeck coefficient, and thermal conductivity are reported.\\u000a Estimated values of lattice thermal conductivity (0.7Wm?1K?1) are lower than some reports of functional melt-alloyed PbSnTe-based material, providing evidence that

Aaron D. LaLonde; Peter D. Moran

2010-01-01

150

Synthesis and Characterization of p-Type Pb0.5Sn0.5Te Thermoelectric Power Generation Elements by Mechanical Alloying  

Microsoft Academic Search

A mechanical alloying (MA) process to transform elemental powders into solid Pb0.5Sn0.5Te with thermoelectric functionality comparable to melt-alloyed material is described. The room-temperature doping level and mobility as well as temperature-dependent electrical conductivity, Seebeck coefficient, and thermal conductivity are reported. Estimated values of lattice thermal conductivity (0.7 W m-1 K-1) are lower than some reports of functional melt-alloyed PbSnTe-based material,

Aaron D. Lalonde; Peter D. Moran

2010-01-01

151

Effects of alloy composition and processing on the microstructure of D-9 type stainless steel. Final report  

SciTech Connect

The effects of composition modifications of Type 316 stainless steel on the constitution and microstructural stability during extended exposure to elevated temperature has been studied. Conventional TEM, (CTEM), Analytical TEM (STEM) and ultra-high resolution TEM have been used. It has been found that several relatively coarse, heterogeneously distributed constituents including Laves and G phases, TiN and M/sub 23/C/sub 6/ can form in addition to a fine, uniform distribution of MC. In the present case, the MC is TiC. The detailed nature of the latter constituent and its relationship to the fcc ..gamma.. matrix have been examined in detail. The results of CTEM are conflicting in that the electron diffraction evidence suggests that the particles should be semicoherent or noncoherent, whereas the images of the MC:..gamma.. interfaces show no structure in the form of ledges or misfit dislocations. Ultra-high resolution TEM showed that the lattice planes were continuous through the matrix and the TiC particles. These results suggest that the TiC is coherent despite the large mismatch between the lattices. This finding has significant bearing on the role of the TiC:..gamma.. interfaces as He sinks in fast neutron environments. 12 figures.

Hwang, M.; Laughlin, D.E.; Williams, J.C.

1983-10-01

152

Use of n-type semiconductor silicon as substrate material for electrodeposition of Zn1-xFex alloy thin films  

NASA Astrophysics Data System (ADS)

Zn1-xFex alloys were electrochemically deposited on semiconductor silicon substrates from sulfate bath. Effect of bath composition on phase formation, chemical composition, crystallite shape, electrical resistivity and magnetoresistance were investigated using appropriate characterization tools. It was shown that Zn-Fe alloys can be successfully deposited directly on semiconductor silicon substrate using electrodeposition technique. Iron content in films influences crystallite size, resistivity and magnetoresistance of films.

?limbey, ?smail; Yurdal, Ka?an; Bakkalo?lu, mer Faruk; Karahan, ?smail Hakk?; Bedir, Metin

2014-11-01

153

Effect of chromium content on stress corrosion cracking susceptibility of shielded metal arc weld metals for 600 type alloy in high-temperature pressurised pure water  

Microsoft Academic Search

The stress corrosion cracking (SCC) susceptibility of SMAW metals for Inconel alloy 600 to which Cr was added to 14.821.4 mass% has been investigated on the basis of a creviced bent beam test in pressurized hot water (corresponding to the service condition of boiling water reactor nuclear power plant), since the TIG weld metal of alloy 82 involving 1822 mass%

Satoru Nishikawa; Yukihiko Horii; Kenji Ikeuchi

2012-01-01

154

Heusler alloys  

Microsoft Academic Search

In 1903 F. Heusler reported that it was possible to make ferromagnetic alloys from non-ferromagnetic constituents copper-manganese bronze and group B elements such as aluminium and tin. Further investigations showed that the magnetic properties of these alloys are related to their chemical, L21, structure, and to the ordering of the manganese atoms on an f.c.c. sublattice.Heusler alloys are properly described

Peter J. Webster

1969-01-01

155

Castability, opaque masking, and porcelain bonding of 17 porcelain-fused-to-metal alloys  

Microsoft Academic Search

Seventeen porcelain-fused-to-metal alloys, which represented a cross section of the various alloy types available, were evaluated for castability, opaque masking, and porcelain bond strength. The base metal alloys generally cast more completely than the noble alloys, with the presence of beryllium as an important factor for greater castability among the base metal alloys. Statistically significant differences were observed in the

Randolph P O'Connor; J. Rodway Mackert; Michael L Myers; Edward E Parry

1996-01-01

156

Competing structural ordering tendencies in Heusler-type alloys with high Curie temperatures: Fe2CoGa1-xZnx studied by first-principles calculations  

NASA Astrophysics Data System (ADS)

The influence of Zn substitution on the structural, magnetic, and electronic properties and lattice vibrations of ferromagnetic Fe2CoGa1-xZnx alloys in the conventional X2YZ and inverse (XY)XZ Heusler structures is investigated, by means of ab initio and Monte Carlo calculations, which predict strong ferromagnetic coupling and high Curie temperatures between 770 and 925 K. In the Ga-rich systems the inverse Heusler structure is energetically favored but no indication for a structural instability is found in contrast to Fe-Co-Ga-Zn alloys in the conventional Heusler structure. The origin of the remarkably strong preference of the cubic (c/a=1) inverse phase is believed to originate from the bcc-like environment of the two inequivalent Fe atoms and their stronger hybridization with the Co states compared to the conventional structure. In the quaternary compounds, Fe2CoGa1-xZnx , substitution of Ga by Zn reduces the energetic preference of the inverse structure caused by weakening of the Co-Fe hybridization. Simultaneously, Zn leads to higher magnetic moments and Curie temperatures because of localization effects. In addition, since Zn weakens the miscibility of the alloys, we propose that the composition of Fe2CoGa1-xZnx alloys has to be carefully chosen in order to yield an interesting future ferromagnetic shape-memory alloy system.

Dannenberg, Antje; Siewert, Mario; Gruner, Markus E.; Wuttig, Manfred; Entel, Peter

2010-12-01

157

The structure, anisotropy and coercivity of rapidly quenched TbCu7-type SmCo7-xZrx alloys and the effects of post-treatments  

NASA Astrophysics Data System (ADS)

The effects of wheel speed, Zr content, post-ball milling process and heat treatment on the structure, anisotropy, magnetic properties and phase transition of the melt-spun SmCo7-xZrx alloys were investigated. The crystallographic c-axis is parallel to the ribbon plane for the ribbons prepared at low speeds of 5 and 15 m/s, and this orientation is reduced at higher speeds. The out-of-plane coercivity of SmCo6.8Zr0.2 ribbon increases from 123 kA/m for 5 m/s to 1076 kA/m for 60 m/s. Zr doping improves the hard magnetic properties and the in-plane coercivity of SmCo7-xZrx alloys increases with the Zr content from 592 kA/m for x=0.1 to 1376 kA/m for x=0.4. The Rietveld refinements and theoretical analysis reveal that Zr atoms occupy the 2e site. The coercivity mechanisms are different for the alloys with various Zr contents. The ball milling process could enhance the coercivity and remanence of the ribbons due to the grain refinement and the precipitation of Co phase. Heat treatment can further modify the magnetic properties of the alloys. SmCo6.7Zr0.3 alloy heat treated at 400 C has the high maximum energy product (BH)max of 64.5 kJ/m3, where the coercivity was enhanced to 1560 kA/m by 650 C heat treatment. In addition, the SmCo7-xZrx alloys exhibit excellent hard magnetic properties at elevated temperatures.

Feng, D. Y.; Liu, Z. W.; Zheng, Z. G.; Zeng, D. C.; Zhang, G. Q.

2013-12-01

158

Effect of phosphorus content on stress corrosion cracking susceptibility of shielded metal arc weld metals for 600 type alloy in high temperature pressurised pure water  

Microsoft Academic Search

The intergranular stress corrosion cracking (IGSCC) susceptibility of shielded metal arc weld metals for Inconel alloy 600 has been investigated with particular reference to the influences of P and Nb contents on the basis of a creviced bent beam (CBB) test in pressurized hot water (corresponding to the service condition of boiling water reactor nuclear power plant). The IGSCC susceptibility

Satoru Nishikawa; Yukihiko Horii; Kenji Ikeuchi

2012-01-01

159

Thermal and transport properties of the Heusler-type Fe2VAl1-xGex(0<=x<=0.20) alloys: Effect of doping on lattice thermal conductivity, electrical resistivity, and Seebeck coefficient  

Microsoft Academic Search

We report on the thermoelectric properties of the Heusler-type Fe2VAl1-xGex alloys with compositions 0<=x<=0.20 . While Fe2VAl(x=0) exhibits a semiconductorlike behavior in electrical resistivity, a slight substitution of Ge for Al causes a significant decrease in the low-temperature resistivity and a large enhancement in the Seebeck coefficient, reaching -130muV\\/K for x=0.05 at around room temperature. Comparison with the Fe2VAl1-xSix system

Y. Nishino; S. Deguchi; U. Mizutani

2006-01-01

160

High-resolution soft x-ray photoelectron study of density of states and thermoelectric properties of the Heusler-type alloys (Fe2\\/3V1\\/3)100-yAly  

Microsoft Academic Search

The high-resolution soft x-ray photoelectron study of Heusler(L21) -type (Fe2\\/3V1\\/3)100-yAly (y=23.8-25.8) alloys directly confirms the correlation between their thermoelectric properties and the electronic structures near the Fermi level. It shows the rigid-band-like shift of the main 3d bands and the increase of the photoelectron intensity at the Fermi edge with the small deviation of the Al content from stoichiometry, i.e.,

K. Soda; H. Murayama; K. Shimba; S. Yagi; J. Yuhara; T. Takeuchi; U. Mizutani; H. Sumi; M. Kato; H. Kato; Y. Nishino; A. Sekiyama; S. Suga; T. Matsushita; Y. Saitoh

2005-01-01

161

Method of producing superplastic alloys and superplastic alloys produced by the method  

NASA Technical Reports Server (NTRS)

A method for producing new superplastic alloys by inducing in an alloy the formation of precipitates having a sufficient size and homogeneous distribution that a sufficiently refined grain structure to produce superplasticity is obtained after subsequent PSN processing. An age-hardenable alloy having at least one dispersoid phase is selected for processing. The alloy is solution heat-treated and cooled to form a supersaturated solid solution. The alloy is plastically deformed sufficiently to form a high-energy defect structure useful for the subsequent heterogeneous nucleation of precipitates. The alloy is then aged, preferably by a multi-stage low and high temperature process, and precipitates are formed at the defect sites. The alloy then is subjected to a PSN process comprising plastically deforming the alloy to provide sufficient strain energy in the alloy to ensure recrystallization, and statically recrystallizing the alloy. A grain structure exhibiting new, fine, equiaxed and uniform grains is produced in the alloy. An exemplary 6xxx alloy of the type capable of being produced by the present invention, and which is useful for aerospace, automotive and other applications, is disclosed and claimed. The process is also suitable for processing any age-hardenable aluminum or other alloy.

Troeger, Lillianne P. (Inventor); Starke, Jr., Edgar A. (Inventor); Crooks, Roy (Inventor)

2002-01-01

162

Precipitates in Biomedical Co-Cr Alloys  

NASA Astrophysics Data System (ADS)

Herein, precipitates in biomedical Co-Cr-Mo and Co-Cr-W-Ni alloys are reviewed with a focus on their phase, chemical composition, morphology, and formation/dissolution during heat treatment. The effects of the heat-treatment conditions and the addition of minor alloying elements such as carbon, nitrogen, Si, and Mn on the precipitates are also discussed. Mostly, the precipitates in the alloys are of the ?-phase, M23X6-type phase, ?-phase (M6X-M12X type), ?-phase (M2T3X type), ?-phase, M7X3-type phase, or M2X-type phase (M and T refer to metallic elements, and X refers to carbon and/or nitrogen); the ?- and ?-phases are intermetallic compounds, and the others are carbides, nitrides, and carbonitrides. The dissolution of the precipitates during solution treatment is delayed by the formation of the ?-phase at temperatures where partial melting occurs in the alloys. In addition, the stability of the precipitates depends on the content of minor alloying elements. For example, the addition of carbon enhances the formation of M23X6-type and M7X3-type precipitates. Nitrogen stabilizes the M2X-type, ?-phase, and ?-phase precipitates, and Si stabilizes the ?-phase and ?-phase precipitates. The balance between the minor alloying element abundances also affects the constitution of the precipitates in Co-Cr alloys.

Narushima, Takayuki; Mineta, Shingo; Kurihara, Yuto; Ueda, Kyosuke

2013-04-01

163

Effect of a microstructure and surface hydrogen alloying of a VT6 alloy on diffusion welding  

NASA Astrophysics Data System (ADS)

The effect of a structural type (lamellar, fine, gradient) and additional surface alloying with hydrogen on the diffusion bonding of titanium alloy VT6 samples is studied. It is shown that the surface alloying of VT6 alloy parts with hydrogen allows one to decrease the diffusion welding temperature by 50-100C, to obtain high-quality pore-free bonding, and to remove the "structural" boundary between materials to be welded that usually forms during welding of titanium alloys with a lamellar structure.

Senkevich, K. S.; Skvortsova, S. V.; Kudelina, I. M.; Knyazev, M. I.; Zasypkin, V. V.

2014-01-01

164

First-principle investigation of electronic structure, magnetism and phase stability of Heusler-type Pt2-xMn1+xGa alloys  

NASA Astrophysics Data System (ADS)

The electronic structure, magnetism and phase stability of Pt2-xMn1+xGa (x=0, 0.25, 0.5, 0.75, 1) alloys are studied by first-principle calculations. The calculations reveal that a potential magnetic martensitic transformation can be expected in all the series. In addition, a large magnetic-field-induced strain is likely to appear in Pt2-xMn1+xGa (x=0, 0.25, 0.75, 1) alloys. The electronic structure calculations indicate that the tetragonal phase is stabilized upon the distortion because of the pseudogap formation at the Fermi Level. The magnetic structure is also investigated and the total magnetic moment of the tetragonal phase is a little larger than that of the cubic austenite phase in all the series.

Feng, L.; Liu, E. K.; Zhang, W. X.; Wang, W. H.; Wu, G. H.

2015-03-01

165

Mechanically Multifunctional Properties and Microstructure of New Beta-Type Titanium Alloy, Ti29Nb13Ta4.6Zr, for Biomedical Applications  

Microsoft Academic Search

A new biomedical titanium alloy, Ti-29Nb-13Ta-4.6Zr, composed of nontoxic elements like Nb, Ta, and Zr, has recently been\\u000a developed in order to achieve a lower Youngs modulus similar to that of human hard tissues in addition to excellent mechanical\\u000a properties for use as structural biomaterials. The characteristics of this material depend on the microstructures obtained\\u000a by heat treatments or thermomechanical

M. Nakai; M. Niinomi; T. Akahori

166

Competing structural ordering tendencies in Heusler-type alloys with high Curie temperatures: Fe2CoGa1-xZnx studied by first-principles calculations  

Microsoft Academic Search

The influence of Zn substitution on the structural, magnetic, and electronic properties and lattice vibrations of ferromagnetic Fe2CoGa1-xZnx alloys in the conventional X2YZ and inverse (XY)XZ Heusler structures is investigated, by means of ab initio and Monte Carlo calculations, which predict strong ferromagnetic coupling and high Curie temperatures between 770 and 925 K. In the Ga-rich systems the inverse Heusler

Antje Dannenberg; Mario Siewert; Markus E. Gruner; Manfred Wuttig; Peter Entel

2010-01-01

167

Properties of the quaternary half-metal-type Heusler alloy Co{sub 2}Mn{sub 1-x}Fe{sub x}Si  

SciTech Connect

This paper reports on the bulk properties of the quaternary Heusler alloy Co{sub 2}Mn{sub 1-x}Fe{sub x}Si with the Fe concentration x=0,1/2,1. All samples, which were prepared by arc melting, exhibit L2{sub 1} long-range order over the complete range of Fe concentration. The structural and magnetic properties of the Co{sub 2}Mn{sub 1-x}Fe{sub x}Si Heusler alloys were investigated by means of x-ray diffraction, high- and low-temperature magnetometry, Moessbauer spectroscopy, and differential scanning calorimetry. The electronic structure was explored by means of high-energy photoemission spectroscopy at about 8 keV photon energy. This ensures true bulk sensitivity of the measurements. The magnetization of the Fe-doped Heusler alloys is in agreement with the values of the magnetic moments expected for a Slater-Pauling-like behavior of half-metallic ferromagnets. The experimental findings are discussed on the basis of self-consistent calculations of the electronic and magnetic structure. To achieve good agreement with experiment, the calculations indicate that on-site electron-electron correlation must be taken into account, even at low Fe concentration. The present investigation focuses on searching for the quaternary compound where the half-metallic behavior is stable against outside influences. Overall, the results suggest that the best candidate may be found at an iron concentration of about 50%.

Balke, Benjamin; Fecher, Gerhard H.; Kandpal, Hem C.; Felser, Claudia; Kobayashi, Keisuke; Ikenaga, Eiji; Kim, Jung-Jin; Ueda, Shigenori [Institut fuer Anorganische und Analytische Chemie, Johannes Gutenberg Universitaet, D-55099 Mainz (Germany); Japan Synchrotron Radiation Research Institute (SPring-8/JASRI), Kouto 1-1-1, Mikaduki-cho, Sayou-gun, Hyogo, 679-5198 (Japan)

2006-09-01

168

Bond Strength of Gold Alloys Laser Welded to Cobalt-Chromium Alloy  

PubMed Central

The objective of this study was to investigate the joint properties between cast gold alloys and Co-Cr alloy laser-welded by Nd:YAG laser. Cast plates were fabricated from three types of gold alloys (Type IV, Type II and low-gold) and a Co-Cr alloy. Each gold alloy was laser-welded to Co-Cr using a dental laser-welding machine. Homogeneously-welded and non-welded control specimens were also prepared. Tensile testing was conducted and data were statistically analyzed using ANOVA. The homogeneously-welded groups showed inferior fracture load compared to corresponding control groups, except for Co-Cr. In the specimens welded heterogeneously to Co-Cr, Type IV was the greatest, followed by low-gold and Type II. There was no statistical difference (P<0.05) in fracture load between Type II control and that welded to Co-Cr. Higher elongations were obtained for Type II in all conditions, whereas the lowest elongation occurred for low-gold welded to Co-Cr. This study indicated that, of the three gold alloys tested, the Type IV gold alloy was the most suitable alloy for laser-welding to Co-Cr. PMID:19088892

Watanabe, Ikuya; Wallace, Cameron

2008-01-01

169

Comparison of Three Primary Surface Recuperator Alloys  

SciTech Connect

Extensive work performed by Capstone Turbine Corporation, Oak Ridge National Laboratory, and various others has shown that the traditional primary surface recuperator alloy, type 347 stainless steel, is unsuitable for applications above 650 C ({approx}1200 F). Numerous studies have shown that the presence of water vapor greatly accelerates the oxidation rate of type 347 stainless steel at temperatures above 650 C ({approx}1200 F). Water vapor is present as a product of combustion in the microturbine exhaust, making it necessary to find replacement alloys for type 347 stainless steel that will meet the long life requirements of microturbine primary surface recuperators. It has been well established over the past few years that alloys with higher chromium and nickel contents than type 347 stainless steel have much greater oxidation resistance in the microturbine environment. One such alloy that has replaced type 347 stainless steel in primary surface recuperators is Haynes Alloy HR-120 (Haynes and HR-120 are trademarks of Haynes International, Inc.), a solid-solution-strengthened alloy with nominally 33 wt % Fe, 37 wt % Ni and 25 wt % Cr. Unfortunately, while HR-120 is significantly more oxidation resistant in the microturbine environment, it is also a much more expensive alloy. In the interest of cost reduction, other candidate primary surface recuperator alloys are being investigated as possible alternatives to type 347 stainless steel. An initial rainbow recuperator test has been performed at Capstone to compare the oxidation resistance of type 347 stainless steel, HR-120, and the Allegheny Ludlum austenitic alloy AL 20-25+Nb (AL 20-25+Nb is a trademark of ATI Properties, Inc. and is licensed to Allegheny Ludlum Corporation). Evaluation of surface oxide scale formation and associated alloy depletion and other compositional changes has been carried out at Oak Ridge National Laboratory. The results of this initial rainbow test will be presented and discussed in this paper.

Matthews, Wendy [Capstone Turbines; More, Karren Leslie [ORNL; Walker, Larry R [ORNL

2010-01-01

170

VAl Alloy  

NASA Astrophysics Data System (ADS)

Power generation performance of a thermoelectric module consisting of the Heusler Fe2VAl alloy was evaluated. For construction of the module, W-doped Fe2VAl alloys were prepared using powder metallurgy process. Power generation tests of the module consisting of 18 pairs of p- n junctions were conducted on a heat source of 373-673 K in vacuum. The reduction of thermal conductivity and improvement of thermoelectric figure of merit by W-doping enhanced the conversion efficiency and the output power. High output power density of 0.7 W/cm2 was obtained by virtue of the high thermoelectric power factor of the Heusler alloy. The module exhibited good durability, and the relatively high output power was maintained after temperature cycling test in air.

Mikami, M.; Mizoshiri, M.; Ozaki, K.; Takazawa, H.; Yamamoto, A.; Terazawa, Y.; Takeuchi, T.

2014-06-01

171

Biological interactions of dental cast alloys with oral tissues  

Microsoft Academic Search

Objective: All dental cast alloys release metal ions into the oral environment which have the potential to interact with the oral tissues. Amount and type of metal elements released are varying and not directly related to the composition of the alloy. The aim of the present literature survey was to describe the interactions of dental cast alloys with living tissues

Gottfried Schmalz; Pauline Garhammer

2002-01-01

172

Pythia: Automatic Generation of Counterexamples for ACL2 using Alloy  

E-print Network

Pythia: Automatic Generation of Counterexamples for ACL2 using Alloy Alexander Spiridonov the dis- covery of proofs. We present Pythia, a framework that con- nects ACL2 with the SAT-based Alloy checking. Pythia takes as in- puts an Alloy model of the ACL2 type system together with an ACL2 formula

Khurshid, Sarfraz

173

Tantalum modified ferritic iron base alloys  

NASA Technical Reports Server (NTRS)

Strong ferritic alloys of the Fe-CR-Al type containing 0.4% to 2% tantalum were developed. These alloys have improved fabricability without sacrificing high temperature strength and oxidation resistance in the 800 C (1475 F) to 1040 C (1900 F) range.

Oldrieve, R. E.; Blankenship, C. P. (inventors)

1977-01-01

174

Alloys of clathrate allotropes for rechargeable batteries  

DOEpatents

The present disclosure is directed at an electrode for a battery wherein the electrode comprises clathrate alloys of silicon, germanium or tin. In method form, the present disclosure is directed at methods of forming clathrate alloys of silicon, germanium or tin which methods lead to the formation of empty cage structures suitable for use as electrodes in rechargeable type batteries.

Chan, Candace K; Miller, Michael A; Chan, Kwai S

2014-12-09

175

New alloys to conserve critical elements  

NASA Technical Reports Server (NTRS)

Based on availability of domestic reserves, chromium is one of the most critical elements within the U.S. metal industry. New alloys having reduced chromium contents which offer potential as substitutes for higher chromium containing alloys currently in use are being investigated. This paper focuses primarily on modified Type 304 stainless steels having one-third less chromium, but maintaining comparable oxidation and corrosion properties to that of type 304 stainless steel, the largest single use of chromium. Substitutes for chromium in these modified Type 304 stainless steel alloys include silicon and aluminum plus molybdenum.

Stephens, J. R.

1978-01-01

176

Nondestructive determination of mechanical properties. [aluminum alloys  

NASA Technical Reports Server (NTRS)

Aluminum alloys of types 1100, 3003, 5052, 6061, and 2024 were used to study the sensitivity of the acousto-elastic constant to changes in the microstructure. Results show that there is a strong relationship between the acousto-elastic constants and the yield strength and hardness. This relationship depends on whether the alloy is strain hardened or precipitation hardened. In strain hardened alloys, the constants increase as the amount of solid solution is decreased, while the behavior is the opposite in precipitation hardened alloys.

Schneider, E.; Chu, S. L.; Salma, K.

1984-01-01

177

Formation of a lamellar 14H-type long period stacking ordered structure in an as-cast MgGdZnZr alloy  

Microsoft Academic Search

A novel as-cast Mg96.82Gd2Zn1Zr0.18 alloy was produced by conventional ingot metallurgy. By scanning electron microscope and transmission electron microscope\\u000a observations, its as-cast microstructure is mainly composed of the ??-Mg solid solution, the coherent fine-lamellae and the\\u000a eutectic. The ?-phase ((Mg,Zn)3Gd) as the second phase in eutectic has a face-center cubic structure. While, the coherent lamellae consist of the 2HMg and

Y. J. Wu; D. L. Lin; X. Q. Zeng; L. M. Peng; W. J. Ding

2009-01-01

178

A highly ductile magnesium alloy system  

NASA Astrophysics Data System (ADS)

Magnesium (Mg) alloys are finding increasing applications in industry mainly due to their high strength-to-weight ratio. However, they have intrinsically poor plastic deformation ability at room temperature. Therefore, the vast majority of Mg alloys are used only in cast state, severely limiting the development of their applications. We have recently discovered a new Mg alloy system that possesses exceptionally high ductility as well as good mechanical strength. The superior plasticity allows this alloy system to be mechanically deformed at room temperature, directly from an as-cast alloy plate, sheet or ingot into working parts. This type of cold mechanical forming properties has never been reported with any other Mg alloy systems.

Gao, W.; Liu, H.

2009-08-01

179

Advanced cutting conditions for the milling of aeronautical alloys  

Microsoft Academic Search

This paper deals with possible improvement aspects on the chip cutting milling of two alloys that are used frequently in the aerospace industry, in particular the titanium alphabeta-based alloy Ti6Al4V and the nickel alloy usually known as type 718. Both alloys are used widely in the manufacture of different turbo-engine parts, considering their excellent mechanic features, and their resistance to

L. N Lpez de lacalle; J Prez; J. I Llorente; J. A Snchez

2000-01-01

180

High-resolution electron microscopy analysis of structural defects in a (2/1, 5/3)-type approximant of a decagonal quasicrystal of an Al-Pd-Mn alloy  

SciTech Connect

Structural defects were analyzed by means of high-resolution electron microscopy (HREM) in a crystalline (2/1, 5/3)-type Fibonacci approximant of an Al-Pd-Mn alloy system. A kind of stacking fault is observed with a projected displacement vector R parallel to the [{minus}3 0 29] direction; its amplitude {vert_bar}R{vert_bar} = 2a sin 18 deg = 1.19 nm, and its habit plane lies in the (1 0 1) plane. Two kinds of domain boundaries have been found and the domains are related by a 180 deg rotation around the c-axis plus a displacement along the [3 0 {minus}29] or the [{minus}3 0 {minus}29] direction in a plane perpendicular to the b-axis. The domain boundary planes are the {l_brace}1 0 1{r_brace} planes.

Yu, D.P.; Ren, G.; Zhang, Z. [Chinese Academy of Sciences, Beijing (China). Beijing Lab. of Electron Microscopy

1996-10-01

181

Alloy softening in binary molybdenum alloys  

NASA Technical Reports Server (NTRS)

An investigation was conducted to determine the effects of alloy additions of Hf, Ta, W, Re, Os, Ir, and Pt on the hardness of Mo. Special emphasis was placed on alloy softening in these binary Mo alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to Mo, while those elements having an equal number or fewer s+d electrons than Mo failed to produce alloy softening. Alloy softening and hardening can be correlated with the difference in number of s+d electrons of the solute element and Mo.

Stephens, J. R.; Witzke, W. R.

1972-01-01

182

The solidification metallurgy of Alloy 718 and other Nb-containing superalloys  

Microsoft Academic Search

The solidification behavior of Alloy 718 and other Nb-bearing austenitic superalloys has been examined using an integrated analytical approach. All alloys of this type begin solidification with the formation of Nb-lean austenitic dendrites. Interdendritic eutectic-type solidification constituents involving MC-type carbides and a Nb-rich Laves phase occur in these alloys. The ..gamma..\\/Laves eutectic constituent terminates solidification in these alloys. Nb is

M. J. Cieslak; G. A. Knorovsky; T. J. Headley; A. D. Jr. Romig

1989-01-01

183

Superplastic behavior in a commercial 5083 aluminum alloy  

Microsoft Academic Search

When considering the forming and post-forming properties required of a superplastic material, attractive candidates are commercial Al-Mg-Mn weldable alloys such as AA5083. There have been several investigations of hot deformation of 5083-type alloys in the literature. Only two studies evaluated commercial-purity 5083 and they achieved tensile elongations of 150% and 200%. Alloy modification has produced improved behavior in three 5083-type

J. S. Vetrano; C. A. Lavender; M. T. Smith; S. M. Bruemmer; C. H. Hamilton

1994-01-01

184

Influence of thermal and mechanical treatment on internal friction, modulus of elasticity and its temperature stability in NiSPAN C type alloy  

NASA Astrophysics Data System (ADS)

The influence of annealing and milling on the modulus of elasticity E, its temperature stability and the internal friction Q-1 in a Ni-Cr-Ti-Fe elinvar has been investigated. The aim of these investigations is to find a suitable heat treatment to obtain Q exceeding 20 000 and the temperature coefficient of the mechanical resonant frequency less than 1010 -6/ K. The coefficient of Q-1 changes from 3 10 -6 to 3 10 -5 by annealing the alloy in a H 2 atmosphere for half an hour at temperatures from 500 to 1000C. The temperature coefficient of E, ? E, is lower than 4 10 -6/ K and becomes zero at 540-620C and 800-850 C. Below 540C and above 850C ? E becomes negative. In the range of positive ? E, maximum values of E and Q = 40 000 were obtained. Such a material is suitable to be applied to ultrasonic delay lines or to electromechanical filters. The influence of the repeated cycle of heat treatment and milling was also observed.

Kaczkowski, Z.

1983-04-01

185

Metal alloy identifier  

DOEpatents

To identify the composition of a metal alloy, sparks generated from the alloy are optically observed and spectrographically analyzed. The spectrographic data, in the form of a full-spectrum plot of intensity versus wavelength, provide the "signature" of the metal alloy. This signature can be compared with similar plots for alloys of known composition to establish the unknown composition by a positive match with a known alloy. An alternative method is to form intensity ratios for pairs of predetermined wavelengths within the observed spectrum and to then compare the values of such ratios with similar values for known alloy compositions, thereby to positively identify the unknown alloy composition.

Riley, William D. (Avondale, MD); Brown, Jr., Robert D. (Avondale, MD)

1987-01-01

186

Fracture of Magnesium Alloy in Cold Forging  

Microsoft Academic Search

In order to clarify the forming limit of magnesium alloy in cold forging, the workability of magnesium alloy AZ31B (Mg-3%Al-1%Zn) is examined by upsetting and backward extrusion. In the upsettability test, shear type fracture occurs at a small equivalent strain of about 0.15 at temperatures lower than 170C. At a higher temperature, the flow stress curve has a peak at

R. Matsumoto; T. Kubo; K. Osakada

2007-01-01

187

Strain engineering of nanoscale Si P-type metal-oxide-semiconductor field-effect transistor devices with SiGe alloy integrated with contact-etch-stop layer stressors.  

PubMed

Strained-silicon (Si) has been incorporated into a leading nanoscale logic technology. By means of silicon-germanium (SiGe) alloy stressor embedded in source and drain (S/D) region, the performance of P-type metal-oxide-semiconductor field-effect transistors (PMOSFETs) is effectively enhanced. However, when a compressive contact-etch-stop layer (CESL) is combined, the stress interaction and relative impacts of SiGe stressor integrated with CESL on mobility enhancement has been little reported. Therefore, the research performs a three dimensional (3D) stress simulation evaluation based on finite element method (FEM) for PMOSFETs with S/D SiGe stressor and compressive CESL. The proposed simulation methodology is validated as compared with other technological literatures. In additions, the gate width dependency is systematically discussed to explore the stress effects on devices. The analysis results indicate that a -2.6 GPa CESL would continue boosting the stress magnitude on Si channel region except for a gate width smaller than 50 nm. The results are useful for nanoscale transistor while selecting a proper CESL in the manufacturing processes of advanced logic technologies. PMID:22966579

Lee, Chang-Chun

2012-07-01

188

Conduction mechanisms in p-type Pb{sub 1-x}Eu{sub x}Te alloys in the insulator regime  

SciTech Connect

Electrical resistivity measurements were performed on p-type Pb{sub 1-x}Eu{sub x}Te films with Eu content x = 4%, 5%, 6%, 8%, and 9%. The well-known metal-insulator transition that occurs around 5% at room temperature due to the introduction of Eu is observed, and we used the differential activation energy method to study the conduction mechanisms present in these samples. In the insulator regime (x > 6%), we found that band conduction is the dominating conduction mechanism for high temperatures with carriers excitation between the valence band and the 4f levels originated from the Eu atoms. We also verified that mix conduction dominates the low temperatures region. Samples with x = 4% and 5% present a temperature dependent metal insulator transition and we found that this dependence can be related to the relation between the thermal energy k{sub B}T and the activation energy {Delta}{epsilon}{sub a}. The physical description obtained through the activation energy analysis gives a new insight about the conduction mechanisms in insulating p-type Pb{sub 1-x}Eu{sub x}Te films and also shed some light over the influence of the 4f levels on the transport process in the insulator region.

Peres, M. L.; Rubinger, R. M.; Ribeiro, L. H.; Rubinger, C. P. L. [Departamento de Fisica e Quimica, Instituto de Ciencias Exatas, Universidade Federal de Itajuba, Itajuba, PB 50, MG CEP 37500-903 (Brazil); Ribeiro, G. M. [Departamento de Fisica, ICEx, Universidade Federal de Minas Gerais, Belo Horizonte, PB 702, MG CEP 30123-970 (Brazil); Chitta, V. A. [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, PB 66318, SP CEP 05315-970 (Brazil); Rappl, P. H. O.; Abramof, E. [Laboratorio Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, Sao Jose dos Campos, PB 515, SP CEP 12201-970 (Brazil)

2012-06-15

189

Magnesium alloys laser (Nd:YAG) cladding and alloying with side injection of aluminium powder  

NASA Astrophysics Data System (ADS)

The development of the high purity magnesium alloys (such as WE43) incites the designers to reconsider them, and the car industry appears, these days, the most interested to use this kind of alloy. However, due to their ignitability and tendency to oxidation, magnesium alloys require surface treatments. A series of experiments was carried out in order to improve the corrosion resistance of two types of magnesium alloys, WE43 and ZE41. In most cases, the substrate surface was treated before laser interaction. Side injection of aluminium powder under a 3 kW cw Nd:YAG laser was employed. The deposited layers present very good bond properties. The resulting microstructure was analysed and some mechanical properties determined, such as hardness, which is increased due to the Al 3Mg 2 and Al 12Mg 17 intermetallic formation. The results obtained represent an important step to achieve an enhanced corrosion resistance for magnesium alloys.

Ignat, Sorin; Sallamand, Pierre; Grevey, Dominique; Lambertin, Michel

2004-03-01

190

Tellurium n-type doping of highly mismatched amorphous GaN1-xAsx alloys in plasma-assisted molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

In this paper we report our study on n-type Te doping of amorphous GaN1-xAsx layers grown by plasma-assisted molecular beam epitaxy. We have used a low temperature PbTe source as a source of tellurium. Reproducible and uniform tellurium incorporation in amorphous GaN1-xAsx layers has been successfully achieved with a maximum Te concentration of 91020 cm-3. Tellurium incorporation resulted in n-doping of GaN1-xAsx layers with Hall carrier concentrations up to 31019 cm-3 and mobilities of ~1 cm2/V s. The optimal growth temperature window for efficient Te doping of the amorphous GaN1-xAsx layers has been determined.

Novikov, S. V.; Ting, M.; Yu, K. M.; Sarney, W. L.; Martin, R. W.; Svensson, S. P.; Walukiewicz, W.; Foxon, C. T.

2014-10-01

191

Titanium-alloy enhances bone-pedicle screw fixation: mechanical and histomorphometrical results of titanium-alloy versus stainless steel  

Microsoft Academic Search

Several types of pedicle screw systems have been utilized to augment lumbar spine fusion. The majority of these systems are\\u000a made of stainless steel (Ss), but titanium-alloy (Ti-alloy) devices have recently been available on the market. Ti-alloy implants\\u000a have several potential advantages over Ss ones. High bioactivity and more flexibility may improve bone ingrowth and mechanical\\u000a fixation, and the material

Finn Bjarke Christensen; Michel Dalstra; Flemming Sejling; Sren Overgaard; Cody Bnger

2000-01-01

192

Calorizing of nickel alloys  

Microsoft Academic Search

1.Calorizing of the I867, I929, and ZhS6K alloys at 8501100C for 28 h leads to the formation of a surface layer which considerably increases the resistance of these alloys to oxidation.2.The thickness of the layer, the incease in weight, the heat resistance, and the hardness of the three calorized alloys are the same.3.Calorizing of nickel alloys leads to an increase

V. V. Terekhova; A. G. Andreeva

1965-01-01

193

Electronic structures of AlB2-type superconducting YbGa1+xSi1-x alloys probed by NMR and Seebeck coefficient  

NASA Astrophysics Data System (ADS)

We report the electronic properties of the AlB2-type compounds YbGa1+xSi1-x (x =0, 0.15, and 0.3) studied by means of the nuclear magnetic resonance (NMR) and the Seebeck coefficient measurements. These materials are of current interest due to the presence of superconductivity with Yb element. From the analysis of G69a NMR spin-lattice relaxation rates, we deduce the Ga 4s partial Fermi level density of states Ns(EF) for these compounds. The result indicates a gradual increase in Ns(EF) with increasing x in YbGa1+xSi1-x. In addition, the evolution of the Seebeck coefficient feature can be understood well within the band-filling scenario. From the Seebeck coefficient analysis, we find that the variation in the total Fermi level density of states N(EF) is not consistent with the trend of superconducting temperature Tc which shows a gradual decrease with Ga content. These observations support the hypothesis that the electronic Fermi level density of states is not the key factor in determining the superconducting transition temperature of YbGa1+xSi1-x.

Fang, C. P.; Lue, C. S.; Hsu, Y. D.; Kuo, Y. K.

2010-10-01

194

Environmental embrittlement in ordered intermetallic alloys  

SciTech Connect

Ordered intermetallics based on aluminides and silicides possess many promising properties for elevated-temperature applications; however, poor fracture resistance and limited fabricability restrict their use as engineering material. Recent studies have shown that environmental embrittlement is a major cause of low ductility and brittle fracture in many ordered intermetallic alloys. There are two types of environmental embrittlement observed in intermetallic alloys. One is hydrogen-induced embrittlement occurring at ambient temperatures in air. The other is oxygen-induced embrittlement in oxidizing atmospheres at elevated temperatures. In most cases, the embrittlements are due to a dynamic effect involving generation and penetration of embrittling agents (i.e., hydrogen or oxygen ) during testing. Diffusion of embrittling agents plays a dominant role in fracture of these intermetallic alloys. This chapter summarizes recent progress in understanding and reducing environmental embrittlement in these alloys.

Liu, C.T. [Oak Ridge National Lab., TN (United States); Stoloff, N.S. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Materials Engineering

1992-12-31

195

The influence of heat treatment and role of boron on sliding wear behaviour of ?-type Ti-35Nb-7.2Zr-5.7Ta alloy in dry condition and in simulated body fluids.  

PubMed

The wear behaviour of heat-treated Ti-35Nb-7.2Zr-5.7Ta (TNZT) and Ti-35Nb-7.2Zr-5.7Ta-0.5B (TNZTB) alloys (all compositions are in wt%) was investigated in dry condition and in simulated body fluids. It has been found that there is no straightforward relationship between the wear rate and the microstructure. The hardness has no appreciable effect on the wear behaviour of these alloys. The presence of boron in the TNZT alloy deteriorates its wear properties. The wear rate of TNZT and TNZTB alloys in various media increases in the following sequence: dry condition < Hank's solution < bovine serum. PMID:21316616

Majumdar, P; Singh, S B; Chakraborty, M

2011-04-01

196

Development of new metallic alloys for biomedical applications.  

PubMed

New low modulus ?-type titanium alloys for biomedical applications are still currently being developed. Strong and enduring ?-type titanium alloy with a low Young's modulus are being investigated. A low modulus has been proved to be effective in inhibiting bone atrophy, leading to good bone remodeling in a bone fracture model in the rabbit tibia. Very recently ?-type titanium alloys with a self-tunable modulus have been proposed for the construction of removable implants. Nickel-free low modulus ?-type titanium alloys showing shape memory and super elastic behavior are also currently being developed. Nickel-free stainless steel and cobalt-chromium alloys for biomedical applications are receiving attention as well. Newly developed zirconium-based alloys for biomedical applications are proving very interesting. Magnesium-based or iron-based biodegradable biomaterials are under development. Further, tantalum, and niobium and its alloys are being investigated for biomedical applications. The development of new metallic alloys for biomedical applications is described in this paper. PMID:22765961

Niinomi, Mitsuo; Nakai, Masaaki; Hieda, Junko

2012-11-01

197

Braze alloy holds bonding strength over wide temperature range  

NASA Technical Reports Server (NTRS)

Copper-based quaternary alloys of the solid solution type is used for vacuum furnace brazing of large stainless steel components at a maximum temperature of 1975 deg F. The alloy has high bonding strength and good ductility over a temperature range extending from the cryogenic region to approximately 800 deg F.

1966-01-01

198

Braze alloy spreading on steel  

NASA Technical Reports Server (NTRS)

Scanning electron microscopy (SEM) and Auger electron microscopy (AEM) were employed to observe elemental surface decomposition resulting from the brazing of a copper-treated steel. Two types of steel were used for the study, stainless steel (treated with a eutectic silver-copper alloy), and low-carbon steel (treated with pure copper). Attention is given to oxygen partial pressure during the processes; a low enough pressure (8 x 10 to the -5th torr) was found to totally inhibit the spreading of the filler material at a fixed heating cycle. With both types of steel, copper treatment enhanced even spreading at a decreased temperature.

Siewert, T. A.; Heine, R. W.; Lagally, M. G.

1978-01-01

199

Analysis of thermoelectric properties of high-temperature complex alloys of nickel-base, iron-base and cobalt-base groups  

NASA Technical Reports Server (NTRS)

The thermoelectric properties alloys of the nickel-base, iron-base, and cobalt-base groups containing from 1% to 25% 106 chromium were compared and correlated with the following material characteristics: atomic percent of the principle alloy constituent; ratio of concentration of two constituents; alloy physical property (electrical resistivity); alloy phase structure (percent precipitate or percent hardener content); alloy electronic structure (electron concentration). For solid-solution-type alloys the most consistent correlation was obtained with electron concentration, for precipitation-hardenable alloys of the nickel-base superalloy group, the thermoelectric potential correlated with hardener content in the alloy structure. For solid-solution-type alloys, no problems were found with thermoelectric stability to 1000; for precipitation-hardenable alloys, thermoelectric stability was dependent on phase stability. The effects of the compositional range of alloy constituents on temperature measurement uncertainty are discussed.

Holanda, R.

1984-01-01

200

Creep crack growth behavior of several structural alloys  

NASA Astrophysics Data System (ADS)

Creep crack growth behavior of several high temperature alloys, Inconel 600, Inconel 625, Inconel X-750, Hastelloy X, Nimonic PE-16, Incoloy 800, and Haynes 25 (HS-25) was examined at 540, 650, 760, and 870 C. Crack growth rates were analyzed in terms of both linear elastic stress intensity factor and J*-integral parameter. Among the alloys Inconel 600 and Hastelloy X did not show any observable crack growth. Instead, they deformed at a rapid rate resulting in severe blunting of the crack tip. The other alloys, Inconel 625, Inconel X-750, Incoloy 800, HS-25, and PE-16 showed crack growth at one or two temperatures and deformed continuously at other temperatures. Crack growth rates of the above alloys in terms ofJ* parameter were compared with the growth rates of other alloys published in the literature. Alloys such as Inconel X-750, Alloy 718, and IN-100 show very high growth rates as a result of their sensitivity to an air environment. Based on detailed fracture surface analysis, it is proposed that creep crack growth occurs by the nucleation and growth of wedge-type cracks at triple point junctions due to grain boundary sliding or by the formation and growth of cavities at the boundaries. Crack growth in the above alloys occurs only in some critical range of strain rates or temperatures. Since the service conditions for these alloys usually fall within this critical range, knowledge and understanding of creep crack growth behavior of the structural alloys are important.

Sadananda, K.; Shahinian, P.

1983-07-01

201

Weldability of High Alloys  

SciTech Connect

The purpose of this study was to investigate the effect of silicon and iron on the weldability of HAYNES HR-160{reg_sign} alloy. HR-I60 alloy is a solid solution strengthened Ni-Co-Cr-Si alloy. The alloy is designed to resist corrosion in sulfidizing and other aggressive high temperature environments. Silicon is added ({approx}2.75%) to promote the formation of a protective oxide scale in environments with low oxygen activity. HR-160 alloy has found applications in waste incinerators, calciners, pulp and paper recovery boilers, coal gasification systems, and fluidized bed combustion systems. HR-160 alloy has been successfully used in a wide range of welded applications. However, the alloy can be susceptible to solidification cracking under conditions of severe restraint. A previous study by DuPont, et al. [1] showed that silicon promoted solidification cracking in the commercial alloy. In earlier work conducted at Haynes, and also from published work by DuPont et al., it was recognized that silicon segregates to the terminal liquid, creating low melting point liquid films on solidification grain boundaries. Solidification cracking has been encountered when using the alloy as a weld overlay on steel, and when joining HR-160 plate in a thickness greater than19 millimeters (0.75 inches) with matching filler metal. The effect of silicon on the weldability of HR-160 alloy has been well documented, but the effect of iron is not well understood. Prior experience at Haynes has indicated that iron may be detrimental to the solidification cracking resistance of the alloy. Iron does not segregate to the terminal solidification product in nickel-base alloys, as does silicon [2], but iron may have an indirect or interactive influence on weldability. A set of alloys covering a range of silicon and iron contents was prepared and characterized to better understand the welding metallurgy of HR-160 alloy.

Maroef, I

2003-01-22

202

Oxidation and sulfidation resistant alloys with silicon additions  

SciTech Connect

The Albany Research Center (ARC) has considerable experience in developing lean chromium, austenitic stainless steels with improved high temperature oxidation resistance. Using basic alloy design principles, a baseline composition of Fe-16Cr-16Ni-2Mn-1Mo alloys with Si and Al addition at a maximum of 5 weight percent was selected for potential application at temperatures above 700C for supercritical and ultra-supercritical power plant application. The alloys were fully austenitic. Cyclic oxidation tests in air for 1000 hours were carried out on alloys with Si only or combined Si and Al additions in the temperature range 700C to 800C. Oxidation resistances of alloys with Si only additions were outstanding, particularly at 800C (i.e., these alloys possessed weight gains 4 times less than a standard type-304 alloy). In addition, Si alloys pre-oxidized at 800C, showed a zero weight gain in subsequent testing for 1000 hours at 700C. Similar improvements were observed for Si only alloy after H2S exposure at 700C compared with type 304 stainless steel. SEM and ESCA analysis of the oxide films and base material at the oxide/base metal interface were conducted to study potential rate controlling mechanisms at ARC. Depth profile analysis and element concentration profiles (argon ion etching/x-ray photoelectron spectroscopy) were conducted on oxidized specimens and base material at the National Energy Technology Laboratory.

Dunning, John S.; Alman, David E.; Poston, J.A., Jr. (NETL); Siriwardane, R. (NETL)

2003-01-01

203

Lithium insertion\\/extraction mechanism in alloy anodes for lithium-ion batteries  

Microsoft Academic Search

The electrochemical performance of alloy anodes has been reviewed in a previous paper [1]. In this work, the fundamental understanding of lithium-insertion\\/extraction mechanism in alloy anodes is discussed. The article summarizes the different types of lithium-reaction processes observed in Si, Sn, Sb, Al, Mg and their alloys, with particular emphasis on the characteristics unique to alloy anodes, including the sloping

Wei-Jun Zhang

2011-01-01

204

On the precipitation of magnesium silicide in irradiated aluminiummagnesium alloys  

Microsoft Academic Search

Thermal neutron irradiation of aluminium or its alloys causes the production of silicon by transmutation. In aluminiummagnesium alloys, the transmutation-produced silicon reacts with magnesium and forms small precipitates. The precipitation in irradiated AlMg alloys is similar to the early stage of aging in thermally treated AlMgSi alloys. This study evidences the simultaneous generation of two crystallographically different precipitate types. On

M. Verwerft

2000-01-01

205

Photoelectron spectroscopic study on the electronic structures of the dental gold alloys and their interaction with L-cysteine  

NASA Astrophysics Data System (ADS)

The valence electronic structures of the dental gold alloys, type 1, type 3, and K14, and their interaction with L-cysteine have been studied by ultraviolet photoelectron spectroscopy with synchrotron radiation. It was found that the electronic structures of the type-1 and type-3 dental alloys are similar to that of polycrystalline Au, while that of the K14 dental alloy is much affected by Cu. The peak shift and the change in shape due to alloying are observed in all the dental alloys. It is suggested that the new peak observed around 2 eV for the L-cysteine thin films on all the dental alloys may be due to the bonding of S 3sp orbitals with the dental alloy surfaces, and the Cu-S bond, as well as the Au-S and Au-O bonds, may cause the change in the electronic structure of the L-cysteine on the alloys.

Ogawa, Koji; Tsujibayashi, Toru; Takahashi, Kazutoshi; Azuma, Junpei; Ichimiya, Masayoshi; Fujimoto, Hitoshi; Sumimoto, Michinori; Kamada, Masao

2011-11-01

206

The Mg impurity in nitride alloys  

NASA Astrophysics Data System (ADS)

Although several magnetic resonance studies address the Mg acceptor in GaN, there are few reports on Mg doping in the alloys, where hole production depends strongly on the Al or In content. Our electron paramagnetic resonance (EPR) measurements of the p-type alloys suggest that the Mg impurity retains the axial symmetry, characteristic of a p-type dopant in both alloys; however, In and Al produce additional, different characteristics of the acceptor. In InGaN, the behavior is consistent with a lowering of the acceptor level and increasing hole density as In concentration increases. For AlGaN, the amount of neutral Mg decreases with increasing Al content, which is attributed to different kinetics of hydrogen diffusion thought to occur in samples with higher Al mole fraction.

Zvanut, M. E.; Willoughby, W. R.; Sunay, U. R.; Koleske, D. D.; Allerman, A. A.; Wang, Ke; Araki, Tsutomu; Nanishi, Yasushi

2014-02-01

207

The Mg impurity in nitride alloys  

SciTech Connect

Although several magnetic resonance studies address the Mg acceptor in GaN, there are few reports on Mg doping in the alloys, where hole production depends strongly on the Al or In content. Our electron paramagnetic resonance (EPR) measurements of the p-type alloys suggest that the Mg impurity retains the axial symmetry, characteristic of a p-type dopant in both alloys; however, In and Al produce additional, different characteristics of the acceptor. In InGaN, the behavior is consistent with a lowering of the acceptor level and increasing hole density as In concentration increases. For AlGaN, the amount of neutral Mg decreases with increasing Al content, which is attributed to different kinetics of hydrogen diffusion thought to occur in samples with higher Al mole fraction.

Zvanut, M. E.; Willoughby, W. R.; Sunay, U. R. [Department of Physics, University of Alabama at Birmingham, Birmingham AL (United States); Koleske, D. D.; Allerman, A. A. [Sandia National Laboratory, Albuquerque NM (United States); Wang, Ke; Araki, Tsutomu [Department of Photonics, Ritsumeikan University, Kusatsu, Shiga (Japan); Nanishi, Yasushi [Department of Photonics, Ritsumeikan University, Kusatsu, Shiga, Japan and WCU Program, Department of Materials Science and Engineering, Seoul National University, Seoul (Korea, Republic of)

2014-02-21

208

Catalyst Alloys Processing  

NASA Astrophysics Data System (ADS)

Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

Tan, Xincai

2014-10-01

209

Low activation ferritic alloys  

DOEpatents

Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

Gelles, David S. (West Richland, WA); Ghoniem, Nasr M. (Granada Hills, CA); Powell, Roger W. (Pasco, WA)

1986-01-01

210

The oxidation of metals and alloys  

NASA Technical Reports Server (NTRS)

This paper reviews the various types of oxidation processes occurring with pure metals and gives explanations for the varying time-temperature-oxidation rate relations that exist for copper, tungsten, zinc, cadmium, and tantalum. The effect of shape and crystal structure on oxidation is discussed. Principles derived are applied to the oxidation of alloys.

Scheil, Erich

1952-01-01

211

Ductile Titanium Alloy with Low Poisson's Ratio  

NASA Astrophysics Data System (ADS)

We report a ductile ?-type titanium alloy with body-centered cubic (bcc) crystal structure having a low Poissons ratio of 0.14. The almost identical ultralow bulk and shear moduli of 24GPa combined with an ultrahigh strength of 0.9GPa contribute to easy crystal distortion due to much-weakened chemical bonding of atoms in the crystal, leading to significant elastic softening in tension and elastic hardening in compression. The peculiar elastic and plastic deformation behaviors of the alloy are interpreted as a result of approaching the elastic limit of the bcc crystal under applied stress.

Hao, Y. L.; Li, S. J.; Sun, B. B.; Sui, M. L.; Yang, R.

2007-05-01

212

Nickel base coating alloy  

NASA Technical Reports Server (NTRS)

Zirconium is added to a Ni-30 Al (beta) intermetallic alloy in the range of 0.05 w/o to 0.25 w/o. This addition is made during melting or by using metal powders. The addition of zirconium improves the cyclic oxidation resistance of the alloys at temperatures above 1100 C.

Barrett, C. A. (inventor); Lowell, C. E. (inventor)

1986-01-01

213

Ductile transplutonium metal alloys  

DOEpatents

Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as sources of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

Conner, William V. (Boulder, CO)

1983-01-01

214

Ductile transplutonium metal alloys  

DOEpatents

Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as souces of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

Conner, W.V.

1981-10-09

215

Surface composition of alloys  

NASA Astrophysics Data System (ADS)

In equilibrium, the composition of the surface of an alloy will, in general, differ from that of the bulk. The broken-bond model is applicable to alloys with atoms of virtually equal size. If the heat of alloy formation is zero, the component of lower heat of atomization is found enriched in the surface. If both partners have equal heats of sublimination, the surface of a diluted alloy is enriched with the minority component. Size effects can enhance or weaken the electronic effects. In general, lattice strain can be relaxed by precipitating atoms of deviating size on the surface. Two-phase alloys are described by the "cherry model", i.e. one alloy phase, the "kernel" is surrounded by another alloy, the "flesh", and the surface of the outer phase, the "skin" displays a deviating surface composition as in monophasic alloys. In the presence of molecules capable of forming chemical bonds with individual metal atoms, "chemisorption induced surface segregation" can be observed at low temperatures, i.e. the surface becomes enriched with the metal forming the stronger chemisorption bonds.

Sachtler, W. M. H.

1984-11-01

216

Neutron Absorbing Alloys  

DOEpatents

The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

Mizia, Ronald E. (Idaho Falls, ID); Shaber, Eric L. (Idaho Falls, ID); DuPont, John N. (Whitehall, PA); Robino, Charles V. (Albuquerque, NM); Williams, David B. (Bethlehem, PA)

2004-05-04

217

Alloys for aerospace  

SciTech Connect

Aerospace industries require special allows with many properties tailored to meet specific needs. Prerequisites include clean melting techniques to maintain low impurity levels, tight control of alloy chemistry, and the analytical capability to characterize the product. Teledyne Wah Chang (TWC) produces specially refractory metals, including zirconium, hafnium, titanium, niobium and vanadium, which are essential components of many aerospace alloys. Alloys are prepared by vacuum-arc-remelting (VAR) or electron beam (EB) melting, and ingots are processed to products ranging from bar and tube stock to wire and foil. Chemical, mechanical, and microstructural tests are all conducted at TWC`s in-house laboratory facilities. Of the alloys described here, Ti-3Al-2.5V, Tiadyne 3515 (Alloy C), NiTiFe, and C-103 are produced commercially, while orthorhombic titanium aluminides are promising candidates for future light-weight composite matrices.

Tuominen, S.; Wojcik, C. [Teledyne Wah Chang, Albany, OR (United States)

1995-04-01

218

Alloys in energy development  

SciTech Connect

The development of new and advanced energy systems often requires the tailoring of new alloys or alloy combinations to meet the novel and often stringent requirements of those systems. Longer life at higher temperatures and stresses in aggressive environments is the most common goal. Alloy theory helps in achieving this goal by suggesting uses of multiphase systems and intermediate phases, where solid solutions were traditionally used. However, the use of materials under non-equilibrium conditions is now quite common - as with rapidly solidified metals - and the application of alloy theory must be modified accordingly. Under certain conditions, as in a reactor core, the rate of approach to equilibrium will be modified; sometimes a quasi-equilibrium is established. Thus an alloy may exhibit enhanced general diffusion at the same time as precipitate particles are being dispersed and solute atoms are being carried to vacancy sinks. We are approaching an understanding of these processes and can begin to model these complex systems.

Frost, B.R.T.

1984-02-01

219

Aging effects on microstructural and mechanical properties of select refractory metal alloys for space-reactor applications  

Microsoft Academic Search

Refractory alloys based on niobium, tantalum and molybdenum are potential candidate materials for structural applications in proposed space nuclear reactors. Long-term microstructural stability is a requirement of these materials for their use in this type of creep dominated application. Early work on refractory metal alloys has shown aging embrittlement occurring for some niobium and tantalum-base alloys at temperatures near 40%

Keith J. Leonard; Jeremy T. Busby; Steven J. Zinkle

2007-01-01

220

Radiation-enhanced recrystallization in copper alloys  

SciTech Connect

Two high-strength copper alloys, cold-worked-and-aged AMZIRC (Cu-Zr) and AMAX-MZC (Cu-Cr-Zr-Mg), were irradiated with 14-MeV Cu ions to a damage level of 10 dpa at temperatures of 100 to 500/sup 0/C. Cross-section examination of the irradiated foils using electron microscopy revealed signs of irradiation-enhanced recrystallization for irradiation temperatures above 300/sup 0/C. The recrystallization temperature for both alloys is about 450/sup 0/C during thermal annealing for a time similar to the ion-irradiation time -1.5 h. A simplified analysis of the results suggests that the accelerated recrystallization kinetics is due to radiation-enhanced diffusion (RED). This process may restrict the maximum operating temperature of fusion reactor components that incorporate these types of alloys to temperatures as low as 200/sup 0/C.

Zinkle, S.J.; Kulcinski, G.L.; Mansur, L.K.

1986-01-01

221

Technology status of tantalum alloys for space nuclear power applications  

NASA Technical Reports Server (NTRS)

Tantalum alloys have a variety of properties which make them attractive candidates for application in nuclear power systems required to operate in space at elevated temperatures (1200 to 1600 K) for extended time periods. Most of the technology development on this class of alloys which is pertinent to space system application occurred during the 1960 to 1972 time period under NASA sponsorship. The most extensive data bases resulting from this earlier work were obtained on the alloys T-111 (Ta-8W-2Hf) and ASTAR 811C (Ta-8W-1Re-0.7Hf-0.025C). Emphasis in this paper is directed at the following technical factors: producibility, creep strength, weldability and compatibility. These factors are considered to be the most important elements in the selection of alloys for this application. Review of the available information indicates that alloys of this type are appropriate for application in many systems, particularly those utilizing alkali metals as the working fluid.

Hoffman, E. E.

1985-01-01

222

Reactivities of aluminium and aluminium-magnesium alloy powders in polymeric composites  

Microsoft Academic Search

Polymeric compositions containing Al-Mg alloys show higher reactivities, in comparison with similar compositions containing aluminium. This is observed irrespective of the amount of oxidizer, type of oxidizer used, type of polymeric binder, and over a range of the particle sizes of the metal additive. This is evident from the higher calorimetric values obtained for compositions containing the alloy, in comparison

S. Deevi

1996-01-01

223

Magnesium secondary alloys: Alloy design for magnesium alloys with improved tolerance limits against impurities  

Microsoft Academic Search

The development of secondary magnesium alloys requires a completely different concept compared with standard alloys which obtain their corrosion resistance by reducing the levels of impurities below certain alloy and process depending limits. The present approach suitable for MgAl based cast and wrought alloys uses a new concept replacing the ?-phase by ?-phase, which is able to incorporate more impurities

C. Blawert; D. Fechner; D. Hche; V. Heitmann; W. Dietzel; K. U. Kainer; P. ivanovi?; C. Scharf; A. Ditze; J. Grbner; R. Schmid-Fetzer

2010-01-01

224

Alloy development of FeAl aluminide alloys for structural use in corrosive environments  

SciTech Connect

Objectives include adequate ductilities ({ge}10%) at ambient temperature, high-temperature strength better than stainless steels (types 304 and 316), and fabricability and weldability by conventional techniques (gas tungsten arc). The alloys should be capable of being corrosion resistant in molten nitrate salts with rates lower than other iron-base structural alloys and coating materials (such as Fe-Cr-Al alloys). Such corrosion rates should be less than 0.3 mm per year. The FeAl aluminide containing 35.8 at. % Al was selected as base composition. Preliminary studies indicate that additions of B and Zr, increase the room-temperature ductility of FeAl. Further alloying with 0.2% Mo, and/or 5% Cr, improves the creep. Our preliminary alloying effort has led to identification of the following aluminide composition with promising properties: Fe - (35 {plus_minus} 2)Al - (0.3 {plus_minus} 0.2)Mo - (0.2 {plus_minus} 0.15)Zr - (0.3 {plus_minus} 0.2)B- up to 5Cr, at. %. However, this composition is likely to be modified in future work to improve the weldability of the alloy. The FeAl alloy FA-362 (Fe-35.8% Al-0.2% Mo-0.05% Zr-0.24% B) produced by hot extrusion at 900C showed a tensile ductility of more than 10% at room temperature and a creep rupture life longer than unalloyed FeAl by more than an order of magnitude at 593C at 138 MPa. Melting and processing of scaled-up heats of selected FeAl alloys are described. Forging, extruding, and hot-rolling processes for the scale-up heats are also described.

Liu, C.T.; Sikka, V.K.; McKamey, C.G.

1993-02-01

225

Alloy development of FeAl aluminide alloys for structural use in corrosive environments  

SciTech Connect

Objectives include adequate ductilities ([ge]10%) at ambient temperature, high-temperature strength better than stainless steels (types 304 and 316), and fabricability and weldability by conventional techniques (gas tungsten arc). The alloys should be capable of being corrosion resistant in molten nitrate salts with rates lower than other iron-base structural alloys and coating materials (such as Fe-Cr-Al alloys). Such corrosion rates should be less than 0.3 mm per year. The FeAl aluminide containing 35.8 at. % Al was selected as base composition. Preliminary studies indicate that additions of B and Zr, increase the room-temperature ductility of FeAl. Further alloying with 0.2% Mo, and/or 5% Cr, improves the creep. Our preliminary alloying effort has led to identification of the following aluminide composition with promising properties: Fe - (35 [plus minus] 2)Al - (0.3 [plus minus] 0.2)Mo - (0.2 [plus minus] 0.15)Zr - (0.3 [plus minus] 0.2)B- up to 5Cr, at. %. However, this composition is likely to be modified in future work to improve the weldability of the alloy. The FeAl alloy FA-362 (Fe-35.8% Al-0.2% Mo-0.05% Zr-0.24% B) produced by hot extrusion at 900C showed a tensile ductility of more than 10% at room temperature and a creep rupture life longer than unalloyed FeAl by more than an order of magnitude at 593C at 138 MPa. Melting and processing of scaled-up heats of selected FeAl alloys are described. Forging, extruding, and hot-rolling processes for the scale-up heats are also described.

Liu, C.T.; Sikka, V.K.; McKamey, C.G.

1993-02-01

226

The microstructure evolution with lamellar 14H-type LPSO structure in an Mg 96.5Gd 2.5Zn 1 alloy during solid solution heat treatment at 773 K  

Microsoft Academic Search

In an as-cast Mg96.5Gd2.5Zn1 alloy, by optical microscope (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations, the as-cast microstructure was confirmed to be composed of the ??-Mg solid solution, and the coherent fine-lamellae and the eutectic, in which the second phase is the ?-phase ((Mg, Zn)3Gd) with a fcc structure. While, the coherent fine-lamellae consist of the

Y. J. Wu; X. Q. Zeng; D. L. Lin; L. M. Peng; W. J. Ding

2009-01-01

227

Mechanical and corrosion resistance of a new nanostructured Ti-Zr-Ta-Nb alloy.  

PubMed

In this work, a multi-elementary Ti-10Zr-5Nb-5Ta alloy, with non-toxic alloying elements, was used to develop an accumulative roll bonding, ARB-type procedure in order to improve its structural and mechanical properties. The alloy was obtained by cold crucible semi-levitation melting technique and then was ARB deformed following a special route. After three ARB cycles, the total deformation degree per layer is about 86%; the calculated medium layer thickness is about 13 ?m. The ARB processed alloy has a low Young's modulus of 46 GPa, a value very close to the value of the natural cortical bone (about 20 GPa). Data concerning ultimate tensile strength obtained for ARB processed alloy is rather high, suitable to be used as a material for bone substitute. Hardness of the ARB processed alloy is higher than that of the as-cast alloy, ensuring a better behaviour as a implant material. The tensile curve for the as-cast alloy shows an elastoplastic behaviour with a quite linear elastic behaviour and the tensile curve for the ARB processed alloy is quite similar with a strain-hardening elastoplastic body. Corrosion behaviour of the studied alloy revealed the improvement of the main electrochemical parameters, as a result of the positive influence of ARB processing. Lower corrosion and ion release rates for the ARB processed alloy than for the as-cast alloy, due to the favourable effect of ARB thermo-mechanical processing were obtained. PMID:21783152

Raducanu, D; Vasilescu, E; Cojocaru, V D; Cinca, I; Drob, P; Vasilescu, C; Drob, S I

2011-10-01

228

Analysis of niobium alloys.  

PubMed

An ion-exchange method was applied to the analysis of synthetic mixtures representing various niobium-base alloys. The alloying elements which were separated and determined include vanadium, zirconium, hafnium, titanium, molybdenum, tungsten and tantalum. Mixtures containing zirconium or hafnium, tungsten, tantalum and niobium were separated by means of a single short column. Coupled columns were employed for the resolution of mixtures containing vanadium, zirconium or titanium, molybdenum, tungsten and niobium. The separation procedures and the methods employed for the determination of the alloying elements in their separate fractions are described. PMID:18960385

Ferraro, T A

1968-09-01

229

Grain boundary segregation in the Ni-base alloy 182  

NASA Astrophysics Data System (ADS)

Grain boundary segregation is often considered to play a role in the various types of intergranular failures observed in austenitic alloys. However, there has been little direct study of this segregation because it is usually very difficult to obtain intergranular fracture in these alloys in the high vacuum required for surface analysis. This paper reports an Auger electron spectroscopy study of grain boundary segregation in the nickel-base Alloy 182. This alloy was used because it would easily fracture along its grain boundaries in high vacuum and because it has a very complex microstructure, as do many nickel-base alloys used in engineering applications. Furthermore, the alloy is widely used as a weld filler metal to join nickel-base alloys to one another or to stainless steels. Phosphorus was found to be the only impurity element that segregated to the grain boundaries. There was considerable variability in segregation from grain boundary to grain boundary and also on a single grain facet. It is suggested that these variations arise primarily from variations in grain boundary structure, in the density and types of precipitates in a grain boundary, and in the consequent variety of precipitate matrix interfaces present at the grain boundary. It is also suggested that quantitative Auger analysis on such a material would be very difficult.

Briant, C. L.

1988-01-01

230

Radiation-induced segregation in candidate fusion-reactor alloys  

SciTech Connect

The effect of radiation on surface segregation of minor and impurity elements has been studied in four candidate fusion reactor alloys. Radiation induced surface segregation of phosphorus was found in both 316 type stainless steel and in Nimonic PE-16. Segregation and depletion of the other alloying elements in 316 stainless steel agreed with that reported by other investigators. Segregation of nitrogen in ferritic HT-9 was enhanced by radiation but no phosphorus segregation was detected. No significant radiation enhanced or induced segregation was observed in a Ti-6Al-4V alloy. The results indicate that radiaton enhanced grain boundary segregation could contribute to the embrittlement of 316 SS and PE-16.

Brimhall, J.L.; Baer, D.R.; Jones, R.H.

1981-07-01

231

Electroplating on titanium alloy  

NASA Technical Reports Server (NTRS)

Activation process forms adherent electrodeposits of copper, nickel, and chromium on titanium alloy. Good adhesion of electroplated deposits is obtained by using acetic-hydrofluoric acid anodic activation process.

Lowery, J. R.

1971-01-01

232

Investigation of surface oxides on aluminum alloys by valence band photoemission  

NASA Astrophysics Data System (ADS)

Core level and valence band x-ray photoelectron spectroscopy are used to study the chemical composition of the surface films on aluminum alloys. Certain alloying elements may preferentially migrate to the surface of an alloy, thereby altering the composition and consequently the chemistry of the surface. The behavior of a 6061 aluminum alloy is compared with that of pure aluminum. It is shown that the type of magnesium film formed at the alloy surface can be determined by comparing the valence band spectra of the aluminum alloy surface with that of known magnesium and aluminum compounds. The experimental valence band spectra of these compounds are supported by spectra generated from band structure calculations. The effect of boiling water on the surface film is discussed, with significant differences in surface chemistry being seen for the metal and the alloy. copyright 2002 American Vacuum Society.

Claycomb, Gregory D.; Sherwood, Peter M. A.

2002-07-01

233

Nanocrystalline intermetallics and alloys  

Microsoft Academic Search

Nanocrystalline intermetallics and alloys are novel materials with high surface areas which are potential low-cost and high-performance\\u000a catalysts. Here, we report a general approach to the synthesis of a large variety of nanocrystalline intermetallics and alloys\\u000a with controllable composition, size, and morphology: these include Au-, Pd-, Pt-, Ir-, Ru-, and Rh-based bi- or tri-metallic\\u000a nanocrystals. We find that only those

Dingsheng Wang; Qing Peng; Yadong Li

2010-01-01

234

The properties of a wrought biomedical cobalt-chromium alloy  

Microsoft Academic Search

Two wrought biomedical cobalt-chromium alloys have been developed, and their mechanical properties and corrosion resistance determined by means of tensile and hardness tests and by electrochemical potential-time curves for isolated specimens in a 6.0 wt% NaCl solution at room temperature. In comparison with a current dental alloy, SC-H, and the basic type 18-8 austenitic stainless steel, it is shown that

Longquan Shi; Derek O. Northwood; Zhengwang Cao

1994-01-01

235

Evaluation of diffusion-bonded aluminum alloys to stainless steel  

Microsoft Academic Search

An investigation was made of the diffusion bonding of 316 stainless steel to two types of Al alloys (6061 (T6 condition) and 1100 (0 condition)) and pure Al metal. A 0.05-mm (0.002-in.) thick silver interface applied by hot hollow cathode plating served as the joining medium. The tensile strengths of bond with all three Al alloys decreased after aging at

Calderon

1983-01-01

236

Effects Of B On Intergranular Hot Cracking In Ni Alloys  

NASA Technical Reports Server (NTRS)

Report describes experiments on role of boron on solidification of 718-type nickel/chromium/iron superalloys containing niobium and relative intergranular segregations of boron, sulfur, and phosphorus in alloys. Ten alloys studied by use of light and scanning electron microscopy (SEM), energy-dispersive x-ray analysis, transmission electron microscopy (TEM) with energy-dispersive analysis of thin-film specimens, mechanical tests for susceptibility to microfissuring, differential thermal analysis (DTA), scanning Auger microscopy, and Gleeble thermal analysis.

Thompson, Raymond G.

1992-01-01

237

Mechanisms for the hot corrosion of nickel-base alloys  

Microsoft Academic Search

The Na2SO4-induced accelerated oxidation of nickel-base alloys containing elements such as Cr, Al, Mo, W, and V has been studied in\\u000a 1.0 atm O2 in the temperature range of 650? to 1000?C. It has been found that the hot corrosion behavior of these alloys can usually\\u000a be characterized according to one of two types of attack: 1) Na2SO4-induced accelerated oxidation;

J. A. Goebel; F. S. Pettit; G. W. Goward

1973-01-01

238

Metallography of dilute Mg-Nd-Zn alloys  

Microsoft Academic Search

Electron microscopy and electrical resistivity techniques have been used to examine the metallography and kinetics of precipitation in a magnesium alloy containing 2.8% Nd and 1.3% Zn. The alloy is shown to be of the age-hardening type with a precipitation sequence: Supersaturated solution-low-temperature reaction-..gamma..''-..gamma... The nature of the low-temperature reaction has not been fully elucidated but is thought not to

P. A. Nuttall; T. J. Pike; B. Noble

1980-01-01

239

Serrated yielding in Al-Li base alloys  

SciTech Connect

Serrated yielding (SY) has been studied in both substitutional and interstitial solid solutions. Three types of serration have been reported: type A (periodic), type B (fine) and type C (high frequency) serration. This phenomenon, generally referred to as the Portevin-Le Chatelier effect, is related to the solute atom-mobile dislocation interactions. Serrated yielding (SY) is observed in conventional aluminum alloys as well as in low-density, high-stiffness Al-Li base alloys, which are used in airframe construction. The aim of this paper is to study such serration and to estimate the influence of strain rate, temperature and composition on the critical strain for serrated yielding in three Al-Li based alloys. The apparent activation energy for SY is evaluated and the influence of quenched-in vacancies and vacancies produced by deformation on {epsilon}{sub c}, is also considered.

Ilic, N.; Jovanovic, M.T.; Markovic, D. [Inst. of Nuclear Sciences Vinca, Belgrade (Yugoslavia). Dept. of Materials Science] [Inst. of Nuclear Sciences Vinca, Belgrade (Yugoslavia). Dept. of Materials Science; Drobnjak, D.; Radmilovic, V. [Univ. of Belgrade (Yugoslavia). Dept. of Physical Metallurgy] [Univ. of Belgrade (Yugoslavia). Dept. of Physical Metallurgy

1996-04-01

240

Static immersion and irritation tests of dental metal-ceramic alloys.  

PubMed

The expansion of the European Union is bringing new types of metal-ceramic alloys to the market, i.e. alloys probably unknown in Western-European dentistry. The aim of this study was to investigate recent developments and "classic" alloy compositions (one iron and two cobalt alloys, unalloyed titanium and an experimental titanium-zirconium alloy, and one gold alloy containing copper and zinc). The alloys and titanium were subject to static immersion in a 0.1 mol l(-1) solution of saline lactic acid before and after oxidation, hence simulating the temperature cycles for the application of ceramic to metal. The greatest amounts of released metal ions were found in the electrolytes of the oxidized gold alloy and of a cobalt alloy not exposed to high-temperature oxidation. Corrosion of the titanium and alloy surfaces was related to the condition of the specimen. The irritation potentials of some metal ions found in the electrolyte were investigated by performing the hen's egg test-chorio-allantoic membrane (HET-CAM) procedure with 1 mmol l(-1) solutions of Ce(3+), Co(2+), Cu(2+), Zn(2+), Fe(2+), and Ti(4+) ions. The irritation potential of the electrolyte of the oxidized gold alloy with a high concentration of metal elements was also investigated. Of these solutions, only the 1 mmol l(-1) Cu(2+) solution was graded as slightly irritating. PMID:15693834

Ardlin, Berit I; Dahl, Jon E; Tibballs, John E

2005-02-01

241

Intralayer magnetic ordering in Ge\\/Mn digital alloys  

Microsoft Academic Search

We present a first-principles investigation of the electronic properties of Ge\\/Mn digital alloys obtained by the insertion of Mn monolayers in the Ge host. The main attention is devoted to the study of the magnetic properties of the Mn layers for various types of ordering of the Mn atoms. Depending on the type of Mn position three different structures are

M. M. Otrokov; A. Ernst; S. Ostanin; G. Fischer; P. Buczek; L. M. Sandratskii; W. Hergert; I. Mertig; V. M. Kuznetsov; E. V. Chulkov

2011-01-01

242

Low-temperature brittleness of Fe-Cr-5% Al alloys  

Microsoft Academic Search

1.A reduction in grain size (by different methods) makes it possible to lower significantly the cold-shortness temperature of high-chromium alloys of the Fe-Cr-5% Al system.2.The increase in the cold-shortness temperature of Fe-Cr-5% Al alloys with increasing grain size is described by a type of Holl-Petch relationship.3.The tendency of alloys of the Fe-Cr-5% Al system to embrittlement as grain size increases

Yu. A. Kurapov; V. N. Minakov; N. D. Rudyk

1991-01-01

243

Literature search update: Fireside corrosion testing of candidate superheater tube alloys, coatings, and claddings  

Microsoft Academic Search

Supercritical units have required superheaters and reheaters constructed of expensive high-chromium\\/high-nickel alloys, and they have been limited to burning coals with low corrosivity. Several high-chromium alloys, such as Type 310 and CR35A, hold promise as claddings for tubes in highly corrosive conditions. Modified lower-alloy steels-HR3C and CR30A, for example -- with much greater corrosion resistance and creep-rupture strength are being

S. Van Weele; J. L. Blough

1990-01-01

244

Structural and Mssbauer spectroscopic study of Fe-Ni alloy nanoparticles  

SciTech Connect

Nano-crystalline Fe-Ni alloys have been synthesized in ethylene glycol medium. Based on XRD studies it is confirmed that, in these alloys Fe atoms are incorporated at Ni site to form Ni-Fe solid solutions. Mssbauer studies have established that for alloy particles having smaller size there is significant concentration of two different types of paramagnetic Fe species and their relative concentration decreased with increase in particle size.

Kumar, Asheesh; Banerjee, S., E-mail: vsudar@barc.gov.in; Sudarsan, V., E-mail: vsudar@barc.gov.in [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085 (India); Meena, S. S. [Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085 (India)

2014-04-24

245

Effects of Rh on the thermoelectric performance of the p-type Zr{sub 0.5}Hf{sub 0.5}Co{sub 1-x}Rh{sub x}Sb{sub 0.99}Sn{sub 0.01} half-Heusler alloys  

SciTech Connect

We show that Rh substitution at the Co site in Zr{sub 0.5}Hf{sub 0.5}Co{sub 1-x}Rh{sub x}Sb{sub 0.99}Sn{sub 0.01} (0<=x<=1) half-Heusler alloys strongly reduces the thermal conductivity with a simultaneous, significant improvement of the power factor of the materials. Thermoelectric properties of hot-pressed pellets of several compositions with various Rh concentrations were investigated in the temperature range from 300 to 775 K. The Rh 'free' composition shows n-type conduction, while Rh substitution at the Co site drives the system to p-type semiconducting behavior. The lattice thermal conductivity of Zr{sub 0.5}Hf{sub 0.5}Co{sub 1-x}Rh{sub x}Sb{sub 0.99}Sn{sub 0.01} alloys rapidly decreased with increasing Rh concentration and lattice thermal conductivity as low as 3.7 W/m*K was obtained at 300 K for Zr{sub 0.5}Hf{sub 0.5}RhSb{sub 0.99}Sn{sub 0.01}. The drastic reduction of the lattice thermal conductivity is attributed to mass fluctuation induced by the Rh substitution at the Co site, as well as enhanced phonon scattering at grain boundaries due to the small grain size of the synthesized materials. - Graphical abstract: Significant reduction of the lattice thermal conductivity with increasing Rh concentration in the p-type Zr{sub 0.5}Hf{sub 0.5}Co{sub 1-x}Rh{sub x}Sb{sub 0.99}Sn{sub 0.01} half-Heusler materials prepared by solid state reaction at 1173 K.

Maji, Pramathesh [Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148 (United States); Department of Chemistry, University of New Orleans, New Orleans, LA 70148 (United States); Takas, Nathan J.; Misra, Dinesh K. [Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148 (United States); Gabrisch, Heike [Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148 (United States); Department of Chemistry, University of New Orleans, New Orleans, LA 70148 (United States); Stokes, Kevin [Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148 (United States); Department of Physics, University of New Orleans, New Orleans, LA 70148 (United States); Poudeu, Pierre F.P., E-mail: ppoudeup@uno.ed [Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148 (United States); Department of Chemistry, University of New Orleans, New Orleans, LA 70148 (United States)

2010-05-15

246

Joints in fiber-reinforced aluminum alloys  

NASA Technical Reports Server (NTRS)

Problems of joining involving structural components made of aluminum alloys with boron-fiber reinforcements are discussed, giving attention to a diffusion-welding process. The tension characteristics and weight factors in the case of various types of welded joints are considered. Diffusion-welding equipment used in the experimental investigation is described. The strength characteristics obtained in various cases of weld and component design are examined, taking into account static and dynamic stresses.

Gerber, K.; Vanrensen, E.

1988-01-01

247

Solidification of an alloy 625 weld overlay  

Microsoft Academic Search

The solidification behavior (microsegregation, secondary phase formation, and solidification temperature range) of an Alloy 625 weld overlay deposited on 2.25Cr - 1Mo steel by gas metal arc welding was investigated by light and electron optical microscopy, electron microprobe, and differential thermal analysis techniques. The overlay deposit was found to terminate solidification at ≈ 1216 C by a gamma\\/Laves eutectic-type reaction.

J. N. Dupont

1996-01-01

248

Solidification of an alloy 625 weld overlay  

Microsoft Academic Search

The solidification behavior (microsegregation, secondary phase formation, and solidification temperature range) of an Alloy\\u000a 625 weld overlay deposited on 2.25Cr - 1Mo steel by gas metal arc welding was investigated by light and electron optical microscopy,\\u000a electron microprobe, and differential thermal analysis techniques. The overlay deposit was found to terminate solidification\\u000a at ? 1216 C by a?\\/Laves eutectic-type reaction. The

J. N. DuPont

1996-01-01

249

Ductile Titanium Alloy with Low Poisson's Ratio  

Microsoft Academic Search

We report a ductile β-type titanium alloy with body-centered cubic (bcc) crystal structure having a low Poisson's ratio of 0.14. The almost identical ultralow bulk and shear moduli of 24 GPa combined with an ultrahigh strength of 0.9 GPa contribute to easy crystal distortion due to much-weakened chemical bonding of atoms in the crystal, leading to significant elastic softening in

Y. L. Hao; S. J. Li; B. B. Sun; M. L. Sui; R. Yang

2007-01-01

250

Ductile Titanium Alloy with Low Poisson's Ratio  

Microsoft Academic Search

We report a ductile beta-type titanium alloy with body-centered cubic (bcc) crystal structure having a low Poisson's ratio of 0.14. The almost identical ultralow bulk and shear moduli of 24GPa combined with an ultrahigh strength of 0.9GPa contribute to easy crystal distortion due to much-weakened chemical bonding of atoms in the crystal, leading to significant elastic softening in tension and

Y. L. Hao; S. J. Li; B. B. Sun; M. L. Sui; R. Yang

2007-01-01

251

Texture Evolution in Mg-Zn-Ca Alloy Sheets  

NASA Astrophysics Data System (ADS)

Ca was added to Mg-1Zn and Mg-6Zn alloys to modify their texture, and the origin of texture modification by Ca addition has been investigated. It shows that Mg-1Zn-1Ca (ZX11) and Mg-6Zn-1Ca (ZX61) alloy sheets in the as-rolled condition show the textures having a splitting of basal poles toward the rolling direction and a splitting of basal poles toward the transverse direction, respectively. An analysis of the microstructure in the as-rolled condition shows that two different types of twins become active during rolling, double twins for ZX11 and tension twins for ZX61, suggesting that double twinning and tension twinning promote a splitting of basal poles toward the rolling direction (ZX11) and transverse direction (ZX61), respectively. On the other hand, after annealing, both alloy sheets show a weakened texture characterized by a splitting of basal poles toward the transverse direction. During annealing, the growth of tension twin-oriented grains occurs, resulting in the texture having a splitting of basal poles toward the transverse direction in both alloys. These alloys show not only higher yield strength but also better stretch formability than Al 5052 alloy, showing their potential as highly formable Mg sheet alloys.

Kim, D.-W.; Suh, B.-C.; Shim, M.-S.; Bae, J. H.; Kim, D. H.; Kim, Nack J.

2013-07-01

252

Reduction in Defect Content in ODS Alloys  

SciTech Connect

The work detailed within this report is a continuation of earlier work that was carried out under contract number IDX-SY382V. The earlier work comprised a literature review of the sources and types of defects found principally in Fe-based ODS alloys together with a series of experiments designed to identify defects in ODS Fe{sub 3}Al material and recommend methods of defect reduction. Defects found in the Mechanically Alloyed (MA) ODS Fe{sub 3}Al included regions of incomplete MA, porosity, intrusions and fine-grained stringers. Some defects tended to be found in association with one another e.g. intrusions and fine-grained stringers. Preliminary powder separation experiments were also performed. The scope and objectives of the present work were laid out in the technical proposal ``Reduction in Defect Content in ODS Alloys--II'' which formed the basis of amendment 3 of the current contract. The current studies were devised in the context of the preceding work with a view to extending and concluding certain experiments while exploring new avenues of investigation of defect control and reduction where appropriate. All work proposed was within the context of achieving an ODS Fe{sub 3}Al alloy of improved overall quality and potential creep performance (particularly) in the consolidated, release condition. The interim outturn of the experimental work performed is also reported.

Ritherdon, J.; Jones, A.R.

2000-02-01

253

Solidification of an alloy 625 weld overlay  

NASA Astrophysics Data System (ADS)

The solidification behavior (microsegregation, secondary phase formation, and solidification temperature range) of an Alloy 625 weld overlay deposited on 2.25Cr - 1Mo steel by gas metal arc welding was investigated by light and electron optical microscopy, electron microprobe, and differential thermal analysis techniques. The overlay deposit was found to terminate solidification at ? 1216 C by a ?/Laves eutectic-type reaction. The Laves phase was highly enriched in Nb, Mo, and Si. The solidification reaction and microsegregation potential of major alloying elements in the overlay deposit are compared to other Nb-bearing Ni base alloys and found to be very similar to those for Alloy 718. Solidification cracks observed in the overlay were attributed to the wide solidification temperature range (?170 C) and formation of interdendritic ( ?+Laves) constituent. Reasonable agreement is obtained between the calculated and measured volume percent ( ?+Laves) constituent with the Scheil equation by treating the overlay system as a simple ?-Nb binary and using an experimentally determined k Nb value from electron microprobe data.

Dupont, J. N.

1996-11-01

254

Modeling dissolution in aluminum alloys  

Microsoft Academic Search

Aluminum and its alloys are used in many aspects of modern life, from soda cans and household foil to the automobiles and aircraft in which we travel. Aluminum alloy systems are characterized by good workability that enables these alloys to be economically rolled, extruded, or forged into useful shapes. Mechanical properties such as strength are altered significantly with cold working,

Tracie Lee Durbin

2005-01-01

255

Process for Nonequilibrium Ternary Alloys  

NASA Technical Reports Server (NTRS)

Proposed metallurgical process yields amorphous ternary alloys of any range of desired compositions. Process produces homogenous alloys even when proportions of constituent metals are not those that exist in equilibrium at solidification temperature. Such alloys are well suited to use in gas turbines and advanced engines.

Lutwack, R.

1986-01-01

256

Laser assisted high entropy alloy coating on aluminum: Microstructural evolution  

NASA Astrophysics Data System (ADS)

High entropy alloy (Al-Fe-Co-Cr-Ni) coatings were synthesized using laser surface engineering on aluminum substrate. Electron diffraction analysis confirmed the formation of solid solution of body centered cubic high entropy alloy phase along with phases with long range periodic structures within the coating. Evolution of such type of microstructure was a result of kinetics associated with laser process, which generates higher temperatures and rapid cooling resulting in retention of high entropy alloy phase followed by reheating and/or annealing in subsequent passes of the laser track giving rise to partial decomposition. The partial decomposition resulted in formation of precipitates having layered morphology with a mixture of high entropy alloy rich phases, compounds, and long range ordered phases.

Katakam, Shravana; Joshi, Sameehan S.; Mridha, Sanghita; Mukherjee, Sundeep; Dahotre, Narendra B.

2014-09-01

257

Iron aluminide alloys with improved properties for high temperature applications  

DOEpatents

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.

McKamey, Claudette G. (Knoxville, TN); Liu, Chain T. (Oak Ridge, TN)

1990-01-01

258

Characteristics of alumina particles in dispersion-strengthened copper alloys  

NASA Astrophysics Data System (ADS)

Two types of alumina dispersion-strengthened copper (ADSC) alloys were fabricated by a novel in-situ reactive synthesis (IRS) and a traditional internal oxidation (IO) process. The features of alumina dispersoids in these ADSC alloys were investigated by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. It is found that nano-sized ?-Al2O3 particles of approximately 10 nm in diameter are homogeneously distributed in the IRS-ADSC composites. Meanwhile, larger-sized, mixed crystal structure alumina with rod-shaped morphology is embedded in the IO-ADSC alloy. The IRS-ADSC composites can obtain better mechanical and physical properties than the IO-ADSC composites; the tensile strength of the IRS-ADSC alloy can reach 570 MPa at room temperature, its electrical conductivity is 85% IACS, and the Rockwell hardness can reach 86 HRB.

Zhang, Xue-hui; Li, Xiao-xian

2014-11-01

259

Effects of Loading Type And Cavity Position On The Pattern Height In Micro-manufacturing of Al5083 Superplastic Alloy And Zr62Cu17Ni13Al8 Metallic Glass  

NASA Astrophysics Data System (ADS)

Vibrational micro-forming of pyramidal shape patterns was conducted for an Al superplastic alloy, Al 5083 and a Zr-based bulk metallic glass, Zr62Cu17Ni13Al8. A vibrational micro-forming system was specially designed for generating vibrational load by combining a PZT actuator with a signal generator. Si micro dies with wet-etched pyramidal patterns were used as master dies for vibrational micro-forming. The micro-formed pattern height was increasing with increasing the frequency of the vibrational load. In particular, the vibrationally-microformed pattern height is similar or even higher than the statically-microformed pattern height when the load frequency exceeded about 125 kHz. It was also observed that the crystal grains affect the surface quality of the microformed pattern and the distribution of the pattern height in the die cavity array.

Na, Young-Sang; Son, Seon-Cheon; Park, Kyu-Yeol; Lee, Jong-Hoon

2009-11-01

260

Compositional dependence of the direct and indirect band gaps in Ge1?ySny alloys from room temperature photoluminescence: implications for the indirect to direct gap crossover in intrinsic and n-type materials  

NASA Astrophysics Data System (ADS)

The compositional dependence of the lowest direct and indirect band gaps in Ge1?ySny alloys has been determined from room-temperature photoluminescence measurements. This technique is particularly attractive for a comparison of the two transitions because distinct features in the spectra can be associated with the direct and indirect gaps. However, detailed modeling of these room temperature spectra is required to extract the band gap values with the high accuracy required to determine the Sn concentration yc at which the alloy becomes a direct gap semiconductor. For the direct gap, this is accomplished using a microscopic model that allows the determination of direct gap energies with meV accuracy. For the indirect gap, it is shown that current theoretical models are inadequate to describe the emission properties of systems with close indirect and direct transitions. Accordingly, an ad hoc procedure is used to extract the indirect gap energies from the data. For y < 0.1 the resulting direct gap compositional dependence is given by ?E0 = ?(3.57 0.06)y (in eV). For the indirect gap, the corresponding expression is ?Eind = ?(1.64 0.10)y (in eV). If a quadratic function of composition is used to express the two transition energies over the entire compositional range 0 ?? y ?? 1, the quadratic (bowing) coefficients are found to be b0 = 2.46 0.06 eV (for E0) and bind = 1.03 0.11 eV (for Eind). These results imply a crossover concentration yc = 0.073-0.006+0.007, much lower than early theoretical predictions based on the virtual crystal approximation, but in better agreement with predictions based on large atomic supercells.

Jiang, L.; Gallagher, J. D.; Senaratne, C. L.; Aoki, T.; Mathews, J.; Kouvetakis, J.; Menndez, J.

2014-11-01

261

Surface modification of high temperature iron alloys  

DOEpatents

A method and article of manufacture of a coated iron based alloy. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700.degree. C.-1200.degree. C. to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy.

Park, Jong-Hee (Clarendon Hills, IL)

1995-01-01

262

Surface modification of high temperature iron alloys  

DOEpatents

A method and article of manufacture of a coated iron based alloy are disclosed. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700--1200 C to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy. 13 figs.

Park, J.H.

1995-06-06

263

Effect of chemical structure of borates on the tribological characteristics of magnesium alloy during sliding  

Microsoft Academic Search

Effects of four borates with different chemical structure on the tribological properties of magnesium alloy in sliding contact with bearing steel were investigated under boundary lubrication using a Timken type tester. It was shown that the borate without active element is not effective at reducing the friction and wear of magnesium alloy, and the borates containing nitrogen, sulfur and chlorine

Weijiu Huang; Ya Fu; Jiu Wang; Zhaofeng Li; Ming Liu

2005-01-01

264

Design Considerations for the Use of Aluminum Alloys for Integral Horsepower Motors  

Microsoft Academic Search

The design considerations on the use of aluminum alloys for the external supporting parts of integral horsepower induction motors are compared with the previously conventional use of cast iron. Covered are such factors as type of aluminum alloy selected considering service requirements and manufacturing methods planned, strength, reliability, durability (including corrosion resistance), effect on overall weight and performance. The tests

William R. Morton

1977-01-01

265

Modifying the properties of the Inconel 625 nickel alloy by glow discharge assisted nitriding  

Microsoft Academic Search

The nickel alloys of the Inconel type (containing above 15wt% of chromium), used in many industrial applications including the manufacture of aircraft, chemistry, power generation, and material processing, have advantageous mechanical properties, high plasticity and good corrosion resistance, but their frictional wear resistance is poor. This drawback can be obviated by subjecting the alloys to various surface treatments.The paper describes

Tomasz Borowski; Agnieszka Brojanowska; Marcin Kost; Halina Garbacz; Tadeusz Wierzcho?

2009-01-01

266

Corrosion of high purity Fe-Cr-Ni alloys in 13 N boiling nitric acid  

SciTech Connect

Corrosion in boiling nitric acid was investigated for high purity Fe-18%Cr-12%Ni alloys and type 304L stainless steels (SS). Owing to very low impurity concentration, the solution treated high purity alloys show almost no intergranular corrosion while the type 304L SS show severe intergranular corrosion. Both in the high purity alloys and type 304L SS, aging treatments ranging from 873 K to 1073 K for 1 h enhance intergranular corrosion. During the aging treatments, impurities should be segregated to the grain boundaries. The corrosion behaviors were discussed from a standpoint of impurity segregation to grain boundaries. This study is of importance for purex reprocessing of spent fuels.

Ohta, Joji; Mayuzumi, Masami; Kusanagi, Hideo; Takaku, Hiroshi [Electric Power Industry, Komae, Tokyo (Japan). Central Research Inst.

1998-12-31

267

Positron-annihilation 2D-ACAR studies of disordered and defected alloys  

SciTech Connect

Theoretical and experimental progess in connection with 2D-ACAR positron annihilation studies of ordered, disordered, and defected alloys is discussed. We present, in particular, some of the recent developments concerning the electronic structure of disordered alloys, and the work in the area of annihilation from positrons trapped at vacancy-type defects in metals and alloys. The electronic structure and properties of a number of compounds are also discussed briefly; we comment specifically on high T/sub c/ ceramic superconductors, Heusler alloys, and transition-metal aluminides. 58 refs., 116 figs.

Bansil, A.; Prasad, R.; Smedskjaer, L.C.; Benedek, R.; Mijnarends, P.E.

1987-09-01

268

Vortex motion and resistivity of type-ll superconductors in a magnetic field  

Microsoft Academic Search

The review analyzes the physical mechanisms of energy dissipation in type-II superconducting alloys in the mixed state. A very simple microscopic theory is presented for the dissipative processes in alloys with paramagnetic impurities. The main premises of the microscopic theory are described and its results are presented for the resistivity in the case of ordinary alloys (without paramagnetic impurities) in

L. P. Gorkov; N. B. Kopnin

1975-01-01

269

Environmentally Assisted Cracking of Nickel Alloys  

SciTech Connect

Environmentally Assisted Cracking (EAC) is a general term that includes phenomena such as stress corrosion cracking (SCC), hydrogen embrittlement (HE), sulfide stress cracking (SSC), liquid metal embrittlement (LME), etc. EAC refers to a phenomenon by which a normally ductile metal looses its toughness (e.g. elongation to rupture) when it is subjected to mechanical stresses in presence of a specific corroding environment. For EAC to occur, three affecting factors must be present simultaneously. These include: (1) Mechanical tensile stresses, (2) A susceptible metal microstructure and (3) A specific aggressive environment. If any of these three factors is removed, EAC will not occur. That is, to mitigate the occurrence of EAC, engineers may for example eliminate residual stresses in a component or limit its application to certain chemicals (environment). The term environment not only includes chemical composition of the solution in contact with the component but also other variables such as temperature and applied potential. Nickel alloys are in general more resistant than stainless steels to EAC. For example, austenitic stainless steels (such as S30400) suffer SCC in presence of hot aqueous solutions containing chloride ions. Since chloride ions are ubiquitous in most industrial applications, the use of stressed stainless steels parts is seriously limited. On the other hand, nickel alloys (such as N10276) are practically immune to SCC in presence of hot chloride solutions and therefore an excellent alternative to replace the troubled stainless steels. Nonetheless, nickel alloys are not immune to other types of EAC. There are several environments (such as hot caustic and hot hydrofluoric acid) that may produce embrittlement in nickel alloys (Crum et al, 2000) (Table 1). The conditions where nickel alloys suffer EAC are highly specific and therefore avoidable by the proper design of the industrial components.

Rebak, R B

2004-02-06

270

Thermal coatings for titanium-aluminum alloys  

SciTech Connect

Titanium aluminides and titanium alloys are candidate materials for use in hot structure and heat-shield components of hypersonic vehicles because of their good strength-to-weight characteristics at elevated temperature. However, in order to utilize their maximum temperature capability, they must be coated to resist oxidation and to have a high total remittance. Also, surface catalysis for recombination of dissociated species in the aerodynamic boundary layer must be minimized. Very thin chemical vapor deposition (CVD) coatings are attractive candidates for this application because of durability and very light weight. To demonstrate this concept, coatings of boron-silicon and aluminum-boron-silicon compositions were applied to the titanium-aluminides alpha2 (Ti-14Al-21Nb), super-alpha2 (Ti-14Al-23-Nb-2V), and gamma (Ti-33Al-6Nb-1Ta) and to the titanium alloy beta-21S (Ti-15Mo-3Al-3Nb-0.2Si). Coated specimens of each alloy were subjected to a set of simulated hypersonic vehicle environmental tests to determine their properties of oxidation resistance, surface catalysis, radiative emittance, and thermal shock resistance. Surface catalysis results should be viewed as relative performance only of the several coating-alloy combinations tested under the specific environmental conditions of the LaRC Hypersonic Materials Environmental Test System (HYMETS) arc-plasma-heated hypersonic wind tunnel. Tests were also conducted to evaluate the hydrogen transport properties of the coatings and any effects of the coating processing itself on fatigue life of the base alloys. Results are presented for three types of coatings, which are as follows: (1) a single layer boron silicon coating, (2) a single layer aluminum-boron-silicon coating, and (3) a multilayer coating consisting of an aluminum-boron-silicon sublayer with a boron-silicon outer layer.

Cunnington, G.R.; Clark, R.K.; Robinson, J.C.

1993-04-01

271

Thermal coatings for titanium-aluminum alloys  

NASA Technical Reports Server (NTRS)

Titanium aluminides and titanium alloys are candidate materials for use in hot structure and heat-shield components of hypersonic vehicles because of their good strength-to-weight characteristics at elevated temperature. However, in order to utilize their maximum temperature capability, they must be coated to resist oxidation and to have a high total remittance. Also, surface catalysis for recombination of dissociated species in the aerodynamic boundary layer must be minimized. Very thin chemical vapor deposition (CVD) coatings are attractive candidates for this application because of durability and very light weight. To demonstrate this concept, coatings of boron-silicon and aluminum-boron-silicon compositions were applied to the titanium-aluminides alpha2 (Ti-14Al-21Nb), super-alpha2 (Ti-14Al-23-Nb-2V), and gamma (Ti-33Al-6Nb-1Ta) and to the titanium alloy beta-21S (Ti-15Mo-3Al-3Nb-0.2Si). Coated specimens of each alloy were subjected to a set of simulated hypersonic vehicle environmental tests to determine their properties of oxidation resistance, surface catalysis, radiative emittance, and thermal shock resistance. Surface catalysis results should be viewed as relative performance only of the several coating-alloy combinations tested under the specific environmental conditions of the LaRC Hypersonic Materials Environmental Test System (HYMETS) arc-plasma-heated hypersonic wind tunnel. Tests were also conducted to evaluate the hydrogen transport properties of the coatings and any effects of the coating processing itself on fatigue life of the base alloys. Results are presented for three types of coatings, which are as follows: (1) a single layer boron silicon coating, (2) a single layer aluminum-boron-silicon coating, and (3) a multilayer coating consisting of an aluminum-boron-silicon sublayer with a boron-silicon outer layer.

Cunnington, George R.; Clark, Ronald K.; Robinson, John C.

1993-01-01

272

?=5/2 fractional quantum Hall state in the presence of alloy disorder.  

PubMed

We report quantitative measurements of the impact of alloy disorder on the ? = 5/2 fractional quantum Hall state. Alloy disorder is controlled by the aluminum content x in the Al(x)Ga(1-x)As channel of a quantum well. We find that the ? = 5/2 state is suppressed with alloy scattering. To our surprise, in samples with alloy disorder the ? = 5/2 state appears at significantly reduced mobilities when compared to samples in which alloy disorder is not the dominant scattering mechanism. Our results highlight the distinct roles of the different types of disorder present in these samples, such as the short-range alloy and the long-range Coulomb disorder. PMID:24702403

Deng, Nianpei; Gardner, G C; Mondal, S; Kleinbaum, E; Manfra, M J; Csthy, G A

2014-03-21

273

Magnetic investigation of Ni50Mn33In12Ga5 alloy  

NASA Astrophysics Data System (ADS)

We have investigated the transport and magnetic properties of the ferromagnetic shape memory alloy of nominal composition Ni50Mn33In12Ga5. The alloy is the outcome of 5% Ga doping at the In site of the Heusler alloy Ni50Mn33In12. The resulting Ga-doped alloy orders ferromagnetically at 300 K and undergoes a martensitic type structural phase transition around 200 K on cooling. However, the parent alloy (Ni50Mn33In12) does not show any structural instability, and it indicates the role of Ga in invoking structural instability in Ni-Mn based Heusler alloys. The studied Ga doped sample indicates field induced metamagnetic transition around the temperature window of structural instability in the magnetization measurement. Cooling the sample under suitable magnetic field indicates that the high temperature austenite is getting kinetically arrested across the first order martensitic transition.

Pramanick, S.; Chatterjee, S.; Majumdar, S.

2013-02-01

274

Correlation of atomic packing with the boson peak in amorphous alloys  

NASA Astrophysics Data System (ADS)

Boson peaks (BP) have been observed from phonon specific heats in 10 studied amorphous alloys. Two Einstein-type vibration modes were proposed in this work and all data can be fitted well. By measuring and analyzing local atomic structures of studied amorphous alloys and 56 reported amorphous alloys, it is found that (a) the BP originates from local harmonic vibration modes associated with the lengths of short-range order (SRO) and medium-range order (MRO) in amorphous alloys, and (b) the atomic packing in amorphous alloys follows a universal scaling law, i.e., the ratios of SRO and MRO lengths to solvent atomic diameter are 3 and 7, respectively, which exact match with length ratios of BP vibration frequencies to Debye frequency for the studied amorphous alloys. This finding provides a new perspective for atomic packing in amorphous materials, and has significant implications for quantitative description of the local atomic orders and understanding the structure-property relationship.

Yang, W. M.; Liu, H. S.; Liu, X. J.; Chen, G. X.; Dun, C. C.; Zhao, Y. C.; Man, Q. K.; Chang, C. T.; Shen, B. L.; Inoue, A.; Li, R. W.; Jiang, J. Z.

2014-09-01

275

Correlation of atomic packing with the boson peak in amorphous alloys  

SciTech Connect

Boson peaks (BP) have been observed from phonon specific heats in 10 studied amorphous alloys. Two Einstein-type vibration modes were proposed in this work and all data can be fitted well. By measuring and analyzing local atomic structures of studied amorphous alloys and 56 reported amorphous alloys, it is found that (a) the BP originates from local harmonic vibration modes associated with the lengths of short-range order (SRO) and medium-range order (MRO) in amorphous alloys, and (b) the atomic packing in amorphous alloys follows a universal scaling law, i.e., the ratios of SRO and MRO lengths to solvent atomic diameter are 3 and 7, respectively, which exact match with length ratios of BP vibration frequencies to Debye frequency for the studied amorphous alloys. This finding provides a new perspective for atomic packing in amorphous materials, and has significant implications for quantitative description of the local atomic orders and understanding the structure-property relationship.

Yang, W. M. [State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, School of Sciences, China University of Mining and Technology, Xuzhou 221116 (China); Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Liu, H. S., E-mail: liuhaishun@126.com, E-mail: blshen@seu.edu.cn, E-mail: runweili@nimte.ac.cn, E-mail: jiangjz@zju.edu.cn; Zhao, Y. C. [State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, School of Sciences, China University of Mining and Technology, Xuzhou 221116 (China); Liu, X. J. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Chen, G. X.; Man, Q. K.; Chang, C. T.; Li, R. W., E-mail: liuhaishun@126.com, E-mail: blshen@seu.edu.cn, E-mail: runweili@nimte.ac.cn, E-mail: jiangjz@zju.edu.cn [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Dun, C. C. [Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109 (United States); Shen, B. L., E-mail: liuhaishun@126.com, E-mail: blshen@seu.edu.cn, E-mail: runweili@nimte.ac.cn, E-mail: jiangjz@zju.edu.cn [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Inoue, A. [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); and others

2014-09-28

276

Characterization of amorphous Co-P alloy coatings electrodeposited with pulse current using gluconate bath  

NASA Astrophysics Data System (ADS)

Co-P alloy coatings were electrodeposited with pulse current using gluconate bath and characterized by XRD, FESEM, AFM, DSC and XPS. Co-P alloy coatings are amorphous in nature as demonstrated by XRD. FESEM exhibits the cauliflower type morphology that is distinctive of nanocrystalline metals and alloys. Co-P alloys are found to follow instantaneous growth mechanism as revealed by AFM studies. Two exothermic peaks at 320 and 340 C in DSC profiles of Co-P deposit correspond to the crystallization of the deposit. Detailed XPS studies of these alloy coatings have shown that as-deposited coatings consist of Co metal as well as oxidized Co species. P has mostly been present as bulk alloy on the surface as P?- form. Increase in the amounts of Co metal and P?- are observed upon intermittent sputtering. No appreciable increase in microhardness is observed with increase in the phosphorous content, but it increases with heat treatment significantly.

Bera, Parthasarathi; Seenivasan, H.; Rajam, K. S.; William Grips, V. K.

2012-10-01

277

Magnesium and magnesium alloys  

Microsoft Academic Search

This new handbook is the most comprehensive publication of engineering information on commercial magnesium alloys under one cover in the last sixty years. Prepared with the cooperation of the International Magnesium Association, it presents the industrial practices currently used throughout the world, as well as the properties of the products critical to their proper application. Contents include: general characteristics; physical

M. Avedesian; H. Baker

1998-01-01

278

Shape Memory Alloy Actuator  

NASA Technical Reports Server (NTRS)

The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

Baumbick, Robert J. (Inventor)

2000-01-01

279

Shape Memory Alloy Actuator  

NASA Technical Reports Server (NTRS)

The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

Baumbick, Robert J. (Inventor)

2002-01-01

280

Interfacial oxidations of pure titanium and titanium alloys with investments.  

PubMed

External oxides of a commercially pure titanium (cpTi), Ti6Al4V alloy, and an experimental beta-type titanium alloy (Ti 53.4 wt%, Nb 29 wt%, Ta 13 wt%, and Zr 4.6 wt%) were characterized after heating to 600, 900, 1150, and 1400 degrees C in contact with three types of investments (alumina cement, magnesia cement, and phosphate-bonded) in air. XRD studies demonstrated that MgO, Li2TiO3 and/or Li2Ti3O7 were formed through reactions with the metal and the constituents in the magnesia cement-investment after heating to 900, 1150, and 1400 degrees C. Except for these conditions, TiO2 (rutile) was only formed on cpTi. For titanium alloys, the other components apart from Ti also formed simple and complex oxides such as Al2O3 and Al2TiO5 on Ti6Al4V, and Zr0.25Ti0.75Nb2O7 on the beta-type titanium alloy. However, no oxides containing V or Ta were formed. These results suggest that the constituents of titanium alloys reacted with the investment oxides and atmospheric oxygen to form external oxides due to the free energy of oxide formation and the concentration of each element on the metal surface. PMID:11816365

Ban, S; Watanabe, T; Mizutani, N; Fukui, H; Hasegawa, J; Nakamura, H

2000-12-01

281

Characterizing alloy additions to high nitrogen steels  

Microsoft Academic Search

Numerous articles of individual high nitrogen stainless steel compositions or alloys with near identical alloy compositions have been published characterizing the properties the alloy or the improvement which an individual element contributes to the base alloy's properties. In this study a series of high nitrogen steels alloys were prepared with the intent of characterizing the advantages and limitations of different

James C. Rawers; Joseph H. Tylczak; D. Blankenship; Sophie J. Bullard

2003-01-01

282

Alloys for hydrogen storage in nickel/hydrogen and nickel/metal hydride batteries  

NASA Technical Reports Server (NTRS)

Since 1990, there has been an ongoing collaboration among the authors in the three laboratories to (1) prepare alloys of the AB(sub 5) and AB(sub 2) types, using arc-melting/annealing and mechanical alloying/annealing techniques; (2) examine their physico-chemical characteristics (morphology, composition); (3) determine the hydrogen absorption/desorption behavior (pressure-composition isotherms as a function of temperature); and (4) evaluate their performance characteristics as hydride electrodes (charge/discharge, capacity retention, cycle life, high rate capability). The work carried out on representative AB(sub 5) and AB(sub 2) type modified alloys (by partial substitution or with small additives of other elements) is presented. The purpose of the modification was to optimize the thermodynamics and kinetics of the hydriding/dehydriding reactions and enhance the stabilities of the alloys for the desired battery applications. The results of our collaboration, to date, demonstrate that (1) alloys prepared by arc melting/annealing and mechanical alloying/annealing techniques exhibit similar morphology, composition and hydriding/dehydriding characteristics; (2) alloys with the appropriate small amounts of substituent or additive elements: (1) retain the single phase structure, (2) improve the hydriding/dehydriding reactions for the battery applications, and (3) enhance the stability in the battery environment; and (3) the AB(sub 2) type alloys exhibit higher energy densities than the AB(sub 5) type alloys but the state-of-the-art, commercialized batteries are predominantly manufactured using Ab(sub 5) type alloys.

Anani, Anaba; Visintin, Arnaldo; Petrov, Konstantin; Srinivasan, Supramaniam; Reilly, James J.; Johnson, John R.; Schwarz, Ricardo B.; Desch, Paul B.

1993-01-01

283

Antiferromagnetic behaviour of Tb2Al alloy  

NASA Astrophysics Data System (ADS)

The structural, thermal and magnetic properties ol the Tb2Al alloy have been investigated by AC/DC magnetic susceptibility, specific heat, X-ray and neutron diffraction measurements. DC and AC-magnetic susceptibility results are consistent with an AFM order at TN = 52 K. The specific heat data show a lambda anomaly associated to the magnetic transition with a peak at 52 K (cord = 99 J/molTbK). The analysis of thermodiffractograms of neutron diffraction patterns indicates that, below the ordering temperature, the magnetic reflections can be indexed with a commensurate lattice related to the crystallographic cell (Pmna) by a propagation vector k = (1/2, 1/2, 1/2). The results are compared with those reported for other magnetic rare earth alloys of R2Al-type (with R = Nd, Gd and Dy).

Rojas, D. P.; Andr, G.; Rodrguez Fernndez, J.; Snchez Marcos, J.; Fernndez Barqun, L.; Echevarria, C.

2011-10-01

284

Optical response of noble metal alloy nanostructures  

NASA Astrophysics Data System (ADS)

The optical response, stability, and cost-effectiveness of individual noble metals can be improved by combining them to form alloy nanostructures. The present work reveals the influence of shape, size, and metal type on the optical response of alloy nanoparticles using discrete dipole approximation (DDA) simulations. It is found that sharp corner nanostructures show enhanced plasmonic properties in comparison to rounded counterpart. For all the three shapes, viz., nanocubes, rectangular, and nanobar particles, the increase in length resulted in redshifts of the longitudinal plasmon resonance alongwith enhancement in the scattering yield as well as relative efficiency parameters except for nanocubes of edge length 120 nm. The effect of size on full width at half maxima (FWHM) has also been studied and found to be maximal for nanocubes in comparison to other nanostructures.

Bansal, Amit; Verma, S. S.

2015-01-01

285

Advanced ordered intermetallic alloy deployment  

SciTech Connect

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 compositions 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.

Liu, C.T.; Maziasz, P.J.; Easton, D.S. [Oak Ridge National Lab., TN (United States)

1997-04-01

286

Corrosion performance of structural alloys.  

SciTech Connect

Component reliability and long-term trouble-free performance of structural materials are essential in power-generating and gasification processes that utilize coal as a feedstock. During combustion and conversion of coal, the environments encompass a wide range of oxygen partial pressures, from excess-air conditions in conventional boilers to air-deficient conditions in 10W-NO{sub x} and gasification systems. Apart from the environmental aspects of the effluent from coal combustion and conversion, one concern from the systems standpoint is the aggressiveness of the gaseous/deposit environment toward structural components such as waterwall tubes, steam superheaters, syngas coolers, and hot-gas filters. The corrosion tests in the program described in this paper address the individual and combined effects of oxygen, sulfur, and chlorine on the corrosion response of several ASME-coded and noncoded structural alloys that were exposed to air-deficient and excess-air environments typical of coal-combustion and gasification processes. Data in this paper address the effects of preoxidation on the subsequent corrosion performance of structural materials such as 9Cr-1Mo ferritic steel, Type 347 austenitic stainless steel, Alloys 800, 825, 625, 214, Hastelloy X, and iron aluminide when exposed at 650 C to various mixed-gas environments with and without HCI. Results are presented for scaling kinetics, microstructural characteristics of corrosion products, detailed evaluations of near-surface regions of the exposed specimens, gains in our mechanistic understanding of the roles of S and Cl in the corrosion process, and the effect of preoxidation on subsequent corrosion.

Natesan, K.

1999-07-15

287

Hydrogen tolerance of a Ti3Al-based alloy  

NASA Technical Reports Server (NTRS)

The Ti-24Al-11Nb (Ti-24-11) alloy heat-treated to the fine basketweave microstructure was shown previously to be hydrogen-tolerant. In order to assess its limit of hydrogen tolerance, the tensile, creep, fracture toughness, and sustained-load crack growth behaviors of this alloy were studied as a function of hydrogen content. The mechanical test results indicated that the fine basketweave microstructure was tolerant to hydride embrittlement for hydrogen contents up to about 1500 wppm. On the other hand, hydrogen charging experiments indicated that the Ti-24-11 alloy was severely cracked and pulverized under zero load when the hydrogen content exceeded 3000 wppm. X-ray diffraction results revealed that the dichotomous behaviors might be due to the formation of face-centered cubic (fcc) delta-type hydrides at higher hydrogen contents but face-centered tetragonal (fct) gamma-type hydrides at lower hydrogen contents.

Chan, Kwai S.

1993-01-01

288

The effect of tensile stress on hydrogen diffusion in metal alloys  

NASA Technical Reports Server (NTRS)

The effect of tensile stress on hydrogen diffusion has been determined for Type 303 stainless steel, A286 CRES, and Waspaloy and IN100 nickel-base alloys. It was found that hydrogen diffusion coefficients are not significantly affected by stress, while the hydrogen permeabilities are greatly affected in Type 303 stainless steel and A286 CRES (iron-based alloys), but are affected little in Waspaloy (nickel-base) and not affected in all in IN100 (nickel base). These observations might be taken as an indication that hydrogen permeabilities are affected by stress in iron-based alloys, but only slightly affected in nickel-based alloys. However, it is too early to make such a generalization based on the study of only these four alloys.

Danford, M. D.

1992-01-01

289

Low modulus Ti-Nb-Hf alloy for biomedical applications.  

PubMed

?-Type titanium alloys with a low elastic modulus are a potential strategy to reduce stress shielding effect and to enhance bone remodeling in implants used to substitute failed hard tissue. For biomaterial application, investigation on the mechanical behavior, the corrosion resistance and the cell response is required. The new Ti25Nb16Hf alloy was studied before and after 95% cold rolling (95% C.R.). The mechanical properties were determined by tensile testing and its corrosion behavior was analyzed by potentiostatic equipment in Hank's solution at 37C. The cell response was studied by means of cytotoxicity evaluation, cell adhesion and proliferation measurements. The stress-strain curves showed the lowest elastic modulus (42GPa) in the cold worked alloy and high tensile strength, similar to that of Ti6Al4V. The new alloy exhibited better corrosion resistance in terms of open circuit potential (EOCP), but was similar in terms of corrosion current density (iCORR) compared to Ti grade II. Cytotoxicity studies revealed that the chemical composition of the alloy does not induce cytotoxic activity. Cell studies in the new alloy showed a lower adhesion and a higher proliferation compared to Ti grade II presenting, therefore, mechanical features similar to those of human cortical bone and, simultaneously, a good cell response. PMID:25063170

Gonzlez, M; Pea, J; Gil, F J; Manero, J M

2014-09-01

290

New Theoretical Technique Developed for Predicting the Stability of Alloys  

NASA Technical Reports Server (NTRS)

When alloys are being designed for aeronautical and other applications, a substantial experimental effort is necessary to make incremental changes in the desired alloy properties. A scheme to narrow the field to the most promising candidates would substantially reduce the high cost of this experimental screening. Such a method for determining alloy properties, called the BFS (Bozzolo, Ferrante, and Smith) method, has been developed at the NASA Lewis Research Center. This method was used to calculate the thermal stability and mechanical strength of 200 alloys of Ni3Al, with Cu and Au impurities forming ternary and quaternary compounds. With recent advances in the method, almost any metallic impurity and crystal structure can be addressed. In addition, thermal effects can be addressed with Monte Carlo techniques. At present, an experimental program is in progress to verify these results. The method identified a small number of the most promising candidates from the 200 alloys with the largest negative heat of formation and the highest bulk modulus. This calculation required only 5 min of CPU time on a VAX computer. It is clear that semi-empirical methods have achieved the level of development and reliability to warrant examining this new approach to the problem of alloy design. The present work was meant to demonstrate, perhaps in a rather simple way, this power. This type of application of atomistic simulation methods can narrow the gap and improve the feedback between theoretical predictions and laboratory experimentation.

1996-01-01

291

Filler metal alloy for welding cast nickel aluminide alloys  

DOEpatents

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.

Santella, Michael L. (Knoxville, TN); Sikka, Vinod K. (Oak Ridge, TN)

1998-01-01

292

Using the method of positron annihilation for detecting defects in structural alloys caused by fatigue  

SciTech Connect

This paper examines the possibilities of using the method ofpositron annihilation for detecting fatigue defects in structural alloys with various types of crystal structure. The parameter of the positron annihilation process most suitable for the inspection was determined.

Arefev, K.P.; Boev, O.V.; Chernitsyn, A.I.; Polukhin, Y.E.; Vordb'ev, S.A.

1986-12-01

293

Two phase titanium aluminide alloy  

DOEpatents

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.

Deevi, Seetharama C. (Midlothian, VA); Liu, C. T. (Oak Ridge, TN)

2001-01-01

294

Magnetic properties of Sm-Fe(Ti)-C(N)/?-Fe alloys prepared by mechanical alloying  

NASA Astrophysics Data System (ADS)

Magnetic properties of Sm-Fe(Ti)-C(N)/alpha-Fe nanocomposite alloys prepared by mechanical alloying (MA) have been studied. The hysteresis loops of MA Sm12Fe74Ti7C7Ndelta, Sm10Fe76Ti7C7Ndelta and Sm19.0Fe66.7C14.3 (i.e. Sm20Fe70C15) made by different processes (annealing, nitriding and re-milling) were measured at the applied magnetic fields with different dH/dt at 400, 350 and 295 K. The main phase with hard magnetic properties is of TbCu7-type. These three alloys have different behaviours of magnetization processes when the magnetic fields with dH/dt = 31.6 and 94.7 MA ms-1 are applied. The magnetic viscosity Sv of Sm12Fe74Ti7C7Ndelta, Sm10Fe76Ti7C7Ndelta and Sm20Fe70C15 is determined from hysteresis loops measured for different dH/dt at various temperatures. The magnetic viscosity Sv in the Sm-Fe(Ti)-C(N)/alpha-Fe alloys is approximately proportional to the coercive field iHc at the measuring temperature.

Geng, Dian-yu; Zhang, Zhi-dong; Liu, Wei; Zhao, Xin-guo; Yu, Ming-hui; Ren, Wei-jun; Xiao, Qun-feng; Grssinger, R.; Hauser, R.

2003-02-01

295

Salt corrosion of titanium alloys  

Microsoft Academic Search

1.The long-term strength (1000 h) of commercial titanium alloys does not decrease under the influence of a film of NaCl at temperatures of 250 or lower.2.With increasing testing temperatures the susceptibility of the alloys to salt increases.3.Natural sea salt is more corrosive than NaCl at temperatures of 250 and higher.4.The corrosion resistance of titanium alloys in contact with salt depends

V. P. Batrakov; L. N. Pivovarova; L. V. Zakharova

1974-01-01

296

Pareto-optimal alloys  

NASA Astrophysics Data System (ADS)

Large databases that can be used in the search for new materials with specific properties remain an elusive goal in materials science. The problem is complicated by the fact that the optimal material for a given application is usually a compromise between a number of materials properties and the cost. In this letter we present a database consisting of the lattice parameters, bulk moduli, and heats of formation for over 64 000 ordered metallic alloys, which has been established by direct first-principles density-functional-theory calculations. Furthermore, we use a concept from economic theory, the Pareto-optimal set, to determine optimal alloy solutions for the compromise between low compressibility, high stability, and cost.

Bligaard, Thomas; Jhannesson, Gisli H.; Ruban, Andrei V.; Skriver, Hans L.; Jacobsen, Karsten W.; Nrskov, Jens K.

2003-12-01

297

Duct and cladding alloy  

DOEpatents

An austenitic alloy having good thermal stability and resistance to sodium corrosion at 700.degree. C. consists essentially of 35-45% nickel 7.5-14% chromium 0.8-3.2% molybdenum 0.3-1.0% silicon 0.2-1.0% manganese 0-0.1% zirconium 2.0-3.5% titanium 1.0-2.0% aluminum 0.02-0.1% carbon 0-0.01% boron and the balance iron.

Korenko, Michael K. (Rockville, MD)

1983-01-01

298

Nanocrystal dispersed amorphous alloys  

NASA Technical Reports Server (NTRS)

Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

2001-01-01

299

Shape memory alloy actuator  

DOEpatents

An actuator for cycling between first and second positions includes a first shaped memory alloy (SMA) leg, a second SMA leg. At least one heating/cooling device is thermally connected to at least one of the legs, each heating/cooling device capable of simultaneously heating one leg while cooling the other leg. The heating/cooling devices can include thermoelectric and/or thermoionic elements.

Varma, Venugopal K. (Knoxville, TN)

2001-01-01

300

Hydrogen tolerance of a Ti3AI-based alloy  

NASA Astrophysics Data System (ADS)

The Ti-24Al-llNb (Ti-24-11) alloy heat-treated to the fine basketweave microstructure was shown previously to be hydrogen-tolerant. In order to assess its limit of hydrogen tolerance, the tensile, creep, fracture toughness, and sustained-load crack growth behaviors of this alloy were studied as a function of hydrogen content. All test specimens were charged thermally with internal hydrogen and tested at 25 C and 600 C. Coupon specimens were used for developing the hydrogen-charging procedures and for studying compatibility of the alloy with high-temperature, high-pressure gaseous hydrogen. The mechanical test results indicated that the fine basketweave microstructure was tolerant to hydride embrittlement for hydrogen contents up to ?1500 wppm. On the other hand, hydrogen charging experiments indicated that the Ti-24-11 alloy was severely cracked and pulverized under zero load when the hydrogen content exceeded 3000 wppm. X-ray diffraction (XRD) results revealed that the dichotomous behaviors might be due to the formation of face-centered cubic (fee) ?-type hydrides at higher hydrogen contents but face-centered tetragonal (fct) ?-type hydrides at lower hydrogen contents. Thus, hydrogen embrittlement in the Ti-24-11 alloy with the fine basketweave microstructure depends on hydrogen content and the nature of hydrides formed.

Chan, Kwai S.

1993-05-01

301

Evaluation of a hydrogen resistant titanium aluminide alloy  

NASA Technical Reports Server (NTRS)

The Ti-24Al-11Nb (Ti-24-11) alloy heat treated to the fine basketweave microstructure was shown previously to be hydrogen tolerant. In order to assess its limit of hydrogen tolerance, the tensile, creep, fracture toughness, and sustained load crack growth behaviors of this alloy were studied as a function of hydrogen content. All test specimens were thermally charged with internal hydrogen and tested at 25 and 600 C. Coupon specimens were used for developing the hydrogen charging procedures and for studying compatibility of the alloy with high temperature, high pressure gaseous hydrogen. The mechanical test results indicated that the fine basketweave microstructure was tolerant to hydride embrittlement for hydrogen contents up to approximately 1500 wt. ppm, providing that the hydride formed was of the TiH2 type. On the other hand, hydrogen charging experiments indicated that the Ti-24-11 alloy was severely cracked and pulverized under zero load when the hydrogen content exceeded 3000 wt. ppm. X-ray diffraction results revealed that the dichotomous behaviors might be due to the formation of TiH(1.924) type hydrides at higher hydrogen contents. Thus, hydrogen embrittlement in the Ti-24-11 alloy with the fine basketweave microstructure depends on hydrogen content and the nature of the hydrides formed.

Chan, K. S.

1991-01-01

302

The electrical characteristics of silicon carbide alloyed with germanium  

E-print Network

The electrical characteristics of silicon carbide alloyed with germanium G. Katulkaa,* , K. Roea material for high power, high voltage applications, silicon carbide (SiC) would be more versatile without Ge. Other p-type substrates implanted with Ge that used chromium/nickel (Cr/Ni) metalization

Kolodzey, James

303

Recent development in aluminium alloys for aerospace applications  

Microsoft Academic Search

Driven by the increasing requirements from aircraft producers, Hoogovens Aluminium Rolled Products GmbH, together with Hoogovens Research & Development, has enhanced the property combinations of their aircraft materials. For these types of material, optimised processing routes as well as new alloy chemistries have been investigated. Whilst retaining the strength levels required by the aerospace industry, new processing routes offer major

A Heinz; A Haszler; C Keidel; S Moldenhauer; R Benedictus; W. S Miller

2000-01-01

304

Tensile and fatigue properties of two titanium alloys as candidate materials for fusion reactors  

NASA Astrophysics Data System (ADS)

Titanium alloys have been identified as candidate structural materials for the first wall, the blanket and the magnetic coil structures of fusion reactors. Titanium alloys are interesting materials because of their high specific strength and low elastic modulus, their low swelling tendency and their fast induced radioactivity decay. Other attractive properties are an excellent resistance to corrosion and good weldability, even in thick sections. Furthermore titanium alloys are suitable for components exposed to heat loads since they have a low thermal stress parameter. Titanium alloys with an ? structure are believed to have a good resistance against radiation embrittlement and ?+? alloys should possess the best tolerance to hydrogen embrittlement. Two classical industrially available alloys in the two families, the Ti5Al2.4Sn and the Ti6Al4V alloys have been used in this study. The tensile properties between room temperature and 450C are reported. A low cycle fatigue analysis has been performed under strain control at total strain ranges between 0.8% and 2% and at a temperature of 350C. The microstructure of both alloys was investigated before and after both types of deformation. Both alloys exhibit excellent mechanical properties comparable to or better than those of ferritic martensitic steels.

Marmy, P.; Leguey, T.; Belianov, I.; Victoria, M.

2000-12-01

305

Status of studies on high-temperature oxidation and quench behaviour of Zircaloy4 and E110 cladding alloys  

Microsoft Academic Search

SUMMARY This paper gives an overview on the status of knowledge of high-temperature oxidation of the two zirconium alloys Zircaloy-4 and E110 with special emphasis on results obtained during the SARNET period. The tin-bearing alloy Zircaloy-4 and the niobium-bearing alloy E110 are the materials for cladding and structures recently mainly used in pressurised water reactors of the Western type and

M. Steinbrck; J. Birchley; A. V. Goryachev; M. Grosse; T. J. Haste; Z. Hozer; A. E. Kisselev; V. I. Nalivaev; V. P. Semishkin; L. Sepold; J. Stuckert; N. Vr; M. S. Veshchunov

306

Army Air Force MMT production of 0. 65 to 0. 85 Ti and quad depleted uranium alloys  

Microsoft Academic Search

This report concerns the less than 50 ton production of U--(0.65-0.85) Ti and quad (0.50 Ti, 0.75 Zr, 0.75 Mo, 0.75 Nb) alloys. It is presented as three parts: casting of low carbon alloy ingots, rolling of U--0.7 Ti ingots, and solution heat treatment and aging of wrought U--0.75 Ti and U--0.75 quad type alloys. (DLC)

C. E. Polson; L. M. Levy; R. L. Schardt

1976-01-01

307

Approach towards full Heusler alloy based CPP-GMR: from Ag and non-magnetic Heusler to binary intermetallic spacers  

Microsoft Academic Search

Recently, it has been demonstrated that GMR response can be significantly enhanced by incorporating high spin polarization ferromagnetic (FM) full Heulser alloy into spin valve nano-structures. Experimental results for two types of non-magnetic spacers (i) elemental metal [1] and (ii) non-magnetic Heusler alloy spacers [2] deserve careful comparison. More practical (110) textured combination of Co2MnGe (CMG) and non-magnetic Heusler alloy

Oleg Mryasov; Sergey Faleev; S. V. Karthik

2011-01-01

308

Microstructural evolution in zirconium based alloys  

NASA Astrophysics Data System (ADS)

Zirconium alloys which exhibit practically all possible solid state phase transformations offer some unique opportunities for studying the fundamental aspects of phase transformations. The crystallographic features associated with the phase changes are much simpler in zirconium based systems, making them more suitable for providing a basic understanding of the relevant phenomena. Some of the important issues related to phase transformations research are identified and the manner, in which studies in zirconium alloys have contributed to the understanding of these issues, is discussed in this paper. Both the types of displacive transformations - shear-dominated and shuffle dominated - are encountered in zirconium alloys. The crystallography and the mechanism of such transformations are discussed, giving special reference to the morphological and sub-structural changes in zirconium martensites and to the fine particle and plate-shaped morphologies of the ?-phase. Morphological and crystallographical features of displacive and diffusional transformations have been compared. Several examples of mixed mode transformations, viz., the formation of ?-hydride phase, the active eutectoid decomposition and the formation of ordered ?-phases are cited and their respective mechanisms described.

Tewari, R.; Srivastava, D.; Dey, G. K.; Chakravarty, J. K.; Banerjee, S.

2008-12-01

309

Alloys by Microwave-Activated Hot Pressing  

NASA Astrophysics Data System (ADS)

The p-type Bi0.4Sb1.6Te3 alloys are prepared using a new method of mechanical alloying followed by microwave-activated hot pressing (MAHP). The effect of sintering temperature on the microstructure and thermoelectric properties of Bi0.4Sb1.6Te3 alloys is investigated. Compared with other sintering techniques, the MAHP process can be used to produce relatively compact bulk materials at lower sintering temperatures owing to its unique sintering mechanism. The grain size of the MAHP specimens increases gradually with the sintering temperature and a partially oriented lamellar structure can be formed in some regions of specimens obtained. The formation of the in situ-generated nano-phase is induced by the arcing effect of the MAHP process, which enhances the phonon scattering effect and decreases the lattice thermal conductivity. A minimum lattice thermal conductivity of 0.41 W/(mK) and a maximum figure of merit value of 1.04 are obtained at 100C for the MAHP specimen sintered at 325C. This technique may also be extended to other functional materials to obtain ultrafine microstructures at low sintering temperatures.

Yang, Fan; Fan, Xi An; Rong, Zhen Zhou; Cai, Xin Zhi; Li, Guang Qiang

2014-11-01

310

Welding of titanium alloy by Disk laser  

NASA Astrophysics Data System (ADS)

The following article describes results of investigations on influence of laser welding parameters on the weld shape, quality and mechanical properties of 2.0 mm thick butt joints of titanium alloy Ti6Al4V (Grade 5 according to ASTM B265) welded with a new generation disk laser TRUMPF TRUDISK 3302, emitting at 1030 nm, with maximum output power 3300 W at circular laser beam spot, characterized by laser beam divergence 8.0 mmmrad. The test butt joints of Ti6Al4V titanium alloy sheets were prepared as single square groove (I-type joint) and one-side laser welded without an additional material, at a flat position, using a specially designed system for shielding gas (purity 99.999%). The investigations at the initial stage were focused on detailed analysis of influence of the basic laser welding parameters such as laser power and welding speed on the shape and quality of single bead produced during bead-on-plate welding. Then the optimal parameters were chosen for laser welding of 2.0 mm thick butt joints of the titanium alloy Ti6Al4V. Edges of the titanium alloy sheets were melted in argon atmosphere by the laser beam focused on the top surface of butt joints. The test welded joints were investigated by visual inspection, metallographic examinations, hardness and micro-hardness measurements and mechanical tests such as tensile tests and bending tests. It was found that the welding mode is a keyhole welding and providing high quality of joints requires a special techniques and conditions of laser welding, as well as special gas shielding nozzles is required.

Lisiecki, Aleksander

2013-01-01

311

A comparison of hydrogen ingress behavior in alloys 625 and 716  

SciTech Connect

Microstructural heterogeneities in alloys provide trapping sites for diffusing hydrogen and so strongly affect the susceptibility of the alloys to hydrogen embrittlement (HE). These traps are able to be classified as reversible or irreversible, according to their energy for trapping hydrogen. Irreversible traps can be highly detrimental to the performance of an alloy in a hydrogen environment. So identification of the dominant types of irreversible traps is crucial to characterizing the susceptibility to HE. Hydrogen trapping has been studied previously for a wide range of alloys using a technique referred to as hydrogen ingress analysis by potentiostatic pulsing (HIAPP). The alloy is charged with hydrogen at a constant potential (E[sub c]) for a time (t[sub c]), after which the potential is stepped anodically, resulting in a current transient with a charge q[sub a]. For all the alloys studied to date, the transients could be analyzed in terms of a diffusion/trapping model involving a constant entry flux; that is, the rate of ingress was found to be controlled by diffusion under the influence of kinetically-limited entry. HIAPP has previously been applied to nickel-base alloys of age-hardened types (718 and 925) and work-hardened types (625 and C-276). In the present study, HIAPP was used to investigate hydrogen ingress in Custom Age 625 PLUS (UNS N07716), which was developed as an age-hardenable alternative to alloy 625. The hydrogen entry and trapping characteristics were obtained for alloy 716 and compared with those for alloy 615, with the objective of relating these characteristics to their HE susceptibilities.

Pound, B.G. (SRI International, Menlo Park, CA (United States). Materials Research Center)

1993-12-01

312

New package cooling technology using low melting point alloys  

Microsoft Academic Search

A novel package cooling technology concept using two kinds of inexpensive low-melting-point alloys is presented. One alloy is Bi-18.0Pb-11.6Sn-21.0In (in wt pct), with a melting point of 57 C; the other is Bi-17.3Sn-25.2In, with a melting point of 77 C. This type of package cooling techology may be extremely useful for high-power circuit packages which are only required to operate

Yoshitake Fukuoka; Masaru Ishizuka

1990-01-01

313

Aluminum and its light alloys  

NASA Technical Reports Server (NTRS)

Report is a summary of research work which has been done here and abroad on the constitution and mechanical properties of the various alloy systems with aluminum. The mechanical properties and compositions of commercial light alloys for casting, forging, or rolling, obtainable in this country are described.

Merica, Paul D

1920-01-01

314

Shape memory alloy thaw sensors  

DOEpatents

A sensor permanently indicates that it has been exposed to temperatures exceeding a critical temperature for a predetermined time period. An element of the sensor made from shape memory alloy changes shape when exposed, even temporarily, to temperatures above the Austenitic temperature of the shape memory alloy. The shape change of the SMA element causes the sensor to change between two readily distinguishable states.

Shahinpoor, Mohsen (Albuquerque, NM); Martinez, David R. (Albuquerque, NM)

1998-01-01

315

Oxidation-resistant nickel alloy  

SciTech Connect

Disclosed is an oxidation resilient nickel alloy containing chromium, tungsten and molybdenum in a critical relationship that provides a combination of engineering properties including a high degree of dynamic oxidation resistance and superior strength. The alloy is especially suited for service under severe conditions, for example, as components of gas turbine engines.

Klarstrom, D.L.

1984-10-09

316

Silicon Solar Cells with Front Hetero-Contact and Aluminum Alloy Back Junction: Preprint  

SciTech Connect

We prototype an alternative n-type monocrystalline silicon (c-Si) solar cell structure that utilizes an n/i-type hydrogenated amorphous silicon (a-Si:H) front hetero-contact and a back p-n junction formed by alloying aluminum (Al) with the n-type Si wafer.

Yuan, H.-C.; Page, M. R.; Iwaniczko, E.; Xu, Y.; Roybal, L.; Wang, Q.; Branz, H. M.; Meier, D. L.

2008-05-01

317

Surface and interfacial phenomena of liquid iron alloys  

NASA Astrophysics Data System (ADS)

Surface tension of a liquid steel and interfacial tension between a liquid steel and a liquid slag play an important role in iron and steelmaking processes as they are key parameters in the understanding of inclusion removal and slag emulsification. The ultimate goal of this work is to better understand the interfacial energies and phenomena that occur during actual steel processing. The effect of sulfur on the surface tension of Fe-30%Cr alloys was determined by a sessile drop technique at 1550C. Sulfur was found to be strongly surface active in liquid Fe-30%Cr alloy and the variation of surface tension of the alloy with sulfur activity is expressed as: g=1592-178ln1+145 asa s>21ppm The contact angles between liquid Fe-30%Cr-S alloys and alumina decreased significantly with increasing sulfur activity. The surface tension of Fe-Cr alloys decreased slightly with increasing Cr content. The contact angle of Fe-13% Cr on alumina increased by 6 and remained unchanged in the range between 13% and 30% Cr. The interfacial tensions of Fe-Cr alloys were determined with three different slags by a sessile drop technique combined with X-ray radiography. Silica and iron oxide additions to the CaO-Al 2O3 slag lead to a significant decrease in the interfacial tension. Chromium addition did not affect interacting force at the interface, which indicates that the interfacial structure between Fe-Cr alloy and the slag is identical to the one between Fe and the slag. Dynamic interfacial tension phenomena between Fe-Al and Fe-Ti alloys in contact with CaO-SiO2-Al2O3 (2:2:1 by weight) slag have been studied by X-ray radiography and by scanning electron microscopy. For Fe-Al alloys, dynamic interfacial tension phenomena were noticed at aluminum content as low as 0.25%. Significant spreading of the alloy interfacial turbulence and spontaneous emulsification were observed in experiments with a Fe-3.28% Al alloy. Generation of Marangoni flow is suggested at the steel-slag interface during reaction as the driving force for instability of interface. For Fe-Ti alloys, dynamic interfacial tension phenomena were observed over 5.8% Ti. Significant spreading of the alloy was observed by X-ray photography at Fe-11% Ti alloy. A less perturbed interface and a film-type of metal emulsification were observed in the quenched sample during reaction. The effect of CaF2, Al2O3 and Na 2O additions to CaO-SiO2 slag on the interfacial tension was determined at 1550C. CaF2 led to a significant decrease in the interfacial tension while the Na2O and Al2O 3 additions led to an increase in the interfacial tension. Carbon addition to mold slag that was in contact with 321 stainless steel led to a decrease in the interfacial tension. A correlation model was developed to predict the equilibrium interfacial tension between Fe-O alloys and an oxide slag. The formation energy difference of the slag was found to be a good linear relationship with the interaction coefficient from the Girifalco-Good's equation: F=0.89-0.0015DGDi The model calculations of interaction coefficient ( F ) and interfacial tension ( g ms) were validated with experimental data. (Abstract shortened by UMI.)

Chung, Yongsug

1999-11-01

318

SCC Initiation in Alloy 600 Heat Affected Zones Exposed to High Temperature Water  

SciTech Connect

Studies have shown that grain boundary chromium carbides improve the stress corrosion cracking (SCC) resistance of nickel based alloys exposed to high temperature, high purity water. However, thermal cycles from welding can significantly alter the microstructure of the base material near the fusion line. In particular, the heat of welding can solutionize grain boundary carbides and produce locally high residual stresses and strains, reducing the SCC resistance of the Alloy 600 type material in the heat affected zone (HAZ). Testing has shown that the SCC growth rate in Alloy 600 heat affected zone samples can be {approx}30x faster than observed in the Alloy 600 base material under identical testing conditions due to fewer intergranular chromium rich carbides and increased plastic strain in the HAZ [1, 2]. Stress corrosion crack initiation tests were conducted on Alloy 600 HAZ samples at 360 C in hydrogenated, deaerated water to determine if these microstructural differences significantly affect the SCC initiation resistance of Alloy 600 heat affected zones compared to the Alloy 600 base material. Alloy 600 to EN82H to Alloy 600 heat-affected-zone (HAZ) specimens where fabricated from an Alloy 600 to Alloy 600 narrow groove weld with EN82H filler metal. The approximate middle third of the specimen gauge region was EN82H such that each specimen had two HAZ regions. Tests were conducted with in-situ monitored smooth tensile specimens under a constant load, and a direct current electric potential drop was used for in-situ detection of SCC. Test results suggest that the SCC initiation resistance of Alloy 600 and its weld metal follows the following order: EN82H > Alloy 600 HAZ > Alloy 600. The high SCC initiation resistance observed to date in Alloy 600 heat affected zones compared to wrought Alloy 600 is unexpected based on the microstructure of HAZ versus wrought material and based on prior SCC growth rate studies. The observed behavior for the HAZ specimens is likely not related to differences in the environment, differences in surface stress/strain between the various specimen regions (weld, HAZ, wrought), differences in surface residual stress, or differences in the microstructure of the various specimen regions (weld, HAZ, wrought). The behavior may be related to differences in the creep behavior of the various weld regions or differences in the surface area of the various materials (weld, HAZ, wrought) exposed to high temperature water.

E Richey; DS Morton; RA Etien; GA Young; RB Bucinell

2006-11-03

319

Microstructural characterization of as-cast biocompatible Co-Cr-Mo alloys  

SciTech Connect

The microstructure of a cobalt-base alloy (Co-Cr-Mo) obtained by the investment casting process was studied. This alloy complies with the ASTM F75 standard and is widely used in the manufacturing of orthopedic implants because of its high strength, good corrosion resistance and excellent biocompatibility properties. This work focuses on the resulting microstructures arising from samples poured under industrial environment conditions, of three different Co-Cr-Mo alloys. For this purpose, we used: 1) an alloy built up from commercial purity constituents, 2) a remelted alloy and 3) a certified alloy for comparison. The characterization of the samples was achieved by using optical microscopy (OM) with a colorant etchant to identify the present phases and scanning electron microscopy (SE-SEM) and energy dispersion spectrometry (EDS) techniques for a better identification. In general the as-cast microstructure is a Co-fcc dendritic matrix with the presence of a secondary phase, such as the M{sub 23}C{sub 6} carbides precipitated at grain boundaries and interdendritic zones. These precipitates are the main strengthening mechanism in this type of alloys. Other minority phases were also reported and their presence could be linked to the cooling rate and the manufacturing process variables and environment. - Research Highlights: {yields}The solidification microstructure of an ASTM-F75 type alloy were studied. {yields}The alloys were poured under an industrial environment. {yields}Carbides and sigma phase identified by color metallography and scanning microscopy (SEM and EDS). {yields}Two carbide morphologies were detected 'blocky type' and 'pearlite type'. {yields}Minority phases were also detected.

Giacchi, J.V., E-mail: jgiacchi@exa.unicen.edu.ar [Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Av. Rivadavia 1917, C1033AAJ Buenos Aires (Argentina); Instituto de Fisica de Materiales Tandil (IFIMAT-FCE-CICPBA) Facultad de Ciencias Exactas, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pinto 399 B7000GHG Tandil (Argentina); Morando, C.N.; Fornaro, O. [Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Av. Rivadavia 1917, C1033AAJ Buenos Aires (Argentina); Instituto de Fisica de Materiales Tandil (IFIMAT-FCE-CICPBA) Facultad de Ciencias Exactas, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pinto 399 B7000GHG Tandil (Argentina); Palacio, H.A. [Comision de Investigaciones Cientificas de la Provincia de Buenos Aires (CICPBA), Calle 526 e/10 y 11 B1096APP La Plata (Argentina); Instituto de Fisica de Materiales Tandil (IFIMAT-FCE-CICPBA) Facultad de Ciencias Exactas, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pinto 399 B7000GHG Tandil (Argentina)

2011-01-15

320

a Study on the Fretting Fatigue Life of Zircaloy Alloys  

NASA Astrophysics Data System (ADS)

Studies on the strength and fatigue life of machines and structures have been conducted in accordance with the development of modern industries. In particular, fine and repetitive cyclic damage occurring in contact regions has been known to have an impact on fretting fatigue fractures. The main component of zircaloy alloy is Zr, and it possesses good mechanical characteristics at high temperatures. This alloy is used in the fuel rod material of nuclear power plants because of its excellent resistance. In this paper, the effect of the fretting damage on the fatigue behavior of the zircaloy alloy is studied. Further, various types of mechanical tests such as tension and plain fatigue tests are performed. Fretting fatigue tests are performed with a flat-flat contact configuration using a bridge-type contact pad and plate-type specimen. Through these experiments, it is found that the fretting fatigue strength decreases by about 80% as compared to the plain fatigue strength. Oblique cracks are observed in the initial stage of the fretting fatigue, in which damaged areas are found. These results can be used as the basic data for the structural integrity evaluation of corrosion-resisting alloys considering the fretting damages.

Kwon, Jae-Do; Park, Dae-Kyu; Woo, Seung-Wan; Chai, Young-Suck

321

General and localized corrosion of magnesium alloys: A critical review  

NASA Astrophysics Data System (ADS)

Magnesium (Mg) alloys as well as experimental alloys are emerging as light structural materials for current, new, and innovative applications. This paper describes the influence of the alloying elements and the different casting processes on the microstructure and performance of these alloys and corrosion. It gives a comprehensible approach for the resistance of these alloys to general, localized and metallurgically influenced corrosion, which are the main challenges for their use. Exposure to humid air with 65% relative humidity during 4 days gives 100-150 nm thickness. The film is amorphous and has an oxidation rate less than 0.01 m/y. The pH values between 8.5 and 11.5 correspond to a relatively protective oxide or hydroxide film; however above 11.5 a passive stable layer is observed. The poor corrosion resistance of many Mg alloys can be due to the internal galvanic corrosion caused by second phases or impurities. Agitation or any other means of destroying or preventing the formation of a protective film leads to increasing corrosion kinetics. The pH changes during pitting corrosion can come from two different reduction reactions: reduction of dissolved oxygen (O) and that of hydrogen (H) ions. Filiform corrosion was observed in the uncoated AZ31, while general corrosion mainly occurred in some deposition coated alloys. Crevice corrosion can probably be initiated due to the hydrolysis reaction. Exfoliation can be considered as a type of intergranular attack, and this is observed in unalloyed Mg above a critical chloride concentration.

Ghali, Edward; Dietzel, Wolfgang; Kainer, Karl-Ulrich

2004-02-01

322

Corrosion behavior of zinc-nickel alloy electrodeposited coatings  

SciTech Connect

Various types of zinc-electrocoated steel sheets are used to improve the durability of car bodies. Among these coatings, the Zn-Ni alloy has higher corrosion resistance than pure Zn, as well as better welding and painting properties. The corrosion mechanism of the Zn-Ni alloy has been investigated mainly on the basis of accelerated tests and electrochemical measurements. There are few data about long-term corrosion tests. In the present study, the behavior of unpainted Zn-Ni alloy coated steel was studied during 3 years of exposure in industrial and marine environments. Electrochemical impedance spectroscopy (EIS) and surface analysis (scanning electron microscopy [SEM] and Auger electron spectroscopy [AES]) were the experimental techniques used. Long-term atmospheric corrosion mechanism of Zn-Ni coatings was discussed and compared with that proposed based on short-term tests.

Fabri Miranda, F.J. [USIMINAS, Ipatinga, Minas Gerais (Brazil); Margarit, I.C.P.; Mattos, O.R.; Barcia, O.E. [UFRJ, Rio de Janeiro (Brazil); Wiart, R. [Univ. Pierre et M. Curie, Paris (France)

1999-08-01

323

Heat treatment in high Cr white cast iron Nb alloy  

NASA Astrophysics Data System (ADS)

Wear resistance of high Cr white cast irons can be improved by means of heat treatment. This type of cast iron alloy may present a microstructure with retained austenite. The amount of retained austenite changes with the applied heat treatment, which will have an influence on wear properties. The purpose of this work was to study the influence of several parameters such as quenching and tempering temperatures and subzero treatment in the wear performance of the high Cr white cast iron Nb alloy. In this way, the performance was evaluated using pin-on-disc abrasion test. The worn surface was examined by scanning electron microscopy, and the main wear mechanisms were identified. The microstructural characterization was also performed with carbide identification. This Fe alloy has proven to be good for applications in mining and alcohol-sugar industries.

Farah, A. F.; Crnkovic, O. R.; Canale, L. C. F.

2001-02-01

324

Behavior of high-performance alloys in sulfuric acid  

SciTech Connect

Sulfuric acid is an important reactant and by-product in the mining and metal extraction industries. Corrosion in sulfuric acid is dependent on both the concentration of the acid and the type of impurities present in the acid. The behavior of a variety of stainless steels and Ni-bse alloys is examined as a function of these factors. The range of acid concentration is divided into three zones, and the alloy performance is examined in each zone. In the lowest-concentration acids, the alloying elements of greatest benefit were Mo, Ni, and Cr, in that order. If oxidizing agents are present, however, both Cr and Mo are necessary for corrosion resistance. In the intermediate-concentration zone, Mo is beneficial as is also Cu. In the highest-concentration zone, Cr, Mo, Cu, and Si are shown to be beneficial. The effects of impurities, such as ferric, cupric, and nitrate ions, are examined in these various concentration zones.

Sridhar, N.

1988-03-01

325

Recrystallization behavior of cold-rolled Zr-1Nb alloy  

NASA Astrophysics Data System (ADS)

The recrystallization behavior of cold-rolled Zr-1Nb alloy was investigated by measuring the micro-Vickers hardness of the specimens annealed for various times. Different deformation reductions and annealing temperatures were coupled to study the effects of deformation and temperature on the recrystallization behavior of Zr-1Nb alloy. The results show that both large deformation reduction and high annealing temperature accelerate the recrystallization process. The microstructural evolution during recrystallization was characterized by optical microscope (OM) and transmission electron microscope (TEM) to correlate with the variation of Vickers hardness. The TEM observation also revealed the distribution of different types of Nb-containing precipitates during recrystallization. The Vickers hardness data were fitted by using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation to derive the activation energies for recrystallization, giving the corresponding recrystallization maps. This study provides useful guidelines for the processing of a broad family of zirconium alloys based on Zr-1Nb.

Tian, Hang; Wang, Xitao; Gong, Weijia; Zhou, Jun; Zhang, Hailong

2015-01-01

326

CO2 laser welding of magnesium alloys  

Microsoft Academic Search

Metallic alloys with a low mass density can be considered to be basic materials in aeronautic and automotive industry. Magnesium alloys have better properties than aluminum alloys in respect of their low density and high resistance to traction. The main problems of magnesium alloy welding are the inflammability, the crack formation and the appearance of porosity during the solidification. The

Mohammed Dhahri; Jean Eric Masse; J. F. Mathieu; Gerard Barreau; Michel L. Autric

2000-01-01

327

High-Alloy Materials for Offshore Applications  

Microsoft Academic Search

High-alloy materials possessing good corrosion resistance in hot, sour brines are being seriously considered for offshore applications. These alloys are available in a wide range of strength levels which can be attained by the methods of cold working or precipitation hardening. Results of testing INCONEL alloys 625 and 718 and INCOLOY alloys 825 and 925 for resistance to general corrosion,

T. F. Lemke; J. A. Harris

1983-01-01

328

Positron annihilation studies on the electronic structure of Ni1-xCux alloys  

NASA Astrophysics Data System (ADS)

The entire concentration range of ?-phase Ni1-xCux alloys has been studied by Angular Correlation and Positron Lifetime methods. The results show inapplicability of the Rigid Band Model to description of the electronic structure of this alloy. Linearity of annihilation rate ?(x) as well as of parameters of correlation curves leading to linearity of s-like and d-like electron numbers with x confirms our earlier expectation as to the character of annihilation parameters for split-band alloys with constant Fermi energy. On the ground of the present results and the previous ones for palladium alloys it was postulated that the behaviour of the bulk annihilation rate in binary alloys can predict which type of the electronic structure, split-band or VCA, is the appropriate one in the given case.

Debowska, E.; Rudzinska-Girulska, J.

1989-06-01

329

Inhibition of Corrosion of 3003 Aluminum Alloy in Ethylene Glycol-Water Solutions  

NASA Astrophysics Data System (ADS)

In this study, the inhibiting effects of four types of inhibitors, including gluconate, cinnamate, molybdate, and nitrate, on corrosion of a 3003 aluminum (Al) alloy were investigated in ethylene glycol-water solutions that simulate the automotive coolant by various electrochemical measurements. It was found that the tested inhibitors were effective to inhibit corrosion of 3003 Al alloy under both static and turbulent flow conditions. They all behave as anodic inhibitors, which inhibit the Al alloy corrosion by passivating Al alloy and decreasing its anodic current density. A turbulent flow of the solution decreases the corrosion resistance of Al alloy and the inhibiting effect of the inhibitors. The inhibiting effect of the inhibitors is ranked as: nitrate > cinnamate > gluconate > molybdate.

Liu, Y.; Cheng, Y. F.

2011-03-01

330

Deformation and fracture behavior of composite structured Ti-Nb-Al-Co(-Ni) alloys  

NASA Astrophysics Data System (ADS)

Tensile ductility of the Ti-based composites, which consist of a ?-Ti phase surrounded by ultrafine structured intermetallics, is tunable through the control of intermetallics. The two Ti-based alloys studied exhibit similar compressive yield strength (about 1000 MPa) and strain (about 35%-40%) but show a distinct difference in their tensile plasticity. The alloy Ti71.8Nb14.1Ni7.4Al6.7 fractures at the yield stress while the alloy Ti71.8Nb14.1Co7.4Al6.7 exhibits about 4.5% of tensile plastic deformation. To clarify the effect of microstructure on the deformation behavior of these alloys, tensile tests were carried out in the scanning electron microscope. It is shown that the distribution as well as the type of intermetallics affects the tensile ductility of the alloys.

Okulov, I. V.; Khn, U.; Marr, T.; Freudenberger, J.; Schultz, L.; Oertel, C.-G.; Skrotzki, W.; Eckert, J.

2014-02-01

331

A neutron diffraction and magnetization study of Heusler alloys containing Co and Zr, Hf, V or Nb  

Microsoft Academic Search

Neutron diffraction, x-ray diffraction, and saturation magnetization ; measurements have been made on a series of ferromagnetic alloys at the ; composition CoYZ, where Y is a group IVA or VA element and Z is a group ; IIIB or IVB element. The alloys are mainly ordered in the Heusler L2 type ; chemical structure, but some show the presence

K. R. A. Ziebeck; P. J. Webster

1974-01-01

332

Microstructures in friction-stir welded dissimilar magnesium alloys and magnesium alloys to 6061-T6 aluminum alloy  

Microsoft Academic Search

Wrought Mg alloy AZ31B-H24 and semisolid-cast Mg alloy AZ91D (approximately 3% primary solid fraction) were friction-stir welded to Al alloy 6061-T6. Semisolid-cast (approximately 3% and approximately 20% primary solid fractions) Mg alloys AZ91D and AM60B were also joined using the same technique, with AZ91D on the advancing side. Numerous welds were made with the Mg alloys and the 6061-T6 Al

A. C Somasekharan; L. E Murr

2004-01-01

333

Mechanisms of deformation in gum metal TNTZ-O and TNTZ titanium alloys: A comparative study on the oxygen influence  

E-print Network

Mechanisms of deformation in gum metal TNTZ-O and TNTZ titanium alloys: A comparative study) and gum metal Ti­23Nb­0.7Ta­2Zr­1.2O (TNTZ-O) alloys were synthesized by cold crucible levitation melting-type Ti-based alloys, the multifunctional Ti­23Nb­0.7Ta­2Zr­1.2O alloy composition (mol.%), called "gum

Boyer, Edmond

334

High-temperature ordered intermetallic alloys II; Proceedings of the Second Symposium, Boston, MA, Dec. 2-4, 1986  

NASA Technical Reports Server (NTRS)

The papers presented in this volume provide on overview of recent theoretical and experimental research in the field of high-temperature ordered intermetallic alloys. The papers are gouped under the following headings: ordering behavior and theory, microstructures, mechanical behavior, alloy design and microstructural control, and metallurgical properties. Specific topics discussed include antiphase domains, disordered films and the ductility of ordered alloys based on Ni3Al; kinetics and mechanics of formation of Al-Ni intermetallics; deformability improvements of L1(2)-type intermetallic compounds; B2 aluminides for high-temperature applications; and rapidly solidified binary TiAl alloys.

Stoloff, N. S. (editor); Koch, C. C. (editor); Liu, C. T. (editor); Izumi, O. (editor)

1987-01-01

335

Improving p-type doping efficiency in Al0.83Ga0.17N alloy substituted by nanoscale (AlN)5/(GaN)1 superlattice with MgGa-ON ?-codoping: Role of O-atom in GaN monolayer  

NASA Astrophysics Data System (ADS)

We calculate Mg-acceptor activation energy EA and investigate the influence of O-atom, occupied the Mg nearest-neighbor, on EA in nanoscale (AlN)5/(GaN)1 superlattice (SL), a substitution for Al0.83Ga0.17N disorder alloy, using first-principles calculations. We find that the N-atom bonded with Ga-atom is more easily substituted by O-atom and nMgGa-ON (n = 1-3) complexes are favorable and stable in the SL. The O-atom plays a dominant role in reducing EA. The shorter the Mg-O bond is, the smaller the EA is. The Mg-acceptor activation energy can be reduced significantly by nMgGa-ON ?-codoping. Our calculated EA for 2MgGa-ON is 0.21 eV, and can be further reduced to 0.13 eV for 3MgGa-ON, which results in a high hole concentration in the order of 1020 cm-3 at room temperature in (AlN)5/(GaN)1 SL. Our results prove that nMgGa-ON (n = 2,3) ?-codoping in AlN/GaN SL with ultrathin GaN-layer is an effective way to improve p-type doping efficiency in Al-rich AlGaN.

Zhong, Hong-xia; Shi, Jun-jie; Zhang, Min; Jiang, Xin-he; Huang, Pu; Ding, Yi-min

2015-01-01

336

Fatigue of die cast zinc alloys  

SciTech Connect

The rotating bending fatigue limit of die cast zinc alloy 2, alloy 3, alloy 5, AcuZinc 5, and ZA-8 were determined as a part of an on-going program by ILZRO into the mechanical properties of die cast zinc. The stress-life (S-N) curves of alloys 3, 5, AcuZinc 5, and ZA-8 were determined previously. This presentation reports the results of the S-N curve for Alloy 2 and the calculated fatigue limits for all five alloys. During the previous stress-life testing, the samples were stopped at 10 million cycles and the fatigue limit for alloy 3, alloy 5, and AcuZinc 5 appeared to be higher and the fatigue limit for ZA-8 appeared to be lower than the values reported in the literature. This was further investigated in alloy 5 and ZA-8 by testing continuous cast bulk alloy 5 and ZA-8.

Schrems, K.K.; Dogan, O.N.; Goodwin, F.E. (International Lead Zinc Research Organization, Inc.)

2006-04-01

337

B Alloy Melt  

NASA Astrophysics Data System (ADS)

The solidification of undercooled Ni-4.5 wt pct B alloy melt was investigated by using the glass fluxing technique. The alloy melt was undercooled up to ? T p ~ 245 K (245 C), where a mixture of ?-Ni dendrite, Ni3B dendrite, rod eutectic, and precipitates was obtained. If ? T p < 175 K 10 K (175 C 10 C), the solidification pathway was found as primary transformation and eutectic transformation (L ? Ni3B and L ? Ni/Ni3B); if ? T p ? 175 K 10 K (175 C 10 C), the pathway was found as metastable eutectic transformation, metastable phase decomposition, and residual liquid solidification (L ? Ni/Ni23B6, Ni23B6 ? Ni/Ni3B, and Lr ? Ni/Ni3B). A high-speed video system was adopted to observe the solidification front of each transformation. It showed that for residual liquid solidification, the solidification front velocity is the same magnitude as that for eutectic transformation, but is an order of magnitude larger than for metastable eutectic transformation, which confirms the reaction as Lr ? Ni/Ni3B; it also showed that this velocity decreases with increasing ? T r, which can be explained by reduction of the residual liquid fraction and decrease of Ni23B6 decomposition rate.

Liu, Feng; Xu, Junfeng; Zhang, Di; Jian, Zengyun

2014-10-01

338

High performance alloy electroforming  

NASA Technical Reports Server (NTRS)

Electroformed copper and nickel are used in structural applications for advanced propellant combustion chambers. An improved process has been developed by Bell Aerospace Textron, Inc. wherein electroformed nickel-manganese alloy has demonstrated superior mechanical and thermal stability when compared to previously reported deposits from known nickel plating processes. Solution chemistry and parametric operating procedures are now established and material property data is established for deposition of thick, large complex shapes such as the Space Shuttle Main Engine. The critical operating variables are those governing the ratio of codeposited nickel and manganese. The deposition uniformity which in turn affects the manganese concentration distribution is affected by solution resistance and geometric effects as well as solution agitation. The manganese concentration in the deposit must be between 2000 and 3000 ppm for optimum physical properties to be realized. The study also includes data regarding deposition procedures for achieving excellent bond strength at an interface with copper, nickel-manganese or INCONEL 718. Applications for this electroformed material include fabrication of complex or re-entry shapes which would be difficult or impossible to form from high strength alloys such as INCONEL 718.

Malone, G. A.; Winkelman, D. M.

1989-01-01

339

Evaluation of surface modifications for oxidation protection of vanadium-base alloys in helium-cooled blanket designs  

NASA Astrophysics Data System (ADS)

Vanadium-base alloys are currently being considered for application to high-temperature helium-cooled fusion reactor blanket designs. A major drawback is their known sensitivity to low levels of oxidizing impurities that would normally be present as water vapor in the helium coolant gas. Although baseline data on the oxidation resistance of vanadium alloys are lacking, protection of vanadium alloy surfaces exposed to the helium coolant will probably be necessary for contiuous blanket operation at temperatures above 875 K. Surface alloying of vanadium-base alloys appears to be a feasible method of creating an oxidation-resistant surface. To examine this approach, a series of V-15Cr-5Ti alloy sheet specimens was surface alloyed with chromium. Oxidation tests were then conducted in flowing helium containing up to 100 vppm H 2O. Temperatures up to 925 K and times up to 1000 h were utilized. Control samples of unmodified V-15Cr-5Ti and a Type 316 stainless steel were also included. Significant reductions in oxygen pickup were observed with surface-alloyed specimens. These results suggest that surface alloying techniques offer great promise for protecting vanadium alloy surfaces against oxidation at blanket operating temperatures.

Tobin, A.; Busch, G.

1986-11-01

340

Fatigue performance and cyto-toxicity of low rigidity titanium alloy, Ti-29Nb-13Ta-4.6Zr.  

PubMed

A beta type titanium alloy, Ti-29Nb-13Ta-4.6Zr, was newly designed and developed for biomedical applications. The new alloy contains non-toxic elements such as Nb, Ta, and Zr. In the present study, phases that appeared in the new alloy through various aging treatments were characterized by hardness tests and microstructural observations in order to identify the phase transformation. Fatigue properties of the new alloy were investigated. Young's modulus and cyto-toxicity of the new alloy were also evaluated. Precipitated phases distribute homogeneously over the whole specimen, and they are alpha phase, a small amount of omega phase, and beta phase when the new alloys are subjected to aging treatment at 673K for 259.2ks after solution treatment at 1063K for 3.6ks. The fatigue strength of the new alloy subjected to aging at 673K for 259.2ks after solution treatment at 1063K for 3.6ks is much better than when subjected to other aging treatments. In this case, the fatigue limit is around 700MPa. Young's modulus of the new alloy is much smaller than that of Ti-6Al-4V ELI. The cyto-toxicity of the new alloy is equivalent to that of pure Ti. Therefore, it is proposed that the new alloy, Ti-29Nb-13Ta-4.6Zr, will be of considerable use in biomedical applications. PMID:12711513

Niinomi, Mitsuo

2003-07-01

341

New Amorphous Silicon Alloy Systems  

NASA Astrophysics Data System (ADS)

The properties of hydrogenated amorphous silicon (a-Si:H) have been modified by alloying with Al, Ga and S respectively. The Al and Ga alloys are in effect quaternary alloys as they were fabricated in a carbon-rich discharge. The alloys were prepared by the plasma assisted chemical vapor deposition (PACVD) method. This method has several advantages, the major one being the relatively low defect densities of the resulting materials. The PACVD system used to grow the alloy films was designed and constructed in the laboratory. It was first tested with known (a-Si:H and a-Si:As:H) materials. Thus, it was established that device quality alloy films could be grown with the home-made PACVD setup. The chemical composition of the alloys was characterized by secondary ion mass spectrometry (SIMS), and electron probe microanalysis (EPMA). The homogeneous nature of hydrogen distribution in the alloys was established by SIMS depth profile analysis. A quantitative analysis of the bulk elemental content was carried out by EPMA. The analysis indicated that the alloying element was incorporated in the films more efficiently at low input gas concentrations than at the higher concentrations. A topological model was proposed to explain the observed behavior. The optical energy gap of the alloys could be varied in the 0.90 to 1.92 eV range. The Al and Ga alloys were low band gap materials, whereas alloying with S had the effect of widening the energy gap. It was observed that although the Si-Al and Si-Ga alloys contained significant amounts of C and H, the magnitude of the energy gap was determined by the metallic component. The various trends in optical properties could be related to the binding characteristics of the respective alloy systems. A quantitative explanation of the results was provided by White's tight binding model. The dark conductivity-temperature dependence of the alloys was examined. A linear dependence was observed for the Al and Ga systems. Electronic conduction in the S-alloys appeared to proceed by a two step mechanism. The thermal activation energies for the high Al content and S-alloys were close to half the band gap value. The photoresponse of the films was determined from the light to dark conductivity ratio. The best photoresponse (sigma_ {L}/sigma_{D} = 4 times 10^2) was obtained for the Si-S alloys showing that they are promising electrode materials for solar cell application. A single unit photovoltaic electrolyzer was constructed by combining a-Si:H solar cells with an electrolysis cell. Several different configurations ((PIN), (PIN)^2 , and (PIN)^3) of the solar cells were tested. Both electric power and chemical energy (H_2) could be simultaneously drawn from the electrolyzer.

Kapur, Mridula N.

1990-01-01

342

Alloys of titanium with refaractory elements  

Microsoft Academic Search

1.We investigated the mechanical properties, structure, and phase composition of binary alloys with up to 30% Mo, V, and Cr, and up to 60% Nb, and ternary and more complex alloys with up to 40% refractory metals Mo, Nb, V, and Cr.2.Alloys with a high concentration of alloying elements (3040%) have a lower plasticity than a and a+ alloys.3.Most of

O. P. Solonina; N. M. Ulyakova

1973-01-01

343

Heat storage in alloy transformations  

NASA Technical Reports Server (NTRS)

The feasibility of using metal alloys as thermal energy storage media was investigated. The elements selected as candidate media were limited to aluminum, copper, magnesium, silicon, zinc, calcium, and phosphorus on the basis of low cost and latent heat of transformation. Several new eutectic alloys and ternary intermetallic phases were determined. A new method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation. The method and apparatus are discussed and the experimental results are presented for aluminum and two aluminum-eutectic alloys. Candidate materials were evaluated to determine suitable materials for containment of the metal alloys. Graphite was used to contain the alloys during the volume change measurements. Silicon carbide was identified as a promising containment material and surface-coated iron alloys were also evaluated. System considerations that are pertinent if alloy eutectics are used as thermal energy storage media are discussed. Potential applications to solar receivers and industrial furnaces are illustrated schematically.

Birchenall, C. E.

1980-01-01

344

Microstructural characterization of low and high carbon CoCrMo alloy nanoparticles produced by mechanical milling  

NASA Astrophysics Data System (ADS)

CoCrMo alloys are utilised as the main material in hip prostheses. The link between this type of hip prosthesis and chronic pain remains unclear. Studies suggest that wear debris generated in-vivo may be related to post-operative complications such as inflammation. These alloys can contain different amounts of carbon, which improves the mechanical properties of the alloy. However, the formation of carbides could become sites that initiate corrosion, releasing ions and/or particles into the human body. This study analysed the mechanical milling of alloys containing both high and low carbon levels in relevant biological media, as an alternative route to generate wear debris. The results show that low carbon alloys produce significantly more nanoparticles than high carbon alloys. During the milling process, strain induces an fcc to hcp phase transformation. Evidence for cobalt and molybdenum dissolution in the presence of serum was confirmed by ICP-MS and TEM EDX techniques.

Simoes, T. A.; Goode, A. E.; Porter, A. E.; Ryan, M. P.; Milne, S. J.; Brown, A. P.; Brydson, R. M. D.

2014-06-01

345

Zirconium alloy E635 as a material for fuel rod cladding and other components of VVER and RBMK cores  

SciTech Connect

Data are given on Zr alloy E635 (Zr-1.2Sn-1Nb-0.4Fe), developed in Russia as a fuel rod cladding and other component material for use in cores of VVER and RBMK types. The alloy is much superior to binary alloys with 1.0 and 2.5% Nb and Zircaloys in terms of its resistance to irradiation-induced creep and growth and nodular corrosion. The creep rate of the alloy is slightly dependent on irradiation temperature, stress, neutron fluence, and neutron density. The alloy is subject to substantial irradiation hardening while retaining its high-percent elongation. Corrosion, creep, and growth resistances are slightly dependent on the structure of components (alloy, final product). Based on the previously studied influence of impurities, structure, heat treatment, and working schedules, the technological processes were designed and mastered commercially for fabrication of tubes, bars, strips, and fuel rod claddings from this alloy. Components are produced commercially. Fuel assemblies with fuel rods clad in the E635 alloy were successfully tested in the RBMK reactor at the Leningrad NPP as well as in experimental reactors under VVER-1000 conditions. Today, the E635 alloy is recommended as a promising material for use in cores of VVER-1000 and VVER of new generations as well as RBMK-type reactors having a longer fuel cycle.

Nikulina, A.V.; Markelov, V.A.; Peregud, M.M. [A.A. Bochvar All-Russia Scientific Research Inst. of Inorganic Materials, Moscow (Russian Federation)] [and others

1996-12-31

346

Dendritic Alloy Solidification Experiment (DASE)  

NASA Technical Reports Server (NTRS)

A space experiment, and supporting ground-based research, is proposed to study the microstructural evolution in free dendritic growth from a supercooled melt of the transparent model alloy succinonitrile-acetone (SCN-ACE). The research is relevant to equiaxed solidification of metal alloy castings. The microgravity experiment will establish a benchmark for testing of equiaxed dendritic growth theories, scaling laws, and models in the presence of purely diffusive, coupled heat and solute transport, without the complicating influences of melt convection. The specific objectives are to: determine the selection of the dendrite tip operating state, i.e. the growth velocity and tip radius, for free dendritic growth of succinonitrile-acetone alloys; determine the growth morphology and sidebranching behavior for freely grown alloy dendrites; determine the effects of the thermal/solutal interactions in the growth of an assemblage of equiaxed alloy crystals; determine the effects of melt convection on the free growth of alloy dendrites; measure the surface tension anisotropy strength of succinon itrile -acetone alloys establish a theoretical and modeling framework for the experiments. Microgravity experiments on equiaxed dendritic growth of alloy dendrites have not been performed in the past. The proposed experiment builds on the Isothermal Dendritic Growth Experiment (IDGE) of Glicksman and coworkers, which focused on the steady growth of a single crystal from pure supercooled melts (succinonitrile and pivalic acid). It also extends the Equiaxed Dendritic Solidification Experiment (EDSE) of the present investigators, which is concerned with the interactions and transients arising in the growth of an assemblage of equiaxed crystals (succinonitrile). However, these experiments with pure substances are not able to address the issues related to coupled heat and solute transport in growth of alloy dendrites.

Beckermann, C.; Karma, A.; Steinbach, I.; deGroh, H. C., III

2001-01-01

347

Nucleation of shear bands in amorphous alloys  

PubMed Central

The initiation and propagation of shear bands is an important mode of localized inhomogeneous deformation that occurs in a wide range of materials. In metallic glasses, shear band development is considered to center on a structural heterogeneity, a shear transformation zone that evolves into a rapidly propagating shear band under a shear stress above a threshold. Deformation by shear bands is a nucleation-controlled process, but the initiation process is unclear. Here we use nanoindentation to probe shear band nucleation during loading by measuring the first pop-in event in the loaddepth curve which is demonstrated to be associated with shear band formation. We analyze a large number of independent measurements on four different bulk metallic glasses (BMGs) alloys and reveal the operation of a bimodal distribution of the first pop-in loads that are associated with different shear band nucleation sites that operate at different stress levels below the glass transition temperature, Tg. The nucleation kinetics, the nucleation barriers, and the density for each site type have been determined. The discovery of multiple shear band nucleation sites challenges the current view of nucleation at a single type of site and offers opportunities for controlling the ductility of BMG alloys. PMID:24594599

Perepezko, John H.; Imhoff, Seth D.; Chen, Ming-Wei; Wang, Jun-Qiang; Gonzalez, Sergio

2014-01-01

348

Nucleation of shear bands in amorphous alloys.  

PubMed

The initiation and propagation of shear bands is an important mode of localized inhomogeneous deformation that occurs in a wide range of materials. In metallic glasses, shear band development is considered to center on a structural heterogeneity, a shear transformation zone that evolves into a rapidly propagating shear band under a shear stress above a threshold. Deformation by shear bands is a nucleation-controlled process, but the initiation process is unclear. Here we use nanoindentation to probe shear band nucleation during loading by measuring the first pop-in event in the load-depth curve which is demonstrated to be associated with shear band formation. We analyze a large number of independent measurements on four different bulk metallic glasses (BMGs) alloys and reveal the operation of a bimodal distribution of the first pop-in loads that are associated with different shear band nucleation sites that operate at different stress levels below the glass transition temperature, Tg. The nucleation kinetics, the nucleation barriers, and the density for each site type have been determined. The discovery of multiple shear band nucleation sites challenges the current view of nucleation at a single type of site and offers opportunities for controlling the ductility of BMG alloys. PMID:24594599

Perepezko, John H; Imhoff, Seth D; Chen, Ming-Wei; Wang, Jun-Qiang; Gonzalez, Sergio

2014-03-18

349

Dynamic compressive behavior of Pr-Nd alloy at high strain rates and temperatures  

SciTech Connect

Based on compressive tests, static on 810 material test system and dynamic on the first compressive loading in split Hopkinson pressure bar (SHPB) tests for Pr-Nd alloy cylinder specimens at high strain rates and temperatures, this study determined a J-C type [G. R. Johnson and W. H. Cook, in Proceedings of Seventh International Symposium on Ballistics (The Hague, The Netherlands, 1983), pp. 541-547] compressive constitutive equation of Pr-Nd alloy. It was recorded by a high speed camera that the Pr-Nd alloy cylinder specimens fractured during the first compressive loading in SHPB tests at high strain rates and temperatures. From high speed camera images, the critical strains of the dynamic shearing instability for Pr-Nd alloy in SHPB tests were determined, which were consistent with that estimated by using Batra and Wei's dynamic shearing instability criterion [R. C. Batra and Z. G. Wei, Int. J. Impact Eng. 34, 448 (2007)] and the determined compressive constitutive equation of Pr-Nd alloy. The transmitted and reflected pulses of SHPB tests for Pr-Nd alloy cylinder specimens computed with the determined compressive constitutive equation of Pr-Nd alloy and Batra and Wei's dynamic shearing instability criterion could be consistent with the experimental data. The fractured Pr-Nd alloy cylinder specimens of compressive tests were investigated by using 3D supper depth digital microscope and scanning electron microscope.

Wang Huanran; Cai Canyuan; Chen Danian [Mechanics and Materials Science Research Center, Ningbo University, Ningbo, Zhejiang 315211 (China); Ma Dongfang [Mechanics and Materials Science Research Center, Ningbo University, Ningbo, Zhejiang 315211 (China); School of Civil Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000 (China)

2012-07-01

350

Some thoughts on alloy design  

SciTech Connect

This paper discusses some of the problems associated with attempts to use first principles in alloy design. We briefly summarize the role of microstructure on the properties of high temperature alloys and illustrate some of the microstructural features of conventional superalloys. We also describe how theory and experiment are converging toward some predictive capabilities for relating microstructure and composition using Ni-Al-Mo-X alloys as an example. Finally, this paper suggests that progress is being made in combining the results of condensed matter theory and experimental research.

Martin, P.L.; Williams, J.C.

1984-01-01

351

Modeling dissolution in aluminum alloys  

NASA Astrophysics Data System (ADS)

Aluminum and its alloys are used in many aspects of modern life, from soda cans and household foil to the automobiles and aircraft in which we travel. Aluminum alloy systems are characterized by good workability that enables these alloys to be economically rolled, extruded, or forged into useful shapes. Mechanical properties such as strength are altered significantly with cold working, annealing, precipitation-hardening, and/or heat-treatments. Heat-treatable aluminum alloys contain one or more soluble constituents such as copper, lithium, magnesium, silicon and zinc that individually, or with other elements, can form phases that strengthen the alloy. Microstructure development is highly dependent on all of the processing steps the alloy experiences. Ultimately, the macroscopic properties of the alloy depend strongly on the microstructure. Therefore, a quantitative understanding of the microstructural changes that occur during thermal and mechanical processing is fundamental to predicting alloy properties. In particular, the microstructure becomes more homogeneous and secondary phases are dissolved during thermal treatments. Robust physical models for the kinetics of particle dissolution are necessary to predict the most efficient thermal treatment. A general dissolution model for multi-component alloys has been developed using the front-tracking method to study the dissolution of precipitates in an aluminum alloy matrix. This technique is applicable to any alloy system, provided thermodynamic and diffusion data are available. Treatment of the precipitate interface is explored using two techniques: the immersed-boundary method and a new technique, termed here the "sharp-interface" method. The sharp-interface technique is based on a variation of the ghost fluid method and eliminates the need for corrective source terms in the characteristic equations. In addition, the sharp-interface method is shown to predict the dissolution behavior of precipitates in aluminum alloys when compared with published experimental results. The influence of inter-particle spacing is examined and shown to have a significant effect on dissolution kinetics. Finally, the impact of multiple particles of various sizes interacting in an aluminum matrix is investigated. It is shown that smaller particles dissolve faster, as expected, but influence the dissolution of larger particles through soft-impingement, even after the smaller particles have disappeared.

Durbin, Tracie Lee

2005-07-01

352

Carbide Formation and Dissolution in Biomedical Co-Cr-Mo Alloys with Different Carbon Contents during Solution Treatment  

NASA Astrophysics Data System (ADS)

The microstructures of as-cast and heat-treated biomedical Co-Cr-Mo (ASTM F75) alloys with four different carbon contents were investigated. The as-cast alloys were solution treated at 1473 to 1548 K for 0 to 43.2 ks. The precipitates in the matrix were electrolytically extracted from the as-cast and heat-treated alloys. An M23C6 type carbide and an intermetallic ? phase (Co(Cr,Mo)) were detected as precipitates in the as-cast Co-28Cr-6Mo-0.12C alloy; an M23C6 type carbide, a ? phase, an ? phase (M6C-M12C type carbide), and a ? phase (M2T3X type carbide with a ?-manganese structure) were detected in the as-cast Co-28Cr-6Mo-0.15C alloy; and an M23C6 type carbide and an ? phase were detected in the as-cast Co-28Cr-6Mo-0.25C and Co-28Cr-6Mo-0.35C alloys. After solution treatment, complete precipitate dissolution occurred in all four alloys. Under incomplete precipitate dissolution conditions, the phase and shape of precipitates depended on the heat-treatment conditions and the carbon content in the alloys. The ? phase was detected in the alloys with carbon contents of 0.15, 0.25, and 0.35 mass pct after heat treatment at high temperature such as 1548 K for a short holding time of less than 1.8 ks. The presence of the ? phase in the Co-Cr-Mo alloys has been revealed in this study for the first time.

Mineta, Shingo; Namba, Shigenobu; Yoneda, Takashi; Ueda, Kyosuke; Narushima, Takayuki

2010-08-01

353

In vitro degradation behavior and cytocompatibility of MgZnZr alloys  

PubMed Central

Zinc and zirconium were selected as the alloying elements in biodegradable magnesium alloys, considering their strengthening effect and good biocompatibility. The degradation rate, hydrogen evolution, ion release, surface layer and in vitro cytotoxicity of two MgZnZr alloys, i.e. ZK30 and ZK60, and a WE-type alloy (MgYREZr) were investigated by means of long-term static immersion testing in Hanks solution, non-static immersion testing in Hanks solution and cell-material interaction analysis. It was found that, among these three magnesium alloys, ZK30 had the lowest degradation rate and the least hydrogen evolution. A magnesium calcium phosphate layer was formed on the surface of ZK30 sample during non-static immersion and its degradation caused minute changes in the ion concentrations and pH value of Hanks solution. In addition, the ZK30 alloy showed insignificant cytotoxicity against bone marrow stromal cells as compared with biocompatible hydroxyapatite (HA) and the WE-type alloy. After prolonged incubation for 7days, a stimulatory effect on cell proliferation was observed. The results of the present study suggested that ZK30 could be a promising material for biodegradable orthopedic implants and worth further investigation to evaluate its in vitro and in vivo degradation behavior. PMID:20532960

Huan, Z. G.; Leeflang, M. A.; Fratila-Apachitei, L. E.; Duszczyk, J.

2010-01-01

354

Effects of Ta content on the phase stability and elastic properties of ? Ti-Ta alloys from first-principles calculations  

NASA Astrophysics Data System (ADS)

The effects of Ta content on the phase stability, the elastic property and the electronic structure of ? type Ti-Ta alloys were studied from first-principles calculations based on the density functional theory. It is found that the phase stability, tetragonal shear constant C', bulk modulus, elastic modulus and shear modulus of ? type Ti-Ta alloys increase with the Ta content increasing monotonously. The lowest elastic modulus of the alloys is realized when the valence electron number ( e/ a) is around 4.25. Moreover, the phase stability of the alloys was discussed based on the calculated density of state (DOS).

Wu, C. Y.; Xin, Y. H.; Wang, X. F.; Lin, J. G.

2010-12-01

355

Thermodynamic modeling and experimental validation of the Fe-Al-Ni-Cr-Mo alloy system  

SciTech Connect

NiAl-type precipitate-strengthened ferritic steels have been known as potential materials for the steam turbine applications. In this study, thermodynamic descriptions of the B2-NiAl type nano-scaled precipitates and body-centered-cubic (BCC) Fe matrix phase for four alloys based on the Fe-Al-Ni-Cr-Mo system were developed as a function of the alloy composition at the aging temperature. The calculated phase structure, composition, and volume fraction were validated by the experimental investigations using synchrotron X-ray diffraction and atom probe tomography. With the ability to accurately predict the key microstructural features related to the mechanical properties in a given alloy system, the established thermodynamic model in the current study may significantly accelerate the alloy design process of the NiAl-strengthened ferritic steels.

Teng, Zhenke [ORNL; Zhang, F [CompuTherm LLC, Madison, WI; Miller, Michael K [ORNL; Liu, Chain T [Hong Kong Polytechnic University; Huang, Shenyan [ORNL; Chou, Y.T. [Multi-Phase Services Inc., Knoxville; Tien, R [Multi-Phase Services Inc., Knoxville; Chang, Y A [ORNL; Liaw, Peter K [University of Tennessee, Knoxville (UTK)

2012-01-01

356

Erosion of iron-chromium alloys by glass particles  

NASA Technical Reports Server (NTRS)

The material loss upon erosion was measured for several iron-chromium alloys. Two types of erodent material were used: spherical glass beads and sharp particles of crushed glass. For erosion with glass beads the erosion resistance (defined as the reciprocal of material loss rate) was linearly dependent on hardness. This is in accordance with the erosion behavior of pure metals, but contrary to the erosion behavior of alloys of constant composition that were subjected to different heat treatments. For erosion with crushed glass, however, no correlation existed between hardness and erosion resistance. Instead, the erosion resistance depended on alloy composition rather than on hardness and increased with the chromium content of the alloy. The difference in erosion behavior for the two types of erodent particles suggested that two different material removal mechanisms were involved. This was confirmed by SEM micrographs of the eroded surfaces, which showed that for erosion with glass beads the mechanism of material removal was deformation-induced flaking of surface layers, or peening, whereas for erosion with crushed glass it was cutting or chopping.

Salik, J.; Buckley, D. H.

1984-01-01

357

Oxide Film Aging on Alloy 22 in Halide Containing Solutions  

SciTech Connect

Passive and corrosion behaviors of Alloy 22 in chloride and fluoride containing solutions, changing the heat treatment of the alloy, the halide concentration and the pH of the solutions at 90 deg. C, was investigated. The study was implemented using electrochemical techniques, which included open circuit potential monitoring over time, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements carried out at open circuit and at passivity potentials. Corrosion rates obtained by EIS measurements after 24 h immersion in naturally aerated solutions were below 0.5 {mu}m/year. The corrosion rates were practically independent of solution pH, alloy heat treatment and halide ion nature and concentration. EIS low frequency resistance values increased with applied potential in the passive domain and with polarization time in pH 6 - 1 M NaCl at 90 deg. C. This effect was attributed to an increase in the oxide film thickness and oxide film aging. High frequency capacitance measurements indicated that passive oxide on Alloy 22 presented a double n-type/p-type semiconductor behavior in the passive potential range. (authors)

Rodriguez, Martin A.; Carranza, Ricardo M. [Dept. Materiales, Comision Nacional de Energia Atomica, Av. Gral. Paz 1499, Villa Maipu, 1650 (Argentina); Rebak, Raul B. [Lawrence Livermore National Laboratory, 7000 East Ave, L-631, Livermore, CA, 94550-9698 (United States)

2007-07-01

358

Magnesium alloys (WE43 and ZE41) characterisation for laser applications  

NASA Astrophysics Data System (ADS)

One of the most important parameters in laser treatment is the quantity of beam energy absorbed by the substrate. Despite its important role played in laser processes, this factor is rarely available for the laser sources wavelengths and at high temperatures reached during such treatments. A series of experiments were carried out in order to characterise, from this point of view, two types of magnesium alloys, WE43 and ZE41, often used in laser applications (cladding, alloying, welding, etc.). The results represent an important step in order to understand Mg-alloys behaviour under laser beam action.

Ignat, Sorin; Sallamand, Pierre; Grevey, Dominique; Lambertin, Michel

2004-06-01

359

Structural and magnetic properties of Co 2CrAl Heusler alloys prepared by mechanical alloying  

NASA Astrophysics Data System (ADS)

Mechanical alloying has been used to produce nanocrystalline samples of Co 2CrAl Heusler alloys. The samples were characterized by using different methods. The results indicate that, it is possible to produce L2 1-Co 2CrAl powders after 15 h of ball-milling. The grain size of 15 h ball milled L2 1-Co 2CrAl Heusler phase, calculated by analyzing the XRD peak broadening using Williamson and Hall approach was 14 nm. The estimated magnetic moment per formula unit is 2 ? B. The obtained magnetic moment is significantly smaller than the theoretical value of 2.96 ? B for L2 1 structure. It seems that an atomic disorder from the crystalline L2 1-type ordered state and two-phase separation depresses the ferromagnetic ordering in alloy. Also, the effect of annealing on the structural and magnetic properties of ball milled powders was investigated. Two structures were identified for annealed sample, namely L2 1 and B2. The obtained value for magnetic moment of annealed sample is smaller than the as-milled sample due to the presence of disordered B2 phase and improvement of phase separation.

Hakimi, M.; Kameli, P.; Salamati, H.

2010-11-01

360

Shape memory alloy cables  

NASA Astrophysics Data System (ADS)

Conventional structural cables (or wire ropes) are composed of steel wires helically wound into strands, which, in turn, are wound around a core. Cables made from shape memory alloy (SMA) wires are a new structural element with promising properties for a broad range of new applications. Among the many potential advantages of this form are increased bending flexibility for spooling/packaging, better fatigue performance, energy absorption and damping, reduced thermal lag, redundancy, and signicant design flexibility. Currently there are no known studies of SMA cables in the literature, so exploratory thermo-mechanical experiments were performed on two commercially available cable designs as part of an ongoing research program to systematically characterize their thermomechanical behavior and demonstrate their potential utility as adaptive or resilient tension elements.

Reedlunn, Benjamin; Shaw, John A.

2008-03-01

361

CREEP AND CREEP-FATIGUE OF ALLOY 617 WELDMENTS  

SciTech Connect

The Very High Temperature Reactor (VHTR) Intermediate Heat Exchanger (IHX) may be joined to piping or other components by welding. Creep-fatigue deformation is expected to be a predominant failure mechanism of the IHX1 and thus weldments used in its fabrication will experience varying cyclic stresses interrupted by periods of elevated temperature deformation. These periods of elevated temperature deformation are greatly influenced by a materials creep behavior. The nickel-base solid solution strengthened alloy, Alloy 617, is the primary material candidate for a VHTR-type IHX, and it is expected that Alloy 617 filler metal will be used for welds. Alloy 617 is not yet been integrated into Section III of the Boiler and Pressure Vessel Code, however, nuclear component design with Alloy 617 requires ASME (American Society of Mechanical Engineers) Code qualification. The Code will dictate design for welded construction through significant performance reductions. Despite the similar compositions of the weldment and base material, significantly different microstructures and mechanical properties are inevitable. Experience of nickel alloy welds in structural applications suggests that most high temperature failures occur at the weldments or in the heat-affected zone. Reliably guarding against this type of failure is particularly challenging at high temperatures due to the variations in the inelastic response of the constituent parts of the weldment (i.e., weld metal, heat-affected zone, and base metal) [ref]. This work focuses on the creep-fatigue behavior of nickel-based weldments, a need noted during the development of the draft Alloy 617 ASME Code Case. An understanding of Alloy 617 weldments when subjected to this important deformation mode will enable determination of the appropriate design parameters associated with their use. Specifically, the three main areas emphasized are the performance reduction due to a weld discontinuity in terms of the reduced number of the cycles to failure and whether a saturation in reduced cycle life with increased hold times is observed, the microstructural stability over long cycle times, and finally, the location of the generated weldment data on a creep-fatigue damage diagram (D-diagram).

Jill Wright; Laura Carroll; Richard Wright

2014-08-01

362

Magnesium Alloys and their Applications  

NASA Astrophysics Data System (ADS)

In the recent years there has been a dramatic increase in research activity and also applications of magnesium alloys. The driving force is the growing demand by the automobile industry resulting from the pressure to reduce weight and hence to reduce the fuel consumption. The U.S. car industry incorporates the largest amount of magnesium at the present time. In Europe, Volkswagen had a history of using magnesium in the VW Beetle. Volkswagen, in common with other major car producers has initiated a major research and development programme for advanced magnesium materials. The main emphasis of this book is in the field of general physical metallurgy and alloy development refelcting the need to provide a wider range of alloys both casting and wrought alloys to meet the increasing demands of industry. Other topics are nevertheless well represented such as casting, recycling, joining, corrosion, and surface treatment.

Kainer, Karl U.

1999-04-01

363

Electrodeposition on magnesium alloy diecasting.  

E-print Network

??Magnesium alloy diecasting AZ91CC, AZ61CC', AZ91HC and AZ71HC were electroplated using different pretreatment sequences which incorporated conventional zincate immersion processes. Satisfactory peel adhesion in excess (more)

Wan, Katy Y.

1986-01-01

364

[MRO] Oligocrystalline Shape Memory Alloys  

E-print Network

Copper-based shape memory alloys (SMAs) exhibit excellent shape memory properties in single crystalline form. However, when they are polycrystalline, their shape memory properties are severely compromised by brittle fracture ...

Chen, Ying

365

Smart interfacial bonding alloys  

SciTech Connect

The goal of this LDRD was to explore the use of the newly discovered strain-stabilized 2-D interfacial alloys as smart interface bonding alloys (SIBA). These materials will be used as templates for the heteroepitaxial growth of metallic thin films. SIBA are formed by two metallic components which mix at an interface to relieve strain and prevent dislocations from forming in subsequent thin film growth. The composition of the SIBA is determined locally by the amount of strain, and therefore can react smartly to areas of the highest strain to relieve dislocations. In this way, SIBA can be used to tailor the dislocation structure of thin films. This project included growth, characterization and modeling of films grown using SIBA templates. Characterization will include atomic imaging of the dislocations structure, measurement of the mechanical properties of the film using interface force microscopy (IFM) and the nanoindenter, and measurement of the electronic structure of the SIBA with synchrotron photoemission. Resistance of films to sulfidation and oxidation will also be examined. The Paragon parallel processing computer will be used to calculate the structure of the SIBA and thin films in order to develop ability to predict and tailor SIBA and thin film behavior. This work will lead to the possible development of a new class of thin film materials with properties tailored by varying the composition of the SIBA, serving as a buffer layer to relieve the strain between the substrate and the thin film. Such films will have improved mechanical and corrosion resistance allowing application as protective barriers for weapons applications. They will also exhibit enhanced electrical conductivity and reduced electromigration making them particularly suitable for application as interconnects and other electronic needs.

R. Q. Hwang; J. C. Hamilton; J. E. Houston

1999-04-01

366

Innovations in cast magnesium alloys  

Microsoft Academic Search

This article examines questions related to aspects of the production of castings of magnesium alloys in molds made by volumetric\\u000a stamping without the use of the corresponding tooling. Information is presented on features of the gating-feeding systems\\u000a used to obtain magnesium-alloy castings in molds made by volumetric stamping. Also examined are features of the effect of\\u000a small additions of calcium

V. D. Belov; A. V. Koltygin; N. A. Belov; I. V. Plisetskaya

2010-01-01

367

Casting Alloys: Side-Effects  

Microsoft Academic Search

Side-effects from dental materials are a minor problem, but should be recognized. In recent questionnaire surveys about side-effects, the incidence was estimated to be 1:300 in periodontics and 1:2600 in pedodontics. None of these reactions was related to dental casting alloys. In prosthodontics, the incidence was calculated to be about 1:400, and about 27% were related to base-metal alloys forremovable

Arne Hensten-Pettersen

1992-01-01

368

Shape memory alloy thaw sensors  

DOEpatents

A sensor permanently indicates that it has been exposed to temperatures exceeding a critical temperature for a predetermined time period. An element of the sensor made from shape memory alloy changes shape when exposed, even temporarily, to temperatures above the austenitic temperature of the shape memory alloy. The shape change of the SMA element causes the sensor to change between two readily distinguishable states. 16 figs.

Shahinpoor, M.; Martinez, D.R.

1998-04-07

369

Castable hot corrosion resistant alloy  

NASA Technical Reports Server (NTRS)

Some 10 wt percent nickel is added to an Fe-base alloy which has a ferrite microstructure to improve the high temperature castability and crack resistance while about 0.2 wt percent zirconium is added for improved high temperatur cyclic oxidation and corrosion resistance. The basic material is a high temperature FeCrAl heater alloy, and the addition provides a material suitable for burner rig nozzles.

Barrett, Charles A. (inventor); Holt, William H. (inventor)

1988-01-01

370

Magnetic moments in heusler alloys  

Microsoft Academic Search

The Heusler alloys are a series of local moment ferromagnets of composition X2MnY, with a magnetization of ~4muB per Mn atom. Magnetic measurements on the alloy series Ni2MnxT1-xSn, where T is Ti, V or Cr, indicate that the T site moment changes from -muB (for Ti), through zero (for V), to +muB (for CR). A simple physical interpretation is proposed

C. C. M. Campbell

1976-01-01

371

Effects of Ir Substitution and Processing Conditions on Thermoelectric Performance of p-Type Zr0.5Hf0.5Co1- x Ir x Sb0.99Sn0.01 Half-Heusler Alloys  

NASA Astrophysics Data System (ADS)

A series of samples with the composition Zr0.5Hf0.5Co1- x Ir x Sb0.99Sn0.01 ( x = 0.0 to 0.7) were synthesized by high-temperature solid-state reaction at 1173 K. High-density pellets of the powders were obtained using hot press (HP) and spark plasma sintering (SPS) techniques. The thermoelectric properties of the pellets were measured from 300 K to 750 K. Independently of the pressing conditions, all Ir-containing samples ( x > 0) showed p-type semiconducting behavior. At 300 K, the electrical conductivity and thermopower of Zr0.5Hf0.5Co1- x Ir x Sb0.99Sn0.01 materials surprisingly increased with increasing Ir concentration. The largest electrical conductivity and thermopower values of 150 S/cm and 140 ?V/K, respectively, were observed at 300 K for x = 0.7. The thermal conductivity of the synthesized materials decreased with increasing Ir content, went through a minimum value ( x = 0.3), and increased thereafter with further addition of Ir. Pellets fabricated by SPS showed smaller thermal conductivity than pellets of the same composition obtained from uniaxial hot pressing. A thermal conductivity value of 2.0 W/m K was observed at 300 K for an SPS pellet with the com- position Zr0.5Hf0.5Co0.5Ir0.5Sb0.99Sn0.01. The thermal conductivity of Zr0.5Hf0.5- Co1- x Ir x Sb0.99Sn0.01 decreased with rising temperature, and the smallest value of 1.5 W/m K was observed at 750 K for the SPS specimen with x = 0.5.

Takas, Nathan J.; Sahoo, Pranati; Misra, Dinesh; Zhao, Hongfang; Henderson, Nathaniel L.; Stokes, Kevin; Poudeu, Pierre F. P.

2011-05-01

372

The Crystal Structure at Room Temperature of Six Cast Heat-Resisting Alloys  

NASA Technical Reports Server (NTRS)

The crystal structures of alloys 61, X-40,X-50, 422-19, 6059, and Vitallium, derived from x-ray diffraction, are discussed. The alloys have been, or are being considered for use in gas turbine applications. The predominant phase was a solid solution of the face centered cubic type of the principal constituent elements.The lattice parameters were found to be between 3.5525 and 3.5662.

Rosenbaum, Burt M.

1947-01-01

373

Evaluation of copper alloys for fusion reactor divertor and first wall components  

Microsoft Academic Search

This paper presents a critical analysis of the main factors of radiation damage limiting the possibility to use copper alloys in the ITER divertor and first wall structure. In copper alloys the most significant types of radiation damage in the proposed temperature-dose operation range are swelling, creep, and low-temperature radiation embrittlement. Low-temperature radiation embrittlement at Tirr < 150C presents considerable

S. A. Fabritsiev; S. J. Zinkle; B. N. Singh

1996-01-01

374

Magnetic after-effect in NiMnSb Heusler alloy  

Microsoft Academic Search

The ferromagnetic Heusler-type alloy Ni50Mn35Sb15 exhibits well defined shape memory behaviour. We have investigated the transport and magnetic properties of this alloy across the martensitic transformation. Pronounced thermo-magnetic irreversibility between zero-field-cooled and field-cooled susceptibility data was observed below the martensitic transition temperature. We observe significant magnetic after-effect in magnetisation in both austenite and martensitic phases. However, a clear change in

S. Chatterjee; S. Giri; S. Majumdar; S. K. De

2008-01-01

375

Magnetic behavior of half-Heusler alloy CuxNi1-xMnSb  

Microsoft Academic Search

We have investigated the effects on the magnetic properties of NiMnSb alloys with the substitution of Cu for Ni. The half-Heusler type alloys, CuxNi1-xMnSb compounds, are fabricated by the arc-melting method and are subsequently annealed at a temperature of 1050 K for 24 h. It was found that at a temperature of 4 K and field of 10 k Oe

S. K. Ren; W. Q. Zou; J. Gao; X. L. Jiang; F. M. Zhang; Y. W. Du

2005-01-01

376

Improvement of the fatigue life of titanium alloys for biomedical devices through microstructural control.  

PubMed

A limited number of reports exist regarding the systematic investigation or comparison of the fatigue strength of titanium alloys for medical devices, including plain, fretting and notch fatigue, for improvement through various treatments and processes, with respect to related microstructures. This article focuses on the changes and improvements in fatigue strength of newly developed beta-type and practically used alpha + beta-titanium alloys for medical devices through heat treatments, thermomechanical treatments and surface modifications. PMID:20583885

Niinomi, Mitsuo; Akahori, Toshikazu

2010-07-01

377

An implantable drug-delivery system based on shape memory alloy micro-actuation  

Microsoft Academic Search

Shape memory alloy actuators feature an extremely high power-to-volume ratio. This property is a major advantage for miniature applications. This paper describes implantable drug-delivery systems based on shape memory alloy micro-actuation. A first type is designed for use with solid drugs while a second design enables delivery of liquid drugs. The operating principle of the latter system is based on

Dominiek Reynaerts; Jan Peirs; Hendrik Van Brussel

1997-01-01

378

Snoek Relaxation in Fe-Cr Alloys and Interstitial-Substitutional Interaction  

Microsoft Academic Search

The internal friction (IF) spectra of -Fe, Fe-Cr ferritic alloys and Cr have been investigated in a frequency range of 0.01 to 10 Hz. A Snoek-type relaxation was found in all the investigated C doped Fe-Cr alloys, starting from pure Fe and finishing with pure Cr. The temperature location of the Snoek peak (Tmax) in -Fe was found to be

I. S. Golovin; M. S. Blanter; R. Schaller

1997-01-01

379

High-Thermoelectric Performance of Nanostructured Bismuth Antimony Telluride Bulk Alloys  

Microsoft Academic Search

The dimensionless thermoelectric figure of merit (ZT) in bismuth antimony telluride (BiSbTe) bulk alloys has remained around 1 for more than 50 years. We show that a peak ZT of 1.4 at 100C can be achieved in a p-type nanocrystalline BiSbTe bulk alloy. These nanocrystalline bulk materials were made by hot pressing nanopowders that were ball-milled from crystalline ingots under

Bed Poudel; Qing Hao; Yi Ma; Yucheng Lan; Austin Minnich; Xiao Yan; Dezhi Wang; Andrew Muto; Daryoosh Vashaee; Xiaoyuan Chen; M. S. Dresselhaus; Mildred S. Dresselhaus; Gang Chen; Zhifeng Ren

2008-01-01

380

Stainless steel-zirconium alloy waste forms  

SciTech Connect

An electrometallurgical treatment process has been developed by Argonne National Laboratory to convert various types of spent nuclear fuels into stable storage forms and waste forms for repository disposal. The first application of this process will be to treat spent fuel alloys from the Experimental Breeder Reactor-II. Three distinct product streams emanate from the electrorefining process: (1) refined uranium; (2) fission products and actinides extracted from the electrolyte salt that are processed into a mineral waste form; and (3) metallic wastes left behind at the completion of the electrorefining step. The third product stream (i.e., the metal waste stream) is the subject of this paper. The metal waste stream contains components of the chopped spent fuel that are unaffected by the electrorefining process because of their electrochemically ``noble`` nature; this includes the cladding hulls, noble metal fission products (NMFP), and, in specific cases, zirconium from metal fuel alloys. The selected method for the consolidation and stabilization of the metal waste stream is melting and casting into a uniform, corrosion-resistant alloy. The waste form casting process will be carried out in a controlled-atmosphere furnace at high temperatures with a molten salt flux. Spent fuels with both stainless steel and Zircaloy cladding are being evaluated for treatment; thus, stainless steel-rich and Zircaloy-rich waste forms are being developed. Although the primary disposition option for the actinides is the mineral waste form, the concept of incorporating the TRU-bearing product into the metal waste form has enough potential to warrant investigation.

McDeavitt, S.M.; Abraham, D.P.; Keiser, D.D. Jr.; Park, J.Y.

1996-07-01

381

Laser alloying and cladding of metallic substrates  

NASA Astrophysics Data System (ADS)

This paper describes the microstructure and properties (chemical composition and microhardness) of the surface laser alloyed layer with tantalum as well as coatings, made of Tribaloy T-400 and Stellite 6 powders, deposited by laser cladding. The surface alloyed zones varied in microstructure, zones depth and width, as well as Ta content related to the thickness of the coated layer, bonding paint type and the process parameters (power and scanning velocity). The electron microprobe analysis of melts shows that higher tantalum content in the melted zone resulted from the thicker original Ta coating as well as slower scanning velocity. Scanning electron microscopy examinations show that dendritic structure is typically martensitic when silicon-containing binder was used for powder deposition. Samples covered with Ta and the carbon containing binder showed after laser alloying higher hardness than in case of using silicon-containing binder. Defect free coatings, made of Tribaloy T-400 and Stellite 6 powders, deposited by laser cladding on iron and nickel based substrates are described. The proper selection of the cladding process parameters permitted to get coatings with low dilution of the base material. Cross-sections of such coatings have been examined revealing their microstructure using optical, SEM and TEM electron microscopy, chemical (EDS microanalysis) and phase composition (XRD), hardness and microhardness testing methods. As compared with other deposition techniques the microstructure of the laser coatings showed a high degree of refinement and chemical homogeneity. The grain coarsening was observed in the heat- affected zones and was explained as to be due to the overlapping of subsequent tracks during the coatings deposition. The erosive wear resistance of the coatings has been investigated. In general, the laser deposited coatings turned out to be susceptible for an extensive erosive wear. The effect was explained by lack of feasibility of the coated material to plastic deformation during erosion.

Kusinski, Jan P.; Przybylowicz, Janusz; Woldan, Agnieszka

2000-11-01

382

Ni{sub 3}Al aluminide alloys  

SciTech Connect

This paper provides a brief review of the recent progress in research and development of Ni{sub 3}Al and its alloys. Emphasis has been placed on understanding low ductility and brittle fracture of Ni{sub 3}Al alloys at ambient and elevated temperatures. Recent studies have resulted in identifying both intrinsic and extrinsic factors governing the fracture behavior of Ni{sub 3}Al alloys. Parallel efforts on alloy design using physical metallurgy principles have led to properties for structural use. Industrial interest in these alloys is high, and examples of industrial involvement in processing and utilization of these alloys are briefly mentioned.

Liu, C.T.

1993-10-01

383

Impurity behavior in V 4Cr 4Ti Y alloys produced by levitation melting  

NASA Astrophysics Data System (ADS)

An alloy of V-4Cr-4Ti-0.15Y was fabricated by 15 kg-scale magnetic levitation melting. The oxygen level was successfully reduced to 108 wppm by slag-out of Y 2O 3 formation on the surface of the melted ingot. Y 2O 3 was identified as a new type of precipitate, in addition to Ti-O type and Ti-N type precipitates common in V-4Cr-4Ti alloys. Y 2O 3 formation is thought to reduce the amount of oxygen in solid solution state and in unstable Ti-O type precipitates. Based on the behavior of the O impurity, optimum fabrication processes for V-4Cr-4Ti-0.15Y alloy were suggested.

Nagasaka, Takuya; Muroga, Takeo; Hino, Takeshi; Satou, Manabu; Abe, Katsunori; Chuto, Toshinori; Iikubo, Tomohito

2007-08-01

384

Electrical transport properties of (BN)-rich hexagonal (BN)C semiconductor alloys  

SciTech Connect

The layer structured hexagonal boron nitride carbon semiconductor alloys, h-(BN)C, offer the unique abilities of bandgap engineering (from 0 for graphite to ?6.4 eV for h-BN) and electrical conductivity control (from semi-metal for graphite to insulator for undoped h-BN) through alloying and have the potential to complement III-nitride wide bandgap semiconductors and carbon based nanostructured materials. Epilayers of (BN)-rich h-(BN){sub 1-x}(C{sub 2}){sub x} alloys were synthesized by metal-organic chemical vapor deposition (MOCVD) on (0001) sapphire substrates. Hall-effect measurements revealed that homogeneous (BN)-rich h-(BN){sub 1-x}(C{sub 2}){sub x} alloys are naturally n-type. For alloys with x = 0.032, an electron mobility of about 20 cm{sup 2}/Vs at 650?K was measured. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical composition and analyze chemical bonding states. Both composition and chemical bonding analysis confirm the formation of alloys. XPS results indicate that the carbon concentration in the alloys increases almost linearly with the flow rate of the carbon precursor (propane (C{sub 3}H{sub 8})) employed during the epilayer growth. XPS chemical bonding analysis showed that these MOCVD grown alloys possess more C-N bonds than C-B bonds, which possibly renders the undoped h-(BN){sub 1-x}(C{sub 2}){sub x} alloys n-type and corroborates the Hall-effect measurement results.

Uddin, M. R.; Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X., E-mail: hx.jiang@ttu.edu [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, TX 79409 (United States); Ziemer, K. S. [Department of Chemical Engineering, Northeastern University, Boston, MA 02115 (United States)

2014-08-15

385

Coating of 6028 Aluminum Alloy Using Aluminum Piston Alloy and Al-Si Alloy-Based Nanocomposites Produced by the Addition of Al-Ti5-B1 to the Matrix Melt  

NASA Astrophysics Data System (ADS)

The Al-12 pctSi alloy and aluminum-based composites reinforced with TiB2 and Al3Ti intermetallics exhibit good wear resistance, strength-to-weight ratio, and strength-to-cost ratio when compared to equivalent other commercial Al alloys, which make them good candidates as coating materials. In this study, structural AA 6028 alloy is used as the base material. Four different coating materials were used. The first one is Al-Si alloy that has Si content near eutectic composition. The second, third, and fourth ones are Al-6 pctSi-based reinforced with TiB2 and Al3Ti nano-particles produced by addition of Al-Ti5-B1 master alloy with different weight percentages (1, 2, and 3 pct). The coating treatment was carried out with the aid of GTAW process. The microstructures of the base and coated materials were investigated using optical microscope and scanning electron microscope equipped with EDX analyzer. Microhardness of the base material and the coated layer were evaluated using a microhardness tester. GTAW process results in almost sound coated layer on 6028 aluminum alloy with the used four coating materials. The coating materials of Al-12 pct Si alloy resulted in very fine dendritic Al-Si eutectic structure. The interface between the coated layer and the base metal was very clean. The coated layer was almost free from porosities or other defects. The coating materials of Al-6 pct Si-based mixed with Al-Ti5-B1 master alloy with different percentages (1, 2, and 3 pct), results in coated layer consisted of matrix of fine dendrite eutectic morphology structure inside ?-Al grains. Many fine in situ TiAl3 and TiB2 intermetallics were precipitated almost at the grain boundary of ?-Al grains. The amounts of these precipitates are increased by increasing the addition of Al-Ti5-B1 master alloy. The surface hardness of the 6028 aluminum alloy base metal was improved with the entire four used surface coating materials. The improvement reached to about 85 pct by the first type of coating material (Al-12 pctSi alloy), while it reached to 77, 83, and 89 pct by the coating materials of Al-6 pct Si-based mixed with Al-Ti5-B1 master alloy with different percentages 1, 2, and 3 pct, respectively.

El-Labban, Hashem F.; Abdelaziz, M.; Mahmoud, Essam R. I.

2014-10-01

386

Evaluation of a diffusion/trapping model for hydrogen ingress in high-strength alloys. Annual report, 15 September 1993-14 September 1994  

SciTech Connect

The ingress of hydrogen in various high-strength alloys was investigated with a view to characterizing their susceptibility to hydrogen embrittlement (HE). A potentiostatic pulse technique was applied to two precipitation-hardened iron-base alloys (AerMet 100 and alloy A-286), two Cu-containing alloys (Be-Cu and alloy K-500), and a superferritic stainless steel (UNS 544660) in 1 mol/L acetic acid-1 mol/L sodium acetate. The data were analyzed using a diffusion/trapping model to obtain the irreversible trapping constant (k) and hydrogen entry flux for each alloy. Irreversible trapping was negligible in overaged AerMet 100 but pronounced in the aged alloy. The order of the k values for AerMet 100 and two steels (4340 and 1 18Ni) previously studied inversely parallels their threshold stress intensities for stress corrosion cracking. Likewise, the k values of alloy A-286, 18Ni steel, and also alloy 718 from earlier work are consistent with test data for their relative resistance to HE. The results for AerMet 100 and alloy A-286 extend the previously reported correlation between k and HE resistance. Unaged Be-Cu is intrinsically more susceptible to HE than unaged alloy K- 500. The type of heat treatment has a marked effect on the rapping behavior of alloy K-500. The intrinsic susceptibility of the annealed and aged alloy is twice that or the direct-aged alloy. The propensity of the S44660 alloy to undergo HE at cathodic protection potentials can be attributed to the absence of an oxide and hence the relatively unrestricted entry of H.

Pound, B.G.

1994-11-01

387

Effects of the third element on creep behavior of Al-Mg and ?Fe-Be solid solution alloys  

Microsoft Academic Search

In creep of alpha-iron, IS effects (interstitial-substitutional interaction) were reported. Similar effects are expected in ternary substitutional solid solutions. In the present report, effects of the second substitute (the third element), whose size misfit is small, on creep behavior and the transition stress from Alloy-type to Metal-type have been investigated experimentally. Three alloy systems are employed, i.e. aluminum-magnesium-zinc, aluminum-magnesium-lithium and

Hiroyuki Sato; Kouichi Maruyama; Hiroshi Oikawa

1997-01-01

388

Alloying element diffusion in alloy 800 H (UNS N08810) and alloy 617 (UNS N06617)  

SciTech Connect

Samples of alloy 800 H (LJNS N08810) and alloy 617 (UNS N06617) were oxidized in a simulated process gas atmosphere. The principal elements of the gaseous environment were 50% H{sub 2}O, 35% H{sub 2} and 5% of CO{sub 2}, CO, and CH{sub 4}, respectively. The experiments were carried out at temperatures from 850 C to 950 C for exposures ranging from 600 to 5,000 hours. After the exposure, the alloy surfaces showed compact oxide layers, which resulted in a depleted zone of oxidizing elements in the substrate layer. Using Electron Probe Microanalysis (EPMA), concentration profiles and the extension of the depleted zone were measured. Calculated theoretical profiles were then fitted to the EPMA-measured profiles, using Fick`s second law of diffusion and resolved by a finite difference method and diffusion coefficients as fitting parameters. The diffusion coefficients for chromium may be represented as D = Do exp.(-Q/RT) with the values Do = 11.4 cm{sup 2}/s and Q = 289 kJ/mol for alloy 800 H and Do = 2.1 cm{sup 2}/s and Q = 280 kJ/ mol for alloy 617. The value of the resulting activation energy Q for diffusion in the investigated alloys is similar to that reported in the literature for f.c.c structures.

Maldonado, L.; Diaz, L. [Unidad Merida (Mexico). Centro de Investigacion y de Estudios Avanzados; Gruebmaier, H.; Naoumidis, A.; Nickel, H. [Research Centre Juelich GmbH (Germany). Inst. for Materials in Energy Systems

1996-10-01

389

Surface modification of 5083 Al alloy by electrical discharge alloying processing with a 75 mass% Si-Fe alloy electrode  

NASA Astrophysics Data System (ADS)

This study experimentally investigates the surface modification of 5083 Al alloy by the electrical discharge alloying (EDA) process with a Si-Fe alloy as an electrode. Samples were analyzed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), micro-hardness and corrosion resistance tests. The micro-hardness of EDA alloyed layer was evidently higher than that of the base metal (5083 Al alloy). The TEM results show that the matrix of the alloyed layer has an amorphous-like structure; the matrix contains fine needle-like Si particles, block-like Si particles and nano-size Al4.5FeSi and Al13Fe4 particles. The TEM results support experimental results for the high hardness of the alloyed layer. Moreover, the EDA alloyed layer with composite microstructures has good corrosion resistance in NaCl aqueous solution.

Stambekova, Kuralay; Lin, Hung-Mao; Uan, Jun-Yen

2012-03-01

390

Characterizing alloy additions to high nitrogen steels  

SciTech Connect

Numerous articles of individual high nitrogen stainless steel compositions or alloys with near identical alloy compositions have been published characterizing the properties the alloy or the improvement which an individual element contributes to the base alloy's properties. In this study a series of high nitrogen steels alloys were prepared with the intent of characterizing the advantages and limitations of different alloy chemistry on the base alloy's material properties such as: microstructure, mechanical properties, environmental interactions (corrosion and oxidation), and wear. A base composition of Fe-15Cr-15 Mn was chosen. Alloys of similar basic compositions are austenitic and often used as a starting composition as a substitute or replacements for Fe-Cr-Ni stainless steel alloys. Mn is less expensive than Ni, is a strong austenizer, enhances nitrogen solubility, and has no allergenic effects. To this base alloy composition additions of C, N, Si, Mo, and Nb was added. Nitrogen (and carbon) alloys as interstitials and have been shown to enhance strength and reduce corrosion. Niobium (or similar elements) is often added to produce intergranular carbide precipitates that further enhance strength. Molybdenum and silicon are added to improve corrosion-oxidation properties. This study was designed to evaluate the action and interaction of these different alloys and suggest what alloys compositions are best used under different engineering requirements. The results of the experimental alloys are compared with that of two experimental higher-nitrogen commercial alloys steels with further alloy addition of Ni and Cu were also studied. Alloy evaluation included: (1) microstructure: optical, SEM, and X-ray diffraction, (2) mechanical properties: yield, tensile, elongation, hardness (room temperature and hot), and energy to failure, (3) oxidation and corrosion, and (4) abrasive wear: scratch, pin-on-drum, and pin-on-disk.

Rawers, James C.; Tylczak, Joseph H.; Blankenship, D.; Bullard, Sophie J.

2003-01-01

391

DEGRADATION MODES OF ALLOY 22 IN YUCCA MOUNTAIN REPOSITORY CONDITIONS  

SciTech Connect

The nuclear waste package design for Yucca Mountain (Nevada, USA), in its current configuration, consists of a double wall cylindrical container fabricated using a highly corrosion resistant Ni-based Alloy 22 for the outer barrier and type 316 stainless steel for the inner structural vessel. A mailbox-shaped drip shield fabricated primarily using Ti Grade 7 will cover the waste packages. The environmental degradation of the relevant materials have been extensively studied and modeled for over ten years. This paper reviews the state-of-the-art understanding of the degradation modes of Alloy 22 (N06022) due to its interaction with the predicted in-drift mountain conditions including temperature and types of electrolytes. Subjects discussed include thermal aging and phase stability, dry oxidation, general and localized corrosion, stress corrosion cracking and hydrogen induced cracking.

F. Hua; G.M. Gordon; R.B. Rebak

2005-10-13

392

Creep and tensile properties of several oxide-dispersion-strengthened nickel-base alloys at 1365 K  

NASA Technical Reports Server (NTRS)

The tensile properties at room temperature and at 1365 K and the tensile creep properties at low strain rates at 1365 K were measured for several oxide-dispersion-strengthened (ODS) alloys. The alloys examined included ODS Ni, ODS Ni-20Cr, and ODS Ni-16Cr-Al. Metallography of creep tested, large grain size ODS alloys indicated that creep of these alloys is an inhomogeneous process. All alloys appear to possess a threshold stress for creep. This threshold stress is believed to be associated with diffusional creep in the large grain size ODS alloys and normal dislocation motion in perfect single crystal (without transverse low angle boundaries) ODS alloys. Threshold stresses for large grain size ODS Ni-20Cr and Ni-16Cr-Al type alloys are dependent on the grain aspect ratio. Because of the deleterious effect of prior creep on room temperature mechanical properties of large grain size ODS alloys, it is speculated that the threshold stress may be the design limiting creep strength property.

Wittenberger, J. D.

1977-01-01

393

JOURNAL DE PHYSIQUE Colloque C 1, supplkment au no 2-3, Tome 32, Fkvrier-Mars 1971,page C 1 -792 MOSSBAUER EFFECT STUDIES IN HEUSLER ALLOYS (*)  

E-print Network

MOSSBAUER EFFECT STUDIES IN HEUSLER ALLOYS (*) R. SEGNAN, W. A. FERRANDO (**), and D. SWEGER (**) American. I. Introduction. -The Heusler alloys, with compo- sitions close to Cu2MnX (where X = Al, In, Sn of the hyperfine field at the 'I9sn nuclei in Cu2MnSn, and the Heusler-type alloys Ni2MnSn and Zn,MnSn by using

Paris-Sud XI, Université de

394

NiSn Half-Heusler Alloy  

NASA Astrophysics Data System (ADS)

We deal here with Sb and Bi doping effects of the n-type half-Heusler (HH) Ti0.3Zr0.35Hf0.35NiSn alloy on the measured thermoelectric properties. To date, the thermoelectric effects upon Bi doping on the Sn site of HH alloys have rarely been reported, while Sb has been widely used as a donor dopant. A comparison between the measured transport properties following arc melting and spark plasma sintering of both Bi- and Sb-doped samples indicates a much stronger doping effect upon Sb doping, an effect which was explained thermodynamically. Due to similar lattice thermal conductivity values obtained for the various doped samples, synthesized in a similar experimental route, no practical variations in the thermoelectric figure of merit values were observed between the various investigated samples, an effect which was attributed to compensation between the power factor and electrical thermal conductivity values regardless of the various investigated dopants and doping levels.

Appel, O.; Gelbstein, Y.

2014-06-01

395

Drilling of Intermetallic Alloys Gamma Tial  

NASA Astrophysics Data System (ADS)

Due to their high strength/weight ratio and resistance to corrosion and wear, superalloys such as gamma TiAl or Inconel 718 appear as the best choice for the high mechanical/thermal demands in the vicinity of the combustion chamber of aircraft engines. There are assembled parts such as cases, disks or blisks; in the manufacturing of these components the last drilling operation could jeopardize the full work integrity adding new costs to the just very expensive parts. Therefore drilling is a high-added value step in the complete sequence. The present work is framed within the study of hole making in advanced materials used for lightweight applications in aerospace sector. Within this context, the paper presents the results from milling tests on three types of gamma TiAl alloys (extruded MoCuSi, ingot MoCuSi and TNB) to define an optimal set of cutting parameters, which will contribute to open the increase in use of these special alloys. Drilling tools made of integral hard metal were used, applying different feeds and cutting speeds. The influence of cutting speed and feed is discussed.

Beranoagirre, A.; Olvera, D.; Lpez de Lacalle, L. N.; Urbicain, G.

2011-01-01

396

Optimization of Iron Cobalt-based Nanocomposite Alloys for High Induction and Increased Resistivity  

NASA Astrophysics Data System (ADS)

FeCo-based nanocrystalline soft magnetic materials are promising to provide high saturation induction, high Curie temperature and excellent soft magnetic properties for electric vehicle and high frequency power conversion applications. The increasing operation frequency of various inductive applications requires nanocomposite alloys with higher resistivity to suppress power losses. In this thesis, the method of measuring as-cast and annealed resistivity of melt-spun ribbon alloys by obtaining alloy densities was established. Archimedes method with deionized water as a medium was used to determine the density of crystalline alloys. A gas pycnometer using dry Helium gas as the medium exhibited improved accuracy in measuring the density of amorphous ribbon alloys compared to the conventional Archimedes method using a liquid medium. This method was applied to previously developed HITPERM (FeCoZrBCu) and HTX002 (FeCoBSiCu) type of alloys as well as carbon-containing (FeCoBCCu) alloys to guide composition adjustments pursuing for improved magnetic properties. In the HITPERM type of alloys, the composition dependence of as-cast resistivity was studied and simulated by Mott's two-current model with a rigid-band assumption which provided guidance for further adjusting alloy composition looking for higher resistivity. An alloy designed with the Fe:Co ratio for maximum as-cast resistivity and Hf as glass former exhibits low power loss values being approximately 1/4 of those measured on the alloy with the original HITPERM composition for a range of frequencies. The Al and Si additions were found effective to achieve a high resistivity of 151.9 muOcm in the as-cast alloys but also lead to embrittlement of melt-spun ribbons. Composition adjustments on the HTX002 type of alloys which are castable in air and available for larger-scale production were also explored. Increasing the ferromagnetic late transition metal content by reducing glass formers was found effective to achieve a high saturation induction above 1.75 T for the electric vehicle applications where high induction is prioritized to reduce size and weight. Due to the insufficient glass former contents in these alloys, however, some unique issues such as castability limits, trade-off between high induction and low power losses, high temperature stability, etc. were studied. As-cast resistivity measurements were utilized to quantify the castability limits of maintaining amorphous nature in the as-cast state. The significant effects of Nb content on the trade-off between high induction and low power losses and on the high temperature crystallization processes were investigated. For the high frequency power conversion applications where high saturation induction can be sacrificed to some extent, HTX002 type of alloys were adjusted in composition pursuing increased resistivity to reduce power losses. Mixed early transition metal content was investigated and the combination of Ta and Nb was found optimal to suppress power losses. High early transition metal content up to 6 at% based on this combination was studied and resulted in larger-scale production. The effect of Co substitution for Fe was explored in carbon-containing alloys which are promising as high induction soft magnetic materials with acceptable low losses and low costs. Higher saturation induction, lower power losses and better high temperature stability of magnetization were exhibited when the Co content was properly chosen. However, these alloys exhibited low annealed resistivity which resulted in dramatic increase of eddy current loss with operation frequency and hence limited for low frequency applications.

Shen, Shen

397

Tribological Properties of Hard Alloys Based on Chromium Carbide  

Microsoft Academic Search

Hard alloys of the type KKhN and KKhNF were studied and shown to have low coefficient of friction (f = 0.21-0.17) and wear rate (I = 5.7-7.0 m\\/km) at sliding velocity 15 m\\/sec and load 7 MPa, which make them promising for use as antifrictional materials in dry friction units under load. Oxide films formed at the surface of the

Vitalii A. Maslyuk; A. D. Kostenko

2003-01-01

398

Modelling the phase diagram of magnetic shape memory Heusler alloys  

Microsoft Academic Search

We have modelled the phase diagram of magnetic shape memory alloys of the Heusler type by using the phenomenological GinzburgLandau theory. When fixing the parameters by realistic values taken from experiment we are able to reproduce most details of, for example, the phase diagram of Ni2+xMn1?xGa in the (T, x) plane. We present the results of ab initio calculations of

P Entel; V D Buchelnikov; V V Khovailo; A T Zayak; W A Adeagbo; M E Gruner; H C Herper; E F Wassermann

2006-01-01

399

Solidification of eutectic system alloys in space (M-19)  

NASA Technical Reports Server (NTRS)

It is well known that in the liquid state eutectic alloys are theoretically homogeneous under 1 g conditions. However, the homogeneous solidified structure of this alloy is not obtained because thermal convection and non-equilibrium solidification occur. The present investigators have clarified the solidification mechanisms of the eutectic system alloys under 1 g conditions by using the in situ observation method; in particular, the primary crystals of the eutectic system alloys never nucleated in the liquid, but instead did so on the mold wall, and the crystals separated from the mold wall by fluid motion caused by thermal convection. They also found that the equiaxed eutectic grains (eutectic cells) are formed on the primary crystals. In this case, the leading phase of the eutectic must agree with the phase of the primary crystals. In space, no thermal convection occurs so that primary crystals should not move from the mold wall and should not appear inside the solidified structure. Therefore no equiaxed eutectic grains will be formed under microgravity conditions. Past space experiments concerning eutectic alloys were classified into two types of experiments: one with respect to the solidification mechanisms of the eutectic alloys and the other to the unidirectional solidification of this alloy. The former type of experiment has the problem that the solidified structures between microgravity and 1 g conditions show little difference. This is why the flight samples were prepared by the ordinary cast techniques on Earth. Therefore it is impossible to ascertain whether or not the nucleation and growth of primary crystals in the melt occur and if primary crystals influence the formation of the equiaxed eutectic grains. In this experiment, hypo- and hyper-eutectic aluminum copper alloys which are near eutectic point are used. The chemical compositions of the samples are Al-32.4mass%Cu (Hypo-eutectic) and Al-33.5mass%Cu (hyper-eutectic). Long rods for the samples are cast by the Ohno Continuous Casting Process and they show the unidirectionally solidified structure. Each flight and ground sample was made of these same rods. The dimensions of all samples are 4.5 mm in diameter and 23.5 mm in length. Each sample is put in a graphite capsule and then vacuum sealed in a double silica ampoule. Then the ampoule is put in the tantalum cartridge and sealed by electron beam welding. For onbard experiments, a Continuous Heating Furnance (CHF) will be used for melting and solidifying samples under microgravity conditions. Six flight samples will be used. Four samples are hypo-eutectic and two are hyper-eutectic alloys. The surface of the two hypo-eutectic alloy samples are covered with aluminum oxide film to prevent Marangoni convection expected under microgravity conditions. Each sample will be heated to 700 C and held at that temperature for 5 min. After that the samples will be allowed to cool to 500 C in the furnace and they will be taken out of the furnace for He gas cooling. The heating and cooling diagrams for the flight experiments are shown. After collecting the flight samples, the solidified structures of the samples will be examined and the mechanisms of eutectic solidification under microgravity conditions will be determined. It is likely that successful flight experiment results will lead to production of high quality eutectic alloys and eutectic composite materials in space.

Ohno, Atsumi

1993-01-01

400

Elevated temperature mechanical behavior of multiphase molybdenum alloys  

NASA Astrophysics Data System (ADS)

Mo-Si-B alloys are being considered as possible candidates for high-temperature applications. In this study, the high-temperature compression response, monotonic and cyclic crack growth behavior (as a function of temperature) of a two-phase Mo-Si-B alloy is discussed and compared to the TZM alloy. The compression response was examined as a function of strain rate in the 1000C-1400C range. A limited number of tests were also conducted on a three-phase alloy. These compression studies confirmed that deformation in the temperature-strain rate space evaluated is matrix-dominated. As a consequence, the response of the three-phase material overlaps that of the two-phase material. In all instances evaluated, the Mo-Si-13 alloys exhibit superior flow stress relative to their TZM counterpart. Finite element analysis assuming an elastic-plastic matrix and an elastic second phase illustrates strain localization in the matrix. The interplay between matrix and T2 properties is used to explain the observed deformed microstructure. Fracture toughness of the Mo-Si-B alloy varies from 8MPa?m at room temperature to 25 MPa?m at 1400C, the increase in toughness with temperature being steepest between 1200C and 1400C. S-N response at room temperature is shallow whereas at 1200C, a definitive fatigue response is observed. Fatigue crack growth in vacuum and air in the temperature interval 20C-600C is similar for the Mo-Si-13 alloy whereas significant deterioration is noted far TZM when it is tested in air. The Paris slopes for the two alloys is high at room temperature (20-30) and decreases with increasing temperature to 3 at 1400C. Apparent activation energies extracted using an Arrhenius-type relationship illustrate grain-boundary diffusion dominance in the 900C-1200C regime and volume diffusion dominance in the 1200C-1400C regime. Creep contributes in a significant way to monotonic and cyclic crack growth at elevated temperatures (1200C-1400C). Clack tip stresses are effective in producing localized microstructural instabilities including recrystallization and creep voiding. Whereas primary creep appears beneficial to toughness and fatigue crack growth resistance, the formation of creep voids and their linkage results in a significant loss of these properties. From these studies, a "fail-safe" regime can be identified for applications where tension-tension cyclic loading is relevant.

Alur, Amruthavalli Pallavi

401

Alloy hardening and softening in binary molybdenum alloys as related to electron concentration  

NASA Technical Reports Server (NTRS)

An investigation was conducted to determine the effects of alloy additions of hafnium, tantalum, tungsten, rhenium, osmium, iridium, and platinum on hardness of molybdenum. Special emphasis was placed on alloy softening in these binary molybdenum alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to molybdenum, while those elements having an equal number or fewer s+d electrons that molybdenum failed to produce alloy softening. Alloy softening and alloy hardening can be correlated with the difference in number of s+d electrons of the solute element and molybdenum.

Stephens, J. R.; Witzke, W. R.

1972-01-01

402

Materials data handbook: Stainless steel type 301  

NASA Technical Reports Server (NTRS)

A summary of the materials property information for stainless steel type 301 is presented. The scope of the information includes physical and mechanical properties at cryogenic, ambient, and elevated temperatures. Information on material procurement, metallurgy of the alloy, corrosion, environmental effects, fabrication, and bonding is developed.

Muraca, R. F.; Whittick, J. S.

1972-01-01

403

Computer-Aided Predictions of Energetics and Thermodynamics of Automotive Aluminum Alloys  

NASA Astrophysics Data System (ADS)

Increasing pressures to further reduce emissions and simultaneously increase fuel economy in automobiles has created a need for lightweight materials (such as Al, Mg, and their alloys). In order to optimize alloy design and processing conditions to achieve Al-alloy castings with the necessary mechanical properties, researchers at Ford Research Laboratory are developing the ``Virtual Aluminum Castings'' methodology: a suite of predictive computational tools that span length scales from atomistic to macroscopic to describe alloy microstructure, precipitation, solidification, and ultimately, mechanical properties. The role of first-principles atomistic computations in this ``Virtual Aluminum Castings'' methodology will be described. Previously, microstructural issues in alloys, such as precipitation, have largely been outside the realm of first-principles calculations. However, the development of a new method enables the prediction of coherent phase equilibria and precipitate shapes in Al-alloys with system sizes up to 250,000 atoms [C. Wolverton, Phil. Mag. Lett. 79, 683 (1999)]. These types of calculations may then be combined with larger-length-scale microstructural models, and in conjunction with experimental efforts, can be used to suggest heat treatments which optimize thermal stability and hardness of industrial alloys.

Wolverton, C.

2000-03-01

404

Heterogeneous magnetism in Fe-doped bulk-amorphous and nanostructured Pd-based alloys  

NASA Astrophysics Data System (ADS)

It has been shown in a previous work (Kapaklis et al 2005 J. Appl. Phys. 98 044319) that whereas the alloy composition Pd40Cu30Ni10P20 can be easily cast as a bulk metallic glass, a partial replacement of Pd by Fe (Pd35Cu30Ni10Fe5P20) leads to a significant crystalline fraction under the same casting conditions. In order to understand the formation and properties of these precipitates, fully amorphous ribbons of both alloy compositions were also prepared by conventional melt-spinning. Magnetic data reveal that doping with 5 at.% iron leads to the formation of nanosized crystalline inclusions in the residual bulk amorphous matrix which are completely absent in the ribbon melt-spun from the same ingot. In both types of Fe-containing alloys the amorphous matrix contains giant moments. Their size is of a few hundred (ingot) and a few tens (ribbon) of Bohr magnetons. The iron-free alloy corrected for the Langevin diamagnetism shows Pauli paramagnetism with similar susceptibility values in both the ingot and the ribbon. These values are close to the Pauli susceptibility of a control sample, a melt-spun Pd82P18 alloy which is expected to be as homogeneous as the typical binary amorphous alloys. The possible origin of different, controversial magnetic behaviors reported in the literature for Fe-doped Pd-based bulk and melt-spun alloys is discussed.

Kiss, L. F.; Kemny, T.; Bujdos, L.; Bakonyi, I.; Baskoutas, S.; Poulopoulos, P.; Kapaklis, V.; Politis, C.

2008-01-01

405

Formation and Applications of Bulk Glassy Alloys in Late Transition Metal Base System  

NASA Astrophysics Data System (ADS)

This paper reviews our recent results of the formation, fundamental properties, workability and applications of late transition metal (LTM) base bulk glassy alloys (BGAs) developed since 1995. The BGAs were obtained in Fe-(Al,Ga)-(P,C,B,Si), Fe-(Cr,Mo)-(C,B), Fe-(Zr,Hf,Nb,Ta)-B, Fe-Ln-B(Ln=lanthanide metal), Fe-B-Si-Nb and Fe-Nd-Al for Fe-based alloys, Co-(Ta,Mo)-B and Co-B-Si-Nb for Co-based alloys, Ni-Nb-(Ti,Zr)-(Co,Ni) for Ni-based alloys, and Cu-Ti-(Zr,Hf), Cu-Al-(Zr,Hf), Cu-Ti-(Zr,Hf)-(Ni,Co) and Cu-Al-(Zr,Hf)-(Ag,Pd) for Cu-based alloys. These BGAs exhibit useful properties of high mechanical strength, large elastic elongation and high corrosion resistance. In addition, Fe- and Co-based glassy alloys have good soft magnetic properties which cannot be obtained for amorphous and crystalline type magnetic alloys. The Fe- and Ni-based BGAs have already been used in some application fields. These LTM base BGAs are promising as new metallic engineering materials.

Inoue, Akihisa; Shen, Baolong

2006-05-01

406

New Theoretical Technique for Alloy Design  

NASA Technical Reports Server (NTRS)

During the last 2 years, there has been a breakthrough in alloy design at the NASA Lewis Research Center. A new semi-empirical theoretical technique for alloys, the BFS Theory (Bozzolo, Ferrante, and Smith), has been used to design alloys on a computer. BFS was used, along with Monte Carlo techniques, to predict the phases of ternary alloys of NiAl with Ti or Cr additions. High concentrations of each additive were used to demonstrate the resulting structures.

Ferrante, John

2005-01-01

407

Nickel aluminide alloys with improved weldability  

DOEpatents

Weldable nickel aluminide alloys which are essentially free, if not entirely free, of weld hot cracking are provided by employing zirconium concentrations in these alloys of greater than 2.6 wt. % or sufficient to provide a substantial presence of Ni--Zr eutectic phase in the weld so as to prevent weld hot cracking. Weld filler metals formed from these so modified nickel aluminide alloys provide for crack-free welds in previously known nickel aluminide alloys.

Santella, Michael L. (Knoxville, TN); Goodwin, Gene M. (Lenior City, TN)

1995-05-09

408

Fatigue behavior of titanium alloys  

SciTech Connect

This symposium was international in nature, with leaders in the fields of fatigue technology and the metallurgy of titanium from the US, Europe and Asia. It covered basic research, development, applications and modeling--life predictions and design of both fatigue crack initiation and propagation of titanium alloys. There were presentations on the full range of titanium alloy systems, from commercially pure and {alpha}-alloys, {alpha}/{beta}- and {beta}-alloys to the gamma titanium aluminides. The effects of processing/heat treatment/microstructure on the fatigue properties were discussed, and models proposed to correlate the microstructures to the observed fatigue performance. Test environments reported on included hard vacuum (and the effect of vacuum level), vacuums with partial pressures of miscellaneous gases, lab air and aqueous media. A session was devoted to the effects of environment and fatigue enhancement via surface treatments using techniques such as shot peening and roller burnishing. The effects of dwell on both S-N and crack growth rate behavior were covered. It was a very comprehensive symposium with presentations from academia, government laboratories and industry, with industrial participants ranging from the petroleum industry to medical and aerospace interests. This book has been separated into four sections, representing the technology areas covered in various sessions, namely Mechanisms of Fatigue crack Initiation and Propagation of Conventional Alloys, Fatigue in Intermetallics, Environmental and Surface Aspects of Fatigue, and Application, Life Prediction and Design. Separate abstracts were prepared for most papers in this volume.

Boyer, R.R.; Eylon, D.; Luetjering, G. [eds.

1999-07-01

409

Oxidation of low cobalt alloys  

NASA Technical Reports Server (NTRS)

Four high temperature alloys: U-700, Mar M-247, Waspaloy and PM/HIP U-700 were modified with various cobalt levels ranging from 0 percent to their nominal commercial levels. The alloys were then tested in cyclic oxidation in static air at temperatures ranging from 1000 to 1150 C at times from 500 to 100 1 hour cycles. Specific weight change with time and X-ray diffraction analyses of the oxidized samples were used to evaluate the alloys. The alloys tend to be either Al2O3/aluminate spinel or Cr2O3/chromite spinel formers depending on the Cr/Al ratio in the alloy. Waspaloy with a ratio of 15:1 is a strong Cr2O3 former while this U-700 with a ratio of 3.33:1 tends to form mostly Cr2O3 while Mar M-247 with a ratio of 1.53:1 is a strong Al2O3 former. The best cyclic oxidation resistance is associated with the Al2O3 formers. The cobalt levels appear to have little effect on the oxidation resistance of the Al2O3/aluminate spinel formers while any tendency to form Cr2O3 is accelerated with increased cobalt levels and leads to increased oxidation attack.

Barrett, C. A.

1982-01-01

410

Corrosion behaviour of a beta-titanium alloy.  

PubMed

The beta-titanium alloy, a particular type of titanium, has been investigated as a biomaterial because of its good mechanical performances and its high corrosion resistance and biocompatibility. This work focuses on the corrosion performance of a beta-titanium alloy of composition Ti-11Mo-2V-4Nb-3Al in Hank's physiological solution. Potentiodynamic tests were performed from -0.25 V to 3.5 V; the breakdown potential was not reached. To observe the behaviour of the alloy while submitted to long-term aggressive conditions, 1, 4 and 8 cycles of cyclic polarization were carried out. Results show a high resistance of the alloy to corrosion and a stabilization of the surface after several corrosion cycles. Pitting was not observed and a fast ability of the surface to repassivate was noticed. The surface was characterized by different techniques before and after corrosion testing. Following the corrosion tests, X-ray Photoelectron Spectroscopy (XPS) showed the presence of calcium and phosphorus, an increase of the oxide layer was measured by Auger Electron Spectroscopy (AES), a relatively smooth surface was visualised by Scanning Electron Microscopy (SEM) and contact-angle measurements showed that the surface energy increased. PMID:16518016

Martin, Edith; Manceur, Aziza; Polizu, Stfania; Savadogo, Oumarou; Wu, Ming H; Yahia, L'Hocine

2006-01-01

411

Friction, wear and electrical contact resistance of precious metal alloys  

NASA Astrophysics Data System (ADS)

The preferred selection of precious metal electrical contact materials depends on the contact geometry, contact stress, test ambient values of electrical contact resistance and whether friction and/or wear must be controlled. Wiper-type contact couples that operate in dry hydrocarbon-free atmospheres, particularly if low and steady friction coefficients and minimal wear are required, are typically that of a palladium alloy pin (ASTM B540) sliding on a gold alloy plate (ASTM B541). These materials have a contact resistance of approximately ten milliohms and a friction coefficient less than 0.5 for the most common operational environments. Segregation of sulfur up to a few atomic percent to wear tracks formed on the gold alloy is not detrimental. The accumulation of larger concentrations of sulfur can form surface films of cuprous sulfide which increases the contact resistance to a few tens of milliohms. Large electrical contact resistances (greater than one ohm) are measured only when rider wear becomes dominant and ridges of Pd-containing material are formed in wear tracks. Ion implantation of carbon into the Au alloy decreases the friction coefficient without increasing the electrical contact resistance.

Pope, L. E.; Peebles, D. E.; Barton, B. M.

412

Properties of titanium-alloyed DLC layers for medical applications.  

PubMed

DLC-type layers offer a good potential for application in medicine, due to their excellent tribological properties, chemical resistance, and bio-inert character. The presented study has verified the possibility of alloying DLC layers with titanium, with coatings containing three levels of titanium concentration prepared. Titanium was present on the surface mainly in the form of oxides. Its increasing concentration led to increased presence of titanium carbide as well. The behavior of the studied systems was stable during exposure in a physiological saline solution. Electrochemical impedance spectra practically did not change with time. Alloying, however, changed the electrochemical behavior of coated systems in a significant way: from inert surface mediating only exchange reactions of the environment in the case of unalloyed DLC layers to a response corresponding rather to a passive surface in the case of alloyed specimens. The effect of DLC layers alloying with titanium was tested by the interaction with a simulated body fluid, during which precipitation of a compound containing calcium and phosphorus--basic components of the bone apatite--occurred on all doped specimens, in contrast to pure DLC. The results of the specimens' surface colonization with cells test proved the positive effect of titanium in the case of specimens with a medium and highest content of this element. PMID:25093457

Joska, Ludek; Fojt, Jaroslav; Cvrcek, Ladislav; Brezina, Vitezslav

2014-01-01

413

Intergranular corrosion of an aluminum-magnesium-silicon-copper alloy  

SciTech Connect

The intergranular (intercrystalline) corrosion (IGC) of a heat-treated aluminum-magnesium-silicon-copper alloy was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM revealed that tall chimneys of corrosion product formed on the surface above the pits during oxygenated salt water immersion. It was postulated that pitting corrosion occurred first and that the corrosion chimneys maintained the acidic, chloride pit environment that subsequently caused IGC (preferential dissolution of the region adjacent to the grain boundaries). TEM foils of the same alloy were immersed in a model pit solution (dilute hydrochloric acid) and showed IGC identical to the corrosion attack seen in the bulk samples. Potentiodynamic polarization in the dilute HCl solution verified that pure Al corroded many times faster than the bulk alloy. These results indicated IGC of this alloy occurred because the depleted region adjacent to the grain boundaries corroded rapidly in acidic solutions. The presence of pits with corrosion chimneys, or some type of occluded cells, must have maintained the acidic environment, which caused IGC.

Burleigh, T.D. [Univ. of Pittsburgh, PA (United States). Materials Science and Engineering Dept.; Ludwiczak, E.; Petri, R.A. [Alcoa Technical Center, Alcoa Center, PA (United States)

1995-01-01

414

Effect of Al-Ti-B on Magnesium Alloy Micro-Alloyed with Ca  

Microsoft Academic Search

Effect of Al-Ti-B master alloy on the microstructure and mechanical properties was investigated in AZ31 magnesium alloys micro-alloyed with Ca. During the casting process, electromagnetic field was also introduced. The results suggest that the micro addition of Ca to magnesium alloy retards the oxidation rate during melting process, improves casting qualities of magnesium alloy ingots. The grain size of AZ31

Canfeng Fang; Guohong Qi; Xingguo Zhang; Hai Hao; Junze Jin

2009-01-01

415

k-resolved alloy bowing in pseudobinary InxGa1-xAs alloys  

Microsoft Academic Search

k-resolved alloy-bowing data for InxGa1-xAs alloys have been taken and used to examine the validity of different alloy formalisms. Although the molecular coherent-potential approximation is considered to be the most complete alloy formalism for zinc-blende pseudobinary alloys, it is not in agreement with the experimental k-resolved data. In contrast, these k-resolved data are in approximate agreement with the coherent-potential-approximation prediction.

J. Hwang; P. Pianetta; Y.-C. Pao; C. K. Shih; Z.-X. Shen; P. A. P. Lindberg; R. Chow

1988-01-01

416

Explosive depassivation of amorphous alloys during corrosion  

SciTech Connect

It has been shown that, during active and passive corrosion, Fe{sub 80-x}Cr{sub x}P{sub 13}C{sub 7} amorphous alloys can be transformed into a crystalline modification. Crystallization of alloys is a result of selective dissolution and can lead to explosive depassivation upon long-term exposure of alloys in HCl solutions.

Vasil`ev, V.Yu.; Mikaelyan, A.S.; Isirikyan, A.A. [Moscow Institute of Steel and Alloys, Moscow (Russian Federation)

1994-09-01

417

Cytotoxicity of Titanium and Titanium Alloying Elements  

Microsoft Academic Search

It is commonly accepted that titanium and the titanium alloying elements of tantalum, niobium, zirconium, molybdenum, tin, and silicon are biocompatible. However, our research in the development of new titanium alloys for biomedical applications indicated that some titanium alloys containing molybdenum, niobium, and silicon produced by powder metallurgy show a certain degree of cytotoxicity. We hypothesized that the cytotoxicity is

Y. Li; C. Wong; J. Xiong; P. Hodgson; C. Wen

2010-01-01

418

SUPERCONDUCTIVITY OF TECHNETIUM ALLOYS AND COMPOUNDS  

Microsoft Academic Search

The superconducting transition temperatures of Mo- Tc alloys are ; reported. Critical field measurements of a 50 atomic per cent alloy indicate ; that it might be a promising material for superconducting magnets. The ; similarity of Tc and Re with respect to alloy and intermetallic compound ; formation is noted. The superconducting transition temperatures of the compounds ; ZrTc

V. B. Compton; E. Corenzwit; J. P. Maita; B. T. Matthias; F. J. Morin

1961-01-01

419

Uranium-fissium alloys containing technetium  

Microsoft Academic Search

A recent study (Report ANL-6495) was completed in which the phase ; relationships and decomposition kinetics of alloys with the complete fissium ; analysis were measured and compared with U-Fs alloys without technetium. The ; presence of the Tc addition appeared to have a relatively minor influence on the ; U-Fs alloys. (W.D.M.);

R. Bohl

1962-01-01

420

Fundamental aspects of the corrosion of alloys  

Microsoft Academic Search

Phenomenological equations are given for the steady state dissolution of alloys and their composition at the surface. The slow component with the smallest rate constant essentially determines the steady state dissolution rate and is enriched in the alloy surface. The phenomenological equations are compared to experimental results both for active and passive alloys. In ideal cases, phenomenological rate constants are

K. E. Heusler

1997-01-01

421

Blood Types  

E-print Network

Broadcast Transcript: According to the Japanese, you can tell a lot about a person by their blood type: Type A is the farmer, calm and responsible; Type B is the hunter, independent and creative; Type AB is humanistic, cool and sociable; and Type O...

Hacker, Randi; Tsutsui, William

2007-03-14

422

Alloy Semiconductor Crystal Growth Under Microgravity  

SciTech Connect

Microgravity studies on the dissolution and crystallization of In{sub x}Ga{sub 1-x}Sb have been done using a sandwich combination of InSb and GaSb as the starting material using the Chinese recoverable satellite. The same type of experiment was performed under 1G gravity condition for comparison. From these experiments and the numerical simulation, it is found that the shape of the solid/liquid interface and composition profile in the solution was found to be significantly affected by gravity. GaSb seed was dissolved faster than GaSb feed even though the GaSb feed temperature was higher than that of GaSb seed temperature. These results clearly indicate that solute transport due to gravity affects dissolution and growth processes of alloy semiconductor bulk crystals.

Hayakawa, Yasuhiro; Arivanandhan, Mukannan; Rajesh, Govindasamy; Tanaka, Akira [Research Institute of Electronics, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu, Shizuoka 432-8011 (Japan); Ozawa, Tetsuo [Shizuoka Institute of Science and Technology, 2200-2 Toyozawa, Fukuroi, Shizuoka 437-8555 (Japan); Okano, Yasunori [Graduate School of Engineering Science, Osaka University, 1-3 Machiganeyama, Osaka 560-8531 (Japan); Sankaranarayanan, Krishnasamy [Alagappa University, Karaikudi, Tamilnadu (India); Inatomi, Yuko [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510 (Japan)

2010-12-01

423

Magnetism in rare-earth alloys  

NASA Astrophysics Data System (ADS)

Low dimensional rare-earth alloys reveal a rich phase diagram which always incorporate a ferromagnetic (FM) phase. Here we show that rare-earth ferromagnetism in low dimensions is due to double-exchange mechanism. We use the bosonized version of the one-dimensional Anderson lattice model in Toulouse limit to characterize the properties of this emerging FM phase. We give a comprehensive description of the FM ordering of the correlated electrons which appears at intermediate couplings and doping. Determine the critical properties of the phase transitions into the quantum disordered paramagnetic phases. The obtained phase transitions have been identified to be an order-disorder transition of the quantum random transverse-field Ising type.

Gulacsi, M.

2014-08-01

424

Development of New Titanium-Molybdenum Alloys with Changeable Young's Modulus for Spinal Fixture Devices  

NASA Astrophysics Data System (ADS)

Metallic implant rods that are used to design spinal fixtures should have a Young's modulus that is not only sufficiently low to prevent stress shielding for the patient but also sufficiently high to suppress springback for the surgeon. Therefore, there is a need for novel titanium alloys with good biocompatibility and a changeable Young's modulus. Molybdenum is non-toxic, and Ti-Mo alloys possess good biocompatibility. In metastable ?-type Ti-Mo alloys, an ? phase can be introduced by deformation at room temperature. This study investigated the effects of deformation-induced phases on the mechanical properties of a metastable ?-type Ti-16Mo alloy. The experimental results indicate that the Young's modulus, tensile strength, and Vickers hardness are increased remarkably by cold rolling. The microstructural observation result by transmission electron microscopy (TEM) shows that the deformation-induced ? phase transformation occurs during cold rolling in the Ti-16Mo alloy. Therefore, the increase in Young's modulus of the alloy after cold rolling at room temperature can be attributed to a deformation-induced ? phase.

Zhao, Xingfeng; Niinomi, Mitsuo; Nakai, Masaaki; Hieda, Junko

425

Ab initio atomistic thermodynamics study on the oxidation mechanism of binary and ternary alloy surfaces.  

PubMed

Utilizing a combination of ab initio density-functional theory and thermodynamics formalism, we have established the microscopic mechanisms for oxidation of the binary and ternary alloy surfaces and provided a clear explanation for the experimental results of the oxidation. We construct three-dimensional surface phase diagrams (SPDs) for oxygen adsorption on three different Nb-X(110) (X = Ti, Al or Si) binary alloy surfaces. On the basis of the obtained SPDs, we conclude a general microscopic mechanism for the thermodynamic oxidation, that is, under O-rich conditions, a uniform single-phase SPD (type I) and a nonuniform double-phase SPD (type II) correspond to the sustained complete selective oxidation and the non-sustained partial selective oxidation by adding the X element, respectively. Furthermore, by revealing the framework of thermodynamics for the oxidation mechanism of ternary alloys through the comparison of the surface energies of two separated binary alloys, we provide an understanding for the selective oxidation behavior of the Nb ternary alloy surfaces. Using these general microscopic mechanisms, one could predict the oxidation behavior of any binary and multi-component alloy surfaces based on thermodynamics considerations. PMID:25681933

Liu, Shi-Yu; Liu, Shiyang; Li, De-Jun; Wang, Sanwu; Guo, Jing; Shen, Yaogen

2015-02-14

426

Microstructure Evaluation of Fe-BASED Amorphous Alloys Investigated by Doppler Broadening Positron Annihilation Technique  

NASA Astrophysics Data System (ADS)

Microstructure of Fe-based amorphous and nanocrystalline soft magnetic alloy has been investigated by X-ray diffraction (XRD), transmission electronic microscopy (TEM) and Doppler broadening positron annihilation technique (PAT). Doppler broadening measurement reveals that amorphous alloys (Finemet, Type I) which can form a nanocrystalline phase have more defects (free volume) than alloys (Metglas, Type II) which cannot form this microstructure. XRD and TEM characterization indicates that the nanocrystallization of amorphous Finemet alloy occurs at 460C, where nanocrystallites of ?-Fe with an average grain size of a few nanometers are formed in an amorphous matrix. With increasing annealing temperature up to 500C, the average grain size increases up to around 12 nm. During the annealing of Finemet alloy, it has been demonstrated that positron annihilates in quenched-in defect, crystalline nanophase and amorphous-nanocrystalline interfaces. The change of line shape parameter S with annealing temperature in Finemet alloy is mainly due to the structural relaxation, the pre-nucleation of Cu nucleus and the nanocrystallization of ?-Fe(Si) phase during annealing. This study throws new insights into positron behavior in the nanocrystallization of metallic glasses, especially in the presence of single or multiple nanophases embedded in the amorphous matrix.

Lu, Wei; Huang, Ping; Wang, Yuxin; Yan, Biao

2013-07-01

427

Structural and magnetic properties of Cu50Mn25Al25-xGax Heusler alloys  

NASA Astrophysics Data System (ADS)

The structural and magnetic behavior of melt spun Cu50Mn25Al25-xGax (x=0, 2, 4, 8 and 10 at%) alloys synthesized in the form of ribbons have been investigated. Formation of Heusler single phase of the Cu2MnAl structure has been found only for the alloys with x?8. Further increase of Ga content gives rise to the formation of ?-Cu9Al4 type phase together with Cu2MnAl Heusler phase. Long term annealing of the Cu50Mn25Al25-xGax (x=0 and 8) alloys at 903 K for 30 h leads to the formation of ?-Mn and ?-Cu9Al4 type phases. The alloys are ferromagnetically ordered and the saturation magnetization (Ms) decreases slightly with increasing Ga concentration. Annealing of the ribbons significantly changes the magnetic properties of Cu50Mn25Al25-xGax alloys. The decomposition of the Cu2MnAl Heusler phase into ?-Mn and ?-Cu9Al4 phases leads to the decrease in the magnitude of Ms. The splitting in the zero field cooled (ZFC) and field cooled (FC) magnetization curves at low temperature has been observed for the Cu50Mn25Al25-xGax (x=0-10) alloys.

Singh, Devinder; Tiwari, R. S.; Srivastava, O. N.

2013-02-01

428

Study of the properties and the choice of alloys for bladed disks (blisks) and a method for their joining  

NASA Astrophysics Data System (ADS)

The choice of materials for the bladed disks (blisks) that are intended for next-generation aviation gas turbine engines is grounded. As blade materials, single crystals of light heterophase ?' + ? VKNA-type alloys based on the ?'(Ni3Al) intermetallic compound with an ordered structure are proposed. The choice of novel deformable EP975-type nickel superalloys, which are intended for operation at 800-850C, as the disk material is grounded. It is shown that the most effective method for forming one-piece joints of an Ni3Al-based alloy and a high-alloy EP975-type nickel superalloy is the new process of solid-phase pressure welding under conditions of high-temperature superplasticity. Solid-phase joints are formed for heterophase Ni3Al-based alloy single crystals and deformable EK61 and EP975 nickel alloys. The gradient structures in the zone of the solid-phase joints that form under the conditions of low- and high-temperature superplasticity at homologous temperatures of 0.6 T m and 0.9 T m are studied. The character and direction of the diffusion processes at the joint of an intermetallic alloy single crystal and a deformable polycrystalline alloy are determined.

Povarova, K. B.; Valitov, V. A.; Obsepyan, S. V.; Drozdov, A. A.; Bazyleva, O. A.; Valitova, E. V.

2014-09-01

429

Experimenting with hot isostatically pressed (HIP) nano grained bismuth-telluride-based alloys  

NASA Astrophysics Data System (ADS)

Hot Isostatic Pressing (HIP) is was used for compaction of nano grained bismuth-telluride samples and results were compared to Spark Plasma Sintered (SPS) samples of the same materials. The powders were essentially the same as presented by Vasilevskiy1 et al, 2010. The (BixSb1-x)2(TeySe1-y)3 thermoelectric alloys studied in this article were produced by mechanical alloying under an inert atmosphere. The p-type alloy composition corresponds to x = 0.2, y = 1 and for the n-type material x = 0.95, y = 0.95. For HIP treatment the n-and p-type powders were encapsulated in copper cylinders under protective argon atmosphere. The HIP temperature was kept low to avoid excess grain growth of the materials. The electrical conductivity, carrier mobility, carrier concentration and Seebeck coefficient of HIP and SPS compacted materials were measured and compared.

Virta, Jouko; Tervo, Jyrki

2012-06-01

430

Chloride ion effect and alloying effect on dealloying-induced formation of nanoporous AuPt alloy  

NASA Astrophysics Data System (ADS)

The dealloying of the rapidly solidified Al66Au23.8Pt10.2 precursor in the 5 wt.% HCl or 20 wt.% NaOH solution has been investigated using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and transmission electron microscopy, in order to clarify the chloride ion effect and alloying effect on the formation of nanoporous Au-Pt alloy. The Al66Au23.8Pt10.2 precursor is composed of a single Al2Au-type intermetallic compound and only Au(Pt) solid solution can be identified in the as-dealloyed sample. The Pt addition can significantly refine the nanoporous structure during the dealloying of the Al66Au23.8Pt10.2 precursor either in the HCl or NaOH solution. Moreover, the alloying effect of Pt markedly exceeds the coarsening effect of chloride ion adsorption for the formation of nanoporous Au-Pt. The average ligament size is 5.2 0.7 and 3.3 0.4 nm for the nanoporous Au-Pt alloy obtained in the HCl and NaOH solution, respectively. In addition, electrochemical measurements including potentiodynamic polarization and cyclic voltammetry have also been performed on the Al66Au23.8Pt10.2 precursor.

Wang, Yan; Xu, Junling; Wu, Bo

2013-07-01

431

Vacuum thermal-mechanical fatigue behavior of two iron-base alloys  

NASA Technical Reports Server (NTRS)

The present study extends the concept of in-phase grain boundary ratcheting to two iron-base alloys (Type 304 stainless steel and A286 alloy) and provides a clearer interpretation of out-of-phase grain boundary ratcheting effects observed in the A286 alloy which does not exhibit geometric instability. Elevated-temperature low-cycle thermal-mechanical fatigue tests in an ion-pumped ultrahigh vacuum chamber revealed significant effects of frequency and combined temperature-strain cycling on fatigue life. In-phase thermal cycling (tension at high temperature and compression at low temperature) caused large life reductions in both materials due to grain boundary cavitation caused by unreversed grain boundary sliding (grain boundary ratcheting). Out-of-phase thermal cycling (tension at low temperature and compression at high temperature) also caused large cyclic life reductions in both materials. In the A286 alloy, out-of-phase life reductions are attributed to compressive ratcheting.

Sheffler, K. D.

1976-01-01

432

Microstructural characterization of selected AEA/UCSB model FeCuMn alloys  

SciTech Connect

A set of 22 model ferritic alloys was purchased as part of a collaborative research program by the AEA Harwell Laboratory and the University of California at Santa Barbara. Nine of these alloys were selected by the Oak Ridge National Laboratory for use in a series of ion irradiation experiments investigating dispersed barrier hardening. These nine alloys contain varying amounts of copper, manganese, titanium, carbon, and nitrogen. The alloys have been characterized by transmission electron microscopy in the as-received condition to provide a baseline for comparison with the irradiated specimens. A description of the microstructural observations is provided for future reference. This summary focuses on the type and size distributions of the precipitates present; grain size and dislocation measurements are also included.

Rice, P.M.; Stoller, R.E.

1996-06-01

433

Ab initio study on stability of half-metallic Co-based full-Heusler alloys  

NASA Astrophysics Data System (ADS)

We perform the first-principles density functional calculations of Co-based full-Heusler alloys, exploring 25 possible combinations of Co2YZ (Y=Ti, V, Cr, Mn, and Fe; Z=Al, Ga, Si, Ge, and Sn) in order to clarify the stability for the Co-related atomic disorder, because this type of disorder is considered to degrade the spin polarization of Co2YZ. We found that the disorder between Co and Y atoms correlates with the total valence electron charges around Y atom, because a difference in valence electron charges between Co and Y atoms leads to a different shape of the local potential at each site. This means that Ti-based alloys are better than Cr-, Mn-, and Fe-based alloys in preventing the atomic disorder between Co and Y atoms. From our results, we propose stable Co-based full-Heusler alloys with excellent prospects for half-metallic ferromagnets.

Miura, Yoshio; Shirai, Masafumi; Nagao, Kazutaka

2006-04-01

434

Mechanisms of linear anelasticity in Fe- M and Fe-Al- M ( M = Ga, Ge) alloys  

NASA Astrophysics Data System (ADS)

Linear anelastic effects in binary and ternary alloys of iron with 13 and 17 at % Ga, 12 at % Ge, and 4-8 at % Al (Fe-13Ga, Fe-17Ga, Fe-12Ge, Fe-8Al-3Ga, Fe-8Al-4Ge, and Fe-4Al-8Ge) have been investigated. In all of these alloys, thermally activated effects of linear anelasticity have been found and identified that are caused by point defects in interstitial (Snoek-type relaxation) and substitutional (Zener relaxation) solid solutions, as well as by dislocations (Hasiguti effect), and by grain boundaries. The effects of the alloy composition on the activation parameters of the above-mentioned relaxation mechanisms have been determined. In addition, frequency-independent effects related to processes of structural rearrangement, such as ordering and disordering of the alloys have been revealed due to the specific features in the curves of the temperature dependences of internal friction for almost all compositions.

Golovin, I. S.

2013-12-01

435

The Effects of Test Temperature, Temper, and Alloyed Copper on the Hydrogen-Controlled Crack Growth Rate of an Al-Zn-Mg-(Cu) Alloy  

SciTech Connect

The hydrogen embrittlement controlled stage II crack growth rate of AA 7050 (6.09 wt.% Zn, 2.14 wt% Mg, 2.19 wt.% Cu) was investigated as a function of temper and alloyed copper level in a humid air environment at various temperatures. Three tempers representing the underaged, peak aged, and overaged conditions were tested in 90% relative humidity (RH) air at temperatures between 25 and 90 C. At all test temperatures, an increased degree of aging (from underaged to overaged) produced slower stage II crack growth rates. The stage II crack growth rate of each alloy and temper displayed Arrhenius-type temperature dependence with activation energies between 58 and 99 kJ/mol. For both the normal copper and low copper alloys, the fracture path was predominantly intergranular at all test temperatures (25-90 C) in each temper investigated. Comparison of the stage II crack growth rates for normal (2.19 wt.%) and low (0.06 wt.%) copper alloys in the peak aged and overaged tempers showed the beneficial effect of copper additions on stage II crack growth rate in humid air. In the 2.19 wt.% copper alloy, the significant decrease ({approx} 10 times at 25 C) in stage II crack growth rate upon overaging is attributed to an increase in the apparent activation energy for crack growth. IN the 0.06 wt.% copper alloy, overaging did not increase the activation energy for crack growth but did lower the pre-exponential factor, {nu}{sub 0}, resulting in a modest ({approx} 2.5 times at 25 C) decrease in crack growth rate. These results indicate that alloyed copper and thermal aging affect the kinetic factors that govern stage II crack growth rate. Overaged, copper bearing alloys are not intrinsically immune to hydrogen environment assisted cracking but are more resistant due to an increased apparent activation energy for stage II crack growth.

G.A. Young, Jr.; J.R. Scully

2000-09-17

436

Diffusion phase transitions in alloys  

NASA Astrophysics Data System (ADS)

We present a critical analysis of research on the thermodynamics, kinetics, and morphology of diffusion phase transitions in alloys. We show that diffusion phase transitions are mainly driven by the chemical potential difference due to a change in the sign of the chemical interaction among the component atoms. We explain how the sign of the chemical interaction energy can be obtained from experimental measurements. Examples are given to illustrate the kinetics and morphology of the ordering-separation phase transition in Ni- and Co-based alloys. We show how introducing the concept of the ordering-separation phase transition may affect our thinking in this area.

Ustinovshchikov, Yu I.

2014-07-01

437

Alloy 718 for Oilfield Applications  

NASA Astrophysics Data System (ADS)

Alloy 718 (UNS N07718) was developed for use in aircraft gas turbine engines, but its unique combination of room-temperature strength and aqueous corrosion resistance made it a candidate for oilfield fasteners, valves, drill tools, and completion equipment. As well environments became more severe, stress corrosion and hydrogen embrittlement failures in production equipment drove the evolution of the composition and microstructure that distinguish today's oilfield-grade 718 from aerospace grades. This paper reviews the development of the grade and its applications and describes some of its unique characteristics, testing, and manufacturing methods as well as newer alloys designed for high-pressure high-temperature (HPHT) conditions.

deBarbadillo, John J.; Mannan, Sarwan K.

2012-02-01

438

Stress corrosion cracking behavior of irradiated model austenitic stainless steel alloys.  

SciTech Connect

Slow-strain-rate tensile tests (SSRTs) and posttest fractographic analyses by scanning electron microscopy were conducted on 16 austenitic stainless steel (SS) alloys that were irradiated at 289 C in He. After irradiation to {approx}0.3 x 10{sup 21} n{center_dot}cm{sup {minus}2} and {approx}0.9 x 10{sup 21} n{center_dot}cm{sup {minus}2} (E >1 MeV), significant heat-to-heat variations in the degree of intergranular and transgranular stress corrosion cracking (IGSCC and TGSCC) were observed. Following irradiation to a fluence of {approx}0.3 x 10{sup 21} n{center_dot}cm{sup {minus}2}, a high-purity laboratory heat of Type 316L SS (Si {approx} 0.024 wt%) exhibited the highest susceptibility to IGSCC. The other 15 alloys exhibited negligible susceptibility to IGSCC at this low fluence. The percentage of TGSCC on the fracture surfaces of SSRT specimens of the 16 alloys at {approx}0.3 x 10{sup 21} n{center_dot}cm{sup {minus}2} (E > 1 MeV) could be correlated well with N and Si concentrations; all alloys that contained <0.01 wt.% N and <1.0 wt. % Si were susceptible, whereas all alloys that contained >0.01 wt.% N or >1.0 wt.% Si were relatively resistant. High concentrations of Cr were beneficial. Alloys that contain <15.5 wt.% Cr exhibited greater percentages of TGSCC and IGSCC than those alloys with {approx}18 wt.% Cr, whereas an alloy that contains >21 wt.% Cr exhibited less susceptibility than the lower-Cr alloys under similar conditions.

Chung, H. M.; Karlsen, T. M.; Ruther, W. E.; Shack, W. J.; Strain, R. V.

1999-07-16

439

Bond Strength of Resin Cements to Noble and Base Metal Alloys with Different Surface Treatments  

PubMed Central

Objectives: The bond strength of resin cements to metal alloys depends on the type of the metal, conditioning methods and the adhesive resins used. The purpose of this study was to evaluate the bond strength of resin cements to base and noble metal alloys after sand blasting or application of silano-pen. Materials and Method: Cylinders of light cured Z 250 composite were cemented to Degubond 4 (Au Pd) and Verabond (Ni Cr) alloys by either RelyX Unicem or Panavia F2, after sandblasting or treating the alloys with Silano-Pen. The shear bond strengths were evaluated. Data were analyzed by three-way ANOVA and t tests at a significance level of P<0.05. Results: When the alloys were treated by Silano-Pen, RelyX Unicem showed a higher bond strength for Degubond 4 (P=0.021) and Verabond (P< 0.001). No significant difference was observed in the bond strength of Panavia F2 to the alloys after either of surface treatments, Degubond 4 (P=0.291) and Verabond (P=0.899). Panavia F2 showed a higher bond strength to sandblasted Verabond compared to RelyX Unicem (P=0.003). The bond strength of RelyX Unicem was significantly higher to Silano-Pen treated Verabond (P=0.011). The bond strength of the cements to sandblasted Degubond 4 showed no significant difference (P=0.59). RelyX Unicem had a higher bond strength to Silano-Pen treated Degubond 4 (P=0.035). Conclusion: The bond strength of resin cements to Verabond alloy was significantly higher than Degubond 4. RelyX Unicem had a higher bond strength to Silano-Pen treated alloys. Surface treatments of the alloys did not affect the bond strength of Panavia F2.

Raeisosadat, Farkhondeh; Ghavam, Maryam; Hasani Tabatabaei, Masoomeh; Arami, Sakineh; Sedaghati, Maedeh

2014-01-01

440

Thermomechanical testing of FeNiCoTi shape memory alloy for active confinement of concrete  

NASA Astrophysics Data System (ADS)

The thermomechanical properties of a new type of shape memory alloy (SMA), FeNiCoTi, are explored in this paper with the aim of examining the feasibility of using this new material as transverse reinforcement for concrete structures subjected to earthquake loading. One advantage of using FeNiCoTi alloy is its cost effectiveness compared to commonly studied NiTi alloy. Differential scanning calorimetry (DSC) tests are conducted to investigate the transformation temperatures of FeNiCoTi alloy under different heat treatment methods and prestrain schemes. First, a heat treatment method is established to produce FeNiCoTi alloy with wide thermal hysteresis that is pertinent to civil structural applications. Next, recovery stress tests are conducted to explore the effect of parameters including heating method, heating temperature, heating rate, heating protocol and prestrain level on the recovery stress. An optimum prestrain level is determined based on the recovery stress results. Moreover, cyclic tests are carried out to examine the cyclic response of FeNiCoTi alloy after stress recovery. Thermal cyclic tests are also carried out on the FeNiCoTi alloy to better understand the effect of temperature variation on the recovery stress. In addition, reheating of the FeNiCoTi alloy after deformation is conducted to examine the reusability of the material after being subjected to excessive deformation. Test results of the FeNiCoTi alloy indicate that this cost-effective SMA can potentially be a promising new material for civil structural applications.

Chen, Qiwen; Andrawes, Bassem; Sehitoglu, Huseyin

2014-05-01