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1

Aluminum diffusion in Al-implanted AISI 321 stainless steel using accelerator-based characterization techniques  

NASA Astrophysics Data System (ADS)

The aluminum diffusion in near-surface layers of Al-implanted AISI 321 austenitic stainless steel (Fe/Cr18/Ni8/Ti) was studied using ion beam analysis techniques. The implanted samples were investigated at temperatures between 450°C and 650°C (treatment times up to 144 h in vacuum and in air). The Al-profiles were determined by the 992 keV resonance of the 27Al(p,?) 28Si nuclear reaction as well as by 4He +-Rutherford Backscattering Spectrometry (RBS). The experimental diffusion coefficients, obtained during this study using Fick's second law, were compared with corresponding literature concerning the aluminum diffusion in other relevant metallic materials. The determination of the depth profiles contributes to the interpretation of the high temperature oxidation behavior of Al-implanted stainless steel surfaces.

Noli, F.; Misaelides, P.; Bethge, K.

1998-04-01

2

Impact-wear behaviors of TiN and Ti–Al–N coatings on AISI D2 steel and WC–Co substrates  

Microsoft Academic Search

TiN and Ti–Al–N coatings were prepared on two different substrates, AISI D2 steel and WC–Co, by an arc ion plating (AIP) technique to investigate the impact-wear behaviors of coatings and substrate effect. The impact-wear behavior of both coatings was examined with a ball-on-plate impact test. The H3\\/E*2 value, the plastic deformation resistance of specimen played an important role to explain

Soon Young Yoon; Seog-Young Yoon; Won-Sub Chung; Kwang Ho Kim

2004-01-01

3

Microstructure and Corrosion Properties of AlCoCrFeNi High Entropy Alloy Coatings Deposited on AISI 1045 Steel by the Electrospark Process  

NASA Astrophysics Data System (ADS)

Electrospark deposition (ESD) was employed to clad the AlCoCrFeNi high-entropy alloy (HEA) on AISI 1045 carbon steel. The relationship between the microstructure and corrosion properties of the HEA-coated specimens was studied and compared with that of the copper-molded cast HEA material. Two major microstructural differences were found between the cast HEA material and the HEA coatings. First, the cast material comprises both columnar and equiaxed crystals with a columnar-to-equiaxed transition (CET), whereas the HEA coatings consist of an entirely columnar crystal structure. The CET phenomenon was analyzed based on Hunt's criterion. Second, unlike the cast HEA material, there was no obvious Cr-rich interdendritic segregation and nano-sized precipitate distributed within the dendrites of the HEA coating. With regard to corrosion properties, the corrosion current of the HEA-coated specimen was significantly lower than for the 1045 steel and the cast HEA material. This was attributed to the ESD specimen having a relatively high Cr oxide and Al oxide content at the surface. Moreover, for the ESD specimen, the absence of Cr-rich interdendritic phase and second-phase precipitation resulted in a relatively uniform corrosion attack, which is different from the severe galvanic corrosion attack that occurred in the cast specimen.

Li, Q. H.; Yue, T. M.; Guo, Z. N.; Lin, X.

2013-04-01

4

Long-term corrosion investigation of AISI 316L, Co-28Cr-6Mo, and Ti-6Al-4V alloys in simulated body solutions  

NASA Astrophysics Data System (ADS)

The long-term weight loss, ion release and surface composition of AISI 316L, the Co-28Cr-6Mo and Ti-6Al-4V alloys were investigated in phosphate buffered solutions (PBS) with various bovine serum albumin (BSA) concentrations. All the samples lost weight up to 14 weeks and then started to gain weight. This can be explained by precipitation of dissolved ions on the surface after 14 weeks of immersion. The quantities of the dissolved ions were measured in immersed solution for 8, 14 and 22 weeks by induced coupled plasma-optical emission spectrometer (ICP-OES). The amounts of Fe released from 316L, and Co and Mo released from the Co-28Cr-6Mo alloy decreased after 14 weeks of immersion in PBS and BSA solutions. This observation coincides with the weight change of the samples. The oxide layer composition and concentration of the specimens exposed to solutions for 22 weeks were identified by X-ray photoelectron spectroscopy (XPS) analysis. The XPS results revealed that chromium is the main component of the 316L and Co-28Cr-6Mo alloy. The high Cr concentration of the 316L and Co-Cr-Mo oxide layer corresponds with the slow dissolution rate of Cr compared to other alloying elements of the 316L and Co-28Cr-6Mo alloy.

Karimi, Shima; Nickchi, Tirdad; Alfantazi, Akram M.

2012-06-01

5

AISI direct steelmaking program  

SciTech Connect

AISI with co-funding from DOE has initiated a research and development program aimed at the development of a new process for direct steelmaking, and the program is discussed in this document. The project is expected to cost about $30 million over a three-year period, with the government providing approximately 77 percent of the funds and AISI the balance. In contrast to current steelmaking processes which are largely open and batch, the direct steelmaking process would be closed and continuous. Further, it would use coal directly, thereby avoiding the need for coke ovens. The second year of the Direct Steelmaking Program (November 29, 1989, through November 28, 1990) was a year of significant accomplishment. The various research programs proceeded essentially on schedule and the pilot plant, the centerpiece of the program, was completed about three months behind schedule but began operation in almost a picture-perfect manner. This report presents the last years accomplishments.

Aukrust, E.

1991-01-09

6

Design optimization of cutting parameters when turning hardened AISI 4140 steel (63 HRC) with Al 2O 3 + TiCN mixed ceramic tool  

Microsoft Academic Search

Due to their high hardness and wear resistance, Al2O3-based ceramics are one of the most suitable cutting tool materials for machining hardened steels. However, their high degree of brittleness usually leads to inconsistent results and sudden catastrophic failures. This necessitates a process optimization when machining hardened steels with Al2O3 based ceramic cutting tools. The present paper outlines an experimental study

Ersan Aslan; Necip Camu?cu; Burak Birgören

2007-01-01

7

Surface fatigue and failure characteristics of hot forged powder metal AISI 4620, AISI 4640, and machined AISI 4340 steel spur gears  

NASA Technical Reports Server (NTRS)

Spur gear surface fatigue endurance tests were conducted to investigate hot forged powder metal AISI 4620 and 4640 steel for use as a gear material, to determine endurance characteristics and to compare the results with machined AISI 4340 and 9310 steel gear materials. The as-forged and unground SISI 4620 gear exhibited a 10 percent fatigue life that was approximately one-fourth of that for AISI 9310 and less than one-half that for the AISI 4340 gears. The forged and finish ground AISI 4620 gears exhibited a 10 percent life, approximately 70 percent that of AISI 9310 and slightly better than that of AISI 4340. The AISI 4640 hot forged gears had less fracture toughness and slightly less fatigue life than the AISI 4620 test gears.

Townsend, D. P.

1986-01-01

8

Comparing statistical models and artificial neural networks on predicting the tool wear in hard machining D2 AISI steel  

Microsoft Academic Search

The current article presents an investigation into predicting tool wear in hard machining D2 AISI steel using neural networks.\\u000a An experimental investigation was carried out using ceramic cutting tools, composed approximately of Al2O3 (70%) and TiC\\u000a (30%), on cold work tool steel D2 (AISI) heat treated to a hardness of 60 HRC. Two models were adjusted to predict tool wear\\u000a for

Ramón Quiza; Luis Figueira; J. Paulo Davim

2008-01-01

9

A life study of AISI M-50 and Super Nitralloy spur gears with and without tip relief  

NASA Technical Reports Server (NTRS)

Tests were conducted at 170 F with groups of 3.5-in.-pitch-diameter spur gear with and without tip relief made of consumable-electrode vacuum melted (CVM) Spur Nitralloy (5Ni-2Al) and CVM AISI M-50 steel. The AISI M-50 gears without tip relief had lives approximately 50 percent longer than the Super Nitralloy gears without tip relief. However, the Super Nitralloy gears with tip relief had lives equal to the AISI M-50 gears without tip relief. The difference in lives were not statistically significant. All gears failed by classical pitting fatigue at the pitch circle. However, the AIAI M-50 gears with tip relief failed by tooth fracture. AISI M-50 gear sets without tip relief having a spalled gear tooth which were deliberately overrun after spalling had occurred, failed by tooth fracture.

Townsend, D. P.; Zaretsky, E. V.

1973-01-01

10

Tribological behaviour when face milling AISI 4140 steel with minimum quantity fluid application  

Microsoft Academic Search

Purpose – The purpose of this paper is to evaluate the performance of cutting fluid applied by minimum quantity technique when milling AISI 4140 steel with TiAlN coated cemented carbide inserts. Design\\/methodology\\/approach – The vegetable oil based cutting fluid evaluated was applied through a nozzle at the centre of the tool holder under vaporized conditions with a flow rate between

Wisley Sales; Marcelo Becker; Clovis S. Barcellos; Jánes Landre Jr; John Bonney; Emmanuel O. Ezugwu

2009-01-01

11

Tool Wear and Surface Roughness in Turning AISI 8620 using Coated Ceramic Tool  

Microsoft Academic Search

The purpose of this research paper is to study the tool wear and surface roughness of AISI 8620 material using coated ceramic tool by turning process. Ceramic cutting tools have outstanding material hardness, resistance to high temperatures, wear resistance, chemical stability and hot hardness. Ceramic tool with Al2O3 + TiC (golden) coating was used to investigate the surface roughness and

S. Thamizhmanii; K. Kamarudin; E. A. Rahim; A. Saparudin; S. Hassan

2007-01-01

12

Hard turning: AISI 4340 high strength low alloy steel and AISI D2 cold work tool steel  

Microsoft Academic Search

The aim of this paper is to evaluate the machinability of hardened steels at different levels of hardness and using a range of cutting tool materials. More specifically, the work was focused on the machinability of hardened AISI 4340 high strength low alloy steel and AISI D2 cold work tool steel. The tests involving the AISI 4340 steel were performed

J. G. Lima; R. F. Ávila; A. M. Abrão; M. Faustino; J. Paulo Davim

2005-01-01

13

Mechanical properties of martensitic alloy AISI 422  

SciTech Connect

HT9 is a martensitic stainless steel that has been considered for structural applications in liquid metal reactors (LMRs) as well as in fusion reactors. AISI 422 is a commercially available martensitic stainless steel that closely resembles HT9, and was studied briefly under the auspices of the US LMR program. Previously unpublished tensile, fracture toughness and charpy impact data on AISI 422 were reexamined for potential insights into the consequences of the compositional differences between the two alloys, particularly with respect to current questions concerning the origin of the radiation-induced embrittlement observed in HT9. 8 refs, 8 figs.

Huang, F.H.; Hu, W.L. (Westinghouse Hanford Co., Richland, WA (United States)); Hamilton, M.L. (Pacific Northwest Lab., Richland, WA (United States))

1992-09-01

14

Mechanical properties of martensitic alloy AISI 422  

SciTech Connect

HT9 is a martensitic stainless steel that has been considered for structural applications in liquid metal reactors (LMRs) as well as in fusion reactors. AISI 422 is a commercially available martensitic stainless steel that closely resembles HT9, and was studied briefly under the auspices of the US LMR program. Previously unpublished tensile, fracture toughness and charpy impact data on AISI 422 were re-examined for potential insights into the consequences of the compositional differences between the two alloys, particularly with respect to current questions concerning the origin of the radiation-induced embrittlement observed in HT9.

Hamilton, M.L. (Pacific Northwest Lab., Richland, WA (United States)); Huang, F.H.; Hu, Wan-Liang (Westinghouse Hanford Co., Richland, WA (United States))

1992-06-01

15

A comparison of borides formed on AISI 1040 and AISI P20 steels  

Microsoft Academic Search

In this study, some properties of borides formed on the AISI 1040 and AISI P20 steel substrates were investigated. Boronizing was performed at 800, 875, and 950°C for 2, 4, 6, and 8h by using Ekabor 2 powders. The hardness of borides was about 1500HVN. The depth of boride layers was ranged from 10?m to 180?m. The presence of borides

I. Uslu; H. Comert; M. Ipek; F. G. Celebi; O. Ozdemir; C. Bindal

2007-01-01

16

Warm multiaxial forging of AISI 1016 steel  

Microsoft Academic Search

In this work, the microstructural evolution in AISI 1016 steel processed by using warm multiaxial forging technique is studied. With increase in multiaxial forging strain, a finer substructure evolved. Structural evolution in pearlite phase is addressed in detail considering the strain paths and strain rate. Pearlitic cementite fragmented into ultrafine particles of about 100–300nm size. Warm multiaxial forging process also

A. K. Padap; G. P. Chaudhari; V. Pancholi; S. K. Nath

2010-01-01

17

Characterization of borided AISI 316L stainless steel implant  

Microsoft Academic Search

The present study reports on characterization of borided AISI 316L stainless steel implant. Boronizing heat treatment was performed on a cylindrical bar of AISI 316L austenitic surgical stainless steel with a diameter of 2mm and a length of 10mm using slurry salt bath consisting of borax, boric acid and ferro-silicon. The susbstrate AISI 316L was essentially containing 0.022wt% C, 0.79wt%

I. Özbek; B. A. Konduk; C. Bindal; A. H. Ucisik

2002-01-01

18

The effects of casting and forging processes on joint properties in friction-welded AISI 1050 and AISI 304 steels  

Microsoft Academic Search

The aim of the present study was to investigate the effects of investment casting and forging process on the microstructure\\u000a and mechanical properties of friction weldments, AISI 1050–AISI 304. A continuous-drive friction welding device with the automatic\\u000a control ability of friction time and forging pressure was designed and constructed. Factorial design of experiments was performed\\u000a to join investment cast AISI

Tolga Y. Sunay; Mumin Sahin; Sabri Altintas

2009-01-01

19

Crack Arrest Toughness of Two High Strength Steels (AISI 4140 and AISI 4340)  

Microsoft Academic Search

The crack initiation toughness (K\\u000a \\u000a c\\u000a ) and crack arrest toughness (K\\u000a \\u000a a\\u000a ) of AISI 4140 and AISI 4340 steel were measured over a range of yield strengths from 965 to 1240 MPa, and a range of test\\u000a temperatures from -53 to +74°C. Emphasis was placed onK\\u000a \\u000a a\\u000a testing since these values are thought to represent the minimum toughness

E. J. Ripling; J. H. Mulherin; P. B. Crosley

1982-01-01

20

Investigation of the mechanical properties and microstructure of friction welded joints between AISI 4140 and AISI 1050 steels  

Microsoft Academic Search

Joining of dissimilar metals is one of the most essential needs of industries. Manufacturing with joint of alloy steel and normal carbon steel is used in production, because it decreases raw material cost. In this study, joining of AISI 4140 steel (medium carbon and low alloy steel) and AISI 1050 steel (medium carbon steel) was successfully achieved. Mechanical properties, macro

Sare Celik; Ismail Ersozlu

2009-01-01

21

Hot hardness characteristics of ausformed AISI M-50, Matrix 2, WD-65, modified AISI 440-C, and Super Nitralloy  

NASA Technical Reports Server (NTRS)

Short-term hot hardness studies were performed with ausformed AISI M-50, Matrix 2, WD-65, modified AISI 440-C (14-4-1) and case hardened Super Nitralloy. Hardness levels of each material were measured at elevated temperatures in an electric furnace with a low oxygen environment. Test temperatures ranged from 294 to 877 K. The hot hardness characteristics of the ausformed AISI-M-50, Matrix 2 WD-65, and modified AISI 440-C were the same as those determined for high-speed tool steels. Hot hardness for these steels can be predicted within one point Rockwell C. The hot hardness characteristics of both the case and core of Super Nitralloy were superior to AISI 52100 but inferior to the high-speed tool steels. The short-term Rockwell C hardness at temperature for the Super Nitralloy material between 294 and 769 K can be predicted within one point Rockwell C hardness.

Chevalier, J. L.; Dietrich, M. W.; Zaretsky, E. V.

1973-01-01

22

Study of face milling of hardened AISI D3 steel with a special design of carbide tools  

Microsoft Academic Search

This paper studies the impact of a special carbide tool design on the process viability of the face milling of hardened AISI\\u000a D3 steel (with a hardness of 60 HRC), in terms of surface quality and tool life. Due to the advances in the manufacturing\\u000a of PVD AlCrN tungsten carbide coated tools, it is possible to use them in the manufacturing

H. R. Siller; C. Vila; C. A. Rodríguez; J. V. Abellán

2009-01-01

23

Stress relaxation of an AISI 1080 steel  

NASA Astrophysics Data System (ADS)

Stress relaxation is a simple test which offers means for evaluating the deformation dynamics of materials. The principal advantage of this method is that it scans a broad range of strain rates while straining the specimen by only a small amount. Therefore, it is possible to assume that the substructure of the material remains approximately constant during the test in order to obtain the stress as a function of the strain rate during this particular strain condition. The principal inconvenience of this test is the requirement of a highly stable testing machine—especially at very slow strain rates. In the present investigation, stress relaxation tests have been done at room temperature on an AISI 1080 steel fabricated by Companhia Belgo-Mineira and used for prestressed concrete. The tests were done using a servohydraulic machine in the strain control mode. The results indicate the existence of a mechanical equation of state.

Medrano, Ricardo E.; Gillis, Peter P.

1989-10-01

24

Cavitation erosion resistance of AISI 420 martensitic stainless steel laser-clad with nickel aluminide intermetallic composites and matrix composites with TiC reinforcement  

Microsoft Academic Search

The cavitation erosion behaviour of AISI 420 Martensitic stainless steel laser clad with NiAl–Ni3Al intermetallic composites (IC) and intermetallic matrix composites (IMC) with TiC reinforcement was investigated using a vibratory cavitation tester. The erosion resistance of IC and IMC coating was 3.3 and 3.6 times that of the as-received specimen and 2.4 and 2.6 times that of the heat treated

Muthukannan Duraiselvam; Rolf Galun; Volker Wesling; Barry L. Mordike; Rolf Reiter; Jörg Oligmüller

2006-01-01

25

Laser Surface Hardening of AISI 1045 Steel  

NASA Astrophysics Data System (ADS)

The study investigates laser surface hardening in the AISI 1045 steel using two different types of industrial laser: a high-power diode laser (HPDL) and a CO2 laser, respectively. The effect of process parameters such as beam power, travel speed on structure, case depth, and microhardness was examined. In most cases, a heat-affected zone (HAZ) formed below the surface; a substantial increase in surface hardness was achieved. In addition, big differences were found between the hardened specimens after HPDL surface hardening and CO2 laser surface hardening. For HPDL, depths of the HAZ were almost equal in total HAZ o, without surface melting. For CO2 laser, the depths changed a lot in the HAZ, with surface melting in the center. To better understand the difference of laser hardening results when use these two types of laser, numerical (ANSYS) analysis of the heat conduction involved in the process was also studied. For HPDL method, a rectangular beam spot and uniform energy distribution across the spot were assumed, while for CO2 laser, a circular beam spot and Gaussian energy distribution were assumed. The results showed that the energy distribution variety altered the thermal cycles of the HAZ dramatically. The rectangular HPDL laser beam spot with uniform energy distribution is much more feasible for laser surface hardening.

Li, Ruifeng; Jin, Yajuan; Li, Zhuguo; Qi, Kai

2014-09-01

26

Aluminum-silicon co-deposition by FB-CVD on austenitic stainless steel AISI 316  

NASA Astrophysics Data System (ADS)

Aluminum-silicon coatings were deposited on stainless steel AISI 316 in the temperature range of 540 to 560°C by CVD-FBR. It was used a fluidized bed with 2.5% silicon and 7.5% aluminum powder and 90% inert (alumina). This bed was fluidized with Ar and as an activator a mixture of HCl/H2 in ratios of 1/10 to 1/16. Furthermore, the deposition time of the coatings was varied between 45 minutes to 1.5 hours, with a 50% active gas, neutral gases 50%. Thermodynamic simulation was conducted with the Thermocalc software to get the possible compositions and amount of material deposited for the chosen conditions. The coatings presented the follow compounds FeAl2Si, FeAl2 and Fe2Al5. Aluminum-silicon coatings were heat treated to improve its mechanical properties and its behavior against oxidation for the inter diffusion of the alloying elements. The heat treatment causes the aluminum diffuse into the substrate and the iron diffuse into coating surface. This leads to the transformation of the above compounds in FeAl, Al2FeSi, Cr3Si, AlFeNi and AlCrFe.

Marulanda, J. L.; Perez, F. J.; Remolina-Millán, A.

2013-11-01

27

The characterization of vanadium boride coatings on AISI 8620 steel  

Microsoft Academic Search

Thermodiffusion coatings containing boron and vanadium (B+V) on AISI 8620 steel have been carried out by an initial boronizing in a salt bath consisting of borax, boric acid and ferro-silicon and followed by saturation with vanadium. The properties of the diffusion layer, namely microstructure, phase composition and elemental distribution of the vanadium boride layer, have been studied. The influence of

Saduman Sen

2005-01-01

28

The wear behaviour of duplex treated AISI 5140 steel  

Microsoft Academic Search

Purpose – This work aims to investigate the wear behavior of manganese phosphate coating on plasma nitrided AISI 5140 steel. Design\\/methodology\\/approach – Prior to manganese phosphate coating, plasma nitriding of substrates was performed at gas mixture of 50 percent H2 and 50 percent N2, for the different treatment parameters. The structural, mechanical and tribological properties of the substrates were determined

Yasar Totik; Akgun Alsaran; Ayhan Celik; Ihsan Efeoglu

2011-01-01

29

Evaluation of borides formed on AISI P20 steel  

Microsoft Academic Search

This study reports on an evaluation of borides formed on AISI P20 steel substrate. Boronizing was performed at 800, 875 and 950°C for 2, 4, 6 and 8h by using Ekabor 2 powders. The hardness of borides measured by means of Vickers indenter was about 1500 HVN. The depth of boride layers depending on temperature and process time was ranged

I. Uslu; H. Comert; M. Ipek; O. Ozdemir; C. Bindal

2007-01-01

30

Surface Fatigue Life of Contour Induction Hardened AISI 1552 Gears.  

National Technical Information Service (NTIS)

Two groups of spur gears manufactured from two different materials and heat treatments were endurance tested for surface fatigue life. One group was manufactured from AISI 1552 and was finished ground to a 0.4 micron (16 micro-in.) rms surface finish and ...

D. P. Townsend, A. Turza, M. Chaplin

1995-01-01

31

Magnetic properties of an AISI 420 martensitic stainless steel  

Microsoft Academic Search

The magnetic properties (coercive force, saturation and residual magnetization, and Curie temperature) of an AISI 420 steel were measured for different heat treatment conditions (quenching and tempering). The results show that the material is magnetically softer in the annealed condition and after oil quenching an increase of coercive force (MHc) and residual induction (Br) and a decrease of saturation magnetization

S. S. M. Tavares; D. Fruchart; S. Miraglia; D. Laborie

2000-01-01

32

Elevated temperature fracture toughness of AISI 403 martensitic stainless steel  

Microsoft Academic Search

The AISI 403 martensitic stainless steel is used as the end fitting material in pressurised heavy water reactors. The fracture toughness of single quenched and tempered, double quenched and tempered, and Nb-modified variety of this steel has been evaluated at 473 and 573 K. Elevated temperature results are compared with the room temperature values reported in earlier studies. The double

J. S Dubey; S. L Wadekar; J. K Chakravartty

1998-01-01

33

HOT FORMING OF AISI A2 TOOL STEEL  

Microsoft Academic Search

For further increase of economy of production of AISI A2 tool steel a study of possibility of expanding the hot working range and better prediction of flow stress has been carried out. By employing hot compression tests it was proved, that initial microstructures have influence on the lower limit and chemical composition on upper limit of hot working range. A

T. Ve; R. Turk; G. Kugler; M. Ter; I. Peru

2008-01-01

34

High Bandwidth Thermal Microscopy of Machining AISI 1045 Steel  

Microsoft Academic Search

A custom thermal microscope was constructed using a high-bandwidth thermal imaging system (40 megapixels\\/sec). The microscope was attached to a high-speed machining centre (20 thousand RPM\\/18.5 kW spindle) that was operated as a high-speed lathe to measure temperature distributions during orthogonal cutting of AISI 1045 steel at surface speeds of up to 605 m\\/min. Measurements were made for a wide

M. A. Davies; A. L. Cooke; E. R. Larsen

2005-01-01

35

Characterization of friction surfaced martensitic stainless steel (AISI 410) coatings  

Microsoft Academic Search

Friction surfacing is a candidate process for depositing corrosion and wear resistant coatings. Being a solid-state process,\\u000a it offers several advantages over conventional fusion welding based surfacing process. In the current work, martensitic stainless\\u000a steel AISI 410 was friction surfaced over mild steel substrates. Coating microstructures were characterized using light microscopy,\\u000a scanning electron microscopy and Xray diffraction. Coatings in as-deposited

Ramesh Puli; E. Nandha Kumar; G. D. Janaki Ram

2011-01-01

36

Corrosion Resistance of Friction Surfaced AISI 304 Stainless Steel Coatings  

NASA Astrophysics Data System (ADS)

Corrosion resistance of friction surfaced AISI 304 coating in boiling nitric acid and chloride containing environments was found to be similar to that of its consumable rod counterpart. This was in contrast to the autogenous fusion zone of GTAW weld which showed inferior corrosion resistance with respect to the consumable rod. The superior corrosion resistance of friction surfaced coatings was attributed to the absence of ?-ferrite in it.

Khalid Rafi, H.; Phanikumar, G.; Prasad Rao, K.

2013-02-01

37

Comparison of pitting fatigue life of ausforged and standard forged AISI M-50 and AISI 9310 spur gears  

NASA Technical Reports Server (NTRS)

Standard forged and ausforged spur gears made of vacuum-induction-melted, consumable-electrode, vacuum-arc-remelted AISI M-50 steel were tested under conditions that produced fatigue pitting. The gears were 8.89 cm (3.5 in.) in pitch diameter and had tip relief. The M-50 standard forged and ausforged test results were compared with each other. They were then compared with results for machined vacuum-arc-remelted AISI 9310 gears tested under identical conditions. Both types of M-50 gears had lives approximately five times that of the 9310 gears. The life at which 10 percent of the M-50 ausforged gears failed was slightly less than that at which the M-50 standard forged gears failed. The ausforged gears had a slightly greater tendency to fail by tooth fracture than did the standard forged gears, most likely because of the better forging and grain flow pattern of standard forged gears.

Townsend, D. P.; Bamberger, E. N.; Zaretsky, E. V.

1975-01-01

38

The growth kinetics of borides formed on boronized AISI 4140 steel  

Microsoft Academic Search

The growth kinetics of boride layer on boronized AISI 4140 steel is reported. Steel samples were boronized in molten borax, boric acid and ferro-silicon bath at 1123, 1173 and 1223K for 2, 4, 6 and 8h, respectively. The morphology and types of borides formed on the surface of AISI 4140 steel substrate were analyzed by means of optical microscopy, scanning

Saduman Sen; Ugur Sen; Cuma Bindal

2005-01-01

39

Evaluation of AISI 316L stainless steel welded plates in heavy petroleum environment  

Microsoft Academic Search

This work presents the study done on the effect of welding heating cycle on AISI 316L austenitic stainless steel corrosion resistance in a medium containing Brazilian heavy petroleum. AISI 316L stainless steel plates were welded using three levels of welding heat input. Thermal treatments were carried out at two levels of temperatures (200 and 300°C). The period of treatment in

Cleiton Carvalho Silva; Jesualdo Pereira Farias; Hosiberto Batista de Sant’Ana

2009-01-01

40

The study of influenced factors affecting to quality of cylindrical grinding harden AISI 4140 steel  

Microsoft Academic Search

The objective of this research was to study factors, which were affected on surface roughness and roundness in cylindrical grinding of harden AISI 4140 steel. Specimen used in the experiment was AISI 4140 steel that hardening at 51±3 HRC. Studied factors were consisted of revolution speed of workpiece, feed rate, and depth of cut. Full factorial experimental design was conducted

Komson Jirapatarasilp; Sittichai Kaewkuekool; P. Klahan

2010-01-01

41

Effect of magnetic treatment on fatigue life of AISI 4140 steel  

Microsoft Academic Search

The effect of magnetic field with different intensities on fatigue life of AISI 4140 steel has been investigated. For this purpose, unnotched and notched specimens were prepared from AISI 4140 steel. It was obtained that when the magnetic field especially was applied to the specimens at the stage of fatigue crack initiation, the fatigue life improved by reason of delaying

Ayhan Çelik; A. Fatih Yetim; Akgün Alsaran; Mehmet Karakan

2005-01-01

42

Evaluation of temperature and properties at interface of AISI 1040 steels joined by friction welding  

Microsoft Academic Search

Purpose – The purpose of this paper is to evaluate temperature and properties at interface of AISI 1040 steels joined by friction welding. Design\\/methodology\\/approach – In this study, AISI 1040 medium carbon steel was used in the experiments. Firstly, optimum parameters of the friction welding were obtained by using a statistical analysis. Later, the microstructures of the heat-affected zone are

Hilmi Kuscu; Ismail Becenen; Mumin Sahin

2008-01-01

43

Fluidized-Bed and Salt-Bath Heat Treating (AISI 4130 and 4340 Alloy Steels).  

National Technical Information Service (NTIS)

Using commercial alloy steels AISI 4130 and AISI 4340, a series of heat treating parametric studies were performed on specimens in both an electric fluidized-bed furnace and an electric neutral-salt-bath furnace. An evaluation of heat treating methods was...

W. L. Cyrus

1983-01-01

44

Fluidized-Bed and Salt-Bath Heat Treating (AISI 4130 and 4340 Alloy Steels).  

National Technical Information Service (NTIS)

Using commercial alloy steels AISI 4130 and AISI 4340, a series of heat-treating, parametric studies were performed on specimens in both an electric fluidized-bed furnace and an electric neutral salt-bath furnace. An evaluation of heat-treating methods wa...

W. L. Cyrus

1983-01-01

45

Assessment of XM-19 as a Substitute for AISI 348 in ATR Service  

Microsoft Academic Search

It has been proposed that XM-19 alloy be considered as a possible replacement steel for AISI 348 in the construction of Advanced Test Reactor (ATR) capsules. AISI 348 works well, but is currently very difficult to obtain commercially. The superior and desirable mechanical properties of XM-19 alloy have been proven in non-nuclear applications, but no data are available regarding its

F. A. Garner; L. R. Greenwood; R. E. Mizia; C. R. Tyler

2007-01-01

46

Inverse magnetostrictive sensitivity of martensitic stainless steel AISI410 and its application to pressure measurements  

Microsoft Academic Search

The inverse magnetostrictive sensitivity of martensitic stainless steel AISI-410 has been examined with intended application for pressure transducers in nuclear environments. The experiments were performed by applying tensile and compressive stresses to a specimen made of AISI-410, and then measuring the voltages induced in the secondary coil of the specimen for various excitation currents of 400 Hz supplied to the

K. Ara; M. Brakas

1975-01-01

47

The Effect of Cryogenic Treatment on the Properties of AISI D2  

Microsoft Academic Search

The tool steel AISI D2 is usually processed by vacuum hardening followed by multiple tempering cycles. Deep cold treatment in between the hardening and tempering processes could reduce processing time and improve the final properties. Blocks of AISI D2 were vacuum hardened from different austenitizing temperatures. The hardened blocks were then subjected to various combinations of single and multiple tempering

C. H. Surberg; P. F. Stratton; K. Lingenhöle

2009-01-01

48

The surface fatigue life of contour induction hardened AISI 1552 gears  

Microsoft Academic Search

Two groups of spur gears manufactured from two different materials and heat treatments were endurance tested for surface fatigue life. One group was manufactured from AISI 1552 and was finished ground to a 0.4 micron (16 micro-in.) rms surface finish and then dual frequency contour induction hardened. The second group was manufactured from CEVM AISI 9310 and was carburized, hardened,

Dennis P. Townsend; Alan Turza; Mike Chaplin

1995-01-01

49

Abrasive wear behavior of different case depth gas carburized AISI 8620 gear steel  

Microsoft Academic Search

In this study, abrasive wear behaviors of gas carburized AISI 8620 steels with different case depths were examined. AISI 8620 steels yield excellent carburizing results and are used in manufacturing of gears. Two carburized and quenched specimens with different case depths were produced. Specimens were prepared at HEMA Gear Factory. Wear tests were carried out using pin-on disc test machine.

M. Izciler; M. Tabur

2006-01-01

50

Weldability of AISI 430\\/AISI 1030 Steel Couples via the Synergic Controlled Pulsed (GMAW-P) and Manual Gas Metal Arc (GMAW) Welding Techniques  

Microsoft Academic Search

In this study, ferritic stainless steel (AISI 430)\\/medium-carbon steel (AISI 1030) couples, having two different properties of 10 mm thick, were welded by using the synergic controlled pulsed (GMAW-P) and manual gas metal arc welding (GMAW) techniques. Constant wire feed speed, voltage, welding speed, and gas flow rates (3.2 m\\/min, 22.5 V, 4 mm\\/s, 16 L\\/min) were used in these techniques. The interface appearances of

Tanju Teker; Turhan Kur?un

2011-01-01

51

A study of cumulative fatigue damage in AISI 4130 steel  

NASA Technical Reports Server (NTRS)

Experimental data were obtained using AISI 4130 steel under stress ratios of -1 and 0. A study of cumulative fatigue damage using Miner's and Kramer's equations for stress ratios of -1 and 0 for low-high, low-high-mixed, high-low, and high-low-mixed stress sequences has revealed that there is a close agreement between the theoretical and experimental values of fatigue damage and fatigue life. Kramer's equation predicts less conservative and more realistic cumulative fatigue damage than the popularly used Miner's rule does.

Jeelani, S.; Musial, M.

1986-01-01

52

Effect of nitrogen alloying and the electroslag refining process on the properties of AISI M41 steel  

NASA Astrophysics Data System (ADS)

Nitrogen produces very beneficial effects in high-speed steel and can therefore be regarded as a significant alloying element in ferrous materials. In order to attain the goal of this study, to investigate the effect of nitrogen alloying and the electroslag refining (ESR) process on the properties of AISI M41 steel, two high-speed steels were melted in an air induction furnace (IF). The first one is a standard AISI M41 high-speed steel. The second one is nitrogen-alloyed M41. The produced ingots were used as consumable electrodes in ESR under three different CaF2-based fluxes. The steel produced from the IF and ESR was heat treated. Hardness, secondary hardness, and microstructure were also studied. It was concluded that both ESR and nitrogen alloying improve the hardness profile of the quenched-tempered high-speed steels. The highest secondary hardness and highest softening resistance were attained by ESR of high-nitrogen high-speed steel (M41N) under CaF2/CaO/Al2O3: 55/30/15 slag. The ESR improves the shape, size, and distribution of precipitates in the produced ingot. Quenching and tempering treatment conditions the retained austenite that is present in the as-cast steel by precipitation of carbide and forming martensite on cooling to room temperature.

Mattar, Taha; El Fawakhry, Kamal; Halfa, Hossam; El Demerdash, Mahmoud

2006-12-01

53

WEAR STUDIES AND CUTTING TESTS OF Ti–Al–N–C NANOCOMPOSITE COATINGS IN MILLING OPERATIONS – TECHNICAL COMMUNICATION  

Microsoft Academic Search

New carbon-based nanostructured composite coatings of the material system Ti–Al–N–C were deposited on cemented carbide milling tools, and their feasibility for selected dry high-speed machining operations was assessed. For this purpose, wear studies with instrumented cutting machines in dry cutting tests were carried out in milling operations on Uddeholm hardened steels (AISI H13, and, AISI A2, respectively). The tools were

M. Stueber; C. Ziebert; H. Leiste; S. Ulrich; C. Sanz; E. Fuentes; I. Etxarri; M. Solay; A. Garcia; P. B. Barna; P. Hovsepian

2009-01-01

54

Formation of titanium aluminum nitride layers on AISI D2 steel by nitro-titanizing treatment  

NASA Astrophysics Data System (ADS)

In this study, titanium aluminum nitride coating was realized on AISI D2 steels by nitro-titanizing treatment. Steel samples were nitrided at 575 °C for 8 h in the first step of the coating process, and then titanized by thermo-reactive diffusion method in the powder mixture consisting of ferro-titanium, aluminum, ammonium chloride and alumina at 1000 °C for 2 h. The effects of the aluminum content to the coating bath were investigated. The thickness of the titanium aluminum nitride layer formed on the steel samples ranged from 6.30±0.5 to 7.89±0.34?m, depending on the aluminum content. The average micro-hardness value of the layer was 1468 ± 96 HV0.005 and 2630± 83 HV0.005. The phases formed on the coating layers are TiN, AlTi3N and Ti3Al2N2 which are characterized by XRD. EDS analysis results showed that coating layer includes titanium, aluminum and nitrogen.

Cegil, Ozkan; Sen, Saduman

2012-09-01

55

Atomic diffusion in laser surface modified AISI H13 steel  

NASA Astrophysics Data System (ADS)

This paper presents a laser surface modification process of AISI H13 steel using 0.09 and 0.4 mm of laser spot sizes with an aim to increase surface hardness and investigate elements diffusion in laser modified surface. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, pulse repetition frequency (PRF), and overlap percentage. The hardness properties were tested at 981 mN force. Metallographic study and energy dispersive X-ray spectroscopy (EDXS) were performed to observe presence of elements and their distribution in the sample surface. Maximum hardness achieved in the modified surface was 1017 HV0.1. Change of elements composition in the modified layer region was detected in the laser modified samples. Diffusion possibly occurred for C, Cr, Cu, Ni, and S elements. The potential found for increase in surface hardness represents an important method to sustain tooling life. The EDXS findings signify understanding of processing parameters effect on the modified surface composition.

Aqida, S. N.; Brabazon, D.; Naher, S.

2013-07-01

56

Electrical Resistivity and Thermal Conductivity of Nine Selected AISI Stainless Steels.  

National Technical Information Service (NTIS)

This technical report reviews the available experimental data and information on the electrical resistivity and thermal conductivity of nine selected AISI stainless steels and presents the recommended values from near absolute zero (1 K) to above the melt...

C. Y. Ho T. K. Chu

1977-01-01

57

Solid-particle erosion of tungsten carbide/cobalt cermet vs. hardened AISI 440C stainless steel.  

SciTech Connect

Solid-particle erosion tests were conducted on hardened AISI 440C stainless steel and a cermet that consisted of {approx}90 vol.% submicrometer WC embedded in {approx}10 vol.% Co. Angular Al{sub 2}O{sub 3} abrasives were used as the erodent. Experimental variables were: angle of impact = 20, 50, or 90 degrees; erodent velocity = 60 or 120 m/s; erodent nominal diameter = 63 or 143 {micro}m. For all test conditions, the stainless steel eroded faster than the cermet. Analysis of weight-loss data and examination of eroded surfaces by scanning electron microscopy indicated that the erosion mechanisms were similar for the two hard materials. Both exhibited significant plasticity when impacted, but the stainless steel's response to impact appeared to have been more ductile in nature.

Rateick, R. G., Jr.; Karasek, K. R.; Cunningham, A.; Goretta, K. C.; Routbort, J. L.; Energy Technology; Honeywell

2006-01-01

58

Texture evolution in thin-sheets on AISI 301 metastable stainless steel under dynamic loading  

SciTech Connect

The evolution of texture in thin sheets of metastable austenitic stainless steel AISI 301 is affected by external conditions such as loading rate and temperature, by inhomogeneous deformation phenomena such as twinning and shear band formation, and by the concurent strain induced phase transformation of the retained austenitc ({gamma}) into martensite ({alpha}). The present paper describes texture measurements on different gauges of AISI 301 prior and after uniaxial stretching under different conditions.

Kim, K.Y. [Posco Steels, Pohan, South Korea (Korea, Republic of); Kozaczek, K. [Oak Ridge National Lab., TN (United States); Kulkarni, S.M. [TRW Vehicle Safety Systems, Mesa, AZ (United States); Bastias, P.C.; Hahn, G.T. [Vanderbilt Univ., Nashville, TN (United States)

1995-05-08

59

The effect of boronizing and boro-chromizing on tribological performance of AISI 52100 bearing steels  

Microsoft Academic Search

Purpose – The purpose of this paper is to study the tribological behavior of hardened, boronized and boro-chromized AISI 52100 steel balls against boro-chromized AISI 1040 steel disk under 2, 5 and 10 N loads at 0.1 and 0.3 m\\/s sliding speeds. Design\\/methodology\\/approach – Boronizing treatment was realized at 1,000°C for 2 h in a slurry salt bath consisting of

Saduman Sen; Ugur Sen

2009-01-01

60

Experimental investigation on corrosion and hardness of ion implanted AISI 316L stainless steel  

Microsoft Academic Search

The AISI 316L stainless steel has been widely used both in artificial knee and hip joints in bio-medical applications. In the present study AISI 316L SS was implanted with two different ions: nitrogen and helium at 100keV with a dose of 1×1017ions\\/cm2 at room temperature. The crystallographic orientation and surface morphology were studied using X-ray diffraction (XRD) and scanning electron

V. Muthukumaran; V. Selladurai; S. Nandhakumar; M. Senthilkumar

2010-01-01

61

Creep behaviour and microstructural evolution in AISI 316LN + Nb steels at 650 °C  

Microsoft Academic Search

The paper deals with the effect of niobium in the wrought AISI 316LN steels on the long-term creep characteristics at 650°C. Casts B and C contained 0.1 and 0.3wt.%Nb, respectively. As a reference material the niobium free Cast A was used. Small additions of niobium to the AISI 316LN steel resulted in a significant reduction of the minimum creep rate

Vlastimil Vodárek

2011-01-01

62

ELECTROSLAG REMELTING OF AISI M41 HIGH SPEED TOOL STEEL SCRAP  

Microsoft Academic Search

Tools of pipes' internal threading manufactured from AISI M 41 high-speed tool steel.The scrap of these tools can not be reformed to a lower dimensions tool due to their complicated form. On the other hand AISI M41 steel con- tains expensive and sensitive alloying elements such as vanadium, chromium, molybdenum and tungsten. The traditional melting process of such scraps in-

Taha Mattar

63

Effect of Cryogenic Treatment on AISI M2 High Speed Steel: Metallurgical and Mechanical Characterization  

Microsoft Academic Search

This study aims to present the metallurgical and mechanical characterization of cryogenically treated AISI M2 high speed steel\\u000a (HSS) in terms of carbide precipitation and wear behavior. The samples of commercially available conventionally quenched and\\u000a tempered AISI M2 HSS were procured and subjected to cryogenic treatment at two levels ?110 °C (shallow treatment) and ?196 °C\\u000a (deep treatment) of temperature. The microstructures

Simranpreet Singh Gill; Jagdev Singh; Rupinder Singh; Harpreet Singh

2011-01-01

64

Fretting of AISI 9310 and selected fretting resistant surface treatments  

NASA Technical Reports Server (NTRS)

Fretting wear experiments were conducted with uncoated AISI 9310 mating surfaces, and with combinations incorporating a selected coating to one of the mating surfaces. Wear measurements and SEM observations indicated that surface fatigue, as made evident by spallation and surface crack formation, is an important mechanism in promoting fretting wear to uncoated 9310. Increasing humidity resulted in accelerated fretting, and a very noticeable difference in nature of the fretting debris. Of the coatings evaluated, aluminum bronze with a polyester additive was most effective at reducing wear and minimizing fretting damage to the mating uncoated surface, by means of a selflubricating film that developed on the fretting surfaces. Chromium plate performed as an effective protective coating, itself resisting fretting and not accelerating damage to the uncoated surface.

Bill, R. C.

1977-01-01

65

CO2 laser welding of AISI 321stainless steel  

NASA Astrophysics Data System (ADS)

CO2 laser welding of AISI 321austenitic stainless steel has been carried out. Bead on plate welds on 2 mm thick steel were performed with 450W CO2 laser at speeds ranging from 200 to 900 mm/min. It was observed that weld depth and width was decreased with increasing the speed at constant laser power. Butt welds on different sheet thickness of 1, 2 and 2.5 mm were performed with laser power of 450 W and at speed 750, 275 and 175 mm/min, respectively. The microstructures of the welded joints and the heat affected zones (HAZ) were examined by optical microscopy and SEM. The austenite/delta ferrite microstructure was reported in the welded zone. The microhardness and tensile strength of the welded joints were measured and found almost similar to base metal due to austenitic nature of steel.

Hussain, A.; Hamdani, A. H.; Akhter, R.

2014-06-01

66

Fretting of AISI 9310 and selected fretting resistant surface treatments  

NASA Technical Reports Server (NTRS)

Fretting wear experiments were conducted with uncoated AISI 9310 mating surfaces, and with combinations incorporating a selected coating to one of the mating surfaces. Wear measurements and SEM observations indicated that surface fatigue, as made evident by spallation and surface crack formation, is an important mechanism in promoting fretting wear to uncoated 9310. Increasing humidity resulted in accelerated fretting, and a very noticeable difference in nature of the fretting debris. Of the coatings evaluated, alumimum bronze with a polyester additive was most effective at reducing wear and minimizing fretting damage to the mating uncoated surface, by means of a self-lubricating film that developed on the fretting surfaces. Chromium plate performed as an effective protective coating, itself resisting fretting and not accelerating damage to the uncoated surface.

Bill, R. C.

1977-01-01

67

Investment cast AISI H13 tooling for automotive applications  

SciTech Connect

While many techniques exist for production of soft tooling, for die casting there is limited recent experience with cast tooling. The most common US alloy used for manufacture of die casting tooling is wrought AISI H13. If the performance of the cast material is comparable to the wrought counterpart, the use of investment cast HI 3 tooling directly from patterns made via rapid prototyping is of considerable interest. A metallurgical study of investment cast H13 was conducted to evaluate the mechanical behavior in simulated die casting applications. Variable thickness plate investment castings of AISI H13 hot work die steel were produced and characterized in the as-cast and heat-treated conditions. The characterization included light microscopy and mechanical testing. Wrought samples of standard and premium grade H13 were heat-treated and characterized similarly for comparison. Microstructural differences were observed in as-cast samples produced in different section thicknesses. Dendrite cell size and carbide morphology constituted the most prominent microstructural differences observed. After a full heat-treatment, microstructural differences between the wrought material and cast materials were slight regardless of section thickness.The mechanical properties of the cast and heat-treated material proved similar to the properties of the standard heat-treated wrought material. A thermal fatigue testing unit was to con-elate the heat checking susceptibility of H13 steel to its processing and consequent microstructural condition. Surface hardness decreased significantly with thermal cycling, and heat checking was observed in as few as 50 cycles. Thermal softening and thermal fatigue susceptibility were quantified and discussed relative to the microstructural conditions created by processing and heat-treatment. It was found that the premium grade wrought H13 steel provided the best overall resistance to heat checking.

Maguire, M.C.; Baldwin, M.D. [Sandia National Labs., Albuquerque, NM (United States); Hochanadel, P.W.; Edwards, G.R. [Colorado School of Mines, Golden, OH (United States)

1995-07-01

68

A Life Study of Ausforged, Standard Forged and Standard Machined AISI M-50 Spur Gears  

NASA Technical Reports Server (NTRS)

Tests were conducted at 350 K (170 F) with three groups of 8.9 cm (3.5 in.) pitch diameter spur gears made of vacuum induction melted (VIM) consumable-electrode vacuum-arc melted (VAR), AISI M-50 steel and one group of vacuum-arc remelted (VAR) AISI 9310 steel. The pitting fatigue life of the standard forged and ausforged gears was approximately five times that of the VAR AISI 9310 gears and ten times that of the bending fatigue life of the standard machined VIM-VAR AISI M-50 gears run under identical conditions. There was a slight decrease in the 10-percent life of the ausforged gears from that for the standard forged gears, but the difference is not statistically significant. The standard machined gears failed primarily by gear tooth fracture while the forged and ausforged VIM-VAR AISI M-50 and the VAR AISI 9310 gears failed primarily by surface pitting fatigue. The ausforged gears had a slightly greater tendency to fail by tooth fracture than the standard forged gears.

Townsend, D. P.; Bamberger, E. N.; Zaretsky, E. V.

1975-01-01

69

Joining of TiAl and steels by induction brazing  

Microsoft Academic Search

In order to develop the joining technology of TiAl and structural steels which gives a low cost and high strength joint, rapid induction brazing was investigated. The active silver based filler metal of 63Ag–35.2Cu–1.8Ti mass% (CUSIL-ABA) and the titanium based filler metal of 70Ti–15Cu–15Ni mass% (TICUNI) were selected. As joining materials, the structural steel AISI4340 and cast TiAl with composition

T. Noda; T. Shimizu; M. Okabe; T. Iikubo

1997-01-01

70

The Surface Fatigue Life of Contour Induction Hardened AISI 1552 Gears  

NASA Technical Reports Server (NTRS)

Two groups of spur gears manufactured from two different materials and heat treatments were endurance tested for surface fatigue life. One group was manufactured from AISI 1552 and was finished ground to a 0.4 micron (16 micro-in.) rms surface finish and then dual frequency contour induction hardened. The second group was manufactured from CEVM AISI 9310 and was carburized, hardened, and ground to a 0.4 micron (16 micro-in.) rms surface finish. The gear pitch diameter was 8.89 cm (3.5 in.). Test conditions were a maximum Hertz stress of 1.71 GPa (248 ksi), a bulk gear temperature of approximately 350 K (170 F) and a speed of 10,000 rpm. The lubricant used for the tests was a synthetic paraffinic oil with an additive package. The test results showed that the 10 percent surface fatigue (pitting) life of the contour hardened AISI 1552 test gears was 1.7 times that of the carburized and hardened AISI 9310 test gears. Also there were two early failures of the AISI 1552 gears by bending fatigue.

Townsend, Dennis P.; Turza, Alan; Chaplin, Mike

1995-01-01

71

The surface fatigue life of contour induction hardened AISI 1552 gears  

NASA Astrophysics Data System (ADS)

Two groups of spur gears manufactured from two different materials and heat treatments were endurance tested for surface fatigue life. One group was manufactured from AISI 1552 and was finished ground to a 0.4 micron (16 micro-in.) rms surface finish and then dual frequency contour induction hardened. The second group was manufactured from CEVM AISI 9310 and was carburized, hardened, and ground to a 0.4 micron (16 micro-in.) rms surface finish. The gear pitch diameter was 8.89 cm (3.5 in.). Test conditions were a maximum Hertz stress of 1.71 GPa (248 ksi), a bulk gear temperature of approximately 350 K (170 F) and a speed of 10,000 rpm. The lubricant used for the tests was a synthetic paraffinic oil with an additive package. The test results showed that the 10 percent surface fatigue (pitting) life of the contour hardened AISI 1552 test gears was 1.7 times that of the carburized and hardened AISI 9310 test gears. Also there were two early failures of the AISI 1552 gears by bending fatigue.

Townsend, Dennis P.; Turza, Alan; Chaplin, Mike

1995-07-01

72

The surface fatigue life of contour induction hardened AISI 1552 gears  

NASA Technical Reports Server (NTRS)

Two groups of spur gears manufactured from two different materials and heat treatments were endurance tested for surface fatigue life. One group was manufactured from AISI 1552 and was finished ground to a 0.4 micron (16 micro-in.) rms surface finish and then dual frequency contour induction hardened. The second group was manufactured from CEVM AISI 9310 and was carburized, hardened, and ground to a 0.4 micron (16 micro-in.) rms surface finish. The gear pitch diameter was 8.89 cm (3.5 in.). Test conditions were a maximum Hertz stress of 1.71 GPa (248 ksi), a bulk gear temperature of approximately 350 K (170 F) and a speed of 10,000 rpm. The lubricant used for the tests was a synthetic paraffinic oil with an additive package. The test results showed that the 10 percent surface fatigue (pitting) life of the contour hardened AISI 1552 test gears was 1.7 times that of the carburized and hardened AISI 9310 test gears. Also there were two early failures of the AISI 1552 gears by bending fatigue.

Townsend, Dennis P.; Turza, Alan; Chaplin, Mike

1995-01-01

73

Hot compression deformation behavior of AISI 321 austenitic stainless steel  

NASA Astrophysics Data System (ADS)

The hot compression behavior of AISI 321 austenitic stainless steel was studied at the temperatures of 950-1100°C and the strain rates of 0.01-1 s-1 using a Baehr DIL-805 deformation dilatometer. The hot deformation equations and the relationship between hot deformation parameters were obtained. It is found that strain rate and deformation temperature significantly influence the flow stress behavior of the steel. The work hardening rate and the peak value of flow stress increase with the decrease of deformation temperature and the increase of strain rate. In addition, the activation energy of deformation ( Q) is calculated as 433.343 kJ/mol. The microstructural evolution during deformation indicates that, at the temperature of 950°C and the strain rate of 0.01 s-1, small circle-like precipitates form along grain boundaries; but at the temperatures above 950°C, the dissolution of such precipitates occurs. Energy-dispersive X-ray analyses indicate that the precipitates are complex carbides of Cr, Fe, Mn, Ni, and Ti.

Haj, Mehdi; Mansouri, Hojjatollah; Vafaei, Reza; Ebrahimi, Golam Reza; Kanani, Ali

2013-06-01

74

Modeling the Flow Curve of AISI 410 Martensitic Stainless Steel  

NASA Astrophysics Data System (ADS)

In the present study, hot deformation behavior of AISI 410 martensitic stainless steel was investigated and modeled after conducting compression tests at the temperature range of 900-1150 °C and strain rate range of 0.001-1 s-1. At the studied temperature and strain rates, the flow curves were typical of dynamic recrystallization (DRX) showing a hardening peak followed by a softening one, and a steady state. The flow curves up to the peaks were modeled using the Estrin and Mecking equation. The softening due to DRX was also considered to increase the consistency of the developed model. The experimental equation proposed by Cingara and McQueen was also used to model the work hardening region. The results showed that the phenomenological model based on the Estrin and Mecking equation resulted in a better model for the work hardening region. Based on the Avrami equation, a model was developed to estimate the flow softening due to DRX between the peak and the starting point of steady state. The average value of the Avrami exponent was determined as 2.2, and it decreased with the increasing Zener-Hollomon parameter.

Momeni, A.; Dehghani, K.; Heidari, M.; Vaseghi, M.

2012-11-01

75

The Forming of AISI 409 sheets for fan blade manufacturing  

SciTech Connect

The necessity of adapting the standardized fan models to conditions of higher temperature has emerged due to the growth of concern referring to the consequences of the gas expelling after the Mont Blanc tunnel accident in Italy and France, where even though, with 100 fans in operation, 41 people died. The objective of this work is to present an alternative to the market standard fans considering a new technology in constructing blades. This new technology introduces the use of the stainless steel AISI 409 due to its good to temperatures of gas exhaust from tunnels in fire situation. The innovation is centered in the process of a deep drawing of metallic sheets in order to keep the ideal aerodynamic superficies for the fan ideal performance. Through the impression of circles on the sheet plane it is shown, experimentally, that, during the pressing process, the more deformed regions on the sheet plane of the blade can not reach the deformation limits of the utilized sheet material.

Foroni, F. D.; Menezes, M. A.; Moreira Filho, L. A. [ITA - Aeronautic Technological Institute, IEM, Praca Mal. Eduardo Gomes, 50 - Vila das Acacias - S. J. Campos, Brasil - CEP 1228-900 (Brazil)

2007-04-07

76

Surface fatigue life of CBN and vitreous ground carburized and hardened AISI 9310 spur gears  

NASA Technical Reports Server (NTRS)

Spur gear surface endurance tests were conducted to investigate CBN ground AISI 9310 spur gears for use in aircraft applications, to determine their endurance characteristics and to compare the results with the endurance of standard vitreous ground AISI 9310 spur gears. Tests were conducted with VIM-VAR AISI 9310 carburized and hardened gears that were finish ground with either CBN or vitreous grinding methods. Test conditions were an inlet oil temeprature of 320 K (116 F), an outlet oil temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. The CBN ground gears exhibited a surface fatigue life that was slightly better than the vitreous ground gears. The subsurface residual stress of the CBN ground gears was approximately the same as that for the standard vitreous ground gears for the CBN grinding method used.

Townsend, Dennis P.; Patel, P. R.

1988-01-01

77

Effect of Cryogenic Treatment on AISI M2 High Speed Steel: Metallurgical and Mechanical Characterization  

NASA Astrophysics Data System (ADS)

This study aims to present the metallurgical and mechanical characterization of cryogenically treated AISI M2 high speed steel (HSS) in terms of carbide precipitation and wear behavior. The samples of commercially available conventionally quenched and tempered AISI M2 HSS were procured and subjected to cryogenic treatment at two levels -110 °C (shallow treatment) and -196 °C (deep treatment) of temperature. The microstructures obtained after cryogenic treatments have been characterized with a prominence to comprehend the influence of cryogenic treatment vis-à-vis conventional quenching and tempering on the nature, size, and distribution of carbides. The mechanical properties such as hardness and wear rate of the specimens have also been compared by performing Rockwell C hardness test and pin-on-disc wear test, respectively. Microstructures, hardness, wear rate and analysis of worn surface reveal the underlying metallurgical mechanism responsible for the improving mechanical properties of the AISI M2 HSS.

Gill, Simranpreet Singh; Singh, Jagdev; Singh, Rupinder; Singh, Harpreet

2012-07-01

78

Laser gas assisted treatment of AISI H12 tool steel and corrosion properties  

NASA Astrophysics Data System (ADS)

Laser gas assisted treatment of AISI H12 tool steel surface is carried out and the electrochemical response of the laser treated surface is investigated. Morphological and metallurgical changes in the treated layer are examined using a scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction. Potentiodynamic polarization tests are carried out for untreated and laser treated specimen in 0.2 M NaCl solution at room temperature. It is found that the laser treated AISI H12 workpiece surfaces exhibit higher corrosion resistance as compared to untreated specimen as confirmed by lower corrosion rate, higher pitting potential, and lower passive current density.

Yilbas, B. S.; Toor, Ihsan-ul-Haq; Malik, Jahanzaib; Patel, F.

2014-03-01

79

Characteristics of complicated AISI316L automobile components manufactured by powder\\/metallurgy  

Microsoft Academic Search

Indirect Selective Laser Sintering\\/Isostatic Pressing (SLS\\/IP), with Cold Isostatic Pressing (CIPing) and Hot Isostatic Pressing\\u000a (HIPing) IPs, is adopted for the manufacture of complicated automobile components. The preparation of PA12-coated AISI316L\\u000a powder and airproof plastic canning during CIPing are also investigated. The influence of technology parameters on the performances\\u000a of AISI316L specimens during SLS\\/IP is likewise analyzed. Results show that

L. Zhong Liang; L. Jin Hui; S. Yu Sheng; Y. Chun Ze

2009-01-01

80

Nanocrystalline Surface Layer on AISI 52100 Steel Induced by Supersonic Fine Particles Bombarding  

NASA Astrophysics Data System (ADS)

Surface treatment of AISI 52100 steel by supersonic fine particles bombarding (SFPB) was studied in this article. The surface topography, morphology of the surface layer, and microhardness distribution of the surface layer have been investigated using a surface profiler system, a scanning electron microscopy (SEM), and a microvickers hardness tester. The microstructure, phase composition, and residual stress distribution of the surface layer in AISI 52100 steel after the SFBP treatment have been characterized by means of x-ray diffraction, SEM, and transmission electron microscopy. The results showed that a nanocrystalline surface (NS) layer was formed on the top surface of the SFBP-treated AISI 52100 steel samples. The NS layer is about 2 ?m in thickness with a surface roughness of R a = 1.2 ?m, R y = 6.7 ?m, R z = 6.0 ?m. Phase transitions occurred in the surface of the SFBP-treated samples. Residual compressive stress is obtained at the surface of the SFBP-treated samples. The maximum value of compressive stress appears at the outermost of the surface, and the affection region of the whole surface is about 60 ?m in thickness. A hardened surface layer has been fabricated in the AISI 52100 steel. The thickness of the hardened surface layer is about 70 ?m. The maximum value of hardness occurs at the depth of 20 ?m from the outermost surface.

Kong, Lingyan; Lao, Yuanxia; Xiong, Tianying; Li, Tiefan

2013-08-01

81

High temperature sensitivity of notched AISI 304L stainless steel tests  

Microsoft Academic Search

Experiments were designed to determine the failure characteristics of AISI 304L stainless steel under different stress triaxialities and temperatures up to 70% of melt. The data show that as temperature increases the displacement to failure of notched tensile specimens increases. The complex interaction of deformation mechanisms, such as twinning and dynamic recrystallization, appears to negate the damage accumulation at higher

W. Y. Lu; M. F. Horstemeyer; J. S. Korellis; R. B. Grishabar; D. Mosher

1998-01-01

82

Research on wear characteristics of AISI 1035 steel boronized at various parameters  

Microsoft Academic Search

Purpose – This paper aims to research the tribological features of AISI 1035 steel, boronized at various parameters. Design\\/methodology\\/approach – The samples were boronized via box boronizing method. By using Ekabor 2 powders, boronizing was conducted at 840, 880, 920, 960 and 1,000°C for two, four and six hours. Wear resistance of boronized samples at determined parameters were analysed. Wear

N. Kiratli; F. Findik

2011-01-01

83

The effect of Pseudomonas NCIMB 2021 biofilm on AISI 316 stainless steel  

Microsoft Academic Search

A bioreactor system operating in a continuous mode was designed to generate biofilms on polished and as?received surfaces of AISI 316 stainless steel coupons exposed for 36 d to a pure culture of marine Pseudomonas NCIMB 2021. Scanning electron microscopy (SEM) and atomic force microscopy were employed to determine the degree of surface colonisation and to examine corrosion damage of

I. B. Beech; V. Zinkevich; L. Hanjangsit; R. Gubner; R. Avci

2000-01-01

84

Investigating the Machinability of AISI 420 Stainless Steel Using Factorial Design  

Microsoft Academic Search

This work aims at studying the machining characteristics of high-strength materials using carbide cutting tool inserts at different cutting conditions. This is an essential step in building up an accurate machining information system. The tested material is high-strength stainless steel of the AISI 420 type. Machining tests were carried out using orthogonal cutting conducted to investigate the machining characteristics for

A. M. El-Tamimi; T. M. El-Hossainy

2008-01-01

85

Genetic algorithm-based burr size minimization in drilling of AISI 316L stainless steel  

Microsoft Academic Search

This study investigates the application of genetic algorithm (GA) for burr size minimization in drilling of AISI 316L stainless steel using HSS twist drills. Experiments were planned as per central composite rotatable design of experiments. The second order mathematical models for burr height and burr thickness were developed using response surface methodology (RSM) with cutting speed, feed, drill diameter, point

V. N. Gaitonde; S. R. Karnik; B. T. Achyutha; B. Siddeswarappa

2008-01-01

86

Investigating early stages of biocorrosion with XPS: AISI 304 stainless steel exposed to Burkholderia species  

Microsoft Academic Search

We have investigated the interactions of an exopolymer-producing bacteria, Burkholderia sp. with polished AISI 304 stainless steel substrates using X-ray photoelectron spectroscopy (XPS). Steel coupons were exposed to the pure bacteria culture in a specially designed flowcell for 6 h during which the experiment was monitored in situ with an optical microscope. XPS results verified the formation of biofilm containing

Leena-Sisko Johansson; Tuomas Saastamoinen

1999-01-01

87

Investigation of abrasive + erosive wear behaviour of surface hardening methods applied to AISI 1050 steel  

Microsoft Academic Search

In the present technology, machine parts which work at the industry area such as agriculture, mining and cement are subjected to wear. The wear resistance of these parts is improved by conventional heat treatments or surface heat treatments, which only improved the property surface and sub-surface of materials.In this study, samples of AISI 1050 steel are subjected to induction hardening

N. Y. Sari; M. Yilmaz

2006-01-01

88

The effects of induction hardening on wear properties of AISI 4140 steel in dry sliding conditions  

Microsoft Academic Search

Wear behaviour of induction hardened AISI 4140 steel was evaluated under dry sliding conditions. Specimens were induction hardened at 1000 Hz for 6, 10, 14, 18, 27 s, respectively, in the inductor which was a three-turn coil with a coupling distance of 2.8 mm. Normalised and induction hardened specimens were fully characterised before and after the wear testing using hardness,

Y Totik; R Sadeler; H Altun; M Gavgali

2003-01-01

89

Cutting fluid efficiency in end milling of AISI 304 stainless steel  

Microsoft Academic Search

Purpose – The purpose of this paper is to investigate the efficiency of cutting fluids when end milling AISI 304 stainless steels. Design\\/methodology\\/approach – Two groups of cutting tests were conducted, one with the application of a coolant (wet machining) and the other – without (dry cutting), using multilayer coated carbide inserts. The findings of tool life and tool wear

K. A. Abou-El-Hossein

2008-01-01

90

Tribological properties of plasma and pulse plasma nitrided AISI 4140 steel  

Microsoft Academic Search

Plasma nitriding is usually used for ferrous materials to improve their surface properties. Knowledge of the properties of thin surface layers is essential for designing engineering components with optimal wear performance. In our study, we investigated the microstructural, mechanical and tribological properties of plasma- and pulse plasma-nitrided AISI 4140 steel in comparison to hardened steel. The influence of nitriding case

B Podgornik; J Vižintin; V Leskovšek

1998-01-01

91

Surface modification of AISI 410 stainless steel using laser engineered net shaping (LENS TM)  

Microsoft Academic Search

Surface modification of AISI 410 martensitic stainless steel was carried out by laser surface-melting using laser engineered net shaping (LENSTM). The microstructures of laser surface-melted specimens showed varying amount of retained austenite depending on the processing parameters. The refinement and high strength of austenite as a result of increased scan speed and decreased laser power resulted in high amount of

B. Vamsi Krishna; Amit Bandyopadhyay

2009-01-01

92

Process parameter influence on performance of friction taper stud welds in AISI 4140 steel  

Microsoft Academic Search

Friction taper stud welding is a new variant of friction welding which has been developed from the principles of friction hydro-pillar processing. This paper considers the effect of weld process parameters on weld defects, macrostructure and mechanical properties in AISI 4140 steel. It also presents 3D residual stress data for a typical friction taper stud weld. Applied downwards force, rotational

D. G. Hattingh; D. L. H. Bulbring; A. Els-Botes; M. N. James

2011-01-01

93

The effects of plasma disruption simulation on AISI 316L stainless steel  

Microsoft Academic Search

The behavior of AISI 316L stainless steel during a disruption simulation is investigated by means of an electron beam gun, and the melt depth is evaluated. The trials are performed on cylindrical samples in the energy density range between 1 and 10 MJ m?2 under static and dynamic conditions. The discharge times range from 1 to 20 ms. The results

E. Campagnoli

1997-01-01

94

Gas Tungsten Arc and Shielded Metal Arc Welding of AISI 41XX Steels. Welding Procedure Specification.  

National Technical Information Service (NTIS)

Procedure WPS-127 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for gas tungsten arc and shielded metal arc welding of AISI 4130 and 4142 steels (ASTM A519) (P-No: None), 0.438-in. wall pipe; filler metal is AMS 6457, Class 413...

C. H. Wodtke, D. R. Frizzell

1985-01-01

95

Welding Procedure Specification: Gas Tungsten Arc Welding of AISI 41XX Steels.  

National Technical Information Service (NTIS)

Procedure WPS-126 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for gas tungsten arc welding of AISI 4130 and 4142 steel (ASTM A519) (P-No: None), 0.438-in. wall pipe; filler metal is AMS 6457, Class 4130 MC (F-, A-No: None). (...

C. H. Wodtke, D. R. Frizzell

1985-01-01

96

On the kinetics of plasma nitriding a martensitic stainless steel type AISI 420  

Microsoft Academic Search

Plasma nitriding was employed to treat martensitic stainless steel type AISI 420. The ability to remove the passive film from the surface is an important advantage in this process in order to guarantee a homogeneous surface treatment. The resulting nitrided surface shows the presence of a compound layer and a diffusion zone. The interface between the diffusion zone and the

Carlos E. Pinedo; Waldemar A. Monteiro

2004-01-01

97

A study of martensitic stainless steel AISI 420 modified using plasma nitriding  

Microsoft Academic Search

We studied martensitic stainless steel AISI 420, modified using glow discharge plasma nitriding. Microhardness measurements, X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) were used to investigate the surface microhardness, crystal structure, microstructure and chemical bonding in the modified surfaces. High surface microhardness (?1300 HV) over a case depth of about 60

I Alphonsa; A Chainani; P. M Raole; B Ganguli; P. I John

2002-01-01

98

Wear reduction in AISI 630 martensitic stainless steel after energetic nitrogen ion implantation  

Microsoft Academic Search

A significant wear reduction by several orders of magnitude is the common result for austenitic stainless steels after energetic nitrogen implantation at medium temperatures around 380 °C. In contrast, martensitic stainless steels are rarely investigated. In this investigation, one steel grade, stainless steel AISI 630\\/DIN 1.4542, is treated using low energy nitrogen implantation at 380 and 600 °C, high voltage

S. Mändl; B. Fritzsche; D. Manova; D. Hirsch; H. Neumann; E. Richter; B. Rauschenbach

2005-01-01

99

Research on new rapid and deep plasma nitriding techniques of AISI 420 martensitic stainless steel  

Microsoft Academic Search

Cyclic plasma oxynitriding and cyclic plasma nitriding catalyzed by rare earth La of AISI 420 martensitic stainless steel were performed and compared with conventional plasma nitriding. The nitrided layers were investigated by means of an optical microscope, microhardness tester, Auger electron spectroscopy (AES), X-ray diffraction (XRD), wear machine, scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show

K. Wu; G. Q. Liu; L. Wang; B. F. Xu

2010-01-01

100

Recrystallization in AISI 304 austenitic stainless steel during and after hot deformation  

Microsoft Academic Search

In order to improve the understanding of the dynamic and post-dynamic recrystallization behaviours of AISI 304 austenitic stainless steel, a series of hot torsion test have been performed under a range of deformation conditions. The mechanical and microstructural features of dynamic recrystallization (DRX) were characterized to compare and contrast them with those of the post-dynamic recrystallization. A necklace type of

A. Dehghan-Manshadi; M. R. Barnett; P. D. Hodgson

2008-01-01

101

Influence of warm working parameters on deformation behavior and microstructure of AISI 1015 carbon steel  

Microsoft Academic Search

This paper presents the influence of warm working parameters (temperature and strain rate) on deformation behavior, microstructure and hardness of a low carbon steel (AISI 1015). Samples were subjected to torsion tests at different temperatures from 550 to 700 oC, in order to determine their resistance to deformation, deformability, microstructure and hardness. Based on deformation behavior of the steel, the

Carmen Medrea-Bichtas; Gavril Negre; Serban Doms

102

Microstructural Modifications During Heating of Warm Rolled AISI 1015 Carbon Steel  

Microsoft Academic Search

For industrial applications, warm working is very attractive due to certain advantages offered by this plastic deformation process. Heat treating of warm worked steels can lead to a significant improvement of their mechanical properties. The paper presents the influence of the heat-treating regime applied to warm rolled AISI 1015 carbon steel. The rolling was performed in the following conditions: temperature

Carmen Medrea; Gavril Negre

103

Deep cryogenic treatment of AISI 302 stainless steel: Part I – Hardness and tensile properties  

Microsoft Academic Search

The effects of deep cryogenic treatment (DCT) on the static mechanical properties of the AISI 302 austenitic stainless steel were investigated through experimental testing. The results of the tensile and hardness tests are discussed and compared to data and microstructural observations from the DCT literature concerning the same class of steel. In addition, the influence of two important treatment parameters,

Paolo Baldissera

2010-01-01

104

Fatigue life improvement of AISI 304L cruciform welded joints by cryogenic treatment  

Microsoft Academic Search

Existing theories and reported practical experience show that cryogenic processing greatly increases abrasion resistance and contact fatigue resistance of some metals and alloys. In the present work, an attempt has been made to investigate the effect of cryogenic treatment on the axial fatigue performance of fillet welded cruciform joints of AISI 304L stainless steel, which failed in the weld metal.

P Johan Singh; B Guha; D. R. G Achar

2003-01-01

105

Fatigue life extension of notches in AISI 304L weldments using deep cryogenic treatment  

Microsoft Academic Search

The fatigue crack initiation lives of notches in AISI 304L austenitic stainless steel weldments were improved after the deep cryogenic treatment of specimens at liquid nitrogen temperature (?185 °C). During this treatment, a significant change in microstructure is developed. Strain induced martensitic transformation occurs. During this transformation, the weld metal expands. This expansion relieves the tensile residual stresses and induces

P. Johan Singh; S. L. Mannan; T. Jayakumar; D. R. G. Achar

2005-01-01

106

Sub-zero treatments of AISI D2 steel: Part II. Wear behavior  

Microsoft Academic Search

Wear behavior of AISI D2 steel specimens subjected to varied sub-zero treatments, namely: cold treatment, shallow cryogenic treatment and deep cryogenic treatment have been studied with respect to that of the conventionally heat treated ones. The wear behavior has been assessed by dry sliding wear tests under varying normal loads as well as by detailed characterizations of worn surfaces, subsurfaces

Debdulal Das; Apurba Kishore Dutta; Kalyan Kumar Ray

2010-01-01

107

Study of the calcium phosphate layer grown on AISI 316 stainless steel from simulated body fluid  

Microsoft Academic Search

A calcium phosphate layer was deposited on the surface of AISI 316 stainless steel by immersion in a solution supersaturated with calcium and phosphorus ions. The substrates were pre-modified by ion implantation of Ca and P, in order to induce nuclei for calcium phosphate growth on the surface. The reactivity of these surfaces towards crystal growth in aqueous solution was

E. Pecheva; L. Pramatarova; M. F. Maitz; M. T. Pham

2003-01-01

108

The microstructural origins of yield strength changes in aisi 316 during fission or fusion irradiation  

Microsoft Academic Search

The changes in yield strength of AISI 316 irradiated in breeder reactors have been successfully modeled in terms of concurrent changes in microstructural components. Two new insights involving the strength contributions of voids and Frank loops have been incorporated into the hardening models. Both the radiation-induced microstructure and the yield strength exhibit transients which are then followed by saturation at

F. A. Garner; M. L. Hamilton; N. F. Panayotou; G. D. Johnson

1981-01-01

109

Repair welding of polymer injection molds manufactured in AISI P20 and VP50IM steels  

Microsoft Academic Search

The objective of this work was to determine the best practices to repair by welding AISI P20 and VP50IM steels during the manufacturing of polymer injection molds, in such a way to obtain similar characteristics in the weld and base metal, to uniformly respond to the processes of polishing and texturing. The welds by the wire feed TIG process were

Wilson Tafur Preciado; Carlos Enrique Niño Bohorquez

2006-01-01

110

Machining of AISI 316 Stainless Steel Under CarbonDioxide Cooling  

Microsoft Academic Search

This work investigates the effect of carbon dioxide (CO2) as the cutting fluid in turning AISI 316 stainless steel work material on cutting temperature, cutting force, tool wear, surface roughness and chip morphology when compared to dry and wet machining. Compared to wet machining, in CO2 machining the cutting temperature was reduced up to 35% and the surface finish of

B. Dilip Jerold; M. Pradeep Kumar

2012-01-01

111

The Mechanical Threshold Stress model for various tempers of AISI 4340 steel  

E-print Network

. In this paper, we determine the Mechanical Threshold Stress model parameters for various tempers of AISI 4340. This paper attempts to redress that lacuna by providing the MTS parameters for a number of tempers of 4340 stress models: the Mie- Gr"u"neisen (MG) equation of state for calculating the pressure, the Steinberg

Utah, University of

112

Ground surface improvement of the austenitic stainless steel AISI 304 using cryogenic cooling  

Microsoft Academic Search

Grinding fluid selection is becoming increasingly constrained by environmental considerations, thus requiring the substitution of the conventionally used oil-based coolants. The work presented in this paper aims at evaluating the ground surface quality improvements of the austenitic stainless steel AISI 304 resulting from the application of cryogenic cooling. The evaluation is based on criteria related to grindability, surface integrity and

Nabil Ben Fredj; Habib Sidhom; Chedly Braham

2006-01-01

113

Economical and ecological cryogenic machining of AISI 304 austenitic stainless steel  

Microsoft Academic Search

While it is a clean alternative to conventional machining using environmentally polluting cutting oils and emulsions, cryogenic machining using liquid nitrogen has been reported to increase cutting forces and shorten tool life when cutting AISI 304 austenitic stainless steel. This paper presents improved results by using an economical cryogenic cooling approach designed after studying the cryogenic properties of the stainless

S. Y. Hong; M. Broomer

2000-01-01

114

Assessment of XM-19 as a Substitute for AISI 348 in ATR Service  

SciTech Connect

It has been proposed that XM-19 alloy be considered as a possible replacement steel for AISI 348 in the construction of Advanced Test Reactor (ATR) capsules. AISI 348 works well, but is currently very difficult to obtain commercially. The superior and desirable mechanical properties of XM-19 alloy have been proven in non-nuclear applications, but no data are available regarding its use in radiation environments. While most 300 series alloys will meet the conditions required in ATR , it cannot be confidently assumed that XM-19 can be substituted without prior qualification in a radiation test. Compared to AISI 348, XM-19 will have an enhanced tendency for phase instabilities due to its higher levels of Ni and, especially, Si. However, transmutation of important elemental components in the highly thermalized ATR spectrum may have a very pronounced effect on its performance during irradiation. Not only will strong transmutation of Mn to Fe reduce the ductility and strength advantages provided by the higher initial Mn content of XM-19, but the extensive loss of Mn will also release from solution much of the N upon which the higher strength of XM-19 depends. In addition, the combined influence of transmutation and Inverse Kirkendall processes may lead to gas-bubble-covered grain boundaries, producing a very fragile alloy after significant irradiation has accumulated. At present, there are no radiation data available to substantiate this possible scenario. An alternate proposal is therefore advanced. Since the response of AISI 348 and 347 to radiation are expected to be relatively indistinguishable, the AISI 347 might serve as an acceptable replacement. While AISI 348 is usually chosen for nuclear service in order to reduce the overall radioactivity arising from relatively small amounts of highly transmutable elements such as cobalt, these elements have very little effect on the radiation performance of the steel. In the proposed application, however, the activity induced in this highly thermalized spectrum to large doses (10 to 50 dpa) will be overwhelmed by the activation arising from the major steel components: Fe, Cr, and especially Ni. The mechanical properties, irradiation creep, and void swelling behavior of the two steels should be practically indistinguishable.

F. A. Garner; L. R. Greenwood; R. E. Mizia; C. R. Tyler

2007-11-01

115

Hard and superhard TiAlBN coatings deposited by twin electron-beam evaporation  

Microsoft Academic Search

Superhard nanostructured coatings, prepared by plasma-assisted chemical vapour deposition (PACVD) and physical vapour deposition (PAPVD) techniques, such as vacuum arc evaporation and magnetron sputtering, are receiving increasing attention due to their potential applications for wear protection. In this study nanocomposite (TiAl)BxNy (0.09?x?1.35; 1.07?y?2.30) coatings, consisting of nanocrystalline (Ti,Al)N and amorphous BN, were deposited onto Si (100), AISI 316 stainless steel

C. Rebholz; M. A. Monclus; M. A. Baker; P. H. Mayrhofer; P. N. Gibson; A. Leyland; A. Matthews

2007-01-01

116

Rolling-element fatigue life of AISI M-50 and 18-4-1 balls  

NASA Technical Reports Server (NTRS)

Rolling element fatigue studies were conducted with AISI M-50, EFR 18-4-1, and VAR 18-4-1. Groups of 12.7 mm (1/2-in) diameter balls of each material were tested in the five ball fatigue tester. Test conditions included a load of 1540 N (347 lbf) giving a maximum Hertz stress of 5520 MPa (800 000 psi), a shaft speed of 10,700 rpm, and a contact angle of 30 deg. Tests were run at a race temperature of 339 K (150 F) with a type 2 ester lubricant. The rolling element fatigue life of AISI M-50 was not significantly different from that of EFR 18-4-1 or VAR 18-4-1 based on a statistical comparison of the test results.

Parker, R. J.; Zaretsky, E. V.

1978-01-01

117

On electrical resistivity of AISI D2 steel during various stages of cryogenic treatment  

NASA Astrophysics Data System (ADS)

The effect of dislocation densities and residual stresses is well known in tool steels. Measurement of electrical resistivity in order to monitor dislocation densities or residual stresses has seldom been used in investigating the effect of cryogenic treatment on tool steels. Monitoring residual stresses during cryogenic treatment becomes important as it is directly related to changes due to cryogenic treatment of tool steels. For high carbon high chromium (HCHC- AISI D2) steels, not only wear resistance but dimensional stability is an important issue as the steels are extensively used in dies, precision measuring instruments. This work comprises of study of measurement of electrical resistivity of AISI D2 steel at various stages of cryogenic treatment. Use of these measurements in order to assess the dimensional stability of these steels is discussed in this paper.

Lomte, Sachin Vijay; Gogte, Chandrashekhar Laxman; Peshwe, Dilip

2012-06-01

118

Fluidized-bed and salt-bath heat treating (AISI 4130 and 4340 alloy steels)  

SciTech Connect

Using commercial alloy steels AISI 4130 and AISI 4340, a series of heat-treating, parametric studies were performed on specimens in both an electric fluidized-bed furnace and an electric neutral salt-bath furnace. An evaluation of heat-treating methods was performed by comparing tensile test data for the two alloy steels. Surface characterization of test specimens was performed using Auger analyses to discern effects, if any, caused by the heat-treatment method. This report presents certain test results for two significantly different heat-treating methods and places them side by side with published mechanical test data. Environmental and safety aspects of salt-bath and fluidized-bed heat treating are discussed.

Cyrus, W.L.

1983-08-01

119

Tribological properties of oxidised boride coatings grown on AISI 4140 steel  

Microsoft Academic Search

In this study, we investigated the wear behaviour of borided and borided + short-duration oxidized AISI 4140 steel. Boronizing was carried out in a slurry salt bath consisting of borax, boric acid and ferro silicon. Also, short-duration oxidizing treatment was applied to borided steel to produce glass-like boron oxide layer. The short-duration oxidizing was performed at 750 °C for 3 min. Optical

Saduman Sen; Ugur Sen; Cuma Bindal

2006-01-01

120

Effect of process time on structural and tribological properties of ferritic plasma nitrocarburized AISI 4140 steel  

Microsoft Academic Search

AISI 4140 steel was plasma nitrocarburized at a gas mixture of 49%N2+49%H2+2%CO2, for different process times (1, 2, 4, 8 and 12 h), at a temperature of 570 °C. The structural, mechanical and tribological properties of nitrocarburized steel were analyzed using a X-ray diffraction, microhardness tester, scanning electron microscopy, optical microscopy and pin-on-disk tribotester. The results have shown that the

Mehmet Karakan; Akgün Alsaran; Ayhan Çelik

2004-01-01

121

Analysis of pulsed Nd:YAG laser welding of AISI 304 steel  

Microsoft Academic Search

Pulsed laser welding of AISI 304 stainless steel plate was simulated using commercial finite element software to determine\\u000a the optimal welding conditions. Due to geometric symmetry, only one plate was modeled to reduce the simulation computation\\u000a time. User subroutines were created to account for a moving three-dimensional heat source and to apply boundary conditions.\\u000a The material properties such as conductivity,

Kwanwoo Kim; Jungkil Lee; Haeyong Cho

2010-01-01

122

The effect of machinability on thermal fields in orthogonal cutting of AISI 4140 steel  

Microsoft Academic Search

The micro-scale temperature fields in the cutting of two AISI 4140 steels with different machinability ratings were measured. A custom infrared microscope was constructed; each pixel was calibrated separately to reduce measurement uncertainty. Orthogonal cutting experiments were performed on a high speed machining center with surface speeds up to 500mmin?1 and uncut chip thicknesses ranging from 0.1mm to 0.3mm. The

P. J. Arrazola; I. Arriola; M. A. Davies; A. L. Cooke; B. S. Dutterer

2008-01-01

123

Impact energy absorption of aluminium foam fitted AISI 304L stainless steel tube  

Microsoft Academic Search

Closed cell aluminium foam fitted AISI 304L stainless steel tube was investigated for its impact energy absorption characteristics. Quasi-static load–deflection tests were employed to establish the foam–tube interaction factor. Drop experiments were carried out using a free flight drop tower on aluminium foam fitted stainless steel tube to obtain the acceleration–time history of the hammer. Estimated deflections compared well with

R. Rajendran; K. Prem Sai; B. Chandrasekar; A. Gokhale; S. Basu

2009-01-01

124

In-reactor creep rupture of 20% cold-worked AISI 316 stainless steel  

Microsoft Academic Search

Results of an experiment designed to measure in-reactor stress-to-rupture properties of 20% cold-worked AISI 316 stainless steel are reported. The in-reactor rupture data are compared with postirradiation and unirradiated test results. In-reactor rupture lives were found to exceed rupture predictions of postirradiation tests. This longer in-reactor rupture life is attributed to dynamic point defect generation which is absent during postirradiation

A. J. Lovell; B. A. Chin; E. R. Gilbert

1981-01-01

125

A Statistical Study on Stress-Strain Relation of AISI 304 Stainless Steel Under Elevated Temperatures  

Microsoft Academic Search

\\u000a This study presents the tensile test results of AISI 304 stainless steel under room and elevated temperatures and the use\\u000a of normal statistical plot to design purpose. The minimum ductility occurs in an intermediate temperature range (650°C). It\\u000a is shown that the precipitation of chrome-carbide is the cause of decrease of elongation at higher temperature from EDX (Energy\\u000a Dispersive X-ray)

S. H. Park; J. K. Kim; J. H. Kim

126

Determination of the optimum conditions for ion nitriding of AISI 5140 steel  

Microsoft Academic Search

AISI 5140 low alloy steel was ion nitrided under different process parameters including time (1, 4, 8 and 12 h), temperature (400, 450, 500 and 550 °C) and gas mixture ratio (0.05, 0.33, 1 and 3 N2\\/H2). By determining the fatigue strength, surface hardness, compound layer thickness and case depth, the optimum working conditions were determined by using a Taguchi

Akgün Alsaran; Ayhan Çelik; Cafer Çelik

2002-01-01

127

Nitrogen implantation of AISI 304 stainless steel with a coaxial plasma gun  

Microsoft Academic Search

The application of a plasma focus (PF) device operated at 1 kJ and 25 kV as a pulsed ion implanter is described. Samples of AISI 304 stainless steel implanted with nitrogen with this device show a reduction of wear of 42 times with respect to the implanted ones, with a reduction, at the same time of the friction coefficient. X-ray

J. N. Feugeas; E. C. Llonch; C. O. de Gonza´lez; G. Galambos

1988-01-01

128

Empirical modeling of hard turning of AISI 6150 steel using design and analysis of computer experiments  

Microsoft Academic Search

In the present paper an experimental study to investigate the turning of hardened AISI 6150 heat treatable steel using polycrystalline\\u000a boron nitride (PCBN) tools is presented. Design and analysis of computer experiments (DACE) was used to generate a comprehensive\\u000a empirical description of the process characteristics. More specific, the effects of the parameters cutting speed, feed and\\u000a depth of cut on

Benedikt Sieben; Tobias Wagner; Dirk Biermann

2010-01-01

129

Laser surface hardening of AISI 420 stainless steel treated by pulsed Nd:YAG laser  

Microsoft Academic Search

The AISI 420 martensitic stainless steel was surface-hardened by a pulsed Nd:YAG laser. The influences of process parameters (laser pulse energy, duration time and travel speed) on the depth and hardness of laser treated area and its corrosion behavior were Investigated. In the optimum process parameters, maximum hardness (490VHN) in the laser surface treated area was achieved. The pitting corrosion

B. Mahmoudi; M. J. Torkamany; A. R. Sabour Rouh Aghdam; J. Sabbaghzade

2010-01-01

130

Surface hardening of AISI 316L stainless steel using plasma carburizing  

Microsoft Academic Search

AISI 316L stainless steel was carburized using CH4\\/H2 plasma to increase surface hardness. Plasma carburizing conditions such as applied voltage, carburizing temperature, gas pressure, CH4\\/ (CH4 + H2) ratio and process time were varied to achieve the desired surface hardness, effective hardening depth and carburizing uniformity. Plasma carburized specimens were analyzed with optical microscopy, microhardness tester, scanning electron microscopy and

Bong-Seok Suh; Won-Jong Lee

1997-01-01

131

Effect of superheat on the solidification structures of AISI 310S austenitic stainless steel  

Microsoft Academic Search

An experimental study was carried out to investigate the evolution of macrostructure and microstructure in AISI 310S stainless\\u000a steel during solidification. Experimental findings suggested that the macrostructure and the microstructure of the cast material\\u000a responded differently to variations in casting temperature. As the casting temperature decreased, the macro structure was\\u000a refined, as expected, but the microstructure coarsened. A relationship was

S. Ozbayraktar; A. Koursaris

1996-01-01

132

Effect of post-oxidizing time on corrosion properties of plasma nitrocarburized AISI 1020 steel  

Microsoft Academic Search

Plasma nitrocarburized AISI 1020 steels are oxidized for 15, 30 and 60 min to evaluate the effect of post-oxidizing time on corrosion behavior. After plasma nitrocarburizing for 3 h at 570 °C, the compound layer composed of ?-Fe2–3(N,C) and ??-Fe4(N,C) phases and the diffusion layer above the matrix are observed. The oxide top layer, mainly consisting of magnetite (Fe3O4) and

Kou Hyun Lee; Ki Suk Nam; Pyung Woo Shin; Deuk Yong Lee; Yo-Seung Song

2003-01-01

133

Microstructure and corrosion behaviour of DC-pulsed plasma nitrided AISI 410 martensitic stainless steel  

Microsoft Academic Search

AISI 410 martensitic stainless steel samples with different metallurgical structures were DC-pulsed plasma nitrided at 623, 723 and 773 K. The samples were ion nitrided in an industrial equipment using a gas mixture consisting of 25% N2+75% H2 under a pulsed DC glow discharge. Optical and scanning electron microscopy, as well as glancing angle X-ray diffraction and microhardness measurements have

P Corengia; Gabriel O. Ybarra; C Moina; A Cabo; E Broitman

2004-01-01

134

Dynamic fracture toughness and Charpy impact properties of an AISI 403 martensitic stainless steel  

Microsoft Academic Search

Dynamic fracture toughness and Charpy impact properties of a normalised and tempered AISI 403 martensitic stainless steel obtained from instrumented impact tests are presented. Procedures for estimating dynamic fracture toughness (KId) from the load-time traces obtained in instrumented tests of unprecracked Charpy V-notch (CVN) specimens are considered. The estimated KId values show reasonable agreement with those obtained from instrumented drop-weight

P. R Sreenivasan; S. K Ray; S. L Mannan; P Rodriguez

1996-01-01

135

Martensitic stainless steel AISI 420—mechanical properties, creep and fracture toughness  

Microsoft Academic Search

In this paper some experimental results and analyses regarding the behavior of AISI 420 martensitic stainless steel under\\u000a different environmental conditions are presented. That way, mechanical properties like ultimate tensile strength and 0.2 percent\\u000a offset yield strength at lowered and elevated temperatures as well as short-time creep behavior for selected stress levels\\u000a at selected elevated temperatures of mentioned material are

J. Brnic; G. Turkalj; M. Canadija; D. Lanc; S. Krscanski

136

Laser transformation hardening of AISI 440C martensitic stainless steel for higher cavitation erosion resistance  

Microsoft Academic Search

Surface hardening of AISI 440C martensitic stainless steel was achieved by laser transformation hardening (LTH) using a high-power CW Nd:YAG laser. A hardened layer of a few 100 ?m thick, composed of martensite, retained austenite and fine carbides was formed. The microstructure and hardness of the laser-treated layer were dependent on the laser processing parameters, with the hardness values reaching

K. H. Lo; F. T. Cheng; H. C. Man

2003-01-01

137

Selective laser melting of Fe-Ni-Cr layer on AISI H13 tool steel  

Microsoft Academic Search

An attempt to fabricate Fe-Ni-Cr coating on AISI H13 tool steel was performed with selective laser melting. Fe-Ni-Cr coating was produced by experimental facilities consisting of a 200 W fiber laser which can be focused to 80 ?m and atmospheric chamber which can control atmospheric pressure with N2 or Ar. Coating layer was fabricated with various process parameters such as

Byeong-Don JOO; Jeong-Hwan JANG; Jae-Ho LEE; Young-Myung SON; Young-Hoon MOON

2009-01-01

138

Investigation on hot deformation behavior of AISI T1 high-speed steel  

Microsoft Academic Search

The hot deformation behavior of AISI T1 (18W–4Cr–1V) high-speed steel has been investigated in the temperature range 950–1150°C at strain rates of 0.001–10 s?1 and true strains of 0–0.6. The results show that the activation energy for deformation, Q, decreases with the increase of strain below 1000°C, and it changes slightly with the strain above 1000°C. Metallography shows that there

Jiantao Liu; Hongbing Chang; Ruiheng Wu; T. Y Hsu; Xueyu Ruan

2000-01-01

139

Hot workability of spray-formed AISI M3:2 high-speed steel  

Microsoft Academic Search

Axisymmetric hot compression tests (900–1100°C) on spray-formed AISI M3:2 high-speed steel were performed in order to establish suitable parameters for hot forging of this material. Special attention was paid to establish the deformation conditions that lead to the breakdown of the carbide network, present after spray forming, and to avoid fracture of the material as a result of deformation. By

C. Rodenburg; M. Krzyzanowski; J. H. Beynon; W. M. Rainforth

2004-01-01

140

Optimization of cold and warm workability in stainless steel type AISI 316L using instability maps  

Microsoft Academic Search

The deformation characteristics of stainless steel type AISI 316L under compression in the temperature range 20 to 600°C and strain rate range 0.001 to 100 s?1 have been studied with a view to characterizing the flow instabilities occurring in the microstructure. At temperatures lower than 100°C and strain rates higher than 0.1 s?1 316L stainless steel exhibits flow localization whereas

S. Venugopal; S. L. Mannan; Y. V. R. K. Prasad

1995-01-01

141

Sub-zero treatments of AISI D2 steel: Part I. Microstructure and hardness  

Microsoft Academic Search

Microstructure, hardness and wear behavior of AISI D2 steel subjected to varied sub-zero treatments have been examined with reference to conventional heat treatment. Part I of this work presents the variations of microstructure and hardness, whereas part II deals with the wear behavior. The sub-zero treatments studied are cold treatment, shallow cryogenic treatment and deep cryogenic treatment. The developed microstructures

Debdulal Das; Apurba Kishore Dutta; Kalyan Kumar Ray

2010-01-01

142

Correlation of yield strength with irradiation-induced microstructure in AISI 316 stainless steel  

Microsoft Academic Search

Improvements in the correlation of radiation-induced change in yield strength in AISI 316 stainless steel with microstructure were made by re-examining the role of short-range obstacles. Effects due to the size of the obstacles relative to their spacing and shape of the obstacles were applied. The concept of shearing the precipitates instead of bowing around them was used to explain

R. L. Simons; L. A. Hulbert

1985-01-01

143

Electrooxidation of stainless steel AISI 304 in carbonate aqueous solution at pH 8  

Microsoft Academic Search

The electrochemical behaviour of stainless steel AISI 304 (SS304) has been investigated in deaerated 0.1–1 m NaHCO3 solutions at pH 8 using a rotating disc electrode. The polarization curves are characterized by a broad range of passivity at low potentials (-0.8 to 0.3 V), a depassivation region at 0.4 V vs SCE and, at high potentials (0.5 to 0.85 V),

M. Drogowska; H. Ménard; L. Brossard

1996-01-01

144

Evaluation of AISI 4140 Steel Repair Without Post-Weld Heat Treatment  

Microsoft Academic Search

The present work evaluates the two-layer technique on the heat affected zone (HAZ) of AISI 4140 steel welded with different\\u000a heat input levels between the first and second layer. The weld heat input levels selected by the Higuchi test were 5\\/5, 5\\/10,\\u000a and 15\\/5 kJ\\/cm. The evaluation of the refining and\\/or tempering of the coarsened grain HAZ of the first

Cleiton C. Silva; Victor H. C. de Albuquerque; Cícero R. O. Moura; Willys M. Aguiar; Jesualdo P. Farias

2009-01-01

145

Evaluation of AISI 4140 Steel Repair Without Post-Weld Heat Treatment  

Microsoft Academic Search

The present work evaluates the two-layer technique on the heat affected zone (HAZ) of AISI 4140 steel welded with different heat input levels between the first and second layer. The weld heat input levels selected by the Higuchi test were 5\\/5, 5\\/10, and 15\\/5 kJ\\/cm. The evaluation of the refining and\\/or tempering of the coarsened grain HAZ of the first

Cleiton C. Silva; Victor H. C. de Albuquerque; Cícero R. O. Moura; Willys M. Aguiar; Jesualdo P. Farias

2009-01-01

146

High temperature oxidation of stainless steel AISI316L in air plasma  

Microsoft Academic Search

A study on surface oxidation of AISI316L stainless steel surface was performed. Stainless steel was oxidized in air plasma with a high degree of dissociation of oxygen molecules of about 70%. The resultant flux of oxygen atoms to the surface was about 1×1024m?2s?1. The oxidation was performed at high temperatures ranging up to 1250K. The oxidation time was 5min. After

Alenka Vesel; Miran Mozetic; Aleksander Drenik; Nina Hauptman; Marianne Balat-Pichelin

2008-01-01

147

Sensitization resistance of friction stir welded AISI 409 M grade ferritic stainless steel joints  

Microsoft Academic Search

Friction stir welded low chromium AISI 409 M ferritic stainless steel was investigated for susceptibility to intergranular\\u000a corrosion by oxalic and double-loop electrochemical potentiodynamic reactivation tests, and the degree of sensitization were\\u000a evaluated by the ratio of the reactivating and activating currents. Stir zone of friction stir welded joint exhibited smaller\\u000a degree of sensitization compared to the base metal and it

A. K. Lakshminarayanan; V. Balasubramanian

148

Corrosion behavior and adhesion of ion-plated TiN films on AISI 304 steel  

Microsoft Academic Search

Titanium nitride films were deposited on AISI 304 steel with a hollow-cathode-discharge (HCD) ion-plating technique. An extensive investigation on the corrosion behavior and adhesion of TiN-coated samples was performed. The corrosion resistance was evaluated by a potentiodynamic polarization method in 1N H2SO4+0.05M KSCN solution and the ASTM standard B-117 salt spray test. The ultimate shear stress, proportional to the bonding

Jia-Yang Chen; Ge-Ping Yu; Jia-Hong Huang

2000-01-01

149

Effects of carburization and hydrogenation on the impact toughness of AISI 4118 steel  

Microsoft Academic Search

The effects of hydrogen charging and carburization on the impact toughness of an AISI 4118 steel were studied. The carburization of impact specimens was conducted using a conventional pack carburizing method and the hydrogen charging was conducted in 1 N H2SO4 solution containing 1 g I?1 of thiourea at 30°C. Charpy V-notch impact tests were carried out on specimens with

Chih Fu Yang; Liu Ho Chiu; Jiann Kuo Wu

1995-01-01

150

Effect of carburizing on notch fatigue behaviour in AISI 316 austenitic stainless steel  

Microsoft Academic Search

The present paper describes the fatigue behaviour of carburized notched specimens in AISI 316 austenitic stainless steel. Cantilever-type rotary bending fatigue tests have been performed using carburized notched specimens with three different stress concentration factors, Kt, of 2.08, 3.55 and 6.50 and the effects of carburizing on fatigue strength and notch sensitivity were discussed. Carburizing was performed at a temperature

Masayuki Akita; Keiro Tokaji

2006-01-01

151

Economical and ecological cryogenic machining of AISI 304 austenitic stainless steel  

Microsoft Academic Search

While it is a clean alternative to conventional machining using environmentally polluting cutting oils and emulsions, cryogenic\\u000a machining using liquid nitrogen has been reported to increase cutting forces and shorten tool life when cutting AISI 304 austenitic\\u000a stainless steel. This paper presents improved results by using an economical cryogenic cooling approach designed after studying\\u000a the cryogenic properties of the stainless

Shane Y. Hong; Mark Broomer

2000-01-01

152

Deposition of titanium nitride on AISI304 in a plasma focus environment  

Microsoft Academic Search

Polycrystalline, smooth, and hard thin films of TiN are successfully deposited on AISI-304 substrates using a 1.5kJ Mather-type dense plasma focus device charged at 18kV. The purpose of this study is to investigate the structural and mechanical properties of the TiN thin films in terms of ion dose and substrate position to establish the optimum deposition conditions. The films are

S. Zeb; A. Qayyum; M. Shafiq; M. Zakaullah

2008-01-01

153

MODELADO DE LA DINMICA DEL CARBONO ORGNICO EN SUELOS USANDO INFORMACIN ISOTPICA: APLICACIN EN PASTIZALES FORESTADOS  

E-print Network

MODELADO DE LA DINÁMICA DEL CARBONO ORGÁNICO EN SUELOS USANDO INFORMACI�N ISOT�PICA: APLICACI�N EN) Dept. Biology, Duke University, Durham NC 27708 (EE.UU.) Introducción Los suelos alojan el mayor orgánico del suelo (COS) tiene en el ciclo global del elemento, la comprensión de su intercambio con otros

Nacional de San Luis, Universidad

154

Corrosion-wear monitoring of TiN coated AISI 316 stainless steel by electrochemical noise measurements  

NASA Astrophysics Data System (ADS)

A modified electrochemical noise (EN) technique has been applied to monitor corrosion-wear of TiN coated AISI 316 stainless steel sliding against corundum in 0.5 M H 2SO 4. Experimental results show that the EN technique can sensitively detect potential and current variations during a corrosion-wear process. Corrosion-wear mechanisms of TiN coatings depend on their substrate properties. When the substrate is passive, such as AISI 316 stainless steel, the potential and current variations reflect the properties of coatings. Depassivation and repassivation alternately take place on the tribo-activated wear area during the steady-state phase.

Quan, Zhenlan; Wu, Pei-Qiang; Tang, Lin; Celis, J.-P.

2006-11-01

155

AISI/DOE Advanced Process Control Program Vol. 6 of 6: Temperature Measurement of Galvanneal Steel  

SciTech Connect

This report describes the successful completion of the development of an accurate in-process measurement instrument for galvanneal steel surface temperatures. This achievement results from a joint research effort that is a part of the American Iron and Steel Institute's (AISI) Advanced Process Control Program, a collaboration between the U.S> Department of Energy and fifteen North American Steelmakers. This three-year project entitled ''Temperature Measurement of Galvanneal Steel'' uses phosphor thermography, and outgrowth of Uranium enrichment research at Oak Ridge facilities. Temperature is the controlling factor regarding the distribution of iron and zinc in the galvanneal strip coating, which in turn determines the desired product properties

S.W. Allison; D.L. Beshears; W.W. Manges

1999-06-30

156

Stress corrosion cracking of AISI 304 and 316 stainless steels in lithiated water at 350°C  

NASA Astrophysics Data System (ADS)

The stress corrosion cracking susceptibility of AISI Types 304 and 316 SS tubes with different heat treatments were investigated in lithiated water at 350°C. A comparison of the behaviour of these steels in the form of tubes with those made of sheets under stress corrosion cracking (SCC tests was discussed. The results showed that the sensitized conditions of both types exhibited the lowest SCC susceptibility compared to the solution-annealed conditions. The hydrogen content near the fracture surface was the highest along the gauge length of the specimens.

Sharkawy, S. W.; Xia, Z.; Szklarska-Smialowska, Z.

1992-10-01

157

Electrochemical investigation of passive film in pre-deformation AISI 304 stainless steels  

NASA Astrophysics Data System (ADS)

The electrochemical measures in deformed AISI 304 stainless steels ranged from 0% to 24% were investigated. With the increasing of the strain ?'-martensite was gradually increasing. Moreover, the morphologies and densities of dislocations changed with increasing strain. The Mott-Schottky plots showed that the maximum total of donor and acceptor densities in passive film occurred in borate buffer solution when ?-martensite was most, while in borate buffer solution with 5000 ppm Cl- the maximum total of donor and acceptor densities occurred when the content of ?-martensite was most. These results were proven by further impedance spectroscopy experiments.

Jinlong, Lv; Hongyun, Luo

2012-12-01

158

Rolling-contact fatigue lives of steel AISI 52100 balls with eight mineral and synthetic lubricants  

Microsoft Academic Search

This work has evaluated the rolling-contact fatigue lives of AISI 52100 steel balls with several mineral and synthetic oils with and without additive using a four-ball tester. The studied lubricants include S.N.-350 (mineral oil), S.N.-600 (mineral oil), TMP-05 (synthetic polyol ester), TMP-05 + 2%ZnDDP, P.A.G.-9 (synthetic polyalkyl glycol), P.A.G.-12 (synthetic polyalkyl glycol) and Breox-B-135X (synthetic polyalkyl glycol). Weibull plots and

Yinglong Wang; J. E. Fernandez; D. G. Cuervo

1996-01-01

159

Wear behavior of AISI 1090 steel modified by pulse plasma technique  

SciTech Connect

AISI 1090 steel was pulse plasma treated (PPT) using a Molybdenum electrode. Two different pulse numbers were chosen to obtain modified layers of 20{+-}5 {mu}m thickness. The dry sliding wear studies performed on this steel with and without PPT against an alumina ball counterpart showed that the PPT improved the wear resistance. The pulse number of the PPT modified layer was found to be highly influential in imparting the wear resistance to this steel, due to enhancement of surface hardness depending on treatment time.

Ayday, Aysun; Durman, Mehmet [Sakarya University, Faculty of Engineering, Department of Metallurgical and Materials Engineering, Adapazar Latin-Small-Letter-Dotless-I , 54187 (Turkey)

2012-09-06

160

Effects of biofilm formation on the electrochemical behavior of AISI 304 SS in board machine environment  

SciTech Connect

The electrochemical behavior of and biofilm formation on AISI 304 stainless steel were studied in board machine environment with natural bacteria population. Open circuit potentials, redox-potential as well as different electrochemical measurements were performed. The biofilms formed were analyzed by microbial cultivation and by epifluorescence microscopy. The results of the measurements were compared with those performed both in sterilized white water and in artificial white water. The anodic polarization behavior of just immersed specimens was very similar in biotic (real), artificial and abiotic (sterilized) white water. Pitting initiated at very low potentials and continued to very negative values. The initiation of pitting became more difficult when the immersion time increased to 7 or 8 days in real, artificial or sterilized water. When the immersion time further increased, the pitting nucleated more easily in sterilized white water as well as in artificial white water than in biotic white water. In the laboratory equipment it was possible to maintain the biofilm already formed in the board mill, but the amount of sulfate reducing bacteria decreased and the amount of biofilm did not further increase. The composition and structure of the biofilm formed in laboratory differed from that formed in board mill conditions. The preliminary results indicate that the formation of biofilm in biotic white water rather inhibits than enhances the pitting corrosion of type AISI 304 stainless steel.

Carp, L.; Hakkarainen, T. [VTT Manufacturing Technology (Finland); Raaska, L. [VTT Biotechnology and Food Research (Finland)

1999-11-01

161

Modeling of the flow stress for AISI H13 Tool Steel during Hard Machining Processes  

SciTech Connect

In general, the flow stress models used in computer simulation of machining processes are a function of effective strain, effective strain rate and temperature developed during the cutting process. However, these models do not adequately describe the material behavior in hard machining, where a range of material hardness between 45 and 60 HRC are used. Thus, depending on the specific material hardness different material models must be used in modeling the cutting process. This paper describes the development of a hardness-based flow stress and fracture models for the AISI H13 tool steel, which can be applied for range of material hardness mentioned above. These models were implemented in a non-isothermal viscoplastic numerical model to simulate the machining process for AISI H13 with various hardness values and applying different cutting regime parameters. Predicted results are validated by comparing them with experimental results found in the literature. They are found to predict reasonably well the cutting forces as well as the change in chip morphology from continuous to segmented chip as the material hardness change.

Umbrello, Domenico; Rizzuti, Stefania [Department of Mechanical Engineering, University of Calabria 87036 Rende (Italy); Outeiro, Jose C. [Portuguese Catholic University, 3080-024 Figueira da Foz (Portugal); Shivpuri, Rajiv [Industrial, Welding and Systems Engineering - Ohio State University 43210 Columbus (United States)

2007-04-07

162

Determination of Proper Austenitization Temperatures for Hot Stamping of AISI 4140 Steel  

NASA Astrophysics Data System (ADS)

High strength steels are desirable materials for use in automobile bodies in order to reduce vehicle weight and increase the safety of car passengers, but steel grades with high strength commonly show poor formability. Recently, steels with controlled microstructures and compositions are used to gain adequate strength after hot stamping while maintaining good formability during processing. In this study, microstructure evolutions and changes in mechanical properties of AISI 4140 steel sheets resulting from the hot stamping process at different austenitization temperatures were investigated. To determine the proper austenitization temperatures, the results were compared with those of the cold-worked and cold-worked plus quench-tempered specimens. Comparisons showed that the austenitization temperatures of 1000 and 1100 °C are proper for hot stamping of 3-mm-thick AISI 4140 steel sheets due to the resultant martensitic microstructure which led to the yield and ultimate tensile strength of 1.3 and 2.1 GPa, respectively. Such conditions resulted in more favorable simultaneous strength and elongation than those of hot-stamped conventional boron steels.

Samadian, Pedram; Parsa, Mohammad Habibi; Shakeri, Amid

2014-04-01

163

Cyclic deformation and near surface microstructures of shot peened or deep rolled austenitic stainless steel AISI 304  

Microsoft Academic Search

Cylindrical specimens of the austenitic stainless steel AISI 304 were shot peened or deep rolled with different peening intensities, and rolling pressures, respectively. The resulting near surface properties were characterized by cross sectioning transmission electron microscopy (TEM), residual stress and phase analysis as well as interference line half-width and microhardness measurements. Cyclic deformation curves were obtained by hysteresis measurements under

I Altenberger; B Scholtes; U Martin; H Oettel

1999-01-01

164

Influence of cutting parameters on drill bit temperature in dry drilling of AISI 1040 steel material using statistical analysis  

Microsoft Academic Search

Purpose – An investigation of drilling temperature is essential in understanding the drilling mechanism of the material, thus improving the process efficiency. The aim of this study is to experimentally investigate influences of drilling conditions such as the drilling depth, feed rate and spindle speed on the twist drill bit temperature and thrust force in the dry drilling of AISI

Eyup Ba?ci; Babur Ozcelik

2007-01-01

165

The effects of cutting tool geometry and processing parameters on the surface roughness of AISI 1030 steel  

Microsoft Academic Search

In this study, we have investigated the effects of different insert radii of cutting tools, different depths of cut and, different feed rates on the surface quality of the workpieces depending on various processing parameters. Properly, the AISI 1030 steel is processed at a digitally controlled computerised numerical control(CNC) turning lathe without using cooling water with three different insert radii

Hasan Gökkaya; Muammer Nalbant

2007-01-01

166

Modeling the reversion of martensite in the cold worked AISI 304 stainless steel by artificial neural networks  

Microsoft Academic Search

In this paper, the effect of annealing temperature and time on the reversion of strain-induced martensite to austenite in the cold worked AISI 304 stainless steel alloy was modeled by means of artificial neural networks (ANNs). The optimal ANN architecture and training algorithm were determined. The results of the ANN model were in good agreement with experimental data taken from

H. Mirzadeh; A. Najafizadeh

2009-01-01

167

Experimental investigation on ductile stable crack growth emanating from wire-cut notch in AISI 4340 steel  

Microsoft Academic Search

An experimental investigation on the stable crack growth (SCG) behaviour in AISI 4340 using CT type specimen with a sharp slit (0.05mm) under mode I and mixed modes (I and II) loading is presented. The slit was made in the specimen through wire cutting technique. Different combinations of loading angle ? and ratio of original crack length to specimen width

A. H. I. Mourad; M. J. Alghafri; O. A. Abu Zeid; S. K. Maiti

2005-01-01

168

Investigation of cylindrical wire electrical discharge turning (CWEDT) of AISI D3 tool steel based on statistical analysis  

Microsoft Academic Search

In this work, a surface roughness (Ra), roundness and material removal rate (MRR) study on the cylindrical wire electrical discharge turning (CWEDT) has been carried out. The material chosen in this case was AISI D3 tool steel due to its growing range of applications in the field of manufacturing tools, dies and molds as punch, tapping, reaming and so on

Mohammad Jafar Haddad; Alireza Fadaei Tehrani

2008-01-01

169

Application of response surface methodology in describing the performance of coated carbide tools when turning AISI 1045 steel  

Microsoft Academic Search

The performance of a multilayer tungsten carbide tool was described using response surface methodology (RSM) when turning AISI 1045 steel. Cutting tests were performed with constant depth of cut and under dry cutting conditions. The factors investigated were cutting speed, feed and the side cutting edge angle (SCEA) of the cutting edge. The main cutting force, i.e. the tangential force

M. Y. Noordin; V. C. Venkatesh; S. Sharif; S. Elting; A. Abdullah

2004-01-01

170

Modelling of surface finish and tool flank wear in turning of AISI D2 steel with ceramic wiper inserts  

Microsoft Academic Search

Tool nose design affects the surface finish and productivity in finish hard turning processes. Surface finishing and tool flank wear have been investigated in finish turning of AISI D2 steels (60 HRC) using ceramic wiper (multi-radii) design inserts. Multiple linear regression models and neural network models are developed for predicting surface roughness and tool flank wear. In neural network modelling,

Tugrul Özel; Yigit Karpat; Luís Figueira; J. Paulo Davim

2007-01-01

171

Cyclic deformation behaviour of AISI 321 austenitic steel and its characterization by means of HTC-SQUID  

Microsoft Academic Search

AISI 321 austenitic steel forms martensite due to quasi-static and cyclic loading. This presupposes the exceeding of the threshold value of cumulated plastic strain. The main aim is to determine the fatigue damage of austenitic steel by characterizing the martensitic structure with the help of the SQUID measuring technique. Several specimen batches were evaluated and thereby the load amplitudes and

Marco Lang; Jane Johnson; Jürgen Schreiber; Gerd Dobmann; Hans-Jürgen Bassler; Dieter Eifler; Ralf Ehrlich; Uwe Gampe

2000-01-01

172

Characterization of stable crack growth through AISI 4340 steel using cohesive zone modeling and CTOD\\/CTOA criterion  

Microsoft Academic Search

The criteria based on cohesive zone model (CZM) and CTOD\\/CTOA have been employed for analysis of stable crack growth (SCG) through AISI 4340 steel. Investigations have been reported first concerning characterization of mode I SCG using the CZM and a particular crack size in a CT specimen 8mm thick. The characteristic data is then verified considering other mode I crack

D. N. Jadhav; S. K. Maiti

2010-01-01

173

Investigating the Tool Life, Cutting Force Components, and Surface Roughness of AISI 302 Stainless Steel Material Under Oblique Machining  

Microsoft Academic Search

The aim of this work is to investigate the machinability of austenitic AISI 302 stainless steel under oblique cutting. This can be achieved by studying the cutting forces, analysis of tool life, and investigation of the surface roughness at different cutting conditions and nose radius. A factorial experiment and analysis of variance technique are used in which several factors are

A. M. El-Tamimi; T. M. El-Hossainy

2008-01-01

174

Void Swelling Of Aisi 321 Analog Stainless Steel Irradiated At Low Dpa Rates In The Bn-350 Reactor  

SciTech Connect

In several recently published studies conducted on a Soviet analog of AISI 321 stainless steel irradiated in either fast reactors or light water reactors, it was shown that the void swelling phenomenon extended to temperatures as low as ~300ºC or less, when produced by neutron irradiation at dpa rates in the range 10-7 to 10-8 dpa/sec. Other studies yielded similar results for AISI 316 and the Russian analog of AISI 316. In the current study a blanket duct assembly from BN-350, constructed from the Soviet analog of AISI 321, also exhibits swelling at dpa rates on the order of 10-8 dpa/sec, with voids seen as low as 281oC and only 0.65 dpa. It appears that low-temperature swelling occurs at low dpa rates in 300 series stainless steels in general, and also occurs during irradiations conducted in either fast or mixed spectrum reactors. Therefore it is expected that a similar behavior will be observed in fusion devices as well.

Maksimkin, O. P.; Tsai, K. V.; Turubarova, L. G.; Doronina, T. A.; Garner, Francis A.

2006-03-01

175

Welding Procedure Specification. Supplement 1. Records of Procedure Qualification Tests. Gas Tungsten Arc Welding of AISI 41XX Steels.  

National Technical Information Service (NTIS)

Procedure WPS-126 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for gas tungsten arc welding of AISI 4130 and 4142 steel (ASTM A519) (P-No: None), 0.438-inch wall pipe; filler metal is AMS 6457, Class 4130 MC (F-, A-No: None). ...

C. H. Wodtke, D. R. Frizzell

1986-01-01

176

Texture analysis of deformation induced martensite in an AISI 301L stainless steel: microtexture and macrotexture aspects.  

E-print Network

Texture analysis of deformation induced martensite in an AISI 301L stainless steel: microtexture, martensite. Introduction Metastable stainless steels are promising engineering materials due to a rewarding of martensite in austenitic stainless steels. The amount of martensite depends on processing parameters

Cambridge, University of

177

Optimization of process parameters for pulsed laser milling of micro-channels on AISI H13 tool steel  

E-print Network

selection Laser milling process a b s t r a c t This paper focuses on understanding the influence of laser. Whenever metals are used, the laser beam heats, melts and vaporizes the metal (metal sublimation), whileOptimization of process parameters for pulsed laser milling of micro-channels on AISI H13 tool

Ozel, Tugrul

178

Surface fatigue life and failure characteristics of EX-53, CBS 1000M, and AISI 9310 gear materials  

NASA Technical Reports Server (NTRS)

Spur gear endurance tests and rolling-element surface fatigue tests are conducted to investigate EX-53 and CBS 1000M steels for use as advanced application gear materials, to determine their endurance characteristics, and to compare the results with the standard AISI 9310 gear material. The gear pitch diameter is 8.89 cm (3.50 in). Gear test conditions are an oil inlet temperature of 320 K (116 F), an oil outlet temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. Bench-type rolling-element fatigue tests are conducted at ambient temperature with a bar specimen speed of 12,500 rpm and a maximum Hertz stress of 4.83 GPa (700 ksi). The EX-53 test gears have a surface fatigue life of twice that of the AISI 9310 spur gears. The CBS 1000M test gears have a surface fatigue life of more than twice that of the AISI 9310 spur gears. However, the CBS 1000M gears experience a 30-percent tooth fracture failure which limits its use as a gear material. The rolling-contact fatigue lines of RC bar specimens of EX-53 and ASISI 9310 are approximately equal. However, the CBS 1000M RC specimens have a surface fatigue life of about 50 percent that of the AISI 9310.

Townsend, D. P.

1985-01-01

179

Artificial neural networks for pitting potential prediction of resistance spot welding joints of AISI 304 austenitic stainless steel  

Microsoft Academic Search

The aim of this work is to predict the influence of welding process on pitting corrosion behaviour (PCB) of resistance spot welding (RSW) joints of AISI 304 austenitic stainless steel (ASS). PCB is estimated from the pitting potential (Epitt), which is predicted from three RSW parameters. The prediction is carried out by artificial neural networks (ANNs) because the phenomena that

Óscar Martín; Pilar De Tiedra; Manuel López

2010-01-01

180

A study on friction and wear behaviour of carburized, carbonitrided and borided AISI 1020 and 5115 steels  

Microsoft Academic Search

The friction and wear characteristics of AISI 1020 and 5115 steel surfaces improved by various thermochemical heat treatments such as carburizing, carbonitriding and boronizing were determined. Samples prepared from the test materials were treated at liquid and gases carburizing, gases carbonitriding and solid boronizing mediums. The hardness distributions, microstructures and X-ray diffraction studies were performed.The wear tests were carried out

B Selçuk; R Ipek; M. B Karam??

2003-01-01

181

Numerical simulations study of the localized corrosion resistance of AISI 316L stainless steel and pure titanium in a simulated body fluid environment  

Microsoft Academic Search

The resistance of both AISI 316L stainless steel (AISI 316L SS) and commercially pure titanium (cpTi) to localized corrosion in a simulated body fluid solution was investigated using numerical simulations. The resulting model, based on transport equations in dilute solutions, is designed to predict the susceptibility of these two biomaterials to crevice corrosion initiation. The results show that cpTi and

K. Yaya; Y. Khelfaoui; B. Malki; M. Kerkar

2011-01-01

182

Microstructural characterization of laser surface melted AISI M2 tool steel.  

PubMed

We describe the microstructure of Nd:YAG continuous wave laser surface melted high-speed steel, namely AISI M2, treated with different laser scanning speeds and beam diameters on its surface. Microstructural characterization of the remelted surface layer was performed using light optical and scanning electron microscopy and X-ray diffraction. The combination of the three techniques provided new insights into the substantial changes induced by laser surface melting of the steel surface layer. The advantage of the method is that it avoids the difficult and tedious work of preparing samples of this hard material for transmission electron microscopy, which is the technique normally used to study these fine microstructures. A melted zone with a dendritic structure and a partially melted zone with a heterogeneous cellular structure were observed. M(2)C carbides with different morphologies were identified in the resolidified surface layer after laser melting. PMID:20701656

Arias, J; Cabeza, M; Castro, G; Feijoo, I; Merino, P; Pena, G

2010-09-01

183

Strength and toughness of aisi 304 and 316 at 4 K  

NASA Astrophysics Data System (ADS)

Structural design of superconducting magnets in fusion energy devices requires reliable property data at 4 K. Nitrogen-strengthened AISI 304 and 316 stainless steels are considered to be the best currently available low temperature structural alloys on the basis of their fabricability and their potential to meet the US fusion research goals of combined 1000 MPa yield strength and 200 MPa m 1/2 fracture toughness at 4 K. This paper presents provisional equations for the yield strength of 304-and 316-type alloys at 4 K as a function of N content and grain size. Provisional equations for the 4 K fracture toughness, KIc( J), of these alloys are presented, in which the effects of yield strength, Ni and Mn content, and inclusion spacing are expressed quantitatively. The equations result from regression analyses of a matrix of NBS measurements that includes more extensive numerical data on alloying, refining, and processing parameters than have previously been available.

Simon, N. J.; Reed, R. P.

1986-11-01

184

Influence of neutron spectra on the radiation-induced evolution of AISI 316  

SciTech Connect

A single heat of AISI 316 stainless steel has been irradiated in both the EBR-II and HFIR reactors. These reactors have significantly different spectra, leading to differences in displacements per neutron, helium/dpa ratio, and solid transmutant generation rates. The influence of reactor spectra can be observed in the transmutation-altered elemental compositions and the void densities. At least in the range of 500 to 650/sup 0/C there does not appear to be any significant spectral-related differences in the dislocation density, phase development or total swelling. It appears that, in this temperature range, the steady-state swelling rate per displaced atom that develops in this steel will be the same in fast and thermal reactors, as well as in projected fusion devices.

Brager, H R; Garner, F A

1981-08-01

185

Antibacterial properties and corrosion resistance of AISI 420 stainless steels implanted by silver and copper ions  

NASA Astrophysics Data System (ADS)

Silver or copper ions are often chosen as antibacterial agents. But a few reports are concerned with these two antibacterial agents for preparation of antibacterial stainless steel (SS). The antibacterial properties and corrosion resistance of AISI 420 stainless steel implanted by silver and copper ions were investigated. Due to the cooperative antibacterial effect of silver and copper ions, the Ag/Cu implanted SS showed excellent antibacterial activities against both Gram-negative Escherichia coli ( E. coli) and Gram-positive Staphylococcus aureus ( S. aureus) at a total implantation dose of 2×1017 ions/cm2. Electrochemical polarization curves revealed that the corrosion resistance of Ag/Cu implanted SS was slightly enhanced as compared with that of un-implanted SS. The implanted layer was characterized by X-ray photoelectron spectroscopy (XPS). Core level XPS spectra indicate that the implanted silver and copper ions exist in metallic state in the implanted layer.

Ni, Hong-wei; Zhang, Han-shuang; Chen, Rong-sheng; Zhan, Wei-ting; Huo, Kai-fu; Zuo, Zhen-yu

2012-04-01

186

X-ray diffraction study on microstructures of shot/laser-peened AISI316 stainless steel  

NASA Astrophysics Data System (ADS)

Microstructural features of AISI316 stainless steels processed by shot peening (SP) and laser peening (LP) were studied using X-ray diffraction line profile analyses. Both specimens exhibited similar compressive residual stress profiles. Although the number of dislocations was increased and the crystallites were refined with both processes, the dislocation density in the SP specimen was significantly greater than that in the LP specimen. The crystallite size in the SP specimen was one-third that in the LP specimen. The SP process induced martensite transformation. The variations in the microstructural features differed between samples subjected to the two processes. The SP process resulted in a greater variation in the microstructural features in a sample in which residual stresses similar to that induced by the LP process were induced. Thus, the variations in the microstructural features differed depending on the deformation process.

Kumagai, Masayoshi; Akita, Koichi; Itano, Yuta; Imafuku, Muneyuki; Ohya, Shin-ichi

2013-11-01

187

Thermomagnetic characterization in AISI 316L austenitic stainless steel fibers with various true strains  

NASA Astrophysics Data System (ADS)

This paper investigated the effect of temperature on the magnetic properties of AISI 316L stainless steel wire drawn to micron-size fibers with various true strains using thermomagnetic analysis (TMA). The volume fraction of martensite induced by deformation was determined using a superconducting quantum interference device and a Ferritescope. During the heating process, the content of ?' martensite in the samples with a true strain of above 2.31 increased at around 460 °C. A shoulder of reverse transformation from ?' to ? was observed at around 625 °C in the TMA heating curves for samples with a true strain above 1.61. The shoulder shifted slightly to a higher temperature as the true strain increased. The relatively small increase in magnetization above approximately 760 °C was related to the ferrite content, as confirmed by electron probe microanalysis-wavelength-dispersive spectrometry. During the cooling process, the Ms temperature decreased as the true strain of fibers increased.

Yang, Shun-Tung; Shyr, Tien-Wei; Hwang, Weng-Sing; Ko, Cheng-Nan

2013-03-01

188

Surface modification of AISI-4620 steel with intense pulsed ion beams  

NASA Astrophysics Data System (ADS)

A 300 keV, 30 kA, 1 ?s intense beam ofcarbon, oxygen, and hydrogen ions is used for the surface treatment of AISI-4620 steel coupons, a common material used in automotive gear applications. The beam is extracted from a magnetically-insulated vacuum diode and deposited into the top 1 ?m of the target surface. The beam-solid interaction causes a rapid melt and resolidification with heating and cooling rates of up to 10 10 K/s. Treated surfaces are smoothed over 1 ?m-scale lengths, but are accompanied by 1 ?m-diameter craters and larger-scale roughening over ? 10 ?m, depending on beam fluence and number of pulses. Treated surfaces are up to 1.8 × harder with no discernible change in modulus over depths of 1 ?m or more. Qualitative improvements in the wear morphology of treated surfaces are reported.

Rej, D. J.; Davis, H. A.; Nastasi, M.; Olson, J. C.; Peterson, E. J.; Reiswig, R. D.; Walter, K. C.; Stinnett, R. W.; Remnev, G. E.; Struts, V. K.

1997-05-01

189

Comparisons of modified Vasco X-2 and AISI 9310 gear steels  

NASA Technical Reports Server (NTRS)

Endurance tests were conducted with four groups of spur gears manufactured from three heats of consumable electrode vacuum melted (CVM) modified Vasco X-2. Endurance tests were also conducted with gears manufactured from CVM AISI 9310. Bench type rolling element fatigue tests were conducted with both materials. Hardness measurements were made to 811 K. There was no statistically significant life difference between the two materials. Life differences between the different heats of modified Vasco X-2 can be attributed to heat treat variation and resultant hardness. Carburization of gear flanks only can eliminate tooth fracture as a primary failure mode for modified Vasco X-2. However, a tooth surface fatigue spall can act as a nucleus of a tooth fracture failure for the modified Vasco X-2.

Townsend, D. P.; Zaretsky, E. V.

1980-01-01

190

Pitting fatigue characteristics of AISI M-50 and super nitralloy spur gears  

NASA Technical Reports Server (NTRS)

Two groups of 3.50-in. pitch-diameter spur gears, without tip relief, made from consumable-electrode vacuum-melted (CVM) AISI M-50 steel and CVM super nitralloy (5Ni-2A1) were tested under conditions which produced fatigue pitting. The M-50 gears had fatigue lives approximately 50 percent longer than the super nitralloy gears. Both groups of gears failed by classical rolling-element fatigue at the pitch circle. When the gears were overrun past initial spall formation, the spalled M-50 gear teeth failed by fatigue fracture. The M-50 material had higher wear than the super nitralloy material. Differences in fatigue life and wear were not considered statistically significant.

Townsend, D. P.; Chevalier, J. L.; Zaretsky, E. V.

1973-01-01

191

Effect of five lubricants on life of AISI 9310 spur gears  

NASA Technical Reports Server (NTRS)

Spur-gear surface fatigue tests were conducted with five lubricants using a single lot of consumable-electrode vacuum melted (CVM) AISI 9310 spur gears. The lot of gears was divided into five groups, each of which was tested with a different lubricant. The test lubricants are classified as either a synthetic hydrocarbon, mineral oil, or ester-based lubricant. All five lubricants have imilar viscosity and pressure-viscosity coefficients. A pentaerythritol base stock without sufficient antiwear additives produced a surface fatigue life pproximately 22 percent that of the same base stock with chlorine and phosphorus type additives. The presence of sulfur type antiwear additives in the lubricant did not appear to affect the surface fatigue life of the gears tested. No statistical difference in the 10-percent surface fatigue life was produced with four of the five lubricants.

Townsend, D. P.; Zaretsky, E. V.

1985-01-01

192

Brazing of hot isostatically pressed-Al 2 O 3 to stainless steel (AlSl 304L) by Mo-Mn route using 72Ag28Cu braze  

Microsoft Academic Search

Joining of stainless steel (AISI 304L) to hot isostatically pressed alumina (HIP-Al2O3) using the brazing alloy 72Ag-28Cu was investigated. The microstructural characterization at various stages of joining, including\\u000a metallization, annealing of overlaid Ni coating, and brazing, was comprehensively evaluated. The interface structure and the\\u000a growth of phases were analyzed with optical microscope, scanning electron microscope, and electron probe microanalyzer (EPMA).

P. Mishra; S. N. Athavale; A. L. Pappachan; A. K. Grover; A. K. Suri; P. Sengupta; G. B. Kale; K. Bhanumurthy; P. K. De

2005-01-01

193

Dynamic behavior analysis of drill-threading process when machining AISI Al-Si-Cu 4 alloy  

Microsoft Academic Search

Conventional threading operations involve two distinct machining processes: drilling and threading. Therefore, it is time\\u000a consuming for the tools must be changed and the workpiece has to be moved to another machine. This paper presents an analysis\\u000a of the combined process (drilling followed by threading) using a single tool for both operations: the tap-milling tool. Before\\u000a presenting the methodology used

Wisley Falco Sales; Marcelo Becker; Alexandre G. Gurgel; Jánes L. Júnior

2009-01-01

194

Modeling tool wear progression by using mixed effects modeling technique when end-milling AISI 4340 steel  

Microsoft Academic Search

Semi-dry and dry machining is being adopted by the metal cutting industry worldwide to reduce the harmful effects of traditional metal cutting fluids and the cost associated with procurement, use, and disposal of these fluids. This research focuses on end-milling of AISI 4340 steel with multi-layer physical vapor deposition (PVD) coated carbide inserts under semi-dry and dry cutting conditions and

Pinaki Chakraborty; Shihab Asfour; Sohyung Cho; Arzu Onar; Matthew Lynn

2008-01-01

195

Quantitative Evaluation of Aged AISI 316L Stainless Steel Sensitization to Intergranular Corrosion: Comparison Between Microstructural Electrochemical and Analytical Methods  

Microsoft Academic Search

The evaluation of the degree of sensitization (DOS) to intergranular corrosion (IGC) of a commercial AISI 316L austenitic\\u000a stainless steel aged at temperatures ranging from 550 °C to 800 °C during 100 to 80,000 hours was carried out using three\\u000a different assessment methods. (1) The microstructural method coupled with the Strauss standard test (ASTM A262). This method\\u000a establishes the kinetics of

H. Sidhom; T. Amadou; H. Sahlaoui; C. Braham

2007-01-01

196

Effect of Ball Burnishing Process on the Surface Quality and Microstructure Properties of AISI 1010 Steel Plates  

Microsoft Academic Search

A newly developed ball burnishing tool was designed and tested for surface finishing of large flat surfaces in a shortest\\u000a possible time. Optimization and analysis of the burnishing process were carried on AISI 1010 steel hot-rolled plates using\\u000a the Taguchi technique and response surface methodology (RSM) to identify the effect of burnishing parameters (i.e., burnishing\\u000a speed, burnishing force, and feed

F. Gharbi; S. Sghaier; K. J. Al-Fadhalah; T. Benameur

2011-01-01

197

An investigation on the microstructure and mechanical properties of direct-quenched and tempered AISI 4140 steel  

Microsoft Academic Search

Direct quenching (DQ) process is an appropriate method in steels heat treatment field. This method enhances production rate, reduces energy consumption and decreases environment contamination. In this study hot-rolled AISI 4140 steel billets with different diameters (75,80,85,100,105 and 115mm) and 20m length were quenched directly in a water tank. Also some samples with similar size and composition were provided by

A. H. Meysami; R. Ghasemzadeh; S. H. Seyedein; M. R. Aboutalebi

2010-01-01

198

Empirical models and optimal cutting parameters for cutting forces and surface roughness in hard milling of AISI H13 steel  

Microsoft Academic Search

In the present research, an attempt has been made to experimentally investigate the effects of cutting parameters on cutting\\u000a forces and surface roughness in hard milling of AISI H13 steel with coated carbide tools. Based on Taguchi’s method, four-factor\\u000a (cutting speed, feed, radial depth of cut, and axial depth of cut) four-level orthogonal experiments were employed. Three\\u000a cutting force components

Tongchao Ding; Song Zhang; Yuanwei Wang; Xiaoli Zhu

2010-01-01

199

Influence of austenitizing temperature on microstructure and mechanical properties of AISI 431 martensitic stainless steel electron beam welds  

Microsoft Academic Search

The relative effects of various austenitizing temperatures on microstructure and mechanical properties of electron beam welds of AISI 431martensitic stainless steel were studied. The post-weld heat treatments consist of austenitizing the weld samples for 1h at various temperatures, i.e., at 950°C, 1000°C, 1050°C, 1100°C and at 1150°C and air cooling followed by double tempering, i.e., tempering at 670+600°C. In the

A. Rajasekhar; G. Madhusudhan Reddy; T. Mohandas; V. S. R. Murti

2009-01-01

200

Effect of processing conditions on the corrosion performance of laser surface-melted AISI 440C martensitic stainless steel  

Microsoft Academic Search

Laser surface melting of AISI 440C martensitic stainless steel was achieved using a 2.5-kW continuous wave Nd:YAG laser. The pitting corrosion behavior of laser surface-melted specimens processed under different processing conditions in 3.5% NaCl solution at 23 °C was studied by potentiodynamic polarization technique. The corrosion resistance of all laser surface-melted specimens was significantly improved, as evidenced by a shift

C. T. Kwok; K. H. Lo; F. T. Cheng; H. C. Man

2003-01-01

201

Friction and rolling–sliding wear of DC-pulsed plasma nitrided AISI 410 martensitic stainless steel  

Microsoft Academic Search

In the present work, industrial-scale DC-pulsed plasma nitriding for 20h at 673K was used to improve the wear resistance of an AISI 410 martensitic stainless steel. The tribological behaviour was studied and compared to the behaviour of the same steel in as-received condition.Pin-on-disc dry tests, using an alumina ball as counter-body, were carried out to determine the evolution of the

P. Corengia; F. Walther; Gabriel O. Ybarra; S. Sommadossi; R. Corbari; E. Broitman

2006-01-01

202

Effect of coatings obtanied by sputtering of chromium catode on the corrosion resistance of AISI H13 steel  

NASA Astrophysics Data System (ADS)

Corrosion resistance of coatings obtained by sputtering a chromium target were evaluated. The films were deposited on substrates of disk-shaped AISI H13 steel. By means of potentiodynamic polarization curves were able to determine the current density vs. potential for the coated and uncoated substrate and the difference in the corrosion potential Ecorr. All samples with coating showed an increase in Ecorr respect to substrate. The electrochemical tests were conducted in an electrolytic solution of 3% NaCl.

Sandoval, A.; Peña, D.; Piratoba, U.

2013-11-01

203

Surface fatigue life of M50NiL and AISI 9310 spur gears and R C bars  

NASA Technical Reports Server (NTRS)

Spur gear endurance tests and rolling element surface fatigue tests were conducted to study vacuum induction melted, vacuum arc remelted (VIM-VAR) M50NiL steel for use as a gear steel in advanced aircraft applications, to determine its endurance characteristics, and to compare the results with those for standard VAR and VIM-VAR AISI 9310 gear material. Tests were conducted with spur gears and rolling contact bars manufactured from VIM-VAR M50NiL and VAR and VIM-VAR AISI 9310. The gear pitch diameter was 8.9 cm. Gear test conditions were an inlet oil temperature of 320 K, and outlet oil temperature of 350 K, a maximum Hertz stress of 1.71 GPa, and a speed of 10000 rpm. Bench rolling element fatigue tests were conducted at ambient temperatures with a bar speed of 12,500 rpm and a maximum Hertz stress of 4.83 GPa. The VIM-VAR M50NiL gears had a surface fatigue life that was 4.5 and 11.5 times that for VIM-VAR and VAR AISI 9310 gears, respectively. The surface fatigue life of the VIM-VAR M50NiL rolling contact bars was 13.2 and 21.6 times that for the VIM-VAR and VAR AISI 9310, respectively. The VIM-VAR M50NiL material was shown to have good resistance to fracture through a fatigue spall and superior fatigue life to both other gears.

Townsend, Dennis P.; Bamberger, Eric N.

1991-01-01

204

Microstructure and mechanical properties of electron beam-welded AISI 409M-grade ferritic stainless steel  

Microsoft Academic Search

This paper deals with the microstructure and mechanical characterization of electron beam-welded AISI 409M-grade ferritic\\u000a stainless steel joints. Single-pass autogenous welds free of volumetric defects were produced at a welding speed of 1,000 mm\\/min.\\u000a The joints were subjected to optical microscopy, scanning electron fractography, microhardness, transverse and longitudinal\\u000a tensile, bend and charpy impact toughness testing. The coarse ferrite grains in the

A. K. Lakshminarayanan; V. Balasubramanian; G. Madhusudhan Reddy

2011-01-01

205

Formation of nanostructured surface layer on AISI 304 stainless steel by means of surface mechanical attrition treatment  

Microsoft Academic Search

A nanostructured surface layer was formed on an AISI 304 stainless steel with low stacking-fault energy by means of the surface mechanical attrition treatment (SMAT). The microstructure of the surface layer of the SMATed sample was characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and cross-sectional TEM observation was performed to reveal the

H. W Zhang; Z. K Hei; G Liu; J Lu; K Lu

2003-01-01

206

Strain-rate effects on the mechanical behavior of the AISI 300 series of austenitic stainless steel under cryogenic environments  

Microsoft Academic Search

A series of uni-axial tensile tests were carried out under various low temperatures and strain-rate ranges for AISI 300 austenitic stainless steel. The strain-rate dependencies of the materials under investigation were evaluated at temperatures ranging from ambient to cryogenic. Non-linear mechanical behavior such as phase transformation, discontinuous yielding and micro-damage of four kinds of commercial stainless steel-based material were quantitatively

Woong Sup Park; Seong Won Yoo; Myung Hyun Kim; Jae Myung Lee

2010-01-01

207

Process parameters selection for laser polishing DF2 (AISI O1) by Nd:YAG pulsed laser using orthogonal design  

Microsoft Academic Search

Mechanisms of laser polishing metals in a continuous scanning mode, as envisaged and analyzed in this paper, are rather complex,\\u000a and experimental optimization of laser polishing metallic material is very time-consuming and difficult. Aiming at shortening\\u000a the experimental time in achieving a better surface finishing of DF2 (AISI 01) tool steel by pulse Nd:YAG laser, we used the\\u000a orthogonal experimental

Wei Guo; Meng Hua; Peter Wai-Tat Tse; Albert Chiu Kam Mok

208

Improvement of erosion and erosion corrosion resistance of AISI420 stainless steel by low temperature plasma nitriding  

NASA Astrophysics Data System (ADS)

Plasma nitriding experiments were carried out with DC-pulsed plasma in 25% N 2 + 75% H 2 atmosphere at low temperature (350 °C) and normal temperature (550 °C) for 15 h. The composition, microstructure, microhardness profiles, residual stress profiles and electrochemical impedance spectrum analyses of the nitrided samples were examined. The influence of plasma nitriding on the erosion and erosion-corrosion resistance of AISI 420 martensitic stainless steel was investigated using a jet solid particle erosion tester and a slurry erosion-corrosion tester. Results showed that the 350 °C nitriding layer was dominated by ?-Fe 3N and ? N phase, a supersaturated nitrogen solid solution. However, nitrogen would react with Cr in the steel to form CrN precipitates directly during 550 °C nitriding, which would lead to the depletion of Cr in the solid solution phase of the nitrided layer. Both 350 and 550 °C plasma nitriding could improve the erosion resistance of AISI420 stainless steel under dry erosion, but the former showed better results. In both neutral and acid environment, while the erosion-corrosion resistance of AISI 420 was improved by means of 350 °C nitriding, it was decreased through 550 °C nitriding.

Xi, Yun-tao; Liu, Dao-xin; Han, Dong

2008-07-01

209

Plasma nitriding process by direct current glow discharge at low temperature increasing the thermal diffusivity of AISI 304 stainless steel  

SciTech Connect

This work reports for the first time on the use of the open photoacoustic cell technique operating at very low frequencies and at room temperature to experimentally determine the thermal diffusivity parameter of commercial AISI304 stainless steel and AISI304 stainless steel nitrided samples. Complementary measurements of X-ray diffraction and scanning electron microscopy were also performed. The results show that in standard AISI 304 stainless steel samples the thermal diffusivity is (4.0 {+-} 0.3) Multiplication-Sign 10{sup -6} m{sup 2}/s. After the nitriding process, the thermal diffusivity increases to the value (7.1 {+-} 0.5) Multiplication-Sign 10{sup -6} m{sup 2}/s. The results are being associated to the diffusion process of nitrogen into the surface of the sample. Carrying out subsequent thermal treatment at 500 Degree-Sign C, the thermal diffusivity increases up to (12.0 {+-} 2) Multiplication-Sign 10{sup -6} m{sup 2}/s. Now the observed growing in the thermal diffusivity must be related to the change in the phases contained in the nitrided layer.

Prandel, L. V.; Somer, A.; Assmann, A.; Camelotti, F.; Costa, G.; Bonardi, C.; Jurelo, A. R.; Rodrigues, J. B.; Cruz, G. K. [Universidade Estadual de Ponta Grossa, Grupo de Espectroscopia Optica e Fotoacustica de Materiais, Departamento de Fisica, Av. Carlos Cavalcanti, 4748, CEP 84030-900, Ponta Grossa, PR (Brazil)

2013-02-14

210

Effect of Austenitizing Heat Treatment on the Microstructure and Hardness of Martensitic Stainless Steel AISI 420  

NASA Astrophysics Data System (ADS)

The effect of austenitizing on the microstructure and hardness of two martensitic stainless steels was examined with the aim of supplying heat-treatment guidelines to the user that will ensure a martensitic structure with minimal retained austenite, evenly dispersed carbides and a hardness of between 610 and 740 HV (Vickers hardness) after quenching and tempering. The steels examined during the course of this examination conform in composition to medium-carbon AISI 420 martensitic stainless steel, except for the addition of 0.13% vanadium and 0.62% molybdenum to one of the alloys. Steel samples were austenitized at temperatures between 1000 and 1200 °C, followed by oil quenching. The as-quenched microstructures were found to range from almost fully martensitic structures to martensite with up to 35% retained austenite after quenching, with varying amounts of carbides. Optical and scanning electron microscopy was used to characterize the microstructures, and X-ray diffraction was employed to identify the carbide present in the as-quenched structures and to quantify the retained austenite contents. Hardness tests were performed to determine the effect of heat treatment on mechanical properties. As-quenched hardness values ranged from 700 to 270 HV, depending on the amount of retained austenite. Thermodynamic predictions (using the CALPHAD™ model) were employed to explain these microstructures based on the solubility of the carbide particles at various austenitizing temperatures.

Barlow, L. D.; Du Toit, M.

2012-07-01

211

On the fatigue crack growth resistance of upper bainite-martensite in an AISI 4330 steel  

SciTech Connect

Investigation on 4340 type low alloy high strength steels have shown that bainite-martensite mixed microstructures display, in certain cases, an improved combination of strength and toughness as compared to the behavior of these steels in the fully martensitic condition. The literature reveals that, in association with tempered martensite, lower bainite is the preferred form of bainite for improved mechanical behavior with about 25% by volume of lower bainite being an optimum proportion. On the other hand, the presence of upper bainite was seen to be detrimental. Contrary to these observations, the recent work on a vanadium containing steel corresponding to the AISI 4330 designation suggests that the presence of upper bainite in a mixed microstructure tempered at 473 K results in a significant improvement in toughness at the same strength level as that of the fully martensitic structure. Here the authors report in the same steel the fatigue crack growth behavior of upper bainite-martensite mixed structure. As was observed in regard to tensile properties and fracture toughness, the fatigue crack growth resistance of upper bainite-martensite mixed microstructure is shown to be superior by comparison with the behavior of the fully martensitic structure.

Saxena, V.K. (Defence Metallurgical Research Lab., Hyderabad (India)); Malakondaiah, G. (Wright-Patterson Air Force Base, OH (United States)); Radhakrishnan, V.M. (Indian Inst. of Tech., Madras (India)); Rao, P.R. (Jawaharlal Nehru Centre for Advance Research, Bangalore (India))

1993-05-15

212

Some Temperature Effects on AISI-304 Nitriding in an Inductively Coupled RF Plasma  

NASA Astrophysics Data System (ADS)

Some recent results obtained from nitriding AISI 304 stainless steel samples, 1.2 cm in diameter and 0.5 cm thick are reported here in the case of an 85% hydrogen and 15% nitrogen mixture work gas. The process was carried out from 300 to 400 W for (13.56 MHz) inductively coupled plasma within a 60 cm long pyrex glass tube 3.5 cm in diameter where the samples were biased up to -300 V with respect to earth. The resulting hardness appears to be a function of the substrate temperature which varied from 200 °C at a 0 V bias to 550 °C at -300 V. The plasma density at 400 W reached 3×1010 cm-3 with a 4 eV electron temperature. Prior to nitriding, all the samples were polished with 0.05 ?m diamond paste, leading to a 30 nm average roughness (Ra). After nitriding at -300 V, the Ra rose until ˜400 nm while hardness values of 1500 HV under 300 g loads were measured. X ray diffraction indicates that the extended phase amplitude (?N), Fe and Cr nitride depends on the substrate temperature.

Valencia-Alvarado, R.; de la Piedad-Beneitez, A.; de la Rosa-Vázquez, J.; López-Callejas, R.; Barocio, S. R.; Godoy-Cabrera, O. G.; Mercado-Cabrera, A.; Peña-Eguiluz, R.; Muñoz-Castro, A. E.

2006-12-01

213

An experimental investigation of pulsed laser-assisted machining of AISI 52100 steel  

NASA Astrophysics Data System (ADS)

Grinding and hard turning are widely used for machining of hardened bearing steel parts. Laser-assisted machining (LAM) has emerged as an efficient alternative to grinding and hard turning for hardened steel parts. In most cases, continuous-wave lasers were used as a heat source to cause localized heating prior to material removal by a cutting tool. In this study, an experimental investigation of pulsed laser-assisted machining of AISI 52100 bearing steel was conducted. The effects of process parameters (i.e., laser mean power, pulse frequency, pulse energy, cutting speed and feed rate) on state variables (i.e., material removal temperature, specific cutting energy, surface roughness, microstructure, tool wear and chip formation) were investigated. At laser mean power of 425 W with frequency of 120 Hz and cutting speed of 70 m/min, the benefit of LAM was shown by 25% decrease in specific cutting energy and 18% improvement in surface roughness, as compared to those of the conventional machining. It was shown that at constant laser power, the increase of laser pulse energy causes the rapid increase in tool wear rate. Pulsed laser allowed efficient control of surface temperature and heat penetration in material removal region. Examination of the machined subsurface microstructure and microhardness profiles showed no change under LAM and conventional machining. Continuous chips with more uniform plastic deformation were produced in LAM.

Panjehpour, Afshin; Soleymani Yazdi, Mohammad R.; Shoja-Razavi, Reza

2014-11-01

214

Fe-Based Amorphous Coatings on AISI 4130 Structural Steel for Corrosion Resistance  

NASA Astrophysics Data System (ADS)

The current study focuses on synthesizing a novel functional coating for corrosion resistance applications, via laser surface alloying. The iron-based (Fe48Cr15Mo14Y2C15B) amorphous precursor powder is used for laser surface alloying on AISI 4130 steel substrate, with a continuous wave ytterbium Nd-YAG fiber laser. The corrosion resistance of the coatings is evaluated for different processing conditions. The microstructural evolution and the response of the microstructure to the corrosive environment is studied using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Microstructural studies indicate the presence of face-centered cubic Fe-based dendrites intermixed within an amorphous matrix along with fine crystalline precipitates. The corrosion resistance of the coatings decrease with an increase in laser energy density, which is attributed to the precipitation and growth of chromium carbide. The enhanced corrosion resistance of the coatings processed with low energy density is attributed to the self-healing mechanism of this amorphous system.

Katakam, Shravana; Santhanakrishnan, S.; Dahotre, Narendra B.

2012-06-01

215

White Layer Formation Due to Phase Transformation to Orthogonal machine of AISI 1045 Annealed Steel  

SciTech Connect

It is commonly believed that the white layer formed during machining of steels is caused primarily by a thermally induced phase transformation resulting from rapid heating and quenching. As a result, it is often assumed that if the temperature at the tool flank-workpiece interface exceeds the nominal phase transformation temperature for the steel, a white layer forms. However, no attempt has been made to actually measure the temperatures produced at the tool flank-workpiece interface and correlate it with microstructural evidence of phase transformation. This paper aims to address these limitations through suitably designed experiments and analysis. Orthogonal machining tests were performed on AISI 1045 annealed steel at different cutting speeds and tool flank wear. During machining, temperature measurements at the tool flank-workpiece interface were made using an exposed thermocouple technique. Metallographic studies of the machined sub-surface and X-ray diffraction (XRD) measurements were performed to determine the presence and depth of white layer, and the presence of the retained austenite phase in the machined surface layer, respectively. Analysis of the data shows that the white layer can form due to phase transformation at temperatures below the nominal austenitization temperature of the steel. Possible causes of this result are presented.

Han, Sangil [ORNL; Melkote, Shreyes N [Georgia Institute of Technology; Haluska, Dr. Michael S [Georgia Institute of Technology; Watkins, Thomas R [ORNL

2008-01-01

216

Evaluation of AISI 4140 Steel Repair Without Post-Weld Heat Treatment  

NASA Astrophysics Data System (ADS)

The present work evaluates the two-layer technique on the heat affected zone (HAZ) of AISI 4140 steel welded with different heat input levels between the first and second layer. The weld heat input levels selected by the Higuchi test were 5/5, 5/10, and 15/5 kJ/cm. The evaluation of the refining and/or tempering of the coarsened grain HAZ of the first layer was carried out using metallographic tests, microhardness measurements, and the Charpy-V impact test. The tempering of the first layer was only reached when the weld heat input ratio was 5/5 kJ/cm. The results of the Charpy-V impact test showed that the two-layer technique was efficient, from the point of view of toughness, since the toughness values reached were greater than the base metal for all weld heat input ratios applied. The results obtained indicate that the best performance of the two-layer deposition technique was for the weld heat input ratio 5/5 kJ/cm employing low heat input.

Silva, Cleiton C.; de Albuquerque, Victor H. C.; Moura, Cícero R. O.; Aguiar, Willys M.; Farias, Jesualdo P.

2009-04-01

217

Spinodal decomposition in AISI 316L stainless steel via high-speed laser remelting  

NASA Astrophysics Data System (ADS)

A 1.5 kW CO2 pulsed laser was used to melt the surface of AISI 316L stainless steel with a view to enhancing the surface properties for engineering applications. A 90 ?m laser beam spot size focused onto the surface was used to provide high irradiances (up to 23.56 MW/cm2) with low residence times (as low as 50 ?s) in order to induce rapid surface melting and solidification. Variations in microstructure at different points within the laser treated region were investigated. From this processing refined lamellar and nodular microstructures were produced. These sets of unique microstructures were produced within the remelted region when the highest energy densities were selected in conjunction with the lowest residence times. The transformation from the typical austenitic structure to much finer unique lamellar and nodular structures was attributed to the high thermal gradients achieved using these selected laser processing parameters. These structures resulted in unique characteristics including elimination of cracks and a reduction of inclusions within the treated region. Grain structure reorientation between the bulk alloy and laser-treated region occurred due to the induced thermal gradients. This present article reports on microstructure forms resulting from the high-speed laser surface remelting and corresponding underlying kinetics.

Chikarakara, Evans; Naher, Sumsun; Brabazon, Dermot

2014-05-01

218

Some Temperature Effects on AISI-304 Nitriding in an Inductively Coupled RF Plasma  

SciTech Connect

Some recent results obtained from nitriding AISI 304 stainless steel samples, 1.2 cm in diameter and 0.5 cm thick are reported here in the case of an 85% hydrogen and 15% nitrogen mixture work gas. The process was carried out from 300 to 400 W for (13.56 MHz) inductively coupled plasma within a 60 cm long pyrex glass tube 3.5 cm in diameter where the samples were biased up to -300 V with respect to earth. The resulting hardness appears to be a function of the substrate temperature which varied from 200 deg. C at a 0 V bias to 550 deg. C at -300 V. The plasma density at 400 W reached 3x1010 cm-3 with a 4 eV electron temperature. Prior to nitriding, all the samples were polished with 0.05 {mu}m diamond paste, leading to a 30 nm average roughness (Ra). After nitriding at -300 V, the Ra rose until {approx}400 nm while hardness values of 1500 HV under 300 g loads were measured. X ray diffraction indicates that the extended phase amplitude ({gamma}N), Fe and Cr nitride depends on the substrate temperature.

Valencia-Alvarado, R.; Barocio, S. R.; Mercado-Cabrera, A.; Pena-Eguiluz, R.; Munoz-Castro, A. E. [Instituto Nacional de Investigaciones Nucleares, Plasma Physics Laboratory, AP. 18-1027, 11801, Mexico, D.F. (Mexico); Piedad-Beneitez, A. de la [Instituto Tecnologico de Toluca, Departamento de Electronica, Apartado Postal 890, Toluca (Mexico); Rosa-Vazquez, J. de la [ESIME-Zacatenco-IPN, 07738, Mexico, D.F. (Mexico); Lopez-Callejas, R.; Godoy-Cabrera, O. G. [Instituto Nacional de Investigaciones Nucleares, Plasma Physics Laboratory, AP. 18-1027, 11801, Mexico, D.F. (Mexico); Instituto Tecnologico de Toluca, Departamento de Electronica, Apartado Postal 890, Toluca (Mexico)

2006-12-04

219

Surface characterisation and corrosion behaviour of SiC-coated AISI 321 stainless steel  

NASA Astrophysics Data System (ADS)

The influence of SiC-coatings on the corrosion properties of AISI 321 austenitic stainless steel (Fe/Cr18/Ni8/Ti) in 1N H 2SO 4 was studied. SiC-coatings of various thicknesses (100-800 nm) were prepared at room temperature (RT) or at temperatures up to 750°C by ion beam sputtering of a SiC-target. The growing films could be continuously bombarded with a 160 keV Ar + ion beam and the role of this Dynamic Ion Mixing (DIM) on both the structure and corrosion resistance was investigated. The chemical composition of the coatings was determined by Rutherford Backscattering (RBS) using 1.8 MeV ?-particles and by Nuclear Reaction Analysis (NRA). Transmission Electron Microscopy (TEM) observations were also performed for the determination of the microstructural state of the samples. The characterisation shows, that for all the deposition temperatures the DIM-treatment promotes the crystallisation of the ?-SiC phase. It was also found, that the corrosion resistance of the stainless steel is considerably improved when the coatings are deposited by DIM regardless of the deposition temperature. The possible mechanisms are discussed and it is suggested that the interface mixing along with the coating densification effect are responsible for the improvement of the corrosion resistance.

Misaelides, P.; Noli, F.; Riviere, J. P.; Delafond, J.

220

Influence of grain size on ultrasonic spectral parameters in AISI type 316 stainless steel  

SciTech Connect

The grain size of a material is an important engineering parameter which influences the mechanical properties such as fatigue, creep, yield strength, impact transition temperature, etc. The reliability of the ultrasonic methods for grain size measurement, particularly amplitude based measurements are highly dependent upon the couplant condition. Therefore, application of these methods may be difficult for some practical applications, where uniform couplant condition can not be maintained. Therefore, it would be useful if a simplified method is developed, which could be used on-line and is free from the above mentioned limitations of the other methods. The shift in the spectral peak frequency has been used for microstructural characterization in carbon steel and for evaluation of structural variations induced by tensile deformation in SUS304 stainless steel. The spectral peak frequency in SUS304 steel was found to increase with increase in the tensile elongation. This was attributed to formation and growth of martensite structures due to tensile deformation resulting in smaller crystalline grains, thus reducing the attenuation due to ultrasonic scattering. The peak frequency has also been found to shift with the change in the grain size in Inconel 600 and copper. In the present study, the shift in the spectral peak frequency and the change in full width at half maximum (FWHM) of the autopower spectrum are correlated with the grain size in AISI type 316 austenitic stainless steel, a widely used structural material in nuclear, chemical, fertilizer and many other industries.

Kumar, A.; Jayakumar, T.; Palanichamy, P.; Raj, B. [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Metallurgy and Materials Group] [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Metallurgy and Materials Group

1999-01-08

221

Investigation of Low-Cycle Bending Fatigue of AISI 9310 Steel Spur Gears  

NASA Technical Reports Server (NTRS)

An investigation of the low-cycle bending fatigue of spur gears made from AISI 9310 gear steel was completed. Tests were conducted using the single-tooth bending method to achieve crack initiation and propagation. Tests were conducted on spur gears in a fatigue test machine using a dedicated gear test fixture. Test loads were applied at the highest point of single tooth contact. Gear bending stresses for a given testing load were calculated using a linear-elastic finite element model. Test data were accumulated from 1/4 cycle to several thousand cycles depending on the test stress level. The relationship of stress and cycles for crack initiation was found to be semilogarithmic. The relationship of stress and cycles for crack propagation was found to be linear. For the range of loads investigated, the crack propagation phase is related to the level of load being applied. Very high loads have comparable crack initiation and propagation times whereas lower loads can have a much smaller number of cycles for crack propagation cycles as compared to crack initiation.

Handschuh, Robert F.; Krantz, Timothy L.; Lerch, Bradley A.; Burke, Christopher S.

2007-01-01

222

Investigation of Low-Cycle Bending Fatigue of AISI 9310 Steel Spur Gears  

NASA Technical Reports Server (NTRS)

An investigation of the low-cycle bending fatigue of spur gears made from AISI 9310 gear steel was completed. Tests were conducted using the single-tooth bending method to achieve crack initiation and propagation. Tests were conducted on spur gears in a fatigue test machine using a dedicated gear test fixture. Test loads were applied at the highest point of single tooth contact. Gear bending stresses for a given testing load were calculated using a linear-elastic finite element model. Test data were accumulated from 1/4 cycle to several thousand cycles depending on the test stress level. The relationship of stress and cycles for crack initiation was found to be semi-logarithmic. The relationship of stress and cycles for crack propagation was found to be linear. For the range of loads investigated, the crack propagation phase is related to the level of load being applied. Very high loads have comparable crack initiation and propagation times whereas lower loads can have a much smaller number of cycles for crack propagation cycles as compared to crack initiation.

Handschuh, Robert F.; Krantz, Timothy L.; Lerch, Bradley A.; Burke, Christopher S.

2007-01-01

223

An Electrochemical Processing Strategy for Improving Tribological Performance of Aisi 316 Stainless Steel Under Grease Lubrication  

NASA Astrophysics Data System (ADS)

In order to improve the tribological performance of AISI 316 stainless steel (316 SS) under grease lubrication, electrochemical processing was conducted on it to obtain a rough (surface texturing-like) surface by making use of the high sensitivity of austenitic stainless steel to pitting corrosion in Cl--rich environment. Numerous corrosion pits or micro-ditches acted as micro-reservoirs on the obtained surface. While the grease could offer consistent lubrication, and then improve the tribological performance of 316 SS. Tribological behaviors of raw 316 SS and the treated sample were measured using a reciprocating type tribometer sliding against GCr15 steel counterpart under dry and grease lubrication conditions. The results showed that the mass losses of the two samples were in the same order of magnitude, and the raw sample exhibited lower friction coefficient in dry sliding. When the tests were conducted under grease lubrication condition, the friction coefficients and mass losses of the treated sample were far lower than those of the raw 316 SS. The tribological performance of 316 SS under grease lubrication was drastically improved after electrochemical processing.

Zou, Jiaojuan; Li, Maolin; Lin, Naiming; Zhang, Xiangyu; Qin, Lin; Tang, Bin

2014-12-01

224

Characterization of irradiated AISI 316L stainless steel disks removed from the Spallation Neutron Source  

SciTech Connect

Irradiated AISI 316L stainless steel disks were removed from the Spallation Neutron Source (SNS) for post-irradiation examination (PIE) to assess mechanical property changes due to radiation damage and erosion of the target vessel. Topics reviewed include high-resolution photography of the disk specimens, cleaning to remove mercury (Hg) residue and surface oxides, profile mapping of cavitation pits using high frequency ultrasonic testing (UT), high-resolution surface replication, and machining of test specimens using wire electrical discharge machining (EDM), tensile testing, Rockwell Superficial hardness testing, Vickers microhardness testing, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The effectiveness of the cleaning procedure was evident in the pre- and post-cleaning photography and permitted accurate placement of the test specimens on the disks. Due to the limited amount of material available and the unique geometry of the disks, machine fixturing and test specimen design were critical aspects of this work. Multiple designs were considered and refined during mock-up test runs on unirradiated disks. The techniques used to successfully machine and test the various specimens will be presented along with a summary of important findings from the laboratory examinations.

Vevera, Bradley J [ORNL] [ORNL; Hyres, James W [ORNL] [ORNL; McClintock, David A [ORNL] [ORNL; Riemer, Bernie [ORNL] [ORNL

2014-01-01

225

Effect of lubricant extreme-pressure additives on surface fatigue life of AISI 9310 spur gears  

NASA Technical Reports Server (NTRS)

Surface fatigue tests were conducted with AISI 9310 spur gears using a formulated synthetic tetraester oil (conforming to MIL-L-23699 specifications) as the lubricant containing either sulfur or phosphorus as the EP additive. Four groups of gears were tested. One group of gears tested without an additive in the lubricant acted as the reference oil. In the other three groups either a 0.1 wt % sulfur or phosphorus additive was added to the tetraester oil to enhance gear surface fatigue life. Test conditions included a gear temperature of 334 K (160 F), a maximum Hertz stress of 1.71 GPa (248 000 psi), and a speed of 10,000 rpm. The gears tested with a 0.1 wt % phosphorus additive showed pitting fatigue life 2.6 times the life of gears tested with the reference tetraester based oil. Although fatigue lives of two groups of gears tested with the sulfur additive in the oil showed improvement over the control group gear life, the results, unlike those obtained with the phosphorus oil, were not considered to be statistically significant.

Scibbe, H. W.; Townsend, D. P.; Aron, P. R.

1984-01-01

226

Effect of two synthetic lubricants on life of AISI 9310 spur gears  

NASA Technical Reports Server (NTRS)

Spur-gear fatigue tests were conducted with two lubricants using a single lot of consumable-electrode vacuum-melted (CVM) AISI 9310 spur gears. The gears were case carburized and hardened to Rockwell C60. The gear pitch diameter was 8.89 cm. The lot of gears was divided into two groups, each of which was tested with a different lubricant. The test lubricants can be classified as synthetic polyol-ester-based lubricants. One lubricant was 30 percent more viscous that the other. Both lubricants have similar pressure viscosity coefficients. Test conditions included a bulk gear temperature of 350 K, a maximum Hertz stress of 1.71 GPa at the pitch line, and a speed of 10,000 rpm. The surface fatigue life of gears tested with one lubricant was approximately 2.4 times that for gears tested with the other lubricant. The lubricant with the 30 percent higher viscosity gave a calculated elastohydrodynamic (EHD) film thickness that was 20 percent higher than the other lubricant. This increased EHD film thickness is the most probable reason for the improvement in surface fatigue life of gears tested with this lubricant over gears tested with the less viscous lubricant.

Townsend, Dennis P.; Shimski, John

1991-01-01

227

Inductive plasma source for the ion treatment of AISI-304 SS  

NASA Astrophysics Data System (ADS)

The design and construction of a simple inductive plasma source is described as constituted by an evacuated Pyrex glass cylinder reactor with 190 mm inner diameter and 500 mm length. This discharge vessel is coaxially surrounded by a cylindrically wound antenna, 240 mm in diameter, made of 3.2 mm wide copper wire. The antenna is supplied by a 13.56 MHz RF generator whose resulting electric field is able to create the plasma. When nitrogen is admitted to the vessel, the plasma generation takes place within the 0.1-50 Pa work pressure and 300-600 W RF power. The plasma density has been established by double Langmuir probes between 3.2 × 1015 and 2.4 × 1018 m-3. This inductive plasma set up is meant to modify the surface of AISI-304 stainless steel by means of ion deposition, thanks to the sample bias provided by an external - 400 V dc supply, in order to improve the steel hardness without compromising its corrosion resistance. Once accelerated by the negative bias, the plasma ions impinge on the sample nitriding it by diffusion. The treated samples were characterized by x-ray diffraction (XRD) indicating the formation of the expanded gamma phase, by scanning electron microscopy (SEM) providing the atomic percentages of nitrogen, and by microhardness (HV) measurement.

de la Piedad-Beneitez, A.; Valencia-Alvarado, R.; López-Callejas, R.; Barocio, S. R.; Mercado-Cabrera, A.; Peña-Eguiluz, R.; Muñoz-Castro, A. E.; Granda-Gutiérrez, E. E.; Rodríguez-Méndez, B. G.; Pérez-Martínez, J. A.; Flores-Fuentes, A. A.

2008-10-01

228

Deposition of titanium nitride on AISI-304 in a plasma focus environment  

NASA Astrophysics Data System (ADS)

Polycrystalline, smooth, and hard thin films of TiN are successfully deposited on AISI-304 substrates using a 1.5kJ Mather-type dense plasma focus device charged at 18kV. The purpose of this study is to investigate the structural and mechanical properties of the TiN thin films in terms of ion dose and substrate position to establish the optimum deposition conditions. The films are analyzed using XRD, SEM, electron microprobe and micro-hardness testing. XRD confirms the deposition of a polycrystalline TiN thin film together with the emergence of an iron chromium nickel phase. The surface hardness-in comparison to the unexposed substrate-is found to increase up to 250% when a film is deposited using 30 focus shots at an axial distance of 6cm. SEM micrographs show that the quality of the film is improved with an increasing number of focus shots. The constituent elements of the film are also confirmed by electron microprobe.

Zeb, S.; Qayyum, A.; Shafiq, M.; Zakaullah, M.

2008-05-01

229

Investigations on friction and wear mechanisms of the PVD-TiAlN coated carbide in dry sliding against steels and cast iron  

Microsoft Academic Search

The tribological behaviour of the monolayer PVD-titanium aluminium nitride (TiAlN) coated carbide inserts in unidirectional dry sliding against steel and cast iron counterparts was investigated using the pin-on-disc standard test with varying sliding speeds and normal loads. Three different materials of various machinability rates were used as the counterparts, namely the normalised medium carbon steel C45 equivalent to AISI 1045,

W. Grzesik; Z. Zalisz; S. Krol; P. Nieslony

2006-01-01

230

Tribological Characteristics of Single-phase AlMgB14 and Nanocomposite AlMgB14-TiB2 Superhard Coatings  

SciTech Connect

This study investigated the friction and wear characteristics of AlMgB14 and AlMgB14-TiB2 superhard coatings, produced by pulse laser deposition (PLD) and physical vapor deposition (PVD), respectively. Tests were conducted under unidirectional and reciprocating sliding against AISI 52100 bearing steel in both dry and oil-lubricated conditions. The AlMgB14 coating exhibited an encouraging but short-lived low friction stage (u = 0.2) in dry sliding. The AlMgB14-TiB2 coating reduced the wear rates by one order of magnitude for itself and three orders of magnitude for the counterface compared with the uncoated M2 tool steel in dry sliding. This nanocomposite coating also demonstrated significant extension (>2.5X) of the low friction (non-scuffing) stage in a lubricant starvation sliding.

Qu, Jun [ORNL; Blau, Peter Julian [ORNL; Zhu, Dong [Eaton Corporation; Cook, Bruce A [Ames Laboratory; Elmoursi, Alaa A [Eaton Corporation

2008-01-01

231

Effect of martensite to austenite reversion on the formation of nano/submicron grained AISI 301 stainless steel  

SciTech Connect

The martensite to austenite reversion behavior of 90% cold rolled AISI 301 stainless steel was investigated in order to refine the grain size. Cold rolled specimens were annealed at 600-900 deg. C, and subsequently characterized by scanning electron microscopy, X-ray diffraction, Feritscope, and hardness measurements. The effects of annealing parameters on the formation of fully-austenitic nano/submicron grained structure and the mechanisms involved were studied. It was found that annealing at 800 deg. C for 10 s exhibited the smallest average austenite grain size of 240 {+-} 60 nm with an almost fully-austenitic structure.

Karimi, M.; Najafizadeh, A. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Kermanpur, A., E-mail: ahmad_k@cc.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Eskandari, M. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

2009-11-15

232

Formation of amorphous Ti alloy layers by excimer laser mixing of Ti on AISI 304 stainless-steel surfaces  

NASA Astrophysics Data System (ADS)

We used excimer laser radiation at 308 nm to mix thin layers of Ti into AISI 304 stainless steel. Different numbers of shots at a fluence about twice the threshold for melting varied the amount of mixing. When mixing is sufficiently complete, an amorphous surface layer is formed with Ti substituting for Fe on a one-to-one basis in the alloy. The laser mixing process, unlike Ti ion implantation, does not result in high incorporation of C in the processed layer, although some C from surface and interface contamination is incorporated into the surface layer.

Jervis, T. R.; Nastasi, M.; Zocco, T. G.; Martin, J. A.

1988-07-01

233

Comparison of Microstructure and Surface Properties of AISI 1045 Steel After Quenching in Hot Alkaline Salt Bath and Oil  

NASA Astrophysics Data System (ADS)

The effect of quenching in molten alkaline salt bath medium on the microstructure and surface properties of AISI 1045 steel in comparison with oil was investigated. Salt bath medium used in this research contained 40% NaOH and 60% KOH with addition of 5 wt.% water at 205 °C. Hardening of 1045 steel in this medium resulted in an almost uniform microstructure, which consisted of fine martensite and bainite. In comparison, the microstructure of oil quenched sample was martensite, ferrite, widmanestatten ferrite, and pearlite. Quenching in salt bath lead to improved surface properties, i.e., decrease in surface roughness and a good bearing area curve.

Raygan, S.; Rassizadehghani, J.; Askari, M.

2009-03-01

234

Analysis of first order kinetics for tertiary creep in AISI 304 stainless steel  

SciTech Connect

The results of constant load creep tests on AISI 304 stainless steel at 873 and 973 K for different test conditions were found to obey the first order kinetics for tertiary creep. Distinct master creep curves were obtained at 873 and 973 K with a separate set of constant values of K{prime}, {epsilon}{sub t}, {beta}{prime} and C{sub MG}. A relationship between steady-state creep rate {dot {epsilon}}{sub s}, time spent in tertiary creep t{sub t} and limiting tertiary creep strain {epsilon}{sub t} is formulated as {dot {epsilon}}{sub s}{center_dot}t{sub t}/{epsilon}{sub t} = constant and is found to be valid for all test conditions. Further, this relation is identical to the modified Monkman-Grant relation (MMGR) for the conditions satisfying f = 1/{lambda}; it is postulated that the validity of MMGR is a consequence of first order kinetics. Another important outcome of this study is a generalized relation of the form {dot {epsilon}}{sub s}{center_dot}t{sub t} = ({epsilon}{sub 23}{center_dot}{epsilon}{sub f}){sup 1/2}, and this relation is compared with the relation proposed by Radhakrishnan, i.e., {dot {epsilon}}{sub s}{center_dot}t{sub t} = ({epsilon}{sub 23}{sup 2}{center_dot}{epsilon}{sub f}){sup 1/3}. It is suggested that cavities act as vacancy sinks and accelerate dislocation climb controlled recovery process leading to tertiary creep.

Phaniraj, C.; Nandagopal, M.; Mannan, S.L.; Rodriguez, P. [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Metallurgy and Materials Programme] [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Metallurgy and Materials Programme; Kashyap, B.P. [Indian Inst. of Tech., Bombay (India). Dept. of Metallurgical Engineering and Materials Science] [Indian Inst. of Tech., Bombay (India). Dept. of Metallurgical Engineering and Materials Science

1996-10-01

235

Multi-component boron coatings on low carbon steel AISI 1018  

NASA Astrophysics Data System (ADS)

Boronizing and metalizing are thermo-chemical surface hardening treatments in which boron and metal atoms diffuse into the metal substrate forming metallic boride layers, providing complex properties of B-Me-Fe system. To study multi-component boron coatings on low carbon steel AISI 1018, the simultaneous powder pack method of boronizing and metalizing was selected to perform the coatings. One B-Fe system and eight boron-metal (B-Me-Fe) systems from transition metals group IVB (Ti, Zr, HO, group VB (Nb, Ta), and group VIB (Cr, Mo, W) were studied. The system specimens were thereto-chemically treated at 950°C for 4 hours in a crucible containing powder mixture of boron source, transition metal powder, and activator. After the heat treatment process, the multi-component boron coatings were characterized by using optical microscope, microhardness tester, TGA, XRD, and Synchrotron microdiffraction. The coating morphology was observed and the coating thickness was measured as well as the microhardness across the depth of coating. The corrosion resistance of the coatings was evaluated by the continuous weighting method. The high temperature oxidation was also detected by isothermal method at a temperature range of 400-800°C for 24 hours. The Rietveld refinement method was used to examine the quantitative phase analysis, crystalline size, microstrain and lattice parameters of the multi-component boron coatings. The results have shown that adding transition metals into the B-Fe system caused the formation of solid solution of transition-metal borides. The distortion of crystal lattice parameters generated microstrain in the boride phase. The Synchrotron microdiffraction confirmed the presence of about 5-10 microns of transition-metal boride phase at the surface. Moreover, the additional transition metal can provide better corrosion and high temperature oxidation resistance to the B-Fe system, preventing the deboronizing and stabilizing the boride phases.

Suwattananont, Naruemon

236

Effects of electroplated zinc-nickel alloy coatings on the fatigue strength of AISI 4340 high-strength steel  

NASA Astrophysics Data System (ADS)

Recovered substrates have been extensively used in the aerospace field. Cadmium electroplating has been widely applied to promote protective coatings in aeronautical components, resulting in excellent corrosion protection combined with a good performance in cyclic loading. Ecological considerations allied to the increasing demands for corrosion resistance have resulted in the search for possible alternatives. Zinc-nickel (Zn-Ni) alloys have received considerable interest recently, because these coatings show advantages such as a good resistance to white and red rust, high plating rates, and acceptance in the market. In this study, the effect of electroplated Zn-Ni coatings on AISI 4340 high-strength steel was analyzed for rotating bending fatigue strength, corrosion, and adhesion resistance. The compressive residual stress field was measured by x-ray diffraction prior to fatigue tests. Optical microscopy documented coating thickness, adhesion characteristics, and coverage extent for nearly all substrates. Fractured fatigue specimens were investigated using scanning electron microscopy (SEM). Three different Zn-Ni coating thicknesses were tested, and comparisons with the rotating bending fatigue data from electroplated Cd specimens were performed. Experimental results differentiated the effects of the various coatings on the AISI 4340 steel behavior when submitted to fatigue testing and the influence of coating thickness on the fatigue strength.

Voorwald, H. J. C.; Miguel, I. M.; Peres, M. P.; Cioffi, M. O. H.

2005-04-01

237

High temperature oxidation behavior of austenitic stainless steel AISI 304 in steam of nanofluids contain nanoparticle ZrO2  

NASA Astrophysics Data System (ADS)

The objective of this study is to evaluate high temperature oxidation behavior of austenitic stainless steel SS 304 in steam of nanofluids contain nanoparticle ZrO2. The oxidation was performed at high temperatures ranging from 600 to 800°C. The oxidation time was 60 minutes. After oxidation the surface of the samples was analyzed by different methods including, optical microscope, scanning electron microscope (SEM) and X-ray diffraction (XRD). X-ray diffraction examination show that the oxide scale formed during oxidation of stainless steel AISI 304 alloys is dominated by iron oxide, Fe2O3. Minor element such as Cr2O3 is also appeared in the diffraction pattern. Characterization by optical microscope showed that cross section microstructure of stainless steel changed after oxidized with the oxide scale on the surface stainless steels. SEM and x-ray diffraction examination show that the oxide of ZrO2 appeared on the surface of stainless steel. Kinetic rate of oxidation of austenite stainless steel AISI 304 showed that increasing oxidation temperature and time will increase oxidation rate.

Prajitno, Djoko Hadi; Syarif, Dani Gustaman

2014-03-01

238

Investigation of the correlation between thermal properties and hardenability of Jominy bars quenched with air–water mixture for AISI 1050 steel  

Microsoft Academic Search

In this study, the hardenability of AISI 1050 steel has been investigated in different cooling media using Jominy test. The temperature values were recorded using the thermocouples that were placed on sample. The relations between the cooling media and the cooling curves, heat flux, hardenability and heat convection coefficient were shown in graphics. The correlation between thermal properties and hardenability

Mehmet Çakir; Abdullah Özsoy

2011-01-01

239

Selection of Optimum Drilling Parameters on Burr Height Using Response Surface Methodology and Genetic Algorithm in Drilling of AISI 304 Stainless Steel  

Microsoft Academic Search

This article illustrates an application of response surface methodology (RSM) and genetic algorithm (GA) for selecting the optimum combination values of drilling parameters affecting the burr height in drilling of AISI 304 stainless steel. The purpose of this article is to investigate the influence of the cutting parameters, such as cutting speed and feed rate, and point angle on burr

Erol Kilickap; Mesut Huseyinoglu

2010-01-01

240

The effect of martensite particle size on tensile fracture of surface-carburised AISI 8620 steel with dual phase core microstructure  

Microsoft Academic Search

In this study, the production of dual phase microstructure in the core of surface-carburised AISI 8620 cementation steel and the effect of martensite particle size at constant martensite volume fraction on tensile fracture have been investigated. The results showed that specimens with dual phase microstructure in the core exhibited slightly lower tensile and yield strength but superior ductility without sacrificing

Mehmet Erdogan; Suleyman Tekeli

2002-01-01

241

The effect of chamfer angle of polycrystalline cubic boron nitride cutting tool on the cutting forces and the tool stresses in finishing hard turning of AISI 52100 steel  

Microsoft Academic Search

Cutting experiments and finite element analysis (FEA) using ANSYS software have been carried out in this paper in order to investigate the effects of chamfer angle on the cutting forces and the cutting tool stresses, principal and von Mises stress, of polycrystalline cubic boron nitride (PCBN) cutting tools in finishing hard turning of AISI 52100 bearing steel. The obtained cutting

Abdullah Kurt; Ulvi ?eker

2005-01-01

242

Development of surface roughness prediction model using response surface methodology in high speed end milling of AISI H13 tool steel  

Microsoft Academic Search

This paper presents a study on the development of an effective method to predict surface roughness for high speed end milling of AISI H13 tool steel using PCBN inserts. The response surface methodology (RSM) has been utilized for the postulation of a second order quadratic model in terms of cutting speed, axial depth of cut and feed. Sufficient numbers of

A. M. K. Hafiz; A. K. M. N. Amin; A. N. M. Karim; M. A. Lajis

2007-01-01

243

Bilinear CTOD\\/CTOA scheme for characterisation of large range mode I and mixed mode stable crack growth through AISI 4340 steel  

Microsoft Academic Search

An investigation has been reported concerning characterisation of large span stable crack growth (SCG) through AISI 4340 steel in terms of CTOD\\/CTOA under both mode I and mixed (I and II) mode loadings. The characterisation has been possible through finite element analysis of published experimental results with compact tension type of specimens. As against the earlier observations by many investigators

S. K. Maiti; G. Krishna Kishore; A.-H. I. Mourad

2008-01-01

244

Welding Procedure Specification. Supplement 1. Records of Procedure Qualification Tests. Gas Tungsten Arc and Shielded Metal Arc Welding of AISI 41XX Steels.  

National Technical Information Service (NTIS)

Procedure WPS-127 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for gas tungsten arc and shielded metal arc welding of AISI 4130 and 4142 steels (ASTM A519) (P-No: None), 0.438-inch wall pipe; filler metal is AMS 6457, Class 41...

C. H. Wodtke, D. R. Frizzell

1986-01-01

245

Effect of Welding Processes on Tensile and Impact Properties, Hardness and Microstructure of AISI 409M Ferritic Stainless Joints Fabricated by Duplex Stainless Steel Filler Metal  

Microsoft Academic Search

The effect of welding processes such as shielded metal arc welding, gas metal arc welding and gas tungsten arc welding on tensile and impact properties of the ferritic stainless steel conforming to AISI 409M grade is studied. Rolled plates of 4 mm thickness were used as the base material for preparing single pass butt welded joints. Tensile and impact properties,

AK Lakshminarayanan; K Shanmugam; V Balasubramanian

2009-01-01

246

Effect of sulphide on the corrosion behaviour of AISI 316L stainless steel and its constituent elements in simulated Kraft digester conditions  

Microsoft Academic Search

The electrochemical behaviour of AISI 316L steel and its constituent metals in simulated Kraft digester white liquor at 170°C has been studied by registering slow scan rate voltammograms and impedance spectra at the corrosion potential. Interpretation of the results in terms of two approaches – the Mixed-Conduction Model for passive films and a two-step dissolution reaction – allowed for the

Iva Betova; Martin Bojinov; Outi Hyökyvirta; Timo Saario

2010-01-01

247

Role of environmental variables on the stress corrosion cracking of sensitized AISI type 304 stainless steel (SS304) in thiosulfate solutions  

Microsoft Academic Search

The stress corrosion cracking (SCC) behavior of sensitized AISI type 304 stainless steel (SS304) has been studied in dilute thiosulfate solutions as a function of thiosulfate concentrations and applied potentials. The susceptibility to SCC was observed to increase with thiosulfate concentrations and applied potentials. The addition of boric acid produced the reverse effect. A critical potential was found to exist,

S. Roychowdhury; S. K. Ghosal; P. K. de

2004-01-01

248

EFFECT OF WELD TYPE AND POST WELD HEAT TREATMENT ON THE CORROSION RESISTANCE OF AISI 321 STAINLESS STEEL IN A TAR SAND DIGESTER  

Microsoft Academic Search

???? ?????? ??? ??? ????? . This work has investigated the effect of lap joint and butt joint electric arc welding together with their post weld heat treatments on the corrosion characteristic (resistance) of a stabilized AISI321 stainless steel in a tar sand digester. Water quenching and furnace cooling were the two heat treatment procedures carried out on the welded

L. E. Umoru

249

Surface fatigue life of carburized and hardened M50NiL and AISI 9310 spur gears and rolling-contact test bars  

NASA Technical Reports Server (NTRS)

Spur gear endurance tests and rolling-element surface tests were conducted to investigate vacuum-induction-melted, vacuum-arc-melted (VIM-VAR) M50NiL steel for use as a gear steel in advanced aircraft applications, to determine its endurance characteristics, and to compare the results with those for standard VAR and VIM-VAR AISI 9310 gear material. Tests were conducted with spur gears and rolling-contact bars manufactured from VIM-VAR M50NiL and VAR and VIM-VAR AISI 9310. The gear pitch diameter was 8.9 cm (3.5 in.). Gear test conditions were an inlet oil temperature of 320 K (116 F), and outlet oil temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. Bench rolling-element fatigue tests were conducted at ambient temperatures with a bar speed of 12,500 rpm and a maximum Hertz stress of 4.83 GPA (700 ksi). The VIM-VAR M50NiL gears had a surface fatigue life that was 4.5 and 11.5 times that for VIM-VAR and VAR AISI 9310 gears, respectively. The surface fatigue life of the VIM-VAR M50NiL rolling-contact bars was 13.2 and 21.6 times that for the VIM-VAR and VAR AISI 9310, respectively. The VIM-VAR M50NiL material was shown to have good resistance to fracture through a fatigue spall and to have fatigue life far superior to that of both VIM-VAR and VAR AISI 9310 gears and rolling-contact bars.

Townsend, Dennis P.; Bamberger, Eric N.

1989-01-01

250

Fractographic evaluation of creep effects on strain-controlled fatigue-cracking of AISI 304LC and 316 stainless steel  

NASA Technical Reports Server (NTRS)

Analysis of high temperature low cycle fatigue of AISI 304LC and 316 stainless steels by the method of strainrange partitioning results in four separate strainrange versus life relationships, depending upon the way in which creep-strain and plastic strain are combined within a cycle. Fractography is used in this investigation of the creep-fatigue interaction associated with these cycles. The PP and PC-cycle fractures were transgranular. The PC-cycle resulted in fewer cycles of initiation and shorter total cyclic life for the same applied inelastic strainrange. The CC-cycle had mixed transgranular and intergranular fracture, fewer cycles of initiation and shorter cycle life than PP or PC. The CP-cycle had fully integranular cracking, and failed in fewer cycles than were required for cracks to initate for PP,PC, and CC.

Oldrieve, R. E.

1978-01-01

251

Effect of postweld treatment on the fatigue crack growth rate of electron-beam-welded AISI 4130 steel  

NASA Astrophysics Data System (ADS)

This article studies the effect of in-chamber electron beam and ex-chamber furnace postweld treatments on the fatigue crack growth rate of electron-beam-welded AISI 4130 steel. Mechanical properties of the weldment are evaluated by tensile testing, while the fatigue properties are investigated by a fatigue crack propagation method. Microstructural examination shows that both postweld treatments temper the weldment by the appropriate control of beam pattern width, input beam energy, and furnace temperature. In addition, the ductility, strength, and microhardness of the weldment also reflect this tempering effect. The fatigue crack growth rate is decreased after both postweld treatments. This is mainly caused by the existence of a toughened microstructure and relief of the residual stress due to the fact that (1) the residual stress becomes more compressive as more beam energy is delivered into the samples and (2) postweld furnace tempering effectively releases the tensile stress into a compressive stress state.

Wang, Chien-Chun; Chang, Yih

1996-10-01

252

Application of strainrange partitioning to the prediction of creep-fatigue lives of AISI types 304 and 316 stainless steel  

NASA Technical Reports Server (NTRS)

As a demonstration of the predictive capabilities of the method of Strainrange Partitioning, published high-temperature, low cycle, creep-fatigue test results on AISI Types 304 and 316 stainless steel were analyzed and calculated, cyclic lives compared with observed lives. Predicted lives agreed with observed lives within factors of two for 76 percent, factors of three for 93 percent, and factors of four for 98 percent of the laboratory tests analyzed. Agreement between observed and predicted lives is judged satisfactory considering that the data are associated with a number of variables (two alloys, several heats and heat treatments, a range of temperatures, different testing techniques, etc.) that are not directly accounted for in the calculations.

Saltsman, J. F.; Halford, G. R.

1976-01-01

253

Evaluation of Microstructure and Toughness of AISI D2 Steel by Bright Hardening in Comparison with Oil Quenching  

NASA Astrophysics Data System (ADS)

AISI D2 is used widely in the manufacture of blanking and cold-forming dies, on account of its excellent hardness and wear behavior. Increasing toughness at a fixed high level of hardness is growing requirement for this kind of tool steel. Improving microstructure characteristics, especially refinement of coarse carbides, is an appropriate way to meet such requirement. In this study, morphology and size of carbides in martensite matrix were compared between two kinds of samples, which were bright hardened (quenching in hot alkaline salt bath consisting of 60% KOH and 40% NaOH) at 230 °C and quenched in oil bath at 60 °C. Results showed that morphology and distribution of carbides in samples performed by bright hardening were finer and almost spherical compared to that of oil quenched. This microstructure resulted in an improvement in toughness and tensile properties of alloy.

Torkamani, H.; Raygan, Sh.; Rassizadehghani, J.

2011-12-01

254

Quantifying Cutting and Wearing Behaviors of TiN- and CrN-Coated AISI 1070 Steel  

PubMed Central

Hard coatings such as titanium nitride (TiN) and chromium nitride (CrN) are widely used in cutting and forming tools against wear and corrosion. In the present study, hard coating films were deposited onto AISI 1070 steels by a cathodic arc evaporation plating (CAVP) technique. These samples were subjected to wear in a conventional lathe for investigating the tribological behaviour of coating structure, and prenitrided subsurface composition was characterized using scanning electron microscopy (SEM), line scan analyses and X-ray diffraction (XRD). The wear properties of TiN- and CrN-coated samples were determined using an on-line monitoring system. The results show that TiN-coated samples demonstrate higher wear resistance than CrN-coated samples.

Cakan, Ahmet; Ozkaner, Vedat; Yildirim, Mustafa M.

2008-01-01

255

Strong et al ALS FTD consensus criteria  

E-print Network

Strong et al ALS FTD consensus criteria 1 Version: 20070606 Frontotemporal syndromes in amyotrophic-663-3609 Email: mstrong@uwo.ca #12;Strong et al ALS FTD consensus criteria 2 Introduction Although amyotrophic

Dickerson, Brad

256

Al Composites  

NASA Astrophysics Data System (ADS)

In the present study, cold spraying technique was used to fabricate a metal matrix composite (MMC) that consists of Ni matrix and 20 vol.% Ni3Al particles at two different particle sizes as reinforcement. This study intends to investigate the effect of reinforcement particle size on microstructural and mechanical properties of cold sprayed MMCs. Two different Ni3Al powders with nominal particle size of -45 to +5 and +45 to 100 ?m were used as reinforcement in this study. Cold sprayed Ni-Ni3Al samples were subjected to the microstructural observation and characterization prior to any mechanical testing. Then, samples were tested using nano-indentation, Knoop hardness, Vickers hardness, and Resonance frequency to evaluate their mechanical properties. No significant changes were observed in microstructural characteristics due to different particle sizes. The results obtained from a variety of mechanical testings indicated that the increasing reinforcement particle size resulted in the slight reduction of mechanical properties such as elastic modulus and hardness in cold sprayed MMCs. The mechanical interlock between deposited particles defines the bonding strength in cold sprayed samples. Small size particles have a higher velocity and impact resulting in stronger interlock between deformed particles.

Chandanayaka, Tharaka; Azarmi, Fardad

2014-05-01

257

The significance of passivation treatments on AISI 314 foam pieces to be used as substrates for catalytic applications  

NASA Astrophysics Data System (ADS)

Several properties of metallic foams such as their low density, high mechanical strength and good coefficients of heat and mass transfer make them attractive for applications in catalysis. Important modifications in the composition and morphology of the metallic foam surfaces can take place when they are submitted to treatments at high temperatures. These surface changes are due to the migration of some elements from the metallic core to the pore surface, thus inducing a passivation via an oxide layer formation. This new layer avoids further metallic segregation and generates a surface roughness, both effects having a significant impact on the catalytic coating quality. This work analyzes the effects of calcination temperature and time on the chemistry and morphology of the metallic surface corresponding to the AISI 314 stainless steel foams of 50 and 60 ppi. The chemical and morphological surface changes were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-Ray (EDX) analysis and Laser Raman Spectroscopy (LRS). The application of high temperature treatments on AISI 314 foams promotes the formation of a surface layer containing chromium oxide and spinel-type compounds of chromium, iron and manganese. The optimum treatment temperature for this type of structures seems to be 900 °C because both the adhesion and thickness of the layer formed are adequate. For the sample with smaller pores (60 ppi) the optimal treatment time is close to 2 h and for that with larger pores (50 ppi) the recommended time is 20 h. Under these conditions, a compromise is found between adhesion, thickness and surface roughness, suitable for the subsequent deposition of catalytic material.

Bortolozzi, J. P.; Banús, E. D.; Milt, V. G.; Gutierrez, L. B.; Ulla, M. A.

2010-11-01

258

Comparison of Austenite Decomposition Models During Finite Element Simulation of Water Quenching and Air Cooling of AISI 4140 Steel  

NASA Astrophysics Data System (ADS)

An indigenous, non-linear, and coupled finite element (FE) program has been developed to predict the temperature field and phase evolution during heat treatment of steels. The diffusional transformations during continuous cooling of steels were modeled using Johnson-Mehl-Avrami-Komogorov equation, and the non-diffusion transformation was modeled using Koistinen-Marburger equation. Cylindrical quench probes made of AISI 4140 steel of 20-mm diameter and 50-mm long were heated to 1123 K (850 °C), quenched in water, and cooled in air. The temperature history during continuous cooling was recorded at the selected interior locations of the quench probes. The probes were then sectioned at the mid plane and resultant microstructures were observed. The process of water quenching and air cooling of AISI 4140 steel probes was simulated with the heat flux boundary condition in the FE program. The heat flux for air cooling process was calculated through the inverse heat conduction method using the cooling curve measured during air cooling of a stainless steel 304L probe as an input. The heat flux for the water quenching process was calculated from a surface heat flux model proposed for quenching simulations. The isothermal transformation start and finish times of different phases were taken from the published TTT data and were also calculated using Kirkaldy model and Li model and used in the FE program. The simulated cooling curves and phases using the published TTT data had a good agreement with the experimentally measured values. The computation results revealed that the use of published TTT data was more reliable in predicting the phase transformation during heat treatment of low alloy steels than the use of the Kirkaldy or Li model.

Babu, K.; Prasanna Kumar, T. S.

2014-08-01

259

Influence of dissolved hydrogen on the fatigue crack growth behaviour of AISI 4140 steel  

NASA Astrophysics Data System (ADS)

Many metallic structural components come into contact with hydrogen during manufacturing processes or forming operations such as hot stamping of auto body frames and while in service. This interaction of metallic parts with hydrogen can occur due to various reasons such as water molecule dissociation during plating operations, interaction with atmospheric hydrogen due to the moisture present in air during stamping operations or due to prevailing conditions in service (e.g.: acidic or marine environments). Hydrogen, being much smaller in size compared to other metallic elements such as Iron in steels, can enter the material and become dissolved in the matrix. It can lodge itself in interstitials locations of the metal atoms, at vacancies or dislocations in the metallic matrix or at grain boundaries or inclusions (impurities) in the alloy. This dissolved hydrogen can affect the functional life of these structural components leading to catastrophic failures in mission critical applications resulting in loss of lives and structural component. Therefore, it is very important to understand the influence of the dissolved hydrogen on the failure of these structural materials due to cyclic loading (fatigue). For the next generation of hydrogen based fuel cell vehicles and energy systems, it is very crucial to develop structural materials for hydrogen storage and containment which are highly resistant to hydrogen embrittlement. These materials should also be able to provide good long term life in cyclic loading, without undergoing degradation, even when exposed to hydrogen rich environments for extended periods of time. The primary focus of this investigation was to examine the influence of dissolved hydrogen on the fatigue crack growth behaviour of a commercially available high strength medium carbon low alloy (AISI 4140) steel. The secondary objective was to examine the influence of microstructure on the fatigue crack growth behaviour of this material and to determine the hydrogen induced failure mechanism in this material during cyclic loading. The secondary objective of this investigation was to determine the role of inclusions and their influence in affecting the fatigue crack growth rate of this material. Compact tension and tensile specimens were prepared as per ASTM E-647, E-399 and E-8 standards. The specimens were tested in three different heat treated conditions i.e. annealed (as received) as well as two austempered conditions. These specimens were precharged with hydrogen (ex situ) using cathodic charging method at a constant current density at three different time periods ranging from 150 to 250 hours before conducting fatigue crack growth tests. Mode 1 type fatigue tests were then performed in ambient atmosphere at constant amplitude using load ratio R of 0.1. The near threshold fatigue crack growth rate, fatigue threshold and the fatigue crack growth rate in the linear region were determined. Fatigue crack growth behaviour of specimens without any dissolve hydrogen were then compared with the specimens with different concentration of dissolved hydrogen. The test results show that the dissolved hydrogen concentration increases with the increase in charging time in all three heat treated conditions and the hydrogen uptake shows a strong dependence on the microstructure of the alloy. It was also observed that the microstructure has a significant influence of on the fatigue crack growth and SCC behaviour of the alloy with dissolved hydrogen. As the dissolved hydrogen concentration increases, the fatigue threshold was found to decrease and the near threshold crack growth rate increases in all three heat treated conditions showing the deleterious effect of hydrogen, but to a different extent in each condition. Current test results also indicate that the fatigue crack growth rates in the linear region increases as the dissolved hydrogen content increases in all three heat treated conditions. It is also observed that increasing the austempering temperature decreases the resistance to hydrogen embrittlement. An interesting p

Ramasagara Nagarajan, Varun

260

Mathematical Modeling of Wear Characteristics of 6061 Al-Alloy-SiCp Composite Using Response Surface Methodology  

NASA Astrophysics Data System (ADS)

In the light of attractive wear characteristics as well as high strength to weight ratio, extensive research on Al-based Metal Matrix Composite (MMC) have been carried out globally in the last two decades. However, very limited research has been pursued on tribological behavior of Al-based MMC under combined action of rolling and sliding. This study investigates the wear behavior of 6061 Al-alloy/SiC with 10 vol.% SiCp against hardened and tempered AISI 4340 steel under combined rolling-sliding conditions. 23 factorial design of experiments have been carried out to see the effect of few parameters, i.e., contact stress, speed and duration with respect to wear. The interaction effect has also been studied by 3D graphical contours. A mathematical model is developed using regression analysis technique for prediction of wear behavior of the MMC and adequacy of the model has been validated using analysis of variance (ANOVA) techniques. Finally, the optimization of parameter has also been done using Design Expert software. The results have shown that Response Surface Methodology (RSM) is an effective tool for prediction of wear behavior under combined sliding and rolling action. It is also found that the wear of MMC is much lower than hardened; tempered AISI 4340 steel and rolling speed has the maximum influence in wear of both materials under investigation.

Mandal, Nilrudra; Roy, H.; Mondal, B.; Murmu, N. C.; Mukhopadhyay, S. K.

2012-01-01

261

Study on welding such dissimilar materials as AISI 304 stainless steel and DHP copper in a sea-water environment. Influence of weld metals on corrosion  

Microsoft Academic Search

This work determines which material performs best according to its specific properties, by means of welding joints and evaluating the different welding processes and weld metals employed, considering their mechanical performance and resistance to sea-water corrosion. The base materials were butt-welded to produce 1.5 mm thick test pieces of AISI 304 stainless steel and copper, and de-oxidized in DHP phosphorus,

E. Zumelzu; C. Cabezas

1996-01-01

262

Estimating the effect of cutting parameters on surface finish and power consumption during high speed machining of AISI 1045 steel using Taguchi design and ANOVA  

Microsoft Academic Search

The present paper outlines an experimental study to investigate the effects of cutting parameters on finish and power consumption\\u000a by employing Taguchi techniques. The high speed machining of AISI 1045 using coated carbide tools was investigated. A combined\\u000a technique using orthogonal array and analysis of variance was employed to investigate the contribution and effects of cutting\\u000a speed, feed rate and

Anirban Bhattacharya; Santanu Das; P. Majumder; Ajay Batish

2009-01-01

263

Integrating Box-Behnken design with genetic algorithm to determine the optimal parametric combination for minimizing burr size in drilling of AISI 316L stainless steel  

Microsoft Academic Search

This paper illustrates the methodology of genetic algorithm (GA) based multi-objective drilling process optimization. The\\u000a optimal values of cutting speed, feed, point angle and lip clearance angle for a specified drill diameter were determined\\u000a using GA, which simultaneously minimize burr height and burr thickness at the exit of holes during drilling of AISI 316L stainless\\u000a steel. The burr size models

V. N. Gaitonde; S. R. Karnik; B. Siddeswarappa; B. T. Achyutha

2008-01-01

264

Silicon deposition on AISI 304 stainless steel by CVD in fluidized bed reactors: analysis of silicide formation and adhesion of coatings  

Microsoft Academic Search

Silica\\/mullite multilayers are designed to protect materials against high temperature corrosion. The deposition of these multilayer systems is performed using CVD in a fluidized bed reactor (CVD-FBR). The preliminary results of silicon layers deposited onto AISI 304 stainless steel by CVD-FBR obtained at 450°C for different processing times are presented in the present paper. Moreover, the effect of subsequent thermal

F. J. Pérez; M. P. Hierro; C. Carpintero; F. Pedraza; C. Gómez

2001-01-01

265

Identification of a friction model—Application to the context of dry cutting of an AISI 1045 annealed steel with a TiN-coated carbide tool  

Microsoft Academic Search

The characterization of friction coefficients at the tool-chip-workpiece interface remains an issue. This paper aims to identify a friction model able to describe the friction coefficient at this interface during the dry cutting of an AISI1045 with TiN coated carbide tools. A new tribometer has been designed in order to reach relevant values of pressures and sliding velocities. This set-up

J. Rech; C. Claudin; E. D’Eramo

2009-01-01

266

A Comparative Investigation on Surface Roughness and Residual Stress during End-Milling AISI H13 Steel with Different Geometrical Inserts  

Microsoft Academic Search

In the present study, an attempt has been made to experimentally investigate the effects of cutting parameters (cutting speed, feed, radial depth of cut, and axial depth of cut) on surface roughness and residual stress during end-milling AISI H13 steel with the different geometrical inserts, i.e., the parallelogram inserts and the round inserts. Seventeen single-factor experiments were conducted on the

T. C. Ding; S. Zhang; H. G. Lv; X. L. Xu

2011-01-01

267

Corrosion properties of plasma nitrided AISI 410 martensitic stainless steel in 3.5% NaCl and 1% HCl aqueous solutions  

Microsoft Academic Search

Samples of an AISI 410 martensitic stainless steel were plasma nitrided at a temperature of 420°C, 460°C or 500°C for 20h. The composition, microstructure and hardness of the nitrided samples were characterised using a variety of analytical techniques. In particular, the corrosion properties of the untreated and plasma nitrided samples were evaluated using anodic polarisation tests in 3.5% NaCl solution

C. X. Li; T. Bell

2006-01-01

268

A unified theory for some effects of hydrogen source, alloying¦elements, and potential on crack growth in martensitic AISI 4340 steel  

Microsoft Academic Search

The effects of hydrogen on crack growth in martensitic AISI 4340 steel are shown to be fundamentally the same whether the\\u000a hydrogen is supplied as molecular gas, through stress corrosion, or by electrolytic charging. At a given yield strength differences\\u000a observed in the values of threshold stress intensity for crack growth are proposed to be linked to the degree of

G. Sandoz

1972-01-01

269

Role of environmental variables on the stress corrosion cracking of sensitized AISI type 304 stainless steel (SS304) in thiosulfate solutions  

Microsoft Academic Search

The stress corrosion cracking (SCC) behavior of sensitized AISI type 304 stainless steel (SS304) has been studied in dilute\\u000a thiosulfate solutions as a function of thiosulfate concentrations and applied potentials. The susceptibility to SCC was observed\\u000a to increase with thiosulfate concentrations and applied potentials. The addition of boric acid produced the reverse effect.\\u000a A critical potential was found to exist,

S. Roychowdhury; S. K. Ghosal; P. K. De

2004-01-01

270

Characterisation of Pristine and Recoated electron beam evaporation plasma-assisted physical vapour deposition Cr–N coatings on AISI M2 steel and WC–Co substrates  

Microsoft Academic Search

This paper is focussed on the characterisation of electron beam evaporation plasma-assisted physical vapour deposition Cr–N coatings deposited on AISI M2 steel and hardmetal (K10) substrates in two different conditions: Pristine (i.e., coated) and Recoated (i.e., stripped and recoated). Analytical methods, including X-ray diffraction (XRD), scanning electron microscopy, scratch adhesion and pin-on-disc tests were used to evaluate several coating properties.

J. C. Avelar-Batista; E. Spain; J. Housden; G. G. Fuentes; R. Rebole; R. Rodriguez; F. Montala; L. J. Carreras; T. J. Tate

2005-01-01

271

The initiation and propagation of stress corrosion cracking in AISI 4340 and 3.5 Ni?Cr?Mo?V rotor steel in constant load tests  

Microsoft Academic Search

Constant load tests with smooth tensile specimens of AISI 4340 and 3.5 Ni?Cr?Mo?V rotor steel were carried out to investigate the influence of prior creep on the initiation of stress corrosion cracking (SCC). SCC did initiate without any significant pitting corrosion or general corrosion. A period of prior creep in a non-SCC environment resulted in significantly reduced localised corrosion along

A. Oehlert; A. Atrens

1996-01-01

272

The effect of martensite volume fraction and particle size on the tensile properties of a surface-carburized AISI 8620 steel with a dual-phase core microstructure  

Microsoft Academic Search

This study is focused on the production of a dual-phase steel structure in the core of a surface-carburized AISI 8620 cementation steel and the effect of martensite volume fraction (MVF) and martensite particle size (MPS) on tensile properties. Experimental results showed that, compared with specimens with a fully martensitic microstructure in the core, those with a dual-phase microstructure in the

Mehmet Erdogan; Suleyman Tekeli

2002-01-01

273

High cycle fatigue resistance of AISI E9310 carburized steel with two different levels of surface retained austenite and surface residual stress  

Microsoft Academic Search

The high cycle fatigue resistance of carburized AISI E9310 steel has been investigated for two different levels of surface\\u000a retained austenite and surface residual stress. Fatigue specimens were carburized to a case depth of 1.9 mm with a surface\\u000a carbon content of 1.0 wt pct carbon. This treatment gave surface retained austenite and surface residual stress levels of\\u000a 56 vol

M. A. Panhans; R. A. Fournelle

1981-01-01

274

An experimental study of uniaxial creep, cyclic creep and relaxation of aisi type 304 stainless steel at room temperature  

NASA Astrophysics Data System (ADS)

FOLLOWING previous work ( KREMPL, 1979), a servocontrolled testing machine and strain measurement at the gage length were used to study the uniaxial rate(time)-dependent behavior of AISI Type 304 stainless steel at room temperature. The test results show that the creep strain accumulated in a given period of time depends strongly on the stress-rate preceding the creep test. In constant stress-rate zero-to-tension loading the creep strain accumulated in a fixed time-period at a given stress level is always higher during loading than during unloading. Continued cycling causes an exhaustion of creep ratchetting which depends on the stress-rate. Periods of creep and relaxation introduced during completely reversed plastic cycling show that the curved portions of the hysteresis loop exhibit most of the inelasticity. In the straight portions, creep and relaxation are small and there exists a region commencing after unloading where the behavior is similar to that at the origin for virgin materials. This region does not extend to zero stress. The results are at variance with creep theory and with viscoplasticity theories which assume that the yield surface expands with the stress. They support the theory of viscoplasticity based on total strain and overstress.

Kujawski, D.; Kallianpur, V.; Krempl, E.

1980-04-01

275

An electrochemical noise study of tribocorrosion processes of AISI 304 L in Cl- and SO_{4}^{2-} media  

NASA Astrophysics Data System (ADS)

Electrochemical noise measurements were performed to investigate the intrinsically stochastic character of the tribocorrosion process. Unidirectional sliding tests (pin-on-disc) were performed using AISI 304L stainless steel sliding against corundum. Experiments were carried out in Cl- and SO_{4}^{2-} containing media under open-circuit and potentiostatic polarization conditions. The power spectral density (PSD) of the current and potential signals showed a strong dependence on the sliding frequency but did not depend significantly on the normal load between 5 and 20 N. The fluctuations of the tangential and normal loads were also recorded, and a critical comparison between the PSD of the electrochemical response and the PSD of the mechanical solicitation (load) is proposed. At high frequencies (f > 0.1 Hz), the PSD of current or potential fluctuations have significantly different shapes than the PSD of load signals: the electrochemical signal PSD is governed by the dynamic balance between local depassivation and repassivation which only depends on the kinetics of the electrochemical phenomena. For lower frequencies, a plateau is observed for both the electrochemical PSD and the load PSD. The electrochemical signal is then governed by the continuous depassivation induced by sliding which appears as a low frequency component. These results suggest that the electrochemical noise technique investigated in the frequency domain might be a promising electrochemical tool for successfully unfolding tribocorrosion signatures for material parings in sliding-corrosion tests.

Berradja, A.; Déforge, D.; Nogueira, R. P.; Ponthiaux, P.; Wenger, F.; Celis, J.-P.

2006-08-01

276

Fracture prediction in hydraulic bulging of AISI 304 austenitic steel sheets based on a modified ductile fracture criterion  

NASA Astrophysics Data System (ADS)

The demand for weight reduction in modern vehicle construction has resulted in an increase in the application of hydroforming processes for the manufacture of automotive lightweight components. This trend led to the research of evaluation on formability of the sheet or tube hydroforming to be noted, particularly the prediction of fracture. In this study, a new proposed approach based on damage theory for fracture prediction considering the deformation history was introduced. And the modified ductile fracture criterion was applied to predict the failure for hydraulic bulging of AISI 304 austenitic steel sheets. The material parameters in terms of the function of strain rate in the failure criterion were determined from the equivalent fracture strains corresponding tensile tests under different stress conditions. Then, in the finite element simulation the effect of strain rates and their distribution as well during practical sheet metal forming process was considered. The hydraulic bulging tests were carried out to identify the fracture behavior predicted from FE analysis. A comparison between the prediction and experimental results showed that the proposed approach with a modified ductile fracture criteria can give better fracture predictions than traditional ways.

Xu, Y.; Song, H. W.; Zhang, S. H.; Cheng, M.

2011-08-01

277

Correlation between surface physicochemical properties and the release of iron from stainless steel AISI 304 in biological media.  

PubMed

Stainless steel is widely used in biological environments, for example as implant material or in food applications, where adsorption-controlled ligand-induced metal release is of importance from a corrosion, health, and food safety perspective. The objective of this study was to elucidate potential correlations between surface energy and wettability of stainless steel surfaces and the release of iron in complexing biological media. This was accomplished by studying changes in surface energies calculated from contact angle measurements, surface oxide composition (X-ray photoelectron spectroscopy), and released iron (graphite furnace atomic absorption spectroscopy) for stainless steel grade AISI 304 immersed in fluids containing bovine serum albumin or citric acid, and non-complexing fluids such as NaCl, NaOH, and HNO3. It was shown that the surface wettability and polar surface energy components were all influenced by adventitious atmospheric carbon (surface contamination of low molecular weight), rather than differences in surface oxide composition in non-complexing solutions. Adsorption of both BSA and citrate, which resulted in ligand-induced metal release, strongly influenced the wettability and the surface energy, and correlated well with the measured released amount of iron. PMID:25048358

Hedberg, Yolanda; Karlsson, Maria-Elisa; Blomberg, Eva; Odnevall Wallinder, Inger; Hedberg, Jonas

2014-10-01

278

Standard test method for electrochemical reactivation (EPR) for detecting sensitization of AISI type 304 and 304L stainless steels  

E-print Network

1.1 This test method covers a laboratory procedure for conducting an electrochemical reactivation (EPR) test on AISI Type 304 and 304L (UNS No. S30400 and S30403, respectively) stainless steels. This test method can provide a nondestructive means of quantifying the degree of sensitization in these steels (1, 2, 3). This test method has found wide acceptance in studies of the effects of sensitization on intergranular corrosion and intergranular stress corrosion cracking behavior (see Terminology G15). The EPR technique has been successfully used to evaluate other stainless steels and nickel base alloys (4), but the test conditions and evaluation criteria used were modified in each case from those cited in this test method. 1.2 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this...

American Society for Testing and Materials. Philadelphia

1994-01-01

279

Nanosecond laser surface modification of AISI 304L stainless steel: Influence the beam overlap on pitting corrosion resistance  

NASA Astrophysics Data System (ADS)

Surface modifications of AISI 304L stainless steel by laser surface melting (LSM) were investigated using a nanosecond pulsed laser-fibre doped by ytterbium at different overlaps. The objective was to study the change in the corrosion properties induced by the treatment of the outer-surface of the stainless steel without modification of the bulk material. Different analytical techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and glow discharge optical emission spectrometry (GDOES) were used to characterize the laser-melted surface. The corrosion resistance was evaluated in a chloride solution at room temperature by electrochemical tests. The results showed that the crystallographic structure, the chemical composition, the properties of the induced oxide layer and consequently the pitting corrosion resistance strongly depend on the overlap rate. The most efficient laser parameters led to an increase of the pitting potential by more than 300 mV, corresponding to a quite important improvement of the corrosion resistance. This latter was correlated to chromium enrichment (47 wt.%) at the surface of the stainless steel and the induced absence of martensite and ferrite phases. However, these structural and chemical modifications were not sufficient to explain the change in corrosion behaviour: defects and adhesion of the surface oxide layer must have been taken into consideration.

Pacquentin, Wilfried; Caron, Nadège; Oltra, Roland

2014-01-01

280

Stress corrosion crack growth studies on AISI type 316 stainless steel in boiling acidified sodium chloride solution  

NASA Astrophysics Data System (ADS)

Stress corrosion cracking (SCC) data for AISI type 316 stainless steel in solution-annealed and sensitized (at 923 K for 20 h) conditions are presented in this paper. The tests were conducted in an environment of boiling 5 M NaCl + 0.15 M Na2SO4 + 2.5 ml/1 HCI using a fracture mechanics approach. Stress parameters, KI and JI, were calculated along with the crack growth rates (da/dt). The tests were conducted under both increasing stress intensity and decreasing stress intensity conditions. The sensitized stainless steel was found to have lower values of KISCC and JISCC and higher plateau crack growth rates than the solution-annealed material. The value of KI for the transition of the cracking mode from transgranular to intergranular in the sensitized stainless steel corresponded to the value of KI above which the plateau region started. In both conditions of the material, the initiation of stress corrosion cracking and the initial crack propagation were transgranular. The sensitized material exhibited a transition to an intergranular cracking mode while the solution-annealed material did not. A large number of secondary cracks were observed in the solution-annealed material.

Vinoy, T. V.; Shaikh, H.; Khatak, H. S.; Sivaibharasi, N.; Gnanamoorthy, J. B.

1996-11-01

281

Exploration of surface hydrophilic properties on AISI 304 stainless steel and silicon wafer against aging after atmospheric pressure plasma treatment  

NASA Astrophysics Data System (ADS)

The aim of this work is to seek the enhanced surface hydrophilic properties on AISI 304 stainless steel and silicon wafer after atmospheric pressure plasma treatment using a specifically designed atmospheric pressure plasma jet. The aging tendency of surface hydrophilic property under air is highlighted. It is concluded that both of the silicon wafer and stainless steel treated with plasma generated from supply gas of argon 15 slm mixed with oxygen 40 sccm shows a better tendency on remaining high water contact angle as compared to that with pure argon and nitrogen addition. Additional peaks of O I (777, 844 nm), O II (408 nm) are detected by optical emission spectroscope indicating the presence of the oxygen radicals and ionic species, which interact with surfaces and thus contribute to low water contact angle (WCA) surfaces. Moreover, the result acquired from X-ray photoelectron spectroscopy (XPS) indicates that the increase in the oxygen-related bonding exhibits a better contribution on remaining high surface energy over a period of time.

Chuang, Shang-I.; Duh, Jenq-Gong

2014-11-01

282

Nano-Borides and Silicide Dispersed Composite Coating on AISI 304 Stainless Steel by Laser-Assisted HVOF Spray Deposition  

NASA Astrophysics Data System (ADS)

The study concerned a detailed microstructural investigation of nano-borides (Cr2B and Ni3B) and nano-silicide (Ni2Si) dispersed ?-nickel composite coating on AISI 304 stainless steel by HVOF spray deposition of the NiCrBSi precursor powder and subsequent laser surface melting. A continuous wave diode laser with an applied power of 3 kW and scan speed of 20 mm/s in argon shroud was employed. The characterization of the surface in terms of microstructure, microtexture, phases, and composition were carried out and compared with the as-coated (high-velocity oxy-fuel sprayed) surface. Laser surface melting led to homogenization and refinement of microstructures with the formation of few nano-silicides of nickel along with nano-borides of nickel and chromium (Ni3B, Cr2B, and Cr2B3). A detailed microtexture analysis showed the presence of no specific texture in the as-sprayed and laser-melted surface of Cr2B and Ni3B phases. The average microhardness was improved to 750-900 VHN as compared to 250 VHN of the as-received substrate. Laser surface melting improved the microhardness further to as high as 1400 VHN due to refinement of microstructure and the presence of silicides.

Sharma, Prashant; Majumdar, Jyotsna Dutta

2014-10-01

283

Effect of Nitrogen and Sensitization on the Microstructure and Pitting Corrosion Behavior of AISI Type 316LN Stainless Steels  

NASA Astrophysics Data System (ADS)

High-nitrogen stainless steels (SS) are receiving increased attention because of the advantages of their strength over the SS with nominal composition. However, they are susceptible to dichromium nitride (Cr2N) precipitation during thermal exposure between 873 and 1323 K resulting in sensitization and subsequent intergranular corrosion. Round tensile specimens of AISI type 316LN SS, with three different nitrogen content 0.07, 0.14, and 0.22 wt.% in mill-annealed and sensitized (973 K for 24 h) condition were studied for their pitting corrosion behavior. The results of the potentiodynamic anodic polarization studies were correlated with the results obtained using electrochemical impedance spectroscopy (EIS) technique. Critical pitting potential ( E pp) increased with increasing nitrogen content but the same was found to decrease on aging. The parameters indicating passive film stability measured by EIS revealed faster passive film dissolution as indicated by low polarization resistance, in sensitized condition and vice-versa in mill-annealed condition. The EIS results correlated well with the variation in the respective E pp obtained from the potentiodynamic polarization diagrams.

Poonguzhali, A.; Pujar, M. G.; Kamachi Mudali, U.

2013-04-01

284

Determination of Neutron Exposure of AISI 304 Stainless Steel from a BWR Top Guide using Retrospective Dosimetry  

SciTech Connect

Retrospective dosimetry was used to determine the accumulated neutron exposure of AISI 304 stainless steel removed from the top guide of a boiling water reactor located at the Oyster Creek nuclear power station. The material was removed from areas adjacent to cracks that were observed after ~20 years of operation. Using the plant operational history and a variety of measurements of various radioisotopes or non-radioactive transmutation products produced by irradiation, it was possible to determine the integrated flux spectra experienced by the cracked region and to specify the accumulated displacement dose. Dose estimates on two separate specimens adjacent to the cracks were found to average 1.5 ± 0.2 dpa, possibly reflecting some uncertainty in measurement but more likely suggesting a small gradient in neutron flux-spectra within the section from which the various analysis specimens were cut. This report demonstrates that it is possible to examine defective components lying outside of the core region and where neutron flux-spectra are not well known, and to use the induced transmutation products to determine the neutron exposure with some confidence by using the examined specimen as its own dosimeter.

Greenwood, Lawrence R.; Garner, Francis A.; Oliver, Brian M.; Bruemmer, Stephen M.

2007-03-31

285

Cobalt-Free Laser Cladding on AISI Type 316L Stainless Steel for Improved Cavitation and Slurry Erosion Wear Behavior  

NASA Astrophysics Data System (ADS)

Laser cladding of Colmonoy-5 (a nickel base alloy) and Metco-41C (an iron base alloy) on AISI type 316L stainless steel (SS316L) and their wear behaviors were investigated to establish Co-free clad layers for potential applications in nuclear industry. A 3.5 kW CO2 laser-based system was used to optimize the laser cladding on SS316L substrate. The observed optimum parameters were: laser power of 1.6 kW, scan speed of 0.6 m/min, and powder feed rate of 8 g/min with 60% overlapping. The microstructure studies revealed that the clad layers primarily comprise very fine columnar dendritic structures, while clad-substrate interface exhibited planar and non-epitaxial mode of solidification due to high cooling rates. The cavitation and slurry erosion behaviors of laser clad layers were also compared to that of Stellite-6 for potential direct replacement. The cavitation erosion resistance was improved by a factor of 1.6, 3.7, and 4.1, while the slurry erosion resistances at an impingement angle of 30° were 1.5, 4.8, and 1.8 times better for laser clad surfaces of Colmonoy-5, Metco-41C, and Stellite-6, respectively, as compared to that of bare SS316L substrate. The study demonstrated that Metco-41C is a better choice as Co-free clad material for potential nuclear applications.

Paul, C. P.; Gandhi, B. K.; Bhargava, P.; Dwivedi, D. K.; Kukreja, L. M.

2014-09-01

286

Microstructure and tribology of ion-mixed Fe/Ti/C multilayers on AISI 304 stainless steel  

NASA Astrophysics Data System (ADS)

A multilayered Fe/Ti/C structure consisting of eleven alternating sublayers, four Fe, four Ti and three C, was ion mixed on an AISI 304 stainless steel substrate with 400 keV Xe 2+. Complete mixing was observed after an irradiation of 1 × 10 17Xe/cm 2 at 550°C. Electron diffraction revealed the formation of the compounds TiC and Fe 3C and a small amount of an amorphous phase. Some samples were given a second irradiation with 5 × 10 15Xe/cm 2 at 0°C. The phases present following the second irradiation were TiC, ?-Fe and an amorphous phase. Tribological and nanoindentation measurements revealed that both types of samples possessed similar hardness and friction properties. The ion mixed samples possessed an increased hardness and a decreased friction coefficient relative to untreated polished stainless-steel substrate. However, the wear life of the hot ion mixed sample was consistently longer than the wear life of the sample processed at both 550 and 0°C. These results are explained by differences in adhesive wear which result from differences in the chemical reactivity of the phases formed during ion beam processing.

Nastasi, M.; Hirvonen, J.-P.; Zocco, T. G.; Jervis, T. R.

1991-07-01

287

The effect of Zr-implantation on the thermal oxidation and aqueous corrosion of AISI 321 stainless steel  

NASA Astrophysics Data System (ADS)

The effect of Zr-implantation (energy: 40 keV, dose: 1 × 10 17 ions/cm 2) on the oxidation of AISI 321 austenitic stainless steel (Fe/Cr18/Ni8/Ti) has been studied at temperatures of 450, 550 and 650°C, in air. The duration of the oxidation was varied between one and six days. The oxygen distribution on the oxidized samples has been determined using the 16O(d, p) 17O nuclear reaction whereas the zirconium depth profile by means of Rutherford backscattering spectroscopy (RBS) using ?-particles as projectiles. X-ray photoelectron spectroscopy (XPS) was used as support to these measurements. The morphology and the surface microstructure of the specimens were investigated by scanning electron and scanning transmission electron microscopy (SEM and STEM). The evaluation of the data has indicated that the implantation of Zr-ions leads to a chromium depletion in the near-surface layers and enhances the oxidation of the implanted samples compared to the initial material. Electrochemical experiments of the Zr-implanted steel performed in 1N sulphuric acid solution (H 2SO 4 1N) showed an increase of the corrosion resistance.

Noli, F.; Misaelides, P.; Giorginis, G.; Baumann, H.; Hatzidimitriou, A.

288

Corrosion behavior and tensile properties of AISI 316LN stainless steel exposed to flowing sodium at 823 K  

SciTech Connect

Austenitic stainless steel of the grade AISI 316 LN was exposed to flowing sodium in a loop at 823 K for 6,000 h to examine the corrosion and mass-transfer behavior. The specimens were incorporated in specially designed sample holders in the loop. These were retrieved and examined by various metallurgical techniques. Specimens were also subjected to thermal aging in the same sample holder to aid in separating the consequences of exposure to sodium from those cause by mere thermal effects. Microstructural investigations have revealed that thermal aging caused the precipitation of carbides at the grain boundaries. Exposure to sodium caused the leaching of elements such as chromium and nickel from the specimen. Loss of nickel from the austenite phase promoted the generation of ferrite phase. Microhardness investigation revealed the hardening of the sodium-exposed surface. Analysis using an electron Probe Microanalyzer revealed that the surface of the steel was both carburized and nitrided. Tensile tests indicated that there is no appreciable difference in the yield strength (YS) and ultimate tensile strength (UTS) of the thermally aged and sodium-exposed specimens when compared with the material in the as-received condition. However, the thermally aged and sodium-exposed specimens showed a decrease in the uniform elongation and total elongation at rupture, perhaps due to carburization and nitridation.

Pillai, S.R.; Barasi, N.S.; Khatak, H.S.; Terrance, A.L.E.; Kale, R.D.; Rajan, M.; Rajan, K.K.

2000-02-01

289

Twinning-induced sluggish evolution of texture during recrystallization in AISI 316L stainless steel after cold rolling  

NASA Astrophysics Data System (ADS)

This paper deals with the evolution of texture in AISI 316L austenitic stainless steel during annealing after 95 pct cold rolling. After 95 pct cold rolling, the texture is mainly of the brass type {110}<112>, along with a scatter toward the S orientation {123}<634> and Goss orientation {011}<100>. Weak evidence of Cu component is observed at this high deformation level. During annealing, recovery is observed before any detectable recrystallization. Recrystallization proceeds through nucleation of subgrain by twinning within the deformed matrix and, later, preferential growth of those to consume the deformed matrix. After recrystallization, the overall texture intensity was weak; however, there are some discernible texture components. There was no existence of the brass component at this stage. Major components are centered on Goss orientation and Cu component {112}<111> as well as the BR component {236}<385>. Also, a few orientations come up after recrystallization ( i.e., {142}<2-11> and {012}<221>). With increase in annealing temperature, the textural evolution shows emergence of weak texture with another new component, {197}<211>. The evolution of texture was correlated with the deformation texture through twin chain reaction.

Chowdhury, Sandip Ghosh; Das, Samar; Ravikumar, B.; de, P. K.

2006-08-01

290

Correlation of microstructure and surface roughness of disc drums fabricated by hot forging of an AISI 430F stainless steel  

NASA Astrophysics Data System (ADS)

The surface roughness of disc drums fabricated by hot forging of an AISI 430F stainless steel was investigated. Emphasis was placed on the role of microstructural changes, which depend on postforging annealing conditions. In the forged drum specimens, MnS inclusions were heavily elongated, and a large amount of martensite was found. Three different annealing conditions were used on the forged drum specimens to completely or partially decompose martensite. The surface roughness tests were conducted on these specimens, and then the test data were compared via hardness and microstructures. The top plane of disc drums, where MnS inclusions were elongated perpendicular to the machined surface, showed a good surface roughness because of the free-machining effect of MnS. However, the side plane, where MnS inclusions were aligned parallel to the machined surface, showed an increased surface roughness due to reduction of the MnS effect. These findings suggested that a proper amount of martensite formed during forging and annealing would be beneficial for cost efficiency, as well as machinability of the 430F stainless steel products.

Kim, Dong-Kuk; Lee, Dong-Geon; Lee, Sunghak

2001-05-01

291

Nano-Borides and Silicide Dispersed Composite Coating on AISI 304 Stainless Steel by Laser-Assisted HVOF Spray Deposition  

NASA Astrophysics Data System (ADS)

The study concerned a detailed microstructural investigation of nano-borides (Cr2B and Ni3B) and nano-silicide (Ni2Si) dispersed ?-nickel composite coating on AISI 304 stainless steel by HVOF spray deposition of the NiCrBSi precursor powder and subsequent laser surface melting. A continuous wave diode laser with an applied power of 3 kW and scan speed of 20 mm/s in argon shroud was employed. The characterization of the surface in terms of microstructure, microtexture, phases, and composition were carried out and compared with the as-coated (high-velocity oxy-fuel sprayed) surface. Laser surface melting led to homogenization and refinement of microstructures with the formation of few nano-silicides of nickel along with nano-borides of nickel and chromium (Ni3B, Cr2B, and Cr2B3). A detailed microtexture analysis showed the presence of no specific texture in the as-sprayed and laser-melted surface of Cr2B and Ni3B phases. The average microhardness was improved to 750-900 VHN as compared to 250 VHN of the as-received substrate. Laser surface melting improved the microhardness further to as high as 1400 VHN due to refinement of microstructure and the presence of silicides.

Sharma, Prashant; Majumdar, Jyotsna Dutta

2014-03-01

292

AISI/DOE Technology Roadmap Program: A Technology of Low Coal Rate and High Productivity of RHF Ironmaking  

SciTech Connect

An economical and environment-friendly ironmaking process based on heating the chemiexecy self-sufficient green balls of iron ore and coal in a hearth furnace is being developed with financial support from AISI members and DOE. DRI, which is hot (1400 C), dense (3.2 g/cm) and of high degree of metallization (95%), has been produced in laboratory and in a pilot plant in Genoa, Italy. Products of such quality have been made from American and Brazilian ores, BOF sludge, EAF dust/BOF sludge mixtures and millscale. The removal of zinc and lead from green balls by this process is essentially complete. In comparison with typical blast furnace operation, the new technology with a melter would have a lower total coal rate by 200kg.THM. The elimination of cokemaking and high temperature agglomeration steps, and a simpler gas handling system would lead to lower capital and operating costs. In comparison with commercial RHF practice it is different in atmosphere (fully oxidized at 1600 to 1650 C), in bed height (120 mm instead of 20-25 mm) and in pellet composition (much less coal but of higher VM). The combined effect leads to three times higher furnace productivity, lower coal consumption and superior DRI quality. The risk of re-oxidation (slag formation) and dusty operation are practiexecy eliminated. The process is stable, tolerant and independent of the size, shape and movement of the hearth. However, materials handling (e.g., discharge of hot DRI) and the exact energy savings have to be established in a larger furnace, straight or rotary, and in a continuous mode of operation.

Wei-Kao Lu

2002-09-15

293

Amyotrophic Lateral Sclerosis (ALS)  

MedlinePLUS Videos and Cool Tools

Amyotrophic Lateral Sclerosis Introduction Amyotrophic Lateral Sclerosis, or ALS, is a serious neurological disease that affects the ability to ... com nr180104 Last reviewed: 03/20/2013 1 ALS ALS attacks the neurons that control muscles, the ...

294

About ALS: FAQ  

MedlinePLUS

... are the potential side effects? What Is ALS? Amyotrophic Lateral Sclerosis (ALS) is a motor neuron disease, first identified in ... neurologist Jean-Martin Charcot. Although the cause of ALS is not completely understood, recent years have brought ...

295

Ion Beam Analysis, structure and corrosion studies of nc-TiN/a-Si3N4 nanocomposite coatings deposited by sputtering on AISI 316L  

NASA Astrophysics Data System (ADS)

In this work, nanocomposite coatings of nc-TiN/a-Si3N4, were deposited on AISI 316L stainless steel substrate by a DC and RF reactive magnetron co-sputtering technique using an A-N2 plasma. The structure of the coatings was characterized by means of XRD (X-ray Diffraction). The substrate and coating corrosion resistance were evaluated by potentiodynamic polarization using a Ringer solution as electrolyte. Corrosion tests were conducted with the purpose to evaluate the potential of this coating to be used on biomedical alloys. IBA (Ion Beam Analysis) techniques were applied to measure the elemental composition profiles of the films and, XPS (X-ray Photoelectron Spectroscopy) were used as a complementary technique to obtain information about the compounds present in the films. The nanocomposite coatings of nc-TiN/a-Si3N4 show crystalline (TiN) and amorphous (Si3N4) phases which confer a better protection against the corrosion effects compared with that of the AISI 316L.

García, J.; Canto, C. E.; Flores, M.; Andrade, E.; Rodríguez, E.; Jiménez, O.; Solis, C.; de Lucio, O. G.; Rocha, M. F.

2014-07-01

296

Evolution of Relationships Between Dislocation Microstructures and Internal Stresses of AISI 316L During Cyclic Loading at 293 K and 573 K (20 °C and 300 °C)  

NASA Astrophysics Data System (ADS)

The evolution of dislocation densities and of dislocation microstructures during cyclic loading of AISI 316L is systematically evaluated. In addition, internal stresses are also measured for every cycle and comprehensively analyzed. These observations are made in order to establish relationships between the evolution of dislocation condition and internal stresses, and ultimately to obtain a thorough insight into the complex cyclic response of AISI 316L. Moreover, the dependencies of established relationships on the variation of temperature and strain amplitude are investigated. The back stresses (long-range stresses associated with the presence of collective dislocations over different length scales) are mainly responsible for the cyclic deformation response at high strain amplitudes where dislocations tend to move more quickly in a wavy manner. In contrast, the effective stress, coupling with short-range dislocation interactions, plays an insignificant role on the material cyclic response for wavy slip conditions, but increasingly becomes more important for planar slip conditions. The additionally strong short-range interactions between dislocations and point defects (initially with solute atoms and later in life with corduroy structure) at 573 K (300 °C) cause dislocations to move in more planar ways, resulting in a significant increase in effective stress, leading to their influential role on the material cyclic response.

Pham, Minh-Son; Holdsworth, Stuart R.

2014-02-01

297

Microstructural Characterization and Properties Evaluation of Ni-Based Hardfaced Coating on AISI 304 Stainless Steel by High Velocity Oxyfuel Coating Technique  

NASA Astrophysics Data System (ADS)

The present study concerns a detailed investigation of microstructural evolution of nickel based hardfaced coating on AISI 304 stainless steel by high velocity oxy-fuel (HVOF) deposition technique. The work has also been extended to study the effect of coating on microhardness, wear resistance and corrosion resistance of the surface. Deposition has been conducted on sand blasted AISI 304 stainless steel by HVOF spraying technique using nickel (Ni)-based alloy [Ni: 68.4 wt pct, chromium (Cr): 17 wt pct, boron (B): 3.9 wt pct, silicon (Si): 4.9 wt pct and iron (Fe): 5.8 wt pct] of particle size 45 to 60 ?m as precursor powder. Under the optimum process parameters, deposition leads to development of nano-borides (of chromium, Cr2B and nickel, Ni3B) dispersion in metastable and partly amorphous gamma nickel (?-Ni) matrix. The microhardness of the coating was significantly enhanced to 935 VHN as compared to 215 VHN of as-received substrate due to dispersion of nano-borides in grain refined and partly amorphous nickel matrix. Wear resistance property under fretting wear condition against WC indenter was improved in as-deposited layer (wear rate of 4.65 × 10-7 mm3/mm) as compared to as-received substrate (wear rate of 20.81 × 10-7 mm3/mm). The corrosion resistance property in a 3.56 wt pct NaCl solution was also improved.

Sharma, Prashant; Majumdar, Jyotsna Dutta

2013-01-01

298

The effect of microstructure on the thermal fatigue resistance of investment cast and wrought AISI H13 hot work die steel  

SciTech Connect

Variable thickness plate investment castings of AISI H13 hot work die steel were pour and characterized in the as-cast and heat treated conditions. The characterization included light microscopy and mechanical testing. Wrought samples of standard and premium grade H13 steel were heat treated and characterized similarly for comparison. Microstructural differences were observed in as-cast samples poured to different section thicknesses. Dendrite cell size and carbide morphology constituted the most prominent microstructural differences observed. After a full heat treatment, however, Microstructural differences between the wrought material and cast materials were slight regardless of section thickness. The mechanical properties of the cast and heat treated material proved similar to the properties of the standard heat treated wrought material. A thermal fatigue testing unit was designed and built to correlate the heat checking susceptibility of AISI H13 steel to its processing and consequent microstructural condition. Surface hardness decreased significantly with thermal cycling, and heat checking was noticed in as few as 50 cycles. Thermal softening and thermal fatigue susceptibility were quantified and discussed relative to the microstructural conditions created by processing and heat treatment. It was found that the premium grade wrought H13 steel provided the best overall resistance to heat checking; however, the heat-treat cast and as-cast H13 tool steel (made from standard grade wrought H13 tool steel) provided comparable resistance to heat checking in terms Of area fraction of heat checking and maximum crack length.

Hochanadel, P.W.; Edwards, G.R. [Colorado School of Mines, Golden, CO (United States); Maguire, M.C.; Baldwin, M.D. [Sandia National Labs., Albuquerque, NM (United States)

1995-07-01

299

Amyotrophic Lateral Sclerosis (ALS)  

MedlinePLUS

NINDS Amyotrophic Lateral Sclerosis (ALS) Information Page Clinical Trials Natural History and Biomarkers of C9ORF72 ALS and FTD The ... Trials Organizations Additional resources from MedlinePlus What is Amyotrophic Lateral Sclerosis (ALS)? Amyotrophic lateral sclerosis (ALS), sometimes ...

300

/Cu-Al System  

NASA Astrophysics Data System (ADS)

Wettability and interfacial interaction of the Ta2O5/Cu-Al system were studied. Pure Cu does not wet the Ta2O5 substrate, and improved spreading is achieved when relatively a high fraction of the active element (~40 at.% Al) was added. The Al2O3 and AlTaO4 phases were observed at the Ta2O5/Cu-Al interface. A thermodynamic evaluation allowed us to suggest that the lack of wetting bellow 40 at.% Al is due to the presence of a native oxide, which covers the drop. The conditions of the native oxide decomposition and the formation of the volatile Al2O suboxide strongly depend on the vacuum level during sessile drop experiments and the composition of the Cu-Al alloy. In our case, Al contents greater than 40% provides thermodynamic conditions for the formation of Al2O (as a result of Al reaction with Al2O3) and the drop spreading. It was suggested that the final contact angle in the Ta2O5/Cu-Al system (50°) is determined by Ta adsorption on the newly formed alumina interlayer.

Kish, Orel; Froumin, Natalya; Aizenshtein, Michael; Frage, Nachum

2014-05-01

301

Effect of cathodic hydrogenation on the mechanical properties of AISI 304 stainless steel nitrided by ion implantation, glow discharge and plasma immersion ion implantation  

NASA Astrophysics Data System (ADS)

Hydrogen embrittlement in austenitic stainless steels is restricted to the surface due to the low hydrogen diffusion in austenitic structures. The effect of three different nitriding processes: ion implantation (II), plasma immersion ion implantation (PI3) and glow discharge (GD), on the mechanical and structural properties of cathodically hydrogenated AISI 304 stainless steel were studied in the present work. Cathodic hydrogenation was made on untreated and nitrided samples. Surface microstructure after nitriding and hydrogenation was investigated by X-ray diffraction. Mechanical properties were measured by instrumented indentation. Surface crack formation and hardness decrease was observed in non-nitrided samples after cathodic hydrogenation. Hardness of nitrided samples decreases after hydrogen degassing but still has values higher than untreated samples. Comparative analysis of nitriding processes and working conditions indicated that glow discharge plasma nitriding process at 400 °C or 450 °C is the most adequate to avoid crack formation in steel surface after cathodic hydrogenation.

Foerster, C. E.; Souza, J. F. P.; Silva, C. A.; Ueda, M.; Kuromoto, N. K.; Serbena, F. C.; Silva, S. L. R.; Lepienski, C. M.

2007-04-01

302

Microstructure and property modifications of an AISI H13 (4Cr5MoSiV) steel induced by pulsed electron beam treatment  

SciTech Connect

In the present work, surface modifications generated by the low energy high current pulsed electron beam (LEHCPEB) treatments have been investigated on an AISI H13 (4Cr5MoSiV) steel. From the observations of scanning electron microscopy, x-ray diffraction, and electron back scattering diffraction determinations, it could be established that the final structure in the melted layer is a mixture of ultrafine {delta} phase, martensite, and residual austenite. The formation of the heterogeneous microstructures on the surface layer is related to the very rapid heating, melting, solidification, and cooling induced by the LEHCPEB irradiation. After the LEHCPEB treatment, the wear resistance of the steel effectively improved. This can be mainly attributed to the higher hardness of the ultrafine structures formed on the top surface and the hardened subsurface layers after the treatment.

Zhang Kemin; Zou Jianxin; Grosdidier, Thierry; Dong Chuang [School of Materials Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China); Shanghai Engineering Research Center of Mg Materials and Applications and School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China) and Laboratoire d'Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), Universite Paul Verlaine Metz, Ile du Saulcy, 57045 Metz (France); Laboratoire d'Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), Universite Paul Verlaine Metz, Ile du Saulcy, 57045 Metz (France) and Laboratory of Materials Modification by Laser, Electron and Ion Beams, Dalian University of Technology, Dalian 116024 (China); Laboratory of Materials Modification by Laser, Electron and Ion Beams, Dalian University of Technology, Dalian 116024 (China)

2010-11-15

303

Strain-induced phase transformation at the surface of an AISI-304 stainless steel irradiated to 4.4 dpa and deformed to 0.8% strain  

NASA Astrophysics Data System (ADS)

Surface relief due to localized deformation in a 4.4-dpa neutron-irradiated AISI 304 stainless steel was investigated using scanning electron microscopy coupled with electron backscattering diffraction and scanning transmission electron microscopy. It was found a body-centered-cubic (BCC) phase (deformation-induced martensite) had formed at the surface of the deformed specimen along the steps generated from dislocation channels. Martensitic hill-like formations with widths of ˜1 ?m and depths of several microns were observed at channels with heights greater than ˜150 nm above the original surface. Martensite at dislocation channels was observed in grains along the [0 0 1]-[1 1 1] orientation but not in those along the [1 0 1] orientation.

Gussev, M. N.; Field, K. G.; Busby, J. T.

2014-03-01

304

Response to annealing and reirradiation of AISI 304L stainless steel following initial high-dose neutron irradiation in EBR-II. [LMFBR  

SciTech Connect

The object of this study was to measure the stability of irradiation-induced microstructure upon annealing and, by selectively annealing out some of these features and reirradiating the material, it was expected that information could be gained concerning the role of microstructural changes in the void swelling process. Transmission electron microscopic examinations of isochronally annealed (200 to 1050/sup 0/C) AISI 304L stainless steel, which had been irradiated at approximately 415/sup 0/C to a fast (E > 0.1 MeV) neutron fluence of approximately 5.1 x 10/sup 26/n/m/sup 2/, verified that the two-stage hardness recovery with temperatures was related to a low temperature annealing of dislocation structures and a higher temperature annealing of voids and solute redistribution.

Porter, D.L.; McVay, G.L.; Walters, L.C.

1980-01-01

305

Effect of Proximity and Dimension of Two Artificial Pitting Holes on the Fatigue Endurance of Aluminum Alloy AISI 6061-T6 Under Rotating Bending Fatigue Tests  

NASA Astrophysics Data System (ADS)

This work deals with the study of the two artificial pitting holes effects, caused by their dimensions and proximity, on the fatigue endurance of aluminum alloy AISI 6061-T6 under rotating bending fatigue tests. Stress concentration induced by artificial pitting holes is analyzed and correlated with the experimental fatigue life. It is found that the stress concentration increases exponentially when the two pitting holes approach, and this induces an important reduction in the fatigue life. Concerning the diameter variation of one pitting in regard to the second, no important influence was observed on fatigue life for a given separation between them; this implies that the separation between the two artificial pitting holes and the associated stress concentration is the principal parameter on the fatigue life under these conditions. Finally, results are discussed and conclusions are presented involving the fatigue life, proximity, and dimension of pitting holes, stress concentration factor, and fracture surfaces where the failure origin is identified.

Dominguez Almaraz, G. M.; Mercado Lemus, V. H.; Villalon Lopez, J. J.

2012-08-01

306

Impact of localized surface preheating on the microstructure and crack formation in laser direct deposition of Stellite 1 on AISI 4340 steel  

NASA Astrophysics Data System (ADS)

Crack formation in laser cladding of the hardfacing alloy Stellite 1 on AISI-SAE 4340 steel was prevented through locally preheating the substrate prior to the deposition process. Numerical analysis showed that the preheating process helps developing a relatively steadier melt temperature as well as decreasing the cooling rates and consequently the thermal stresses during the subsequent deposition process. Microstructural analysis revealed a thicker cross-section with smoother surface profile, more uniform surface hardness and even distribution of a dendritic morphology in the preheated sample. This confirmed the presence of a well-developed melt pool with a homogeneous composition at solidification. The microstructure of non-preheated sample was, however, considerably non-uniform consisting of macro-scale colonies of dendritic and lamellar (eutectic) structures. The experimental observations, as implied through the numerical results, showed that the preheated sample, in general, reveals more uniform structure and properties making it less prone to cracking during the deposition process.

Fallah, Vahid; Alimardani, Masoud; Corbin, Stephen F.; Khajepour, Amir

2010-12-01

307

Amyotrophic Lateral Sclerosis (ALS)  

Microsoft Academic Search

ALS, commonly called Lou Gehrig's disease, is a devastating neurological dis- order characterized by selective upper and lower somatic, but not autonomic, motor neurone degeneration leading to paralysis and eventually death. The diagnosis of ALS requires the presence of both upper and lower motor neu- rone degeneration and progressive motor dysfunction. ALS occurs in 1 to 2.5 cases per 100,000

Chris G. Parsons; Wojciech Danysz

308

AISI Direct Steelmaking Program  

SciTech Connect

Pilot plant trials with the horizontal vessel were completed. Design of a third pressurized vessel and an offgas cleaning and tempering system was completed. Installation is now underway. A basic study and a pre-engineering design of a 350,000-metric ton/y demonstration plant were completed, and efforts are underway to develop such a demonstration plant at a host steel company. Foreign filings have been prepared for the two-zone countercurrent smelter (patent applied for). Work with a water model of two-zone smelter was completed. The horizontal smelter program was completed. Trials were conducted to determine how sulfur is partitioned among the hot metal, slag, and offgas. Design of offgas cleaning and tempering loop was completed.

Aukrust, E.

1993-01-01

309

Influence of nickel ion implantation on the inactive braze joining abilities of Al 2O 3 ceramics  

NASA Astrophysics Data System (ADS)

Multi-crystalline Al 2O 3 ceramics were implanted with 130 keV Ni + ion beams at 225 °C in a vacuum of 1.33 × 10 -3 Pa. The inactive braze joining abilities of the implanted ceramic to 1Cr18Ni9Ti (AISI 321) stainless steel with Ag 34Cu 16Zn 50 (wt%) brazing material were investigated. The relationships between the joining abilities and the surface compressive stresses produced by the ion implantation were studied for the first time. The results showed that when the fluence was less than 5 × 10 16 ions/cm 2, the surface properties including wetting ability, braze joining ability and produced surface compressive stresses, increased with ion implantation fluence, and reached the maximum value at a point of 5 × 10 16 ions/cm 2. After this point, the properties decreased upon further increasing the ion implantation fluence.

Zhao, B. R.; Li, G. B.; Gao, P.; Lei, T. Q.; Song, S. C.; Cao, X. J.

2005-09-01

310

Brazing of hot isostatically pressed-Al2O3 to stainless steel (AlSl 304L) by Mo-Mn route using 72Ag-28Cu braze  

NASA Astrophysics Data System (ADS)

Joining of stainless steel (AISI 304L) to hot isostatically pressed alumina (HIP-Al2O3) using the brazing alloy 72Ag-28Cu was investigated. The microstructural characterization at various stages of joining, including metallization, annealing of overlaid Ni coating, and brazing, was comprehensively evaluated. The interface structure and the growth of phases were analyzed with optical microscope, scanning electron microscope, and electron probe microanalyzer (EPMA). Additionally, the leak tightness of these joints was assessed using a He-leak detector. Experimental results indicated the development of the manganese aluminate spinel (MnAl2O4) layer at the metallizing stage, which penetrated into HIP-Al2O3. The Ni overlaid coating further resulted in the formation of the Ni(Mo) solid solution layer followed by the Mo-rich phase. During the solid-state reaction and subsequent brazing cycle, the growth of the spinel layer close to HIP-Al2O3 was not adversely affected. The microstructure of the brazed joint was complex. It showed a eutectic structure within the brazed zone and a thin layer of Mo-rich, Ni-rich phases close to HIP-Al2O3. Increasing the brazing time resulted in the excessive growth of the thin layer that seriously affected the leak tightness of the joint.

Mishra, P.; Athavale, S. N.; Pappachan, A. L.; Grover, A. K.; Suri, A. K.; Sengupta, P.; Kale, G. B.; Bhanumurthy, K.; de, P. K.

2005-06-01

311

Study on the effects of pulsed TIG welding parameters on delta-ferrite content, shape factor and bead quality in orbital welding of AISI 316L stainless steel plate  

Microsoft Academic Search

The TIG pulse welding parameters of AISI 316L stainless steel plate of 3mm thickness at the welding positions of 6–12h were investigated. The weld bead profiles corresponded to DIN 8563 class BS. The studied parameters were welding speed, pulse\\/base currents, pulse frequency, and % on time. Pure argon and argon with nitrogen contents of 1–4vol.% were used as shielding gas

G Lothongkum; E Viyanit; P Bhandhubanyong

2001-01-01

312

Long-term evaluation of solid oxide fuel cell candidate materials in a 3-cell generic stack test fixture, part III: Stability and microstructure of Ce-(Mn,Co)-spinel coating, AISI441 interconnect, alumina coating, cathode and anode  

NASA Astrophysics Data System (ADS)

A generic solid oxide fuel cell stack test fixture was developed to evaluate candidate materials and processing under realistic conditions. Part III of the work investigated the stability of Ce-(Mn,Co) spinel coating, AISI441 metallic interconnect, alumina coating, and cell's degradation. After 6000 h test, the spinel coating showed densification with some diffusion of Cr. At the metal interface, segregation of Si and Ti was observed, however, no continuous layer formed. The alumina coating for perimeter sealing areas appeared more dense and thick at the air side than the fuel side. Both the spinel and alumina coatings remained bonded. EDS analysis of Cr within the metal showed small decrease in concentration near the coating interface and would expect to cause no issue of Cr depletion. Inter-diffusion of Ni, Fe, and Cr between spot-welded Ni wire and AISI441 interconnect was observed and Cr-oxide scale formed along the circumference of the weld. The microstructure of the anode and cathode was discussed relating to degradation of the top and middle cells. Overall, the Ce-(Mn,Co) spinel coating, alumina coating, and AISI441 steel showed the desired long-term stability and the developed generic stack fixture proved to be a useful tool to validate candidate materials for SOFC.

Chou, Yeong-Shyung; Stevenson, Jeffry W.; Choi, Jung-Pyung

2014-07-01

313

ALS: AN ETHICAL PERSPECTIVE  

Microsoft Academic Search

Amyotrophic lateral sclerosis (ALS), or Lou Gehrig's disease, is a relentlessly progressive, fatal and presently incurable motor neuron disorder caused by degeneration of both upper and lower neurons that control voluntary skeletal muscle. ALS variants include a progressive lower motor neuron disorder, Progressive Muscular Atrophy (PMA); a progressive upper motor neuron disorder, Primary Lateral Sclerosis (PLS); and a progressive disorder

Leo McCluskey

314

[Environmental factors in ALS].  

PubMed

ALS is likely to be a disorder of multifactorial origin. Among all the factors that may increase the risk of ALS, environmental ones are being studied for many years, but in the recent years, several advances have pointed to a new interest in their potential involvement in the disease process, especially for the cyanotoxin BMAA. Food containing BMAA has been found on Guam, a well-known focus of ALS/parkinsonism/dementia and high levels of BMAA have been identified into the brain of these patients. The BMAA cyanotoxin is potentially ubiquitous and have also been found into the food of patients who died from ALS both in Europe and USA. BMAA can be wrongly integrated into the protein structure during mRNA traduction, competing with serine. This may induce abnormal protein folding and a subsequent cell death. Heavy metals, such as lead or mercury may be directly toxic for neuronal cells. Several works have suggested an increased risk of ALS in individuals chronically exposed to these metals. Exposure to pesticides has been suggested to be linked to an increased risk of developing ALS. The mechanism of their toxicity is likely to be mediated by paraoxonases. These proteins are in charge of detoxifying the organism from toxins, and particularly organophosphates. To date, there are insufficient scientific data to suggest that exposure to electromagnetic fields may increase the risk of having ALS. We are particularly missing longitudinal cohorts to demonstrate that risk. PMID:24703731

Juntas-Morales, Raul; Pageot, Nicolas; Corcia, Philippe; Camu, William

2014-05-01

315

Wear behavior of Al2O3-TiCN composite ceramic sliding on stainless steel  

NASA Astrophysics Data System (ADS)

It is well known that austenitic stainless steel AISI302 is relatively difficult to cut. In order to investigate the wear behavior of Al2O3-TiCN composite ceramic when machining austenitic stainless steels, a blockon-ring tribometer was used to simulate a real machining process. The test results showed that the wear of both the ceramic and the stainless steel increased rapidly with increasing load and speed. The boundary lubrication actions of water and oil used in this test could not reduce the wear of the rubbing materials. Scanning electron microscopy and energy-dispersive x-ray spectroscopy analyses identified material transferred between the ceramic and the stainless steel surfaces in rubbing process. On the one hand, stainless steel transferred on the ceramic surface because of adhesion; on the other, some ceramic fragments caused by microfracture of the ceramic were found to be embedded in the worn stainless steel surface. The wear of Al2O3-TiCN ceramic sliding against stainless steel was caused primarily by adhesion between the rubbing surfaces and the microfracture of the ceramic.

Zhao, X. Z.; Liu, J. J.; Zhu, B. L.; Luo, Z. B.; Miao, H. Z.

1996-08-01

316

Primary AL Amyloidosis  

MedlinePLUS

... AL amyloidosis is a hematological disorder, associated with plasma cell dyscrasia that means an abnormal condition of ... fibrils, formed by an errant (monoclonal) group of plasma cells in the bone marrow, consist of abnormal ...

317

Malnutrition in ALS  

MedlinePLUS

... weakened tongue can make it difficult to swallow. Anorexia and depression may also contribute to the patient’s ... difficulty swallowing and/or breathing, constipation, pressure sores, anorexia, fatigue, spasms and confusion. ALS patients particularly susceptible ...

318

Advanced aerospace Al alloys  

Microsoft Academic Search

SiC particulate or whisker-reinforced aluminum alloys are very attractive for applications requiring high stiffness coupled with a comparatively light weight. The dispersion strengthened Al alloys produced through the rapid solidification processing\\/powder metallurgy route demonstrate superior elevated temperature strength and microstructural stability, extending the useful service temperature of Al alloys to 350 C. However, low ductility and poor fracture toughness levels

K. S. Ravichandran; E. S. Dwarakadasa

1987-01-01

319

Thermally Nitrided Stainless Steels for Polymer Electrolyte Membrane Fuel Cell Bipolar Plates: Part 2: Beneficial Modification of Passive Layer on AISI446  

SciTech Connect

Thermal nitridation of AISI446 mod-1 superferritic stainless steel for 24 h at 1100 C resulted in an adherent, inward growing surface layer based on (Cr, Fe){sub 2}N{sub 1-x} (x = 0--0.5). The layer was not continuous, and although it resulted in low interfacial contact resistance (ICR) and good corrosion resistance under simulated polymer electrolyte membrane fuel cell (PEMFC) cathodic conditions; poor corrosion resistance was observed under simulated anodic conditions. Nitridation for 2 h at 1100 C resulted in little nitrogen uptake and a tinted surface. Analysis by SEM, XPS, and AES suggested a complex heterogeneous modification of the native passive oxide film by nitrogen rather than the desired microns-thick exclusive Cr-rich nitride layer. Surprisingly, this modification resulted in both good corrosion resistance under simulated cathodic and anodic conditions and low ICR, well over an order of magnitude lower than the untreated alloy. Further, little increase in ICR was observed under passivating polarization conditions. The potential of this phenomenon for PEMFC bipolar plates is discussed.

Wang, Heli [National Renewable Energy Laboratory (NREL); Brady, Michael P [ORNL; More, Karren Leslie [ORNL; Meyer III, Harry M [ORNL; Turner, John [National Renewable Energy Laboratory (NREL)

2004-01-01

320

The effect of gas mixture of post-oxidation on structure and corrosion behavior of plasma nitrided AISI 316 stainless steel  

NASA Astrophysics Data System (ADS)

In this research, microstructure and corrosion properties of plasma nitriding and post-oxidation treated AISI 316 austenitic stainless steel have been studied. The plasma nitriding treatment was carried out at 450 °C for 5 h in a D.C. plasma setup with a gas mixture of 25% N2-75% H2 followed by post-oxidation in gas mixtures of O2/H2: 1/3, 1/5, 1/9 and 1/12 for 30 min. The treated samples were characterized by SEM, XRD and roughness testing. Potentiodynamic and cyclic polarization tests were also employed to evaluate the corrosion resistance of the samples. The results showed that plasma nitriding treatment decreases corrosion resistance of the steel substrate. However, post-oxidizing treatment improves both uniform and pitting corrosion resistances of the nitrided specimens. This effect was most pronounced by post-oxidizing at lower O2/H2 ratios due to the development of magnetite as a more dense oxide phase over the modified layer.

Karimzadeh, N.; Moghaddam, E. G.; Mirjani, M.; Raeissi, K.

2013-10-01

321

Finite Element Modelling of the effect of tool rake angle on tool temperature and cutting force during high speed machining of AISI 4340 steel  

NASA Astrophysics Data System (ADS)

In this paper, a Finite Element Method (FEM) based on the ABAQUS explicit software which involves Johnson-Cook material model was used to simulate cutting force and tool temperature during high speed machining (HSM) of AISI 4340 steel. In this simulation work, a tool rake angle ranging from 0° to 20° and a range of cutting speeds between 300 to 550 m/min was investigated. The purpose of this simulation analysis was to find optimum tool rake angle where cutting force is smallest as well as tool temperature is lowest during high speed machining. It was found that cutting forces to have a decreasing trend as rake angle increased to positive direction. The optimum rake angle observed between 10° and 18° due to decrease of cutting force as 20% for all simulated cutting speeds. In addition, increasing cutting tool rake angle over its optimum value had negative influence on tool's performance and led to an increase in cutting temperature. The results give a better understanding and recognition of the cutting tool design for high speed machining processes.

Sulaiman, S.; Roshan, A.; Ariffin, M. K. A.

2013-12-01

322

In-situ measurements of the oxidation of AISI 316L(NG) and its constituents (Fe,Cr, Ni) in ultra-supercritical water  

SciTech Connect

Several new nuclear reactor designs utilizing supercritical water as coolant are currently being developed. In the European concept the design pressure is 25 MPa and reactor inlet/outlet temperatures 290 deg C/520 deg C. While benefits include better coolant thermal conductivity, increase in efficiency and simpler overall design, many material related questions need to be solved such as oxidation and radiation resistance with simultaneous need to maintain creep strength. This calls for the development of in-situ monitoring methods for the material/environment combination in question. In the present paper, in-situ electrical and electrochemical measurements during oxidation of AISI 316L(NG) and its pure metal constituents (Fe,Cr and Ni) in ultra-supercritical water (500-700 deg C, 30 MPa) have been reproducibly obtained. The oxidation kinetics was followed using the contact electric resistance (CER) and contact electric impedance (CEI) techniques. First attempts have been made to correlate properties of the resulting oxides with the corresponding weight gain data. In addition, impedance spectra of the Ni-Ni contact during oxidation have been reproducibly measured at 500 and 600 deg C. They could be quantitatively interpreted using general considerations of the corrosion process and the Mixed-Conduction Model for oxide films. Preliminary estimates of the diffusion coefficients of principal ionic and electronic current carriers have been obtained and their relevance with respect to available data on Ni oxidation is discussed. (authors)

Betova, Iva [Institute of Electrochemistry and Energy Systems, Bulgarian Academy of Science, 1113 Sofia (Bulgaria); Bojinov, Martin [Department of Physical Chemistry, University of Chemical Technology and Metallurgy, 1756 Sofia (Bulgaria); Kinnunen, Petri; Lehtovuori, Viivi; Peltonen, Seppo; Penttila, Sami; Saario, Timo [VTT Materials and Building, Technical Research Centre of Finland, P.O.Box 1000, FIN-02044 VTT, Espoo (Finland)

2006-07-01

323

Role of environmental variables on the stress corrosion cracking of sensitized AISI type 304 stainless steel (SS304) in thiosulfate solutions  

NASA Astrophysics Data System (ADS)

The stress corrosion cracking (SCC) behavior of sensitized AISI type 304 stainless steel (SS304) has been studied in dilute thiosulfate solutions as a function of thiosulfate concentrations and applied potentials. The susceptibility to SCC was observed to increase with thiosulfate concentrations and applied potentials. The addition of boric acid produced the reverse effect. A critical potential was found to exist, below which no SCC took place. Potential fluctuations, as recorded in the tests under open circuit conditions, appeared to be correlated with crack initiation and propagation during SCC. Current fluctuations observed in the controlled potential tests also gave indications of crack nucleation; however, at higher applied potentials such fluctuations were absent. The formation and presence of martensite in the specimens seemed to have a minor role in the overall SCC process. The aggressiveness of the thiosulfate concentration was also an important factor in determining the degree of susceptibility to SCC. The results obtained in the slow strain rate tests under open circuit as well as under potential-controlled conditions suggested a film ruptureanodic dissolution type of mechanism operative during SCC of sensitized SS304 in thiosulfate solutions.

Roychowdhury, S.; Ghosal, S. K.; de, P. K.

2004-10-01

324

Effect of Welding Current and Time on the Microstructure, Mechanical Characterizations, and Fracture Studies of Resistance Spot Welding Joints of AISI 316L Austenitic Stainless Steel  

NASA Astrophysics Data System (ADS)

This article aims at investigating the effect of welding parameters, namely, welding current and welding time, on resistance spot welding (RSW) of the AISI 316L austenitic stainless steel sheets. The influence of welding current and welding time on the weld properties including the weld nugget diameter or fusion zone, tensile-shear load-bearing capacity of welded materials, failure modes, energy absorption, and microstructure of welded nuggets was precisely considered. Microstructural studies and mechanical properties showed that the region between interfacial to pullout mode transition and expulsion limit is defined as the optimum welding condition. Electron microscopic studies indicated different types of delta ferrite in welded nuggets including skeletal, acicular, and lathy delta ferrite morphologies as a result of nonequilibrium phases, which can be attributed to a fast cooling rate in the RSW process. These morphologies were explained based on Shaeffler, WRC-1992, and pseudo-binary phase diagrams. The optimum microstructure and mechanical properties were achieved with 8-kA welding current and 4-cycle welding time in which maximum tensile-shear load-bearing capacity or peak load of the welded materials was obtained at 8070 N, and the failure mode took place as button pullout with tearing from the base metal. Finally, fracture surface studies indicated that elongated dimples appeared on the surface as a result of ductile fracture in the sample welded in the optimum welding condition.

Kianersi, Danial; Mostafaei, Amir; Mohammadi, Javad

2014-09-01

325

Performance of NiCrAlY Coatings Deposited by Oxyfuel Thermal Spraying in High Temperature Chlorine Environment  

NASA Astrophysics Data System (ADS)

A microcrystalline Ni-22Cr-10Al-1Y (wt.%) coating was deposited on AISI 304 stainless steel by the oxyfuel thermal spray technique. The deposited coating was subjected to heat treatment to improve the microstructure characteristics and its corresponding high-temperature properties. The isothermal high-temperature corrosion behavior at 650 and 700 °C in synthetic air and in the presence of 1% Cl2 was investigated using thermogravimetric analysis, x-ray diffraction, and scanning electron microscopy with energy-dispersive x-ray spectroscopy. The results indicated that the deposited NiCrAlY coating possessed acceptable oxidation-corrosion resistance at 650 °C owing to the formation of extensive amounts of the protective oxide of Cr2O3; NiO and a lesser amount of a Cr1.12 Ni2,88 metallic phase are also formed. At 700 °C, the coating lost its protective characteristic because of the excessive consumption of thermodynamically stable phases by oxidation-chlorination process. In this case, the steel base and the coating were attacked by chlorine during the exposure time; the mass gain of the NiCrAlY coating was slightly higher and provided only a limited protection up to 11 h; thereafter, breakdown of the layer of oxides occurred and this is attributed to the formation of non-protective oxides mainly ?-Fe2O3 and Fe21.33O32 and the depletion of chromium.

Habib, K. A.; Damra, M. S.; Carpio, J. J.; Cervera, I.; Saura, J. J.

2014-10-01

326

ALS superbend magnet performance  

SciTech Connect

The Lawrence Berkeley National Laboratory has been engaged in the design, construction and testing of four superconducting dipoles (Superbends) that are installed in three arcs of the Advanced Light Source (ALS), with the fourth magnet as a spare. This represents a major upgrade to the ALS providing an enhanced flux and brightness at photon energies above 10 keV. In preparation for installation, an extensive set of tests and measurements have been conducted to characterize the magnetic and cryogenic performance of the Superbends and to fiducialize them for accurate placement in the ALS storage ring. The magnets are currently installed, and the storage ring is undergoing final commissioning. This paper will present the results of magnetic and cryogenic testing.

Marks, Steve; Zbasnik, John; Byrne, Warren; Calais, Dennis; Chin, Michael; DeMarco, Richard; Fahmie, Michael; Geyer, Alan; Krupnick, Jim; Ottens, Fred; Paterson, James A.; Pipersky, Paul; Robin, David S.; Schlueter, RossD.; Steier, Christoph; Wandesforde, Alan

2001-12-10

327

Rapidly solidified NiAl and FeAl  

NASA Technical Reports Server (NTRS)

Melt spinning was used to produce rapidly solidified ribbons of the B2 intermetallics NiAl and FeAl. Both Fe-40Al and Fe-45Al possessed some bend ductility in the as spun condition. The bend ductility of Fe-40Al, Fe-45Al, and equiatomic NiAl increased with subsequent heat treatment. Heat treatment at approximately 0.85 T (sub m) resulted in significant grain growth in equiatomic FeAl and in all the NiAl compositions. Low bend ductility in both FeAl and NiAl generally coincided with intergranular failure, while increased bend ductility was characterized by increasing amounts of transgranular cleavage fracture.

Gaydosh, D. J.; Crimp, M. A.

1984-01-01

328

The effect of substrate bias voltages on impact resistance of CrAlN coatings deposited by modified ion beam enhanced magnetron sputtering  

NASA Astrophysics Data System (ADS)

CrAlN coatings were deposited on silicon and AISI H13 steel substrates using a modified ion beam enhanced magnetron sputtering system. The effect of substrate negative bias voltages on the impact property of the CrAlN coatings was studied. The X-ray diffraction (XRD) data show that all CrAlN coatings were crystallized in the cubic NaCl B1 structure, with the (1 1 1), (2 0 0) (2 2 0) and (2 2 2) diffraction peaks observed. Two-dimensional surface morphologies of CrAlN coatings were investigated by atomic force microscope (AFM). The results show that with increasing substrate bias voltage the coatings became more compact and denser, and the microhardness and fracture toughness of the coatings increased correspondingly. In the dynamic impact resistance tests, the CrAlN coatings displayed better impact resistance with the increase of bias voltage, due to the reduced emergence and propagation of the cracks in coatings with a very dense structure and the increase of hardness and fracture toughness in coatings.

Chunyan, Yu; Linhai, Tian; Yinghui, Wei; Shebin, Wang; Tianbao, Li; Bingshe, Xu

2009-01-01

329

Al Qaeda Training Manual  

NSDL National Science Digital Library

The first resource is a US Department of Justice release of portions of an English translation of the Al Qaeda training manual located by police in Manchester, England during a search of an Al Qaeda member's home. The manual was found in a computer file described as "the military series" related to the "Declaration of Jihad." The cover and excerpts from the 12 chapters can be viewed as a .pdf file. Content of the text includes religious commentary, organizational tactics, guidelines for member selection, techniques for spying, and security measures. The DOJ does not provide the entire document because it does not want to encourage terrorism.

2001-01-01

330

Al Shanker Remembers.  

ERIC Educational Resources Information Center

In a 1996 interview shortly before his death, Al Shanker, longtime president of the American Federation of Teachers, discussed such topics as: his own educational experiences; how he learned about political fighting in the Boy Scouts; the appeal of socialism; multinational corporations and the nation state; teaching tough students; and John Dewey…

American Educator, 2000

2000-01-01

331

Smith et al Supporting Information  

E-print Network

Smith et al 1 Supporting Information for Smith et al. 2006, PLoS Computational Biology 2:e161-hyperpallium apicale; HF-hippocampal formation, and M-mesopallium. #12;Smith et al 2 FigureS2,nolinkswerefoundbetweenelectrodesindifferentbirds,andnolinkswerefoundintothesoundstimulusvariable. CombinedAnalysisofAllBirds'ElectrodesPlusSound #12;Smith et al 3 Analysis of Data from Subsections

Jarvis, Erich D.

332

Characterization and optimization of pulse electrodeposition of Ni/nano-Al2O3 composite coatings  

NASA Astrophysics Data System (ADS)

Nickel/nano-Al2O3 composite coatings produced by the pulse electrodeposition method and the influence of pulse parameters, i.e., pulse frequency, duty cycle, and current density on the microstructure, hardness, and corrosion resistance, were critically investigated on an AISI 1018 mild steel specimen electroplated in a Watt's type bath. The experiments were carried out with different combinations of pulse parameters using Taguchi's L27 orthogonal array, and 27 trials were conducted to study the effect of pulse parameters in view to maximize the hardness of the specimen. The assessment results clearly reveal that the specimen exhibits the maximum hardness at the pulse frequency of 20 Hz, duty cycle of 30%, and peak current density of 0.4 A/cm2, which are designated as the optimal parameters herein. Furthermore, the influences of those optimized pulse parameters over the microstructure and corrosion resistance were investigated, and some conclusions were drawn. Also, from the ANOVA examination, it is clear that duty cycle is predominant in affecting the hardness, while current density has relatively low impact.

Jegan, A.; Venkatesan, R.

2013-05-01

333

/Al-Si Composite  

NASA Astrophysics Data System (ADS)

The cyclic fatigue characteristics of spray-deposited SiCp/Al-Si composite were investigated in comparison with the unreinforced Al-Si alloy. The as-extruded specimens were cyclically deformed with fully reversed loading under a range of total strain amplitudes. The results show that the cyclic response characteristics for the reinforced and unreinforced materials are similar to each other. Both the composite and matrix alloys display cyclic hardening under total strain amplitude of 0.35-0.5%. Otherwise, the composite exhibits higher degree of strain hardening than that of the matrix alloy. Dislocation substructure developed during cyclic deformation was analyzed using transmission electron microscopy. The discrepancy between dislocation substructures obtained from processing compared to its development during cyclic strain loading is thought to give rise to the observed cyclic stress response behavior. Fractographic analysis shows that particle/matrix debonding and particle cracking are the main mechanisms of failure in the SiC particle-reinforced composite.

Li, Wei; Chen, Jian; Hu, Yongle; Cong, Li; Sun, YouPing; Yang, JiMing

2014-08-01

334

Al Parker: American Illustrator  

NSDL National Science Digital Library

This tribute to Al Parker, the noted magazine illustrator and artist, was fashioned from extensive holdings at the Washington University Library in St. Louis. Known as "The Dean of Illustrators," Al Parker attended school at the St. Louis School of Fine Arts at Washington University and went on to become of the most prolific and important American illustrators of the twentieth century. Parker was best-known for his modernist deployment of line, patterning, and bold, flat colors, which helped shape the general "look" of the period from the 1930s to the 1960s. Using short clips of Parker's original illustrations and drawings, this exhibit offers a glimpse into his work and contributions to the medium. Of particular interest is the section devoted to Parker's famous "Mother-Daughter" covers for the Ladies Home Journal, which began in 1939 and ran for 17 years.

2001-01-01

335

ALS Project Management Manual  

SciTech Connect

This manual has been prepared to help establish a consistent baseline of management practices across all ALS projects. It describes the initial process of planning a project, with a specific focus on the production of a formal project plan. We feel that the primary weakness in ALS project management efforts to date stems from a failure to appreciate the importance of ''up-front'' project planning. In this document, we present a guide (with examples) to preparing the documents necessary to properly plan, monitor, and control a project's activities. While following the manual will certainly not guarantee good project management, failure to address the issues we raise will dramatically reduce the chance of success. Here we define success as meeting the technical goals on schedule and within the prescribed budget.

Krupnick, Jim; Harkins, Joe

2000-05-01

336

Partnerwahl als konsensuelle Entscheidung  

Microsoft Academic Search

Zusammenfassung  Die vorliegende Studie setzt unsere Analysen der Kontaktierungsprozesse im Online-Dating (KZfSS 2\\/2009) fort. Da Paarbeziehungen\\u000a auf einer konsensuellen Entscheidung für eine gemeinsame Beziehung beruhen, widmet sich der vorliegende Beitrag der Frage,\\u000a wie Männer und Frauen auf Erstkontaktversuche reagieren. Die Datenstruktur von Online-Dating-Börsen bietet eine einzigartige\\u000a Chance, soziologisch im Detail zu rekonstruieren, wie Paarbeziehungen als konsensuelle Wahlhandlung nach und nach entstehen.

Florian Schulz; Jan Skopek; Hans-Peter Blossfeld

2010-01-01

337

Abu Musab Al Suri: Architect of the New Al Qaeda  

Microsoft Academic Search

Drawing on new sources, the authors argue that Abu Musab al Suri (real name Mustafa Setmariam Nasar), now in U.S. custody, is the principle architect of Al Qaeda's post–9\\/11 structure and strategy. His vision, which predated 9\\/11, of transforming Al Qaeda from a vulnerable hierarchical organization into a resilient decentralized movement, was largely the formula Al Qaeda adopted after the

Paul Cruickshank; Mohannad Hage Ali

2007-01-01

338

THARYAN ET AL'S REPLY  

E-print Network

The comment by Dr. Andrade raising the possibility of missed subclinical fractures as a complication of unmodified ECT in some patients in our study is valid as patients were investigated radiographically only on clinical indication. Ihe aim of the study, however, was to survey the frequency of clinically significant physical complications. Crush fractures of the vertebrae, whether overt or covert, caused during unmodified electrconvulsivc therapy are clinically of little significance. They were frequently overlooked in the early years after the introduction of convulsive therapy as they were often painless or only caused transient pain that was often mistaken for myalgia. There were also no sequelae and no treatment was required (Kiloh et al,

unknown authors

339

Al Jazirah, Sudan  

NASA Technical Reports Server (NTRS)

Al Jazirah (also Gezira) is one of the 26 states of Sudan. The state lies between the Blue Nile and the White Nile in the east-central region of the country. It is a well populated area suitable for agriculture. The area was at the southern end of Nubia and little is known about its ancient history and only limited archaeological work has been conducted in this area. The region has benefited from the Gezira Scheme, a program to foster cotton farming begun in 1925. At that time the Sennar Dam and numerous irrigation canals were built. Al Jazirah became the Sudan's major agricultural region with more than 2.5 million acres (10,000 km) under cultivation. The initial development project was semi-private, but the government nationalized it in 1950. Cotton production increased in the 1970s but by the 1990s increased wheat production has supplanted a third of the land formerly seeded with cotton.

The image was acquired December 25, 2006, covers an area of 56 x 36.4 km, and is located near 14.5 degrees north latitude, 33.1 degrees east longitude.

The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

2008-01-01

340

Submicron Nb-Al/Al oxide-Nb tunnel junctions sandwiched between Al films  

NASA Astrophysics Data System (ADS)

A process has been developed to embed Nb-Al/Al oxide-Nb junctions in planar structures of Al films. The submicron junctions are defined by photoresist lines. Motivation for this effort is a possible application of Nb junctions confined between normal conducting Al films as mixers above 700 GHz where Nb films loose their superconductive properties and tuning circuits made out of Nb therefore exhibit losses. First mixer results at 816 GHz are presented.

Maier, D.; Rothermel, H.; Gundlach, K. H.; Zimmermann, R.

1996-02-01

341

Microstructure and Mechanical Properties of HoAl-Al2O3\\/Ti Al Composite  

Microsoft Academic Search

HoAl-Al2O3\\/TiAl composites were fabricated by in-situ reaction synthesis using Al, Ti, TiO2 and Ho2O3 powders as raw materials. The effects of Ho2O3 content on the microstructure and mechanical properties of the composites were investigated. The phase constitution and microstructure of the composites were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicate that the ultimate phases

Hongya Xu; Fen Wang; Jianfeng Zhu; Yuxing Xie

2011-01-01

342

Descenso al Infierno de VenusDescenso al Infierno de VenusDescenso al Infierno de VenusDescenso al Infierno de Venus Manuel Alfonseca  

E-print Network

Descenso al Infierno de VenusDescenso al Infierno de VenusDescenso al Infierno de VenusDescenso al Infierno de Venus Manuel Alfonseca #12;Manuel Alfonseca 2 #12;Descenso al infierno de Venus 3 Descenso al infierno de Venus Manuel Alfonseca RESERVADOS TODOS LOS DERECHOS. Salvo usos razonables destinados al

Alfonseca, Manuel

343

Multiaxial fatigue criteria for AISI 304 and 2-1/4 Cr-1 Mo steel at 538/sup 0/C with applications to strain-range partitioning and linear summation of creep and fatigue damage  

SciTech Connect

An improved multiaxial fatigue failure criterion was developed based on the results of combined axial-torsional strain cycling tests of AISI 304 and 2-1/4 Cr-1 Mo steel conducted at 538/sup 0/C (1000/sup 0/F). The formulation of this criterion involves the shear and normal components of inelastic strain range on the planes of maximum inelastic shear strain range. Optimum values of certain parameters contained in the formulation were obtained for each material by the method of least squares. The ability of this criterion to correlate the test results was compared with that of the usual (Mises) equivalent inelastic strain range criterion. An improved definition of equivalent inelastic strain range resulting from these considerations was used to generalize the theory of Strain Range Partitioning to multiaxial stress-strain conditions and was also applied to the linear summation of creep and fatigue damage.

Blass, J.J.

1982-01-01

344

Alexandria (Al Iskandariya), Egypt  

NASA Technical Reports Server (NTRS)

This image of Alexandria was taken by astronauts on board the International Space Station in December 2000 using an Electronic Still Camera. A wider-angle view (STS088-739-90) taken from the Space Shuttle in December 1998 is available for context. Alexandria (Al Iskandariya) occupies a T-shaped peninsula and strip of land separating the Mediterranean from Lake Mariout. Originally the town was built upon a mole (stone breakwater) called Heptastadium, which joined the island of Pharos (see referenced website, below) to the mainland. Since then sedimentary deposits have widened the mole. Since 1905, when the 370,000 Alexandrians lived in an area of about 4 sq km between the two harbors, the city (population 4 million; see referenced website, below) has grown beyond its medieval walls and now occupies an area of about 300 sq km. The Mahmudiya Canal, connecting Alexandria with the Nile, runs to the south of the city and, by a series of locks, enters the harbor of the principal port of Egypt (note ships). The reddish and ochre polygons west of Lake Mariout are salt-evaporation, chemical-storage, and water-treatment ponds within the coastal lagoon. Reference Youssef Halim and Fatma Abou Shouk, 2000, Human impacts on Alexandria's marine environment: UNESCO, Coastal Regions and Small Islands Unit (CSI), Coastal Management Sourcebooks 2 (accessed December 20, 2000) Additional photographs taken by astronauts can be viewed at NASA-JSC's Gateway to Astronaut Photography of Earth. Image ISS001-ESC-5025 provided by the Earth Sciences and Image Analysis Laboratory, Johnson Space Center.

2002-01-01

345

A progress report on the use of electrochemical noise to investigate the effects of zebra mussel attachment on the corrosion resistance of AISI Type 304 stainless steel and carbon steel in lake water  

SciTech Connect

The electrochemical noise technique was used to determine the effect of zebra mussel settlement on the corrosion performance of AISI Type 304 stainless steel and carbon steel (ASTM A53 Grade B). These materials represent alloys commonly used for handling untreated Great Lakes water at Ontario Hydro`s power generating plants. This work was motivated by a concern that zebra mussel settlement will lead to accelerated attack of these materials as a result of the establishment of stable crevice conditions and the growth of corrosion influencing anaerobic sulfate-reducing bacteria (SRB). Corrosion monitoring was carried out in a field test facility that uses the same untreated Lake Erie water as Ontario Hydro`s Nanticoke Thermal Generating Station. The test program extended from May through December 1993. During this period, a number of electrochemical parameters were monitored simultaneously, including coupling current, electrochemical potential noise (EPN), electrochemical current noise (ECN), degree of localization (DoL), and resistance noise (R{sub n}). Differences were observed in the performance of the control samples and the samples to which mussels were attached. The results for the AISI Type 304 stainless steel suggested that over the period monitored, mussel attachment reduced corrosion activity. Similarly, signals from carbon steel, samples exposed to mussels, although initially displaying relatively high corrosion rates, exhibited less corrosion damage than did control samples over the longer term. The reason for this difference in performance is not known but is considered to have resulted from a change in the surface environment as a result of mussel attachment, which appeared to diminish corrosion. One possible explanation may be the generation of inhibitive species by the mussels.

Brennenstuhl, A.M.; Sim, B. [Ontario Hydro Technologies, Toronto, Ontario (Canada); Claudi, R. [Ontario Hydro, Toronto, Ontario (Canada). Environmental Dept.

1996-12-31

346

Al Qaeda's Scorecard: A Progress Report on Al Qaeda's Objectives  

Microsoft Academic Search

Terrorism scholars are divided over whether terrorism is an effective tactic. Disagreement derives from the fact that the objectives of terrorist groups are often highly contested. Nowhere is this clearer than in contemporary statements on Al Qaeda. This article explores the most common interpretations for why Al Qaeda attacked the United States on 11 September 2001, and then analyzes their

Max Abrahms

2006-01-01

347

Al Qaeda: Ideology and action  

Microsoft Academic Search

Serious threats to global order are said to emanate from Al Qaeda, exemplified by bombings and multiple deaths in, inter alia, Bali, Dar es Salaam, Istanbul, Nairobi, New York and Madrid. These outrages raise the question about the ideological assumptions and goals of Al Qaeda – given that the majority of the dead were not Jews or Christians, but Muslims. What

JEFFREY HAYNES

2005-01-01

348

How al Qaeda lost Iraq  

Microsoft Academic Search

Al Qaeda in Iraq (AQI) has suffered a grave setback in the context of its ongoing campaign there. Since late 2006 Sunni tribal militias working in conjunction with Coalition forces have decimated AQI's ranks, and the organisation has been largely expelled from its former sanctuaries in western Iraq. This article seeks to explain the causes of al Qaeda's defeat with

Andrew Phillips

2009-01-01

349

Thin Films Using Al Doping  

NASA Astrophysics Data System (ADS)

We have studied the influence of Al doping on the microstructural, optical, and electrical properties of spray-deposited WO3 thin films. XRD analyses confirm that all the films are of polycrystalline WO3 in nature, possessing monoclinic structure. EDX profiles of the Al-doped films show aluminum peaks implying incorporation of Al ions into WO3 lattice. On Al doping, the average crystallite size decreases due to increase in the density of nucleation centers at the time of film growth. The observed variation in the lattice parameter values on Al doping is attributed to the incorporation of Al ions into WO3 lattice. Enhancement in the direct optical band gap compared to the undoped film has been observed on Al doping due to decrease in the width of allowed energy states near the conduction band edge. The refractive indices of the films follow the Cauchy relation of normal dispersion. Electrical resistivity compared to the undoped film has been found to increase on Al doping.

Mukherjee, Ramnayan; Prajapati, C. S.; Sahay, P. P.

2014-09-01

350

Effects of Si content on microstructure and mechanical properties of TiAlN/Si3N4-Cu nanocomposite coatings  

NASA Astrophysics Data System (ADS)

TiAlN/Si3N4-Cu nanocomposite coatings of various Si content (0-5.09 at.%) were deposited on AISI-304 stainless steel by DC reactive magnetron sputtering technique. The chemical composition, microstructure, mechanical and tribological properties of these coatings were systematically investigated by means of X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), nanoindentation tester, a home-made indentation system, a scratch tester and a wear tester. Results indicated that with increasing Si content in these coatings, a reduction of grain size and surface roughness, a transformation of the (1 1 1) preferred orientation was detected by XRD and FESEM. Furthermore the hardness of these coatings increase from 9.672 GPa to 18.628 GPa, and the elastic modulus reveal the rising trend that increase from 224.654 GPa to 251.933 GPa. However, the elastic modulus of TiAlN/Si3N4-Cu coating containing 3.39 at.% Si content dropped rapidly and changed to about 180.775 GPa. The H3/E2 ratio is proportional to the film resistance to plastic deformation. The H3/E2 ratio of the TiAlN/Si3N4-Cu coating containing 3.39 at.% Si content possess of the maximum of 0.11 GPa, and the indentation test indicate that few and fine cracks were observed from its indentation morphologies. The growth pattern of cracks is mainly bending growing. The present results show that the best toughness is obtained for TiAlN/Si3N4-Cu nanocomposite coating containing 3.39 at.% Si content. In addition, the TiAlN/Si3N4-Cu coating containing 3.39 at.% Si content also has good adhesion property and superior wear resistance, and the wear mechanism is mainly adhesion wear.

Feng, Changjie; Hu, Shuilian; Jiang, Yuanfei; Wu, Namei; Li, Mingsheng; Xin, Li; Zhu, Shenglong; Wang, Fuhui

2014-11-01

351

Allegato "B" DOMANDA DI PARTECIPAZIONE AL CONCORSO DI AMMISSIONE AL  

E-print Network

IN ROBOTICA, NEUROSCIENZE, NANOTECNOLOGIE E SCOPERTA FARMACI IN COLLABORAZIONE CON LA FONDAZIONE IIT Si prega'ammissione al Corso di Dottorato di Ricerca in Robotica, Neuroscienze, Nanotecnologie e Scoperta Farmaci

Sandini, Giulio

352

[ALS and excitatory amino acid].  

PubMed

AMPA receptor, one of ionotropic glutamate receptors, has been proposed to play a critical role to initiate the neuronal death cascade in motor neuron disease by an increase of Ca2+ influx. There are at least two mechanisms to increase Ca2+ influx through Ca2+-permiable AMPA receptor: a decrease of RNA editing efficacy at the GluR2 Q/R site and a decrease of GluR2 level relative to AMPA receptor subunits. Deficient RNA editing of the AMPA receptor subunit GluR2 at the Q/R site is a primary cause of neuronal death and recently has been reported to be a tightly linked etiological cause of motor neuron death in sporadic amyotrophic lateral sclerosis (ALS). On the other hand, relative low GluR2 level among AMPA receptor subunits seems to increase Ca2+ permeability of motor neurons in familial ALS (ALS1) linked to mutated cupper-zinc superoxide dismutase gene (SOD1). AMPA receptor-mediated mechanism does not seem to play any role in death of motor neurons in X-linked spinal and bulbar muscular atrophy (SBMA). From the molecular pathomechanism of sporadic ALS and ALS1, drugs which increase RNA editing efficacy at the GluR2 Q/R site could be a potent therapy for sporadic ALS, while AMPA receptor antagonists could prevent deterioration from ALS1. PMID:17969352

Aizawa, Hitoshi; Kwak, Shin

2007-10-01

353

Synthesis, processing and characterization of NiAl-AlN-Al(2)O(3) composites  

NASA Astrophysics Data System (ADS)

A hybrid composite based on nickel aluminide (NiAl) was developed, which contains both aluminum nitride (AlN) dispersoids and short alumina (Alsb2Osb3) fibers, with the strategy being the combination of the two different strengthening mechanisms, one microscopic and the other macroscopic, to provide a synergistic improvement in the mechanical properties. The AlN dispersion strengthened NiAl was synthesized by mechanical alloying of nickel and aluminum elemental powders in a nitrogen atmosphere and the alumina fibers were added during consolidation. The microstructure of the NiAl-(AlN)sb{Dispersion}-(Alsb2Osb3)sb{Fiber} composites showed a fine grain sized, near-stoichiometric NiAl matrix, submicron size AlN particles and randomly oriented Alsb2Osb3 fibers dispersed homogeneously in the matrix. The thermal residual stresses in the composites were measured at room temperature as well as at high temperatures using neutron diffraction and Rietveld refinement. The residual stresses in the as-processed composites were tensile in the NiAl matrix and compressive in the AlN and Alsb2Osb3 reinforcements. Upon heating these stresses relaxed at temperatures that are lower than the processing temperature due to the creep in the matrix. A simple finite element analysis was used to estimate the residual stress in the composites and showed reasonable agreement with the experimental results. The compressive strength of these composites was characterized both at 300K and 1300K and showed a significant strengthening compared with the base material at both temperatures. The relationship between the microstructure, residual stress and the mechanical properties was studied and the strengthening mechanisms were identified.

Choo, Hahn

354

diez cosas a hacer:Quieres ayudar a parar el Calentamiento Global? Haz estas 10 simples cosas para hacer y cunto dixido de carbono ahorrars.  

E-print Network

de CO2 de la atmósfera. Usa menos agua caliente Se requiere mucha energía para calentar agua. Usa menos agua instalando una ducha de 1.5 galones por minuto (150 libras de CO2 ahorrado anual) y usa agua de CO2 al año bajando 2 grados el calentador de agua y el aire acondicionado. Si usas el abanico

Cruz-Pol, Sandra L.

355

Modeling of the ALS linac  

SciTech Connect

The ALS injector linac is used for the Beam Test Facility (BTF) and the Damping Experiments when it is available in between the ALS filings. These experiments usually require higher quality beams and a better characterization than is normally required for ALS operations. This paper focuses on the beam emittance, energy tilt, and especially the longitudinal variation of the beam parameters. For instance, the authors want to avoid longitudinal variations at the low beta section of the BTF. On the other hand, a large energy tilt is required for post-acceleration compression of the bunch using an alpha magnet. The PARMELA code was modified to calculate and display longitudinal variations of the emittance ellipse. Using the Microsoft Development Studio under Windows NT environment the code can handle a much larger number of particles than was previously possible.

Kim, C.H. [Lawrence Berkeley Lab., CA (United States). Advanced Light Source Center

1996-08-01

356

-and -Coordinated Al in AlC2 . A Combined  

E-print Network

/Al/Si composite target, respectively, with a pure helium carrier gas, and detected by a time-of-flight mass energies: 355 (3.496 eV) and 266 nm (4.661 eV). Photoelectron time-of-flight spectra were measured neutral species. The experiments were carried out with a magnetic- bottle time-of-flight PES apparatus

Simons, Jack

357

Triple A syndrome mimicking ALS.  

PubMed

We report a 22-year-old female who presented with distal muscular atrophy and weakness in all limbs for two years. Reflexes were symmetrically brisk and electrodiagnostic studies were consistent with upper and lower motor neuron involvement. A diagnosis of juvenile ALS was considered. However, surgery for achalasia in childhood and identification of alacrima and adrenal insufficiency suggested Triple A syndrome accompanied by neurological symptoms. Sequencing of the AAAS gene identified compound heterozygous mutations confirming the clinical diagnosis and demonstrating that Triple A syndrome can mimic juvenile ALS. PMID:18615337

Strauss, Maria; Koehler, Katrin; Krumbholz, Manuela; Huebner, Angela; Zierz, Stephan; Deschauer, Marcus

2008-10-01

358

A nuclear magnetic resonance probe of Fe-Al and Al20V2Eu intermetallics  

E-print Network

Al-rich Fe-Al systems (FeAl2, Fe2 Al5 and Fe4Al13) and Al20V2Eu have complicated structures with quasicrystal-like features making these materials potentially of interest for magnetic behavior. However, there is not much work on these materials...

Chi, Ji

2009-05-15

359

Dynamic Modeling of ALS Systems  

NASA Technical Reports Server (NTRS)

The purpose of dynamic modeling and simulation of Advanced Life Support (ALS) systems is to help design them. Static steady state systems analysis provides basic information and is necessary to guide dynamic modeling, but static analysis is not sufficient to design and compare systems. ALS systems must respond to external input variations and internal off-nominal behavior. Buffer sizing, resupply scheduling, failure response, and control system design are aspects of dynamic system design. We develop two dynamic mass flow models and use them in simulations to evaluate systems issues, optimize designs, and make system design trades. One model is of nitrogen leakage in the space station, the other is of a waste processor failure in a regenerative life support system. Most systems analyses are concerned with optimizing the cost/benefit of a system at its nominal steady-state operating point. ALS analysis must go beyond the static steady state to include dynamic system design. All life support systems exhibit behavior that varies over time. ALS systems must respond to equipment operating cycles, repair schedules, and occasional off-nominal behavior or malfunctions. Biological components, such as bioreactors, composters, and food plant growth chambers, usually have operating cycles or other complex time behavior. Buffer sizes, material stocks, and resupply rates determine dynamic system behavior and directly affect system mass and cost. Dynamic simulation is needed to avoid the extremes of costly over-design of buffers and material reserves or system failure due to insufficient buffers and lack of stored material.

Jones, Harry

2002-01-01

360

Al Qaeda: A Different Diagnosis  

Microsoft Academic Search

When doubt and confusion reign, when things are--or look--complicated, one should revert to fundamental questions. What is Al Qaeda? This is the question addressed by this article. But as a first step, and in a broader perspective, the real danger in the world today is defined.?

XAVIER RAUFER

2003-01-01

361

Phase equilibria between NiAl and RuAl in the Ni-Al-Ru system  

SciTech Connect

Phase equilibria between NiAl and RuAl in Ni-Al-Ru alloys were studied by means of light microscopy and scanning electron microscopy. The JEOL JSM-35CF instrument was used in the electron probe microanalyses. The results indicate that the miscibility gap between NiAl and RuAl extends up to the solidus. The lattice parameter mismatch between the coexisting solid solutions based on NiAl and RuAl at temperatures of 1273 K and above is less than 0.6 percent. 10 references.

Chakravorty, S.; West, D.R.F.

1985-11-01

362

Thermal conductance of a pressed Al-Al contact  

NASA Astrophysics Data System (ADS)

Thermal conductance of a screw-fastened joint between two blocks of Al-alloys has been measured. An AlMg4.5Mn-block, the end of which is cooled by liquid helium, constitutes the upper part of the sample and the contact is formed at the face surface of a cylindrical extension of that block onto which a cylinder, made of AlMgSi1, is pressed by means of a copper-nickel screw. Pressing of the contact was carried out at room temperature by applying a defined torque, M, to the fastening screw. Three samples of the same shape but with differently treated surfaces of contact (machined flat, electro-chemically polished, with gold plated contacts) were studied. The results showed that the machined flat surfaces yield the best contact and that the contact conductance (measured in the range 4.2 K to 1.8 K) of all samples increased with increasing torque. In addition to thermal measurements, a study of the electrical conductance would be very interesting to determine the different contributions of phonon and electron heat conduction by means of the Wiedemann-Franz law. The work is useful for the GIRL (German Infra-Red Laboratory) space experiment.

Wanner, M.

1981-01-01

363

Ab? al-usayn al-Bar? and his Transmission of Biblical Materials from Kit?b al-D?n wa-al-Dawla by Ibn Rabban al-abar?: The Evidence from Fakhr al-D?n al-R?z?'s Maf?t? al-ghayb  

Microsoft Academic Search

The authenticity of the Kit?b al-d?n wa-al-dawla by the Nestorian convert to Islam, Ab? al-asan ?Al? b. Sahl Rabban al-abar? (d. ca. 251\\/865), has been discussed since the publication of the text by A. Mingana in 1922\\/23. A comparison between the chapter of the Twelver Sh??? Sad?d al-D?n Mam?d b. ?Al? al-imma? al-R?z?'s (d. after 600\\/1204) Munqidh min al-taql?d discussing

Sabine Schmidtke

2009-01-01

364

Al in computer games: Survey and perspectives  

Microsoft Academic Search

Computer games have traditionally implemented empirical solutions to many Al problems and are now turning to more traditional Al algorithms. After introducing the role of Al in gameplay, we review the main techniques used in current computer games such as Finite-State Transition Networks, rule-based systems and search algorithms. We describe the implementation of Al in several commercial computer games, as

M. Cavazza

2000-01-01

365

Tunneling through Al/AlOx/Al junction: Analytical models and first-principles simulations  

NASA Astrophysics Data System (ADS)

Ultrathin AlOx layers are nowadays widely employed to make tunneling junctions and, as a common practice, experimental transport data are often rationalized in terms of analytical models invoking effective electronic and geometric properties of the oxide layer. In this paper we examine the reliability of such models by performing first-principles simulations of the transport properties of Al/AlOx/Al junctions. The band gap, effective mass, and interface width obtained from ground state density-functional calculations are used within a potential barrier model, known also as the Simmons model, and its predictions of the conductance are compared with first-principles results. We also propose an analytical expression for the conductance based on a tight-binding model of the interface oxide. We show that the success of the potential barrier model in fitting experimental transport measurements rests on its formal similarity with the tight binding model which, in contrast to the former, is directly related to the realistic electronic structure of the interface.

Zemanová Diešková, M.; Ferretti, A.; Bokes, P.

2013-05-01

366

Inhibition of Al-induced root elongation and enhancement of Al-induced peroxidase activity in Al-sensitive and Al-resistant barley cultivars are positively correlated  

Microsoft Academic Search

The quantitative changes in peroxidase activity and composition of anionic and cationic isoperoxidases were investigated in roots of two barley cultivars differing in Al resistance. Root growth of Al-resistant cv. Bavaria was in lesser extent reduced by Al treatment (23% after 24 h Al-treatment), whereas 40% reduction of the root growth was observed in Al-sensitive cv. Alfor. The strong root

Ladislav Tamás; Jana Huttová; Igor Mistrík

2003-01-01

367

Applied Kinesiology als funktionelle Neurologie  

Microsoft Academic Search

Die muskuläre Diagnostik und Therapie, die noch vor einigen Jahren als die Domäne der Physiotherapie angesehen wurde, hält\\u000a erfreulicherweise mehr und mehr Einzug in die ärztliche Manualtherapie. Und auch hier setzt sich das Bewußtsein durch, dass\\u000a Knochen von Muskeln bewegt werden und es nicht ausreicht, Gelenke zu manipulieren, sondern dass ebenso die sie bewegenden\\u000a Muskeln behandelt werden müssen. Oder, nach

H. Garten

2000-01-01

368

Al-Hadith Text Classifier  

Microsoft Academic Search

This study explore the implementation of a text classification method to classify the prophet Mohammed (PBUH) hadiths (sayings) using Sahih Al-Bukhari classification. The sayings explain the Holy Qur`an, which considered by Muslims to be the direct word of Allah. Present method adopts TF\\/IDF (Term Frequency-Inverse Document Frequency) which is used usually for text search. TF\\/IDF was used for term weighting,

Mohammed Naji Al-Kabi; Ghassan Kanaan; Riyad Al-Shalabi; Saja I. Al-Sinjilawi; Ronza S. Al-Mustafa

2005-01-01

369

Al-Hadith Text Classifier  

Microsoft Academic Search

This study explores the implementation of a text classification method to classify the prophet Mohammed (PBUB) hadiths (sayings) using Sahih Al-Bukhari classification. The sayings explain the Holy Qur'an, which considered by Muslims to be the direct word of Allah. Present method adopts TF\\/IDF (Term Frequency-Inverse Document Frequency) which is used usually for text search. TF\\/IDF was used for term weighting,

Mohammed Naji Al-Kabi

2005-01-01

370

Nucleants of Eutectic Silicon in Al-Si Hypoeutectic Alloys: ?-(Al, Fe, Si) or AlP Phase  

NASA Astrophysics Data System (ADS)

A thermodynamic description of the Al-Si-P-Fe quaternary system focused on Al-(Si)-rich alloys is developed. The solidification sequence in typical Al-7Si cast alloys is derived using thermodynamic calculations of the phase diagrams and solidification simulation under Scheil and constrained Scheil conditions. The previously claimed nucleation of eutectic silicon by ?-(Al,Fe,Si) particles is not possible because under all conditions, ?-(Al,Fe,Si) precipitates after (Si) in pertinent alloys. Variation of P in the ppm range is crucial because it changes the solidification sequence of AlP and (Si).

Liang, Song-Mao; Schmid-Fetzer, Rainer

2014-11-01

371

Nucleants of Eutectic Silicon in Al-Si Hypoeutectic Alloys: ?-(Al, Fe, Si) or AlP Phase  

NASA Astrophysics Data System (ADS)

A thermodynamic description of the Al-Si-P-Fe quaternary system focused on Al-(Si)-rich alloys is developed. The solidification sequence in typical Al-7Si cast alloys is derived using thermodynamic calculations of the phase diagrams and solidification simulation under Scheil and constrained Scheil conditions. The previously claimed nucleation of eutectic silicon by ?-(Al,Fe,Si) particles is not possible because under all conditions, ?-(Al,Fe,Si) precipitates after (Si) in pertinent alloys. Variation of P in the ppm range is crucial because it changes the solidification sequence of AlP and (Si).

Liang, Song-Mao; Schmid-Fetzer, Rainer

2014-09-01

372

The Collections - Dar al-Athar al-Islamiyyah  

NSDL National Science Digital Library

Regarded by experts as one of a handful of the most comprehensive collections of Islamic art in the world, the al-Sabah holdings in Kuwait feature 20,000 objects from geographically and chronologically diverse locations. Nine categories - Metals, Ceramics, Glass, Ivory & Wood, Jewelry & Hardstone, Numismatics, Rugs & Textiles, Manuscripts & Calligraphy, and Stone & Stucco - can be accessed from the collections page with the click of a mouse. Within each category, short essays contextualize the beautiful photographs of ancient, medieval, and modern Islamic art in a wide variety of mediums and styles.

373

Synthesis of AlN/Al Polycrystals along with Al Nanoparticles Using Thermal Plasma Route  

NASA Astrophysics Data System (ADS)

This paper for the first time reports the (200) oriented growth of hexagonal Aluminum nitride crystals during synthesis of aluminum nanoparticles in dc transferred arc thermal plasma reactor by gas phase condensation in nitrogen plasma. The structural and morphological study of as synthesized AlN crystal and aluminium nanoparticles was done by using the x-ray diffraction method, scanning electron microscopy and transmission electron microscopy.

Kanhe, Nilesh S.; Nawale, A. B.; Kulkarni, N. V.; Bhoraskar, S. V.; Mathe, V. L.; Das, A. K.

2011-07-01

374

Investigation of Wear Anisotropy in a Severely Deformed Al-Al3Ti Composite  

NASA Astrophysics Data System (ADS)

In the current investigation, Al-Al3Ti composite was processed by equal channel angular pressing (ECAP). ECAP was carried out using routes A and BC up to eight passes of deformation. It was observed that increasing the number of ECAP passes causes fragmentation of Al3Ti platelet particles and decreases their sizes compared to their original sizes in the undeformed Al-Al3Ti specimens. Moreover, the microstructure of route A-ECAPed Al-Al3Ti composite samples showed a strong alignment of the fragmented Al3Ti particles parallel to the pressing axis. On the other hand, ECAPed Al-Al3Ti alloy specimens by route BC have a relatively homogeneous distribution of Al3Ti particles. Because of the platelet Al3Ti particle fragmentation by ECAP, all the ECAPed specimens showed small anisotropy in their wear property in spite of this observed anisotropic microstructure induced by route A-ECAP.

El-Hadad, Shimaa; Sato, Hisashi; Watanabe, Yoshimi

2012-09-01

375

Investigation of Wear Anisotropy in a Severely Deformed Al-Al3Ti Composite  

NASA Astrophysics Data System (ADS)

In the current investigation, Al-Al3Ti composite was processed by equal channel angular pressing (ECAP). ECAP was carried out using routes A and BC up to eight passes of deformation. It was observed that increasing the number of ECAP passes causes fragmentation of Al3Ti platelet particles and decreases their sizes compared to their original sizes in the undeformed Al-Al3Ti specimens. Moreover, the microstructure of route A-ECAPed Al-Al3Ti composite samples showed a strong alignment of the fragmented Al3Ti particles parallel to the pressing axis. On the other hand, ECAPed Al-Al3Ti alloy specimens by route BC have a relatively homogeneous distribution of Al3Ti particles. Because of the platelet Al3Ti particle fragmentation by ECAP, all the ECAPed specimens showed small anisotropy in their wear property in spite of this observed anisotropic microstructure induced by route A-ECAP.

El-Hadad, Shimaa; Sato, Hisashi; Watanabe, Yoshimi

2012-05-01

376

Benefits for Military Veterans with ALS  

MedlinePLUS

... Share Print Military Veterans Resources for Military Veterans, Families & Survivors The ALS Association is working everyday to support people with ALS and their families, including our heroes who have served in the ...

377

Effects of the Al content on pore structures of porous TieAl alloys  

SciTech Connect

Porous TieAl alloys with different nominal compositions were fabricated through a reactive synthesis of Ti and Al elemental powders. It has been found that the pore parameters vary with the Al contents, indicating that the nature of the pores can be manipulated through changing the Al contents. In addition, detailed structural characterizations showed that the fabricated porous TieAl alloys can have three crystalline phases (i.e., a2-Ti3Al, g-TiAl, and TiAl3) when using different compositions. The fundamental reasons behind these phenomena have been explored.

Jaing, Y [State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China; He, Y H [State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China; Xu, N P [Membrane Science and Technology Research Center, Nanjing University of Technology, Nanjing 210009, C; Zou, J [School of Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, QLD; Huang, B [State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China; Lui, C T [Oak Ridge National Laboratory (ORNL)

2008-01-01

378

Delsuc et al. Hexapods resurrected Hexapods Resurrected  

E-print Network

Delsuc et al. Hexapods resurrected - 1 - Hexapods Resurrected (Technical comment on: "Hexapod.1126/science.1086558 #12;Delsuc et al. Hexapods resurrected - 2 - Abstract Nardi et al. (Science, 21 March 2003, 1887) suggested that extant hexapods might be diphyletic based on the analysis of amino acids sequences

Paris-Sud XI, Université de

379

(12) United States Patent Glazer et al.  

E-print Network

. Dynamite Blvd., Phoenix, AZ (US) 85085; Michael Barrett, 9182 E. Carribean La., Scottsdale, AZ (US) 85260 2003/0131048 Al 7/2003 Najork 5,892,904 A 411999 Atkinson et aI. 2003/0158823 Al 8/2003 Fulton et al. 5

Shamos, Michael I.

380

(12) United States Patent Bezos et al.  

E-print Network

et al. 5,724,424 A 311998 Gifford 5,745,681 A 411998 Levine et al. 5,812,769 A * 911998 Graber et al by that associate. 25 Claims, 14 Drawing Sheets 120 ",,//~~ENRO;PAllS~7~s~:W~I COOKIE PROCESSING SY I IREFERRAL

Shamos, Michael I.

381

Aluminium distribution in ZSM-5 revisited: The role of Al-Al interactions  

SciTech Connect

We present a theoretical study of the distribution of Al atoms in zeolite ZSM-5 with Si/Al=47, where we focus on the role of Al-Al interactions rather than on the energetics of Al/Si substitutions at individual sites. Using interatomic potential methods, we evaluate the energies of the full set of symmetrically independent configurations of Al siting in a Si{sub 94}Al{sub 2}O{sub 192} cell. The equilibrium Al distribution is determined by the interplay of two factors: the energetics of the Al/Si substitution at an individual site, which tends to populate particular T sites (e.g., the T14 site), and the Al-Al interaction, which at this Si/Al maximises Al-Al distances in general agreement with Dempsey's rule. However, it is found that the interaction energy changes approximately as the inverse of the square of the distance between the two Al atoms, rather than the inverse of the distance expected if this were merely charge repulsion. Moreover, we find that the anisotropic nature of the framework density plays an important role in determining the magnitude of the interactions, which are not simply dependent on Al-Al distances. - Graphical abstract: Role of Al-Al interactions in high silica ZSM-5 is shown to be anisotropic in nature and not dependent solely on Coulombic interactions. Highlights: Black-Right-Pointing-Pointer Si-Al distribution in ZSM-5 is revisited, stressing the role of the Al-Al interaction. Black-Right-Pointing-Pointer Coulomb interactions are not the key factors controlling the Al siting. Black-Right-Pointing-Pointer Anisotropy of the framework is identified as a source of departure from Dempsey's rule.

Ruiz-Salvador, A. Rabdel, E-mail: rabdel@imre.oc.uh.cu [Group of Materials Developed by Design, Division of Chemistry and Technology of Materials, Institute of Materials Science and Engineering (IMRE), University of Havana, Havana 10400 (Cuba); Grau-Crespo, Ricardo; Gray, Aileen E.; Lewis, Dewi W. [Department of Chemistry, University College London, 20 Gordon Street, London, WC1H OAJ (United Kingdom)] [Department of Chemistry, University College London, 20 Gordon Street, London, WC1H OAJ (United Kingdom)

2013-02-15

382

Opportunity's 'Rub al Khali' Panorama  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Click on the image for Opportunity's 'Rub al Khali' Panorama (QTVR)

This panoramic image, dubbed 'Rub al Khali,' was acquired by NASA's Mars Exploration Rover Opportunity on the plains of Meridiani during the period from the rover's 456th to 464th sols on Mars (May 6 to May 14, 2005). Opportunity was about 2 kilometers (1.2 miles) south of 'Endurance Crater' at a place known informally as 'Purgatory Dune.'

The rover was stuck in the dune's deep fine sand for more than a month. 'Rub al Khali' (Arabic translation: 'the empty quarter') was chosen as the name for this panorama because it is the name of a similarly barren, desolate part of the Saudi Arabian desert on Earth.

The view spans 360 degrees. It consists of images obtained in 97 individual pointings of the panoramic camera. The camera took images with five camera filters at each pointing. This 22,780-by-6,000-pixel mosaic is an approximately true-color rendering generated using the images acquired through filters admitting light wavelengths of 750, 530, and 480 nanometers.

Lighting varied during the nine sols it took to acquire this panorama, resulting in some small image seams within the mosaic. These seams have been smoothed in sky parts of the mosaic to better simulate the vista that a person would see if able to view it all at the same time on Mars.

Opportunity's tracks leading back to the north (center of the panorama) are a reminder of the rover's long trek from Endurance Crater. The deep ruts dug by Opportunity's wheels as it became stuck in the sand appear in the foreground. The crest and trough of the last ripple the rover crossed before getting stuck is visible in the center. These wind-formed sand features are only about 10 to 15 centimeters (4 to 6 inches) tall. The crest of the actual ripple where the rover got stuck can be seen just to the right of center. The tracks and a few other places on and near ripple crests can be seen in this color image to be dustier than the undisturbed or 'normal' plains soils in Meridiani. Since the time these ruts were made, some of the dust there has been blown away by the wind, reaffirming the dynamic nature of the martian environment, even in this barren, ocean-like desert of sand.

2005-01-01

383

The effects of boron in TiAl/Ti/sub 3/Al  

SciTech Connect

The authors discuss the TiAl/Ti/sub 3/Al interfacial misfit dislocations structures investigated by TEM in Ti-45Al alloy and Ti-45Al/TiB/sub 2/ composite. For TiAl with c/a = 1.02, only a single set of misfit dislocation arrays are crystallographically possible; these were observed in Ti-45Al alloy. However, the observation of three sets of misfit dislocation arrays in the Ti-45Al/TiB/sub 2/ composite suggests that the occupation of octahedral sites in the TiAl structure by excess boron was responsible for a decrease in the c/a ratio leading to an increased fcc character of the TiAl at the TiAl/Ti/sub 3/Al interface.

Feng, C.R.; Michel, D.J.; Crowe, C.R. (Naval Research Lab., Washington, DC (USA). Material Science and Technology Div.)

1989-10-01

384

Instandhaltungsmanagement als Gestaltungsfeld Ganzheitlicher Produktionssysteme  

NASA Astrophysics Data System (ADS)

Sich kontinuierlich verändernde Rahmenbedingungen, wie beispielsweise eine steigende Variantenvielfalt, verkürzte Produktlebenszyklen sowie Kundenforderungen nach höherer Qualität, kürzeren Lieferzeiten und geringeren Kosten, fordern von produzierenden Unternehmen eine stetige Anpassung der Prozesse, der Organisation und der Strukturen. Seit den 90er Jahren versuchen immer mehr deutsche Unternehmen diesen veränderten Anforderungen mit der Einführung eines Ganzheitlichen Produktionssystems (GPS) zu begegnen. Ganzheitliche Produktionssysteme sind dabei in ihren Grundlagen an das Toyota Produktionssystem angelehnt, vereinigen aber auch weitere Methoden zu einem unternehmensspezifischen Regelwerk. Im Rahmen des langfristigen Trends zu unternehmensindividuellen Produktionssystemen wird sowohl in der Industrie als auch in der Forschung intensiv über das Toyota Produktionssystem, Lean Production, Lean Management und Ganzheitliche Produktionssysteme diskutiert, werden Konzepte zu Implementierung und Betrieb erstellt und die Wirtschaftlichkeit untersucht.

Dombrowski, Uwe; Schulze, Sven; Otano, Isabel Crespo

385

Oxidation induced softening in Al nanowires  

NASA Astrophysics Data System (ADS)

The mechanical properties of metallic nanowires depend dramatically on the atmospheric conditions. Molecular-dynamics simulations with ReaxFF were conducted to study tensile elastic deformation of oxidized Al nanowires. The thin amorphous oxide shell formed around Al nanowires had a very low Young's modulus of 26 GPa, due to its low density and low Al-O coordination. Consequently, for diameters less than 100 nm, the composite Young's modulus of oxide-covered Al nanowires showed a size dependence implying that in this case "smaller is softer." The model developed also explained the discrepancies in the reported modulus values of nanometer-scale Al thin films.

Sen, Fatih G.; Qi, Yue; van Duin, Adri C. T.; Alpas, Ahmet T.

2013-02-01

386

Accumulation of Al in Root Mucilage of an Al-Resistant and an Al-Sensitive Cultivar of Wheat.  

PubMed Central

To estimate rates of Al accumulation within the symplasm, all apoplastic pools of Al need to be eliminated or accounted for. We have developed a revised kinetic protocol that allows us to estimate the contribution of mucilage-bound Al to total, nonexchangeable Al, and to eliminate the mucilage as an apoplastic pool of Al. By comparing the Al content of excised root tips (2 cm) of wheat (Triticum aestivum L.) with and without the removal of the mucilage (using a 10-min wash in 1 M NH4Cl), we found that Al bound to the mucilage accounted for approximately 25 to 35% of Al remaining after desorption in citric acid. The kinetics of Al uptake into mucilage were biphasic, with a rapid phase occurring in the first 30 min of uptake, followed by a linear phase occurring in the remainder of the experimental period (180 min). By adopting a step for removal of mucilage into our existing kinetic protocol, we have been able to isolate a linear phase of uptake with only a slight deviation from linearity in the first 5 min. Although we cannot unambiguously identify this phase of uptake as uptake into the symplasm, we believe this new protocol provides us with the most accurate quantitative estimate of symplastic Al yet available. PMID:12226458

Archambault, D. J.; Zhang, G.; Taylor, G. J.

1996-01-01

387

Diffusion in the Ti-Al system  

SciTech Connect

Many properties of industrial Ti-Al alloys, such as high-temperature stability of the lamellar structure and creep resistance, are determined by diffusion rates in the phases and along the interfaces. The knowledge of diffusion characteristics and fundamental understanding of diffusion mechanisms are of great importance to the research and design of industrial Ti-Al alloys. This paper gives an overview of recent progress in experimental and theoretical studies of diffusion behavior in the phases of the Ti-Al system. The experimental methods used in modern diffusion measurements are briefly described, and recent experimental results for Ti and Al diffusion in {alpha}-Ti(Al), {beta}-Ti(Al), and intermetallic phases {alpha}{sub 2}-Ti{sub 3}Al and {gamma}-TiAl, are summarized. The results for interdiffusion and impurity diffusion in these phases are also discussed in detail. The second part of the paper provides an overview of current understanding of point defects and diffusion mechanisms in Ti{sub 3}Al and TiAl. A statistical model of point-defect disorder in ordered compounds is presented and applied to Ti{sub 3}Al and TiAl using input data generated with embedded-atom potentials. Possible atomic mechanisms of diffusion in these compounds are analyzed in detail, and methods of diffusion calculations under different mechanisms are reviewed. The relative importance of different mechanisms in Ti{sub 3}Al and TiAl is evaluated by comparing their estimated activation energies. Prospective topics of further experimental and theoretical research in this area are outlined.

Mishin, Y.; Herzig, C.

2000-02-09

388

Reactive Plasma Spraying of Fine Al2O3/AlN Feedstock Powder  

NASA Astrophysics Data System (ADS)

Reactive plasma spraying (RPS) is a promising technology for in situ formation of aluminum nitride (AlN) coatings. Recently, AlN-based coatings were fabricated by RPS of alumina (Al2O3) powder in N2/H2 thermal plasma. This study investigated the feasibility of RPS of a fine Al2O3/AlN mixture and the influence of the plasma gases (N2, H2) on the nitriding conversion, and coating microstructure and properties. Thick AlN/Al2O3 coatings with high nitride content were successfully fabricated. The coatings consist of h-AlN, c-AlN, Al5O6N, ?-Al2O3, and a small amount of ?-Al2O3. Use of fine particles enhanced the nitriding conversion and the melting tendency by increasing the surface area. Furthermore, the AlN additive improved the AlN content in the coatings. Increasing the N2 gas flow rate improved the nitride content and complete crystal growth to the h-AlN phase, and enhanced the coating thickness. On the other hand, though the H2 gas is required for plasma nitriding of the Al2O3 particles, increasing its flow rate decreased the nitride content and the coating thickness. Remarkable influence of the plasma gases on the coating composition, microstructure, and properties was observed during RPS of the fine particles.

Shahien, Mohammed; Yamada, Motohiro; Yasui, Toshiaki; Fukumoto, Masahiro

2013-12-01

389

Comparative studies on the thermal stability and corrosion resistance of CrN, CrSiN, and CrSiN/AlN coatings  

SciTech Connect

In this work, three kinds of Cr-based nitride coatings such as monolithic CrN, CrSiN coatings, and multilayered CrSiN/AlN coating with bilayer period of 3.0 nm were deposited on both Si (100) wafer and AISI H13 steel substrates by unbalanced magnetron sputtering. Thermal stability of these coatings was evaluated by annealing the coatings at temperatures between 600 and 1000 degree sign C for 30 min in air. In addition, the corrosion behaviors of these coatings were investigated by potentiodynamic polarization tests in a deaerated 3.5 wt. % NaCl solution at 40 degree sign C. Results from annealing test show the monolithic CrN and CrSiN coatings were completely oxidized after annealed at 800 and 900 degree sign C, and their cross sectional images and atomic force microscopy showed a loose and very porous morphology due to the oxidation. Also, the hardness values of the monolithic CrN and CrSiN coatings were decreased significantly from 22 and 27 GPa to 8 and 14 GPa, respectively. However, the multilayered CrSiN/AlN coating still exhibited a dense microstructure without visible change after annealed at 1000 degree sign C, and moreover, the relatively high hardness of 25 GPa was maintained. The superior thermal stability of the CrSiN/AlN multilayer coating could be attributed to the formation of the dense and stable oxidation barrier consisted of the Al{sub 2}O{sub 3}, Cr{sub 2}O{sub 3}, and amorphous SiO{sub 2} phases near the surface region, which retard the diffusion of oxygen into the coating. In the potentiodynamic polarization test results, it was found that the significantly improved corrosion resistance of the multilayered CrSiN/AlN coating was observed in comparison with those from the monolithic CrN and CrSiN coatings, and its corrosion current density (i{sub corr}) and protective efficiency were measured to be approximately 4.21 {mu}A/cm{sup 2} and 95%, respectively.

Kim, Gwang Seok; Kim, Sung Min; Lee, Sang Yul; Lee, Bo Young [Department of Materials Engineering, NRL for Cracking Control and Management, Korea Aerospace University, Hangkongdae-Gil 100, KoYang-Si, KyungKi-Do 412-791 (Korea, Republic of); NRL for Cracking Control and Management, Faculty of Mechanical and Aerospace Engineering, Korea Aerospace University, Hangkongdae-Gil 100, KoYang-Si, KyungKi-Do 412-791 (Korea, Republic of)

2009-07-15

390

Atom probe analysis of AlN interlayers in AlGaN/AlN/GaN heterostructures  

SciTech Connect

Atom probe tomography was used to characterize AlN interlayers in AlGaN/AlN/GaN heterostructures grown by plasma-assisted molecular beam epitaxy (PAMBE), NH{sub 3}-based molecular beam epitaxy (NH{sub 3}-MBE), and metal-organic chemical vapor deposition (MOCVD). The PAMBE-grown AlN interlayer had the highest purity, with nearly 100% of group-III sites occupied by Al. The group-III site concentrations of Al for interlayers grown by NH{sub 3}-MBE and MOCVD were {approx}85% and {approx}47%, respectively. Hall measurements were performed to determine the two-dimensional electron gas mobility and sheet concentration. Sheet concentrations were {approx}25%-45% higher with molecular beam epitaxy than with MOCVD, and these results matched well with atom probe data.

Mazumder, Baishakhi; Kaun, Stephen W.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)] [Materials Department, University of California, Santa Barbara, California 93106 (United States); Lu, Jing; Keller, Stacia; Mishra, Umesh K. [Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)] [Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

2013-03-18

391

Adhesion and nonwetting-wetting transition in the Al\\/alpha-Al2O3 interface  

Microsoft Academic Search

Using a reactive force field (ReaxFF), we investigated the structural, energetic, and adhesion properties, of both solid and liquid Al\\/alpha-Al2O3 interfaces. The ReaxFF was developed solely with ab initio calculations on various phases of Al and Al2O3 and Al-O-H clusters. Our computed lattice constants, elastic constants, surface energies, and calculated work of separation for the solid-solid interface agree well with

Qing Zhang; Tahir Çagin; Adri van Duin; William A. Goddard; Yue Qi; Louis G. Hector

2004-01-01

392

Oxidation resistance of intermetallic compounds Al 3 Ti and TiAl  

Microsoft Academic Search

The oxidation kinetics and morphological features of Al3Ti and TiAl were investigated. The oxidation resistance of Al3Ti is much better than that of TiAl, for example, by a factor of about 30 at 1000° C for 48 h. The big difference in the oxidation resistance is related to the characteristics of the external oxide scales of a protective Al2O3 or

Y. Umakoshi; M. Yamaguchi; T. Sakagami; T. Yamane

1989-01-01

393

Abrasive wear behavior of NiAl and NiAl–TiB 2 composites  

Microsoft Academic Search

Abrasive wear of NiAl and NiAl with 10, 20, and 40 vol.% TiB2 has been investigated using particles of different types and sizes. The addition of TiB2 as a particulate reinforcement to NiAl increases the hardness of the composite with respect to NiAl, and reduces the wear rate at all volume fractions on garnet and Al2O3 abrasives. Abrasion on SiC

Jeffrey A. Hawk; David E. Alman

1999-01-01

394

Toxicity of Al to Desulfovibrio desulfuricans  

SciTech Connect

The toxicity of Al to Desulfovibrio desulfuricans G20 was assessed over a period of eight weeks in a modified lactate-C medium buffered at four initial pHs (5.0, 6.5, 7.2, and 8.3) and treated with five levels of added Al (none, 0.01, 0.1, 1.0, and 10 mM). At pH 5, cell populations decreased significantly and any effect of Al was negligible compared to that of pH. At higher pH, no direct impact of Al was seen at concentrations of soluble Al below 5x10-5 M. Soluble Al concentrations exceeded this level in the pH-6.5 and pH-7.2 treatments having total-Al concentrations= 1 mM and caused substantial and proportional decreases in cell populations. In contrast to the small size and vibrio morphology seen in most treatments, substantial numbers of large spirilloidal bacteria were seen in the pH-8.3 treatments, and their incidence was correlated with greater total-Al concentrations. This effect was believed to be a result of Mg deprivation stemming from adsorption/coprecipitation of Mg with Al hydroxy-sulfate gels rather than a direct response to high total-Al levels. Calculations of soluble-Al speciation suggested the presence of the Al13O4(OH)24(H2O)127+''tridecamer'' cation in the pH-6.5 and pH-7.2 treatments showing direct Al toxicity. Analysis of inoculated and control samples from the pH-6.5 and pH-8.3 10-mM Al treatments by 27Al nuclear-magnetic-resonance spectroscopy yielded broad 4800-Hz resonances at 58 ppm, near the 63-ppm resonance expected for the tridecamer cation. These resonances were independent of sample filtration through 25,000 MWCO membranes and attributed to self-assembled colloidal clusters of hydrophobic tridecamer species that had been neutralized by sorption of lactate and sulfate anions. Although indirect effects of Al addition were believed to have caused the lower cell populations observed in the pH-8.3 treatments, the NMR data suggest that direct effects of Al toxicity stemming from tridecamer colloids cannot be excluded.

Amonette, James E.; Russell, Colleen K.; Carosino, Katie A.; Robinson, Nicole L.; Ho, Jennifer T.

2003-07-02

395

New Al–Mg–Sc alloys  

Microsoft Academic Search

Data on new 01515, 01523, 01535, 01545, 01570 and 01571 wrought weldable alloys based on the Al–Mg–Sc system are presented. These alloys differ from each other, mainly, by magnesium content and belong to the family of non-heat-treatable alloys. Wrought Al–Mg–Sc alloy semiproducts as-hot worked or as-annealed show much higher properties (especially yield strength) than those made from conventional Al–Mg alloys

Yu. A Filatov; V. I Yelagin; V. V Zakharov

2000-01-01

396

Al Pie De La Letra  

PubMed Central

Background and Purpose Ethnic minorities are at higher stroke risk than non-Hispanic whites yet are less likely to have optimal vascular risk factor control. There is a need to develop culturally sensitive strategies for enhancing vascular risk reduction in minority patients with stroke. This study aimed to develop a postdischarge report card to boost treatment adherence among elderly Spanish-speaking patients with stroke within an urban health system. Methods This study included a total of 13 Spanish-only speaking participants aged ?60 years discharged from a local government hospital in Los Angeles within 18 months of an index ischemic stroke and 6 caregivers engaged in focus groups and interviews. Structured interviews were conducted with 11 care providers and 9 administrators at the hospital. Framework analysis examined the data and elicited themes to adapt a pre-existing patient report card tool. Results Spontaneously using the same phrase, “Al pie de la letra,” several participants expressed a need to follow medical instructions accurately to prevent recurrent stroke and identified barriers/facilitators for doing so. They made comments about the pre-existing report card, advising several changes, including the clarification of phrases, and written instructions to explain the need for the card and how to fill it out. The providers and administrators recommended avenues for successfully using the card at the hospital. A new report card was created that incorporated all major perspectives. Conclusions Crafting a culturally sensitive tool for promoting treatment adherence in elderly Spanish-only-speaking patients with stroke within an urban health system using a participatory methodology is feasible. The efficacy of this new report card should be tested in a randomized controlled trial. PMID:20167904

Ovbiagele, Bruce

2014-01-01

397

Internal Detoxification Mechanism of Al in Hydrangea (Identification of Al Form in the Leaves).  

PubMed Central

An internal detoxification mechanism for Al was investigated in an Al-accumulating plant, hydrangea (Hydrangea macrophylla), focusing on Al forms present in the cells. The leaves of hydrangea contained as much as 15.7 mmol Al kg-1 fresh weight, and more than two-thirds of the Al was found in the cell sap. Using 27Al- nuclear magnetic resonance, the dominant peak of Al was observed at a chemical shift of 11 to 12 parts per million in both intact leaves and the extracted cell sap, which is in good accordance with the chemical shift for the 1:1 Al-citrate complex. Purification of cell sap by molecular sieve chromatography (Sephadex G-10) combined with ion-exclusion chromatography indicated that Al in fractions with the same retention time as citric acid contributed to the observed 27Al peak in the intact leaves. The molar ratio of Al to citric acid in the crude and purified cell sap approximated 1. The structure of the ligand chelated with Al was identified to be citric acid. Bioassay experiments showed that the purified Al complex from the cell sap did not inhibit root elongation of corn (Zea mays L.) and the viability of cells on the root tip surface was also not affected. These observations indicate that Al is bound to citric acid in the cells of hydrangea leaves. PMID:12223659

Ma, J. F.; Hiradate, S.; Nomoto, K.; Iwashita, T.; Matsumoto, H.

1997-01-01

398

Exercise does not Increase ALS Risk  

MedlinePLUS

... for potentially confounding variables, such as the degree athletes who developed ALS used legal or illegal medications, took dietary supplements, and were exposed to pesticides or other toxins ...

399

Interfacial Phenomena in Al/Al, Al/Cu, and Cu/Cu Joints Soldered Using an Al-Zn Alloy with Ag or Cu Additions  

NASA Astrophysics Data System (ADS)

The studies of soldered joints were carried out in systems: Al/solder/Al, Al/solder/Cu, Cu/solder/Cu, where the solder was (Al-Zn)EUT, (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Ag and (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Cu addition. Brazing was performed at 500 °C for 3 min. The EDS analysis indicated that the composition of the layers starting from the Cu pad was CuZn, Cu5Zn8, and CuZn4, respectively. Wetting tests were performed at 500 °C for 3, 8, 15, and 30 min, respectively. Thickness of the layers and their kinetics of growth were measured based on the SEM micrographs. The formation of interlayers was not observed from the side of Al pads. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed.

Pstru?, Janusz; Gancarz, Tomasz

2014-05-01

400

[Management and care for patients with ALS].  

PubMed

For the past decade or so, the research in ALS has dramatically changed, coinciding with the discovery of SOD1 mutations, the generation of SOD1 transgenic rodents, and the introduction of riluzole. The ALS practice guidelines have been published in a number of countries, whereas the National Database has shown the actual reality of patient practice in ALS. Multidisciplinary ALS Clinics, consisting of a team of health care professionals, provide highly specialized quality care for patients and families, and have become the standard of care in many countries. A number of mostly retrospective studies report that non-invasive positive pressure ventilation prolongs survival and improves the quality of life and other functions. Enteral feeding certainly improves quality of life, but it is still uncertain if it prolongs survival. Although end of life issues in ALS care have been difficult more and more ALS clinicians are paying serious attention to it. Clinical trials are imperative to find effective medications for ALS, and many different pharmacological agents, based on a number of different hypotheses in ALS, are being actively tested or are about to be tested in the near future. Undoubtedly, we are in the midst of incredible progress in ALS. PMID:17432192

Mitsumoto, Hiroshi; Howe, Wesley J

2006-11-01

401

?-Phase Formation in Ni-Al Systems  

NASA Astrophysics Data System (ADS)

First-principles full-potential linear muffin-tin orbital method (FPLMTO) were performed for ?-type structural phase transformation for B2 (b.c.c.) NiAl and Ni_2Al alloys. In contrast to the NiAl system but in agreement with experiments, the results of our calculation showed that the Ni_2Al system is unstable with respect to this kind of transformation. To better understand the origin of stability and instability in each system, we also used a pair potential for modeling the interactions between the atoms. Calculated lattice parameters for the structures are in excellent agreement with the experimental data.

Albers, R. C.; Sanati, M.; Pinski, F. J.

1998-03-01

402

Anodic Behavior of Al and the Alloys Al-In and Al-In-Ga in Aluminum-Air Batteries.  

National Technical Information Service (NTIS)

By recording of the polarization characteristics and measurement of the currents of self-dissolution, the anodic behavior of aluminum and the alloys Al-In and Al-In-Ga was tested under the operating conditions of aluminum-air batteries. The tests were con...

D. M. Drazic, A. R. Despic, S. K. Zecevic

1979-01-01

403

Effects of the Al content on pore structures of porous TieAl alloys  

SciTech Connect

PorousTi Alalloys with different nominal compositions were fabricated through a reactive synthesis of Ti and Al elemental powders. It has been found that the pore parameters vary with the Al contents, indicating that the nature of the pores can be manipulated through changing the Al contents. In addition, detailed structural characterizations showed that the fabricated porousTi Alalloys can have three crystalline phases (i.e., 2-Ti3Al, -TiAl, and TiAl3) when using different compositions. The fundamental reasons behind these phenomena have been explored.

Jiang, Y [State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China; He, Y H [State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China; Zou, J [School of Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, QLD; Huang, B [State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China; Liu, C [Oak Ridge National Laboratory (ORNL)

2008-01-01

404

Investigation of TiAl\\/Ti 2AlC composites prepared by spark plasma sintering  

Microsoft Academic Search

TiAl\\/Ti2AlC composites were produced by spark plasma sintering technology from mixed powders of Ti, Al and TiC. X-ray diffraction (XRD) patterns showed that the sintered products mainly consisted of TiAl and Ti2AlC phases. Electric probe microcosmic analysis (EPMA) photos indicated different microstructures depending on composition. In one case, when 7vol.%TiC was mixed in the starting powders, the produced Ti2AlC particles

Bingchu Mei; Yoshinari Miyamoto

2002-01-01

405

United States Patent [19] Miura et al.  

E-print Network

such as boron neutron capture therapy and photodynamic therapy. 3 Therapy for Cancer, Kobe, Japan (Oct. 31--Nov. 4, 1994). Miura et al., "Synthesis and Spectroscopic Capture Therapy", Tetrahedron Letters, 31(16), pp. 2247--2250 (1990). Chiusoli et al., "Synthesis

Shelnutt, John A.

406

Al Shabaab's Foreign Threat to Somalia  

Microsoft Academic Search

This article focuses on the threat to Somalia by al Shabaab (The Youth), an extremist organization that controls most of southern and central Somalia. It learned its strategy and tactics from al Qaeda and the Taliban and relies heavily on a relatively small number of foreign fighters, most of whom are Somalis with foreign passports from the large Somali diaspora.

David Shinn

2011-01-01

407

Everyday Life with ALS: A Practical Guide  

MedlinePLUS

... MDA. Flu shots can help protect the respiratory system. Online support MDA’s ALS Division offers news and a series of regularly scheduled online chats, plus occasional conferences with ALS specialists and experts. Transcripts of past chats are posted. MDA also ...

408

United States Patent [19] Church et al.  

E-print Network

United States Patent [19] Church et al. [54] CHARACTERIZATION OF INDIVIDUAL POLYMER MOLECULES BASED al.. "Effect of Point Mutations on the in-Vitro Pore Properties ofMaltoporin. a Protein physical changes across an interface between two pools of media as the linear polymer traverses

Church, George M.

409

Quantitatively probing the Al distribution in zeolites.  

PubMed

The degree of substitution of Si(4+) by Al(3+) in the oxygen-terminated tetrahedra (Al T-sites) of zeolites determines the concentration of ion-exchange and Brønsted acid sites. Because the location of the tetrahedra and the associated subtle variations in bond angles influence the acid strength, quantitative information about Al T-sites in the framework is critical to rationalize catalytic properties and to design new catalysts. A quantitative analysis is reported that uses a combination of extended X-ray absorption fine structure (EXAFS) analysis and (27)Al MAS NMR spectroscopy supported by DFT-based molecular dynamics simulations. To discriminate individual Al atoms, sets of ab initio EXAFS spectra for various T-sites are generated from DFT-based molecular dynamics simulations, allowing quantitative treatment of the EXAFS single- and multiple-photoelectron scattering processes out to 3-4 atom shells surrounding the Al absorption center. It is observed that identical zeolite types show dramatically different Al distributions. A preference of Al for T-sites that are part of one or more 4-member rings in the framework over those T-sites that are part of only 5- and 6-member rings in an HBEA150 zeolite has been determined using this analysis. PMID:24815517

Vjunov, Aleksei; Fulton, John L; Huthwelker, Thomas; Pin, Sonia; Mei, Donghai; Schenter, Gregory K; Govind, Niranjan; Camaioni, Donald M; Hu, Jian Zhi; Lercher, Johannes A

2014-06-11

410

[Electrodiagnosis of ALS: its practical aspects].  

PubMed

Electrodiagnostic methods, especially needle EMG plays an important role for the ALS diagnosis. Existing diagnostic criteria such as revised El Escorial criteria (R-EEC) and Awaji algorithm have a drawback of low sensitivity. Our study revealed that the percentage of patients classified as confirmed ALS, i.e. clinically probable (laboratory supported) or higher, was 43% using the R-EEC and 37% using the Awaji algorithm. Needle EMG can strongly suggest ALS beyond these criteria. Fasciculation potentials (FPs) are sufficiently specific for ALS, and we have argued its diagnostic utitlity in ALS diagnosis. FPs are rare in other neurogenic diseases, such as cervical or lumbar spine disorders and spinal and bulbar muscular atrophy. Profuse FPs observed in both upper and lower limbs would strongly suggest ALS. EMG of the upper trapezius muscle is useful since it is easily relaxed, and the spontaneous activities in this muscle are sufficiently sensitive and specific for ALS. Inclusion body myositis (IBM) might be confused with ALS, but its differentiation is actually easy since a normal recruitment in a chronically weak muscle definitely indicates myopathy. Furthermore, EMG of the flexor digitorum profundus muscle in IBM patients would reveal typical myopathic, i.e. low-amplitude and thin, motor unit potentials. PMID:22277500

Sonoo, Masahiro; Higashihara, Mana; Hokkoku, Keiichi

2011-11-01

411

Stress Corrosion Cracking of Al-Mg and Mg-Al Alloys  

SciTech Connect

Aluminum and magnesium based alloys are being used for reducing the weight of automobiles. For structural applications they must have adequate stress corrosion resistance and yet, under some circumstances, stress corrosion cracking can occur in both alloy systems. Precipitation of the Mg rich Beta-phase (Al3Mg2) at grain boundaries of Al-Mg alloys and the Beta-phase (Mg17Al12) at grain boundaries of the Mg-Al alloys are critical factors in their stress corrosion performance. In Mg-Al, the Beta-phase is cathodic to the matrix while in the Al-Mg case, the Beta-phase is anodic to the matrix. These phases produce localized galvanic induced-corrosion that leads to intergranular stress corrosion cracking and cracking growth rates of 5 and 103 times faster than the solution treated condition, for Al-Mg and Mg-Al, respectively.

Jones, Russell H.; Vetrano, John S.; Windisch, Charles F.

2004-12-01

412

NiAl alloys for structural uses  

NASA Technical Reports Server (NTRS)

Alloys based on the intermetallic compound NiAl are of technological interest as high temperature structural alloys. These alloys possess a relatively low density, high melting temperature, good thermal conductivity, and (usually) good oxidation resistance. However, NiAl and NiAl-base alloys suffer from poor fracture resistance at low temperatures as well as inadequate creep strength at elevated temperatures. This research program explored macroalloying additions to NiAl-base alloys in order to identify possible alloying and processing routes which promote both low temperature fracture toughness and high temperature strength. Initial results from the study examined the additions of Fe, Co, and Hf on the microstructure, deformation, and fracture resistance of NiAl-based alloys. Of significance were the observations that the presence of the gamma-prime phase, based on Ni3Al, could enhance the fracture resistance if the gamma-prime were present as a continuous grain boundary film or 'necklace'; and the Ni-35Al-20Fe alloy was ductile in ribbon form despite a microstructure consisting solely of the B2 beta phase based on NiAl. The ductility inherent in the Ni-35Al-20Fe alloy was explored further in subsequent studies. Those results confirm the presence of ductility in the Ni-35Al-20Fe alloy after rapid cooling from 750 - 1000 C. However exposure at 550 C caused embrittlement; this was associated with an age-hardening reaction caused by the formation of Fe-rich precipitates. In contrast, to the Ni-35Al-20Fe alloy, exploratory research indicated that compositions in the range of Ni-35Al-12Fe retain the ordered B2 structure of NiAl, are ductile, and do not age-harden or embrittle after thermal exposure. Thus, our recent efforts have focused on the behavior of the Ni-35Al-12Fe alloy. A second parallel effort initiated in this program was to use an alternate processing technique, mechanical alloying, to improve the properties of NiAl-alloys. Mechanical alloying in the conventional sense requires ductile powder particles which, through a cold welding and fracture process, can be dispersion strengthened by submicron-sized oxide particles. Using both the Ni-35Al-Fe alloys to contain approx. 1 v/o Y2O3. Preliminary results indicate that mechanically alloyed and extruded NiAl-Fe + Y2O3 alloys when heat treated to a grain-coarsened condition, exhibit improved creep resistance at 1000 C when compared to NiAl; oxidation resistance comparable to NiAl; and fracture toughness values a factor of three better than NiAl. As a result of the research initiated on this NASA program, a subsequent project with support from Inco Alloys International is underway.

Koss, D. A.

1991-01-01

413

Al-Akhawayni's description of pulmonary circulation.  

PubMed

Since antiquity, heart function and the mechanism of blood circulation within the human body have been the focus of attention of scientists from different parts of the world. Over the passage of time, the theories and works of these scientists have resulted in the achievement of today's knowledge of circulation. The medieval Persian scholar, Al-Akhawayni Bukhari (?-983AD), is among the physicians who investigated both the anatomy and the physiology of the human body. Al-Akhawayni describes the mechanism of pulmonary circulation in his only extant book, "Hidayat al-Muta`llemin fi al-Tibb" (A Scholar's Guide to Medicine) with which he made a contribution to the development of knowledge regarding this mechanism in the medicine of the Islamic world. In this paper, Al-Akhawayni's viewpoints on anatomy and the function of the heart, its related vessels, and also pulmonary circulation will be briefly discussed. PMID:23890868

Yarmohammadi, Hassan; Dalfardi, Behnam; Rezaian, Jafar; Ghanizadeh, Ahmad

2013-10-01

414

AL(0) in municipal waste incinerator ash  

NASA Astrophysics Data System (ADS)

Disposal of municipal waste is a challenge to society. Waste volume is substantially decreased by incineration but residual ash usually contains a number of toxic components which must be immobilised to insure environmental protection. One element, chromium, is mobile and toxic in its oxidised state as Cr(VI) but it can be reduced to Cr(III) and immobilised. Reduction can be promoted by ash treatment with Fe(0) or Fe(II), but recent evidence shows that at least some Cr(VI) is reduced spontaneously in the ash. Aspects of ash behaviour suggest metallic aluminium as the reducing agent, but no direct evidence of Al(0) has been found until now. We examined filter ash from an energy-producing, municipal-waste incinerator (Vest-forbrænding) near Copenhagen. X-ray diffraction (XRD) identified expected salts of Na, K and Ca such as halite, sylvite, calcite, anhydrite and gypsum as well as quartz, feldspar and some hematite. Wave-dispersive electron microprobe produced elemen-tal maps of the ash; Al-rich areas were analysed quantitatively by comparison with standards. We identified metallic Al particles, averaging 50 to 100 micrometers in di-ameter, often with a fractured, glassy border of aluminum oxide. The particles were porous, explaining fast Cr(VI) reduction and they contained thin exsolution lamellae of Al-alloys of Pb and Cu or Mn, Fe and Ag, which provide clues of the Al(0) origin in the waste. Sometimes Al(0) occurred inside glassy globes of Al2O3. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) proved that surface Al concentrations on ash particles were below detection, confirming reactivity of the Al(0) bulk. The persistence of reduced Al through the highly oxidising combustion procedure comes as a surprise and is a benefit in the immobilisation of Cr(VI) from municipal-waste incineration residues.

Stipp, S. L.; Ronsbo, J. G.; Zunic, T. B.; Christensen, T. H.

2003-04-01

415

High temperature creep behaviour of Al-rich Ti-Al alloys  

NASA Astrophysics Data System (ADS)

Compared to Ti-rich ?-TiAl-based alloys Al-rich Ti-Al alloys offer an additional reduction of in density and a better oxidation resistance which are both due to the increased Al content. Polycrystalline material was manufactured by centrifugal casting. Microstructural characterization was carried out employing light-optical, scanning and transmission electron microscopy and XRD analyses. The high temperature creep of two binary alloys, namely Al60Ti40 and Al62Ti38 was comparatively assessed with compression tests at constant true stress in a temperature range between 1173 and 1323 K in air. The alloys were tested in the cast condition (containing various amounts of the metastable phases Al5Ti3 and h-Al2Ti) and after annealing at 1223 K for 200 h which produced (thermodynamically stable) lamellar ?-TiAl + r-Al2Ti microstructures. In general, already the as-cast alloys exhibit a reasonable creep resistance at 1173 K. Compared with Al60Ti40, both, the as-cast and the annealed Al62Ti38 alloy exhibit better creep resistance up to 1323 K which can be rationalized by the reduced lamella spacing. The assessment of creep tests conducted at identical stress levels and varying temperatures yielded apparent activation energies for creep of Q = 430 kJ/mol for the annealed Al60Ti40 alloy and of Q = 383 kJ/mol for the annealed Al62Ti38 material. The latter coincides well with that of Al diffusion in ?-TiAl, whereas the former can be rationalized by the instability of the microstructure containing metastable phases.

Sturm, D.; Heilmaier, M.; Saage, H.; Aguilar, J.; Schmitz, G. J.; Drevermann, A.; Palm, M.; Stein, F.; Engberding, N.; Kelm, K.; Irsen, S.

2010-07-01

416

Infrared brazing of TiAl using Al-based braze alloys  

Microsoft Academic Search

A novel approach for joining TiAl by infrared vacuum brazing using pure aluminum and BAlSi-4 filler metal has been reported in the study. For pure Al filler metal, the extensive presence of stable TiAl3 phase in the joint results in inherent brittleness of the bond, and it is difficult to completely remove the stable TiAl3 by heat treatment after infrared

R. K. Shiue; S. K. Wu; S. Y. Chen

2003-01-01

417

Tree fine root Ca\\/Al molar ratio – Indicator of Al and acidity stress  

Microsoft Academic Search

High soil acidity and elevated soil Al concentrations limit plant growth in many terrestrial ecosystems. Aluminium toxicity can be ameliorated by Ca. Thus, Ca\\/Al molar ratios in soil solution and in plant tissues have been proposed as superior indicators than Al concentration itself for evaluating the Al toxicity stress to trees (Cronan & Grigal, J Environ Qual 1995;24:209 – 226). This article

E. I. Vanguelova; Y. Hirano; T. D. Eldhuset; L. Sas-Paszt; M. R. Bakker; Ü. Püttsepp; I. Brunner; K. Lõhmus; D. Godbold

2007-01-01

418

Linewidth and underlayer influence on texture in submicrometer-wide Al and AlCu lines  

Microsoft Academic Search

The local texture in three types of patterned, thin-film, Al and AlCu interconnections on Si semiconductor devices is investigated by electron backscatter diffraction. Two types of standard planar metal structures were investigated: (1) blanket Al and (2) blanket Al-0.5 wt % Cu on TiN\\/Ti underlayers. Both were deposited on amorphous SiO2 substrates followed by reactive ion etching to define 0.45-10

J. L. Hurd; K. P. Rodbell; L. M. Gignac; L. A. Clevenger; R. C. Iggulden; R. F. Schnabel; S. J. Weber; N. H. Schmidt

1998-01-01

419

Linewidth and underlayer influence on texture in submicrometer-wide Al and AlCu lines  

Microsoft Academic Search

The local texture in three types of patterned, thin-film, Al and AlCu interconnections on Si semiconductor devices is investigated by electron backscatter diffraction. Two types of standard planar metal structures were investigated: (1) blanket Al and (2) blanket Al–0.5 wt % Cu on TiN\\/Ti underlayers. Both were deposited on amorphous SiO2 substrates followed by reactive ion etching to define 0.45–10

J. L. Hurd; K. P. Rodbell; L. M. Gignac; L. A. Clevenger; R. C. Iggulden; R. F. Schnabel; S. J. Weber; N. H. Schmidt

1998-01-01

420

The site occupancies of alloying elements in TiAl and Ti 3Al alloys  

Microsoft Academic Search

The site occupancies of V, Cr, Mn, Fe, Ni, Zr, Nb, Mo, Ta, Ga and Sn (1–5at.%) in TiAl alloys with different compositions, and in Ti3Al with the compositions of Ti–26at.%Al–(1–2at.%)X, were measured by the atom location channelling enhanced microanalysis (ALCHEMI) method. For TiAl alloys, the results show that Zr, Nb and Ta atoms invariably occupy Ti sites, while Fe,

Y. L. Hao; D. S. Xu; Y. Y. Cui; R. Yang; D. Li

1999-01-01

421

Corrosion Studies of 2195 Al-Li Alloy and 2219 Al Alloy with Differing Surface Treatments  

NASA Technical Reports Server (NTRS)

Corrosion studies of 2195 Al-Li and 2219 Al alloys have been conducted using the scanning reference electrode technique (SRET) and the polarization resistance (PR) technique. The SRET was used to study corrosion mechanisms, while corrosion rate measurements were studied with the PR technique. Plates of Al203 blasted, soda blasted and conversion coated 2219 Al were coated with Deft primer and the corrosion rates studied with the EIS technique. Results from all of these studies are presented.

Danford, M. D.; Mendrek, M. J.

1998-01-01

422

27Al-NQR\\/NMR Study of Kondo Semiconductor CeFe2Al10  

Microsoft Academic Search

27Al-NQR\\/NMR measurements have been performed on CeFe2Al10 in relevance to the novel phase below T0=27 K of isostructural CeRu2Al10. NQR peaks are assigned to five crystallographically inequivalent Al sites. No splitting of the NQR spectra down to 1.5 K confirms the lack of phase transition in this compound. The gaplike decrease in the spin-lattice relaxation rate 1\\/T1 above about 20

Yukihiro Kawamura; Shingo Edamoto; Tomoaki Takesaka; Takashi Nishioka; Harukazu Kato; Masahiro Matsumura; Yo Tokunaga; Shinsaku Kambe; Hiroshi Yasuoka

2010-01-01

423

A Revision of the Al-rich Region of the Sm-Al Phase Diagram: The Sm 3 Al 11 Phase  

Microsoft Academic Search

Phase equilibria in the Al-rich region of the Sm-Al binary system has been revised and updated: it has been confirmed that\\u000a Sm3Al11 is a congruently melting phase which, on cooling, undergoes catatectic decomposition Sm3Al11 ? liquid + SmAl3.

S. Delsante; R. Raggio; G. Borzone; R. Ferro

2007-01-01

424

Phase Constituents of Al-rich U-Mo-Al Alloys Examined by Transmission Electron Microscopy  

SciTech Connect

To supplement the understanding of diffusional interactions involving Al-rich region of the U-Mo-Al system, alloys with composition 85.7Al-11.44U-2.86Mo and 87.5Al-10U-2.5Mo in at.%, were examined to determine the equilibrium phase constituents at 500?C. These alloys were triple arc-melted, homogenized at 500?C for 200 hours, and water-quenched to preserve the high temperature microstructure. X-ray diffraction, scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (XEDS), and transmission electron microscopy (TEM) with high angle annular dark field (HAADF) imaging via scanning transmission electron microscopy (STEM) were employed for the characterization. Alloy specimens for TEM/STEM were prepared using site-specific focused ion beam (FIB) in-situ lift-out (INLO) technique. Despite the homogenization time and temperature, five different phases, namely fcc-Al solid solution, cubic-UAl3, orthorhombic-UAl4, hexagonal-U6Mo4Al43 and diamond cubic-UMo2Al20, were observed. Based on U-Al, U-Mo and Al-Mo binary phase diagrams, previously proposed U-Mo-Al isotherms, and the solidification microstructure of these alloys, the Al-rich region of the equilibrium ternary isotherm at 500?C was constructed. The fcc-Al solid solution, orthorhombic-UAl4, and diamond cubic-UMo2Al20, which were determined to be the equilibrium phases in 85.7Al-11.44U-2.86Mo and 87.5Al-10U-2.5Mo alloys.

E. Perez; A. Ewh; J. Liu; B. Yuan; D. D. Keiser, Jr.; Y. H. Sohn

2009-11-01

425

Evaluating Zn, Al and Al-Zn coatings on carbon steel in a special atmosphere  

SciTech Connect

This paper presents a comparative evaluation of Al, Zn and Al-Zn coatings on carbon steel exposed to a coastal-marine atmosphere. It is a very aggressive atmosphere with high wind velocities (corrosion-erosion rate = 1.4 mm/year for ASTM 1029 steel). A metallized zinc coating with a pore sealer was also evaluated. ISO and ASTM standards were used for the evaluation. After a two-year exposure the best performance was achieved by the Al and Al rich alloy (85%Al-15%Zn) with some damage of the coatings. But the Zn metallized coating, with a pore sealer, did not show signs of damage.

Troconis de Rincon, O.; Delgado, R.; Lopez, B. [Univ. del Zulia, Maracaibo (Venezuela). Centro de Estudios de Corrosion; Uruchutu, J. [Univ. de Cuernavaca (Mexico)

1999-11-01

426

Atomistic Modeling of RuAl and (RuNi) Al Alloys  

NASA Technical Reports Server (NTRS)

Atomistic modeling of RuAl and RuAlNi alloys, using the BFS (Bozzolo-Ferrante-Smith) method for alloys is performed. The lattice parameter and energy of formation of B2 RuAl as a function of stoichiometry and the lattice parameter of (Ru(sub 50-x)Ni(sub x)Al(sub 50)) alloys as a function of Ni concentration are computed. BFS based Monte Carlo simulations indicate that compositions close to Ru25Ni25Al50 are single phase with no obvious evidence of a miscibility gap and separation of the individual B2 phases.

Gargano, Pablo; Mosca, Hugo; Bozzolo, Guillermo; Noebe, Ronald D.; Gray, Hugh R. (Technical Monitor)

2002-01-01

427

Reassessment of NiAl and Ni-Fe-Al solidus temperatures  

Microsoft Academic Search

Solidus temperatures of the B2 NiAl phase have been determined by high-temperature differential thermal analysis for binary\\u000a melt compositions NixAl100?x\\u000a (45xyNi50?yAl50 (0?y?50). It was shown that the melting temperature of the stoichiometric Ni50Al50 phase is 1681 °C, which is 43 K higher than some literature data. The solidus line at the Ni-rich side of the Ni-Al phase\\u000a diagram exhibits a

H. Bitterlich; W. Löser; L. Schultz

2002-01-01

428

Anodic behavior of Al and the alloys Al-In and Al-In-Ga in aluminum-air batteries  

Microsoft Academic Search

The anodic behavior of aluminum and the alloys Al-In and Al-In-Ga was tested under the operating conditions of aluminum-air batteries. The tests were conducted in an aqueous solution of 2 M NaCl, and the results obtained were compared with the results obtained from a special test of these alloys as the anode in a standard electrochemical cell. Significant results and

D. M. Drazic; A. R. Despic; S. K. Zecevic

1979-01-01

429

Reaction of Ti and Ti-Al alloys with alumina  

NASA Technical Reports Server (NTRS)

The reaction of single-crystal Al2O3 with pure Ti and Ti-Al alloys with different Al concentrations was examined in the temperature range of 1173 to 1573 K. Significant reaction occurred between Al2O3 and the Ti-Al alloys with Al concentrations lower than that corresponding to the gamma-TiAl phase. The reaction mechanism was determined to be simultaneous diffusion of Al and atomic oxygen from Al2O3 into Ti and the Ti-Al alloys.

Misra, Ajay K.

1991-01-01

430

Thermal diffusion in Ni/Al multilayer  

SciTech Connect

Two Ni/Al multilayers deposited by ion beam sputtering of nominal design [Ni(200A)/Al(100A)] Multiplication-Sign 5 and [Ni(50A)/Al(227A)] Multiplication-Sign 5 on Si substrates were annealed at 200 Degree-Sign C. As-deposited and annealed samples were characterized by x-ray diffraction (XRD) and x-ray reflectometry (XRR). The effort was to study the path of alloying in the above two multilayers of same elements but of opposite stoichiometric ratio. We find distinct differences in alloying of these samples.

Swain, M.; Bhattacharya, D.; Singh, S.; Basu, S. [Solid State Physics Division, Bhabha Atomic Research Center, Mumbai 400085 (India); Gupta, M. [UGC-DAE-Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017 (India)

2013-02-05

431

[A strategy to develop effective ALS therapy].  

PubMed

In the early 1990s, a number of major events took place in the history of the treatment and science of ALS. A cause of familial ALS, the mutation of superoxide dismutase 1, was discovered and very shortly after, an animal model expressing the human SOD1 mutation for familial ALS was generated. Around the same time, the first medication for the treatment of ALS, riluzole, was approved. Clinical neurologists started to focus more attention on quality of life and standardizing care for patients with ALS, including devising approaches for presenting and discussing the diagnosis, using aggressive symptomatic treatments, and developing a multidisciplinary care system. Since then, nutritional and respiratory care has markedly improved. Respiratory care for those with terminal ALS in Japan has been distinct and perhaps more effective compared to the rest of the world, and this unique experience must be broadly published and shared with others. In 1999, the ALS Treatment Guidelines were published by the American Academy of Neurology and are now under revision. A monitoring system to determine the impact the Guidelines had on actual patient care has taught us that caregivers have only slowly accepted the recommendation to improve quality of care. The team approach, using a multidisciplinary care system from diagnosis to the end of life, is essential to improve care for both the patient and family. Coinciding with the progress in ALS treatment, basic science and translational research also produced dramatic progress in ALS drug discovery. Over the past 15 years, more than 25 potential drugs have been tested in randomized controlled trials. Despite this progress, we have no medications other than riluzole. Although it may be true that ALS research is in its early stages compared to research in other diseases with no cure--it is probably behind cancer research by at least 20 or 30 years--we need to drastically change our approach to drug development. At a national level, we need to create a strong, cohesive team with support from a number of funding agencies, oversight from a regulatory agency, and investigators who all think "outside the box." In addition, we should obtain ideas and suggestions from accomplished experts outside of the field of ALS and put competition aside as we work together to develop strategic plans for the ALS drug development that is essential to beat this devastating disease. PMID:17447525

Mitsumoto, Hiroshi

2007-04-01

432

Wetting of polycrystalline SiC by molten Al and Al-Si alloys  

NASA Astrophysics Data System (ADS)

The wetting of ?-SiC by molten Al and Al-Si alloys was investigated using a dispensed sessile drop method in a high vacuum. In the Al-SiC system, representative wetting stages were identified. The liquid spreading was initially controlled by the deoxidation of the SiC surface and then by the formation of Al4C3 at the interface. The intrinsic contact angle for molten Al on the polycrystalline ?-SiC surface was suggested to be lower than 90? provided that the oxide films covering the Al and SiC surfaces were removed, i.e., the system is partial wetting in nature. An increase in the Si concentration in liquid Al weakened the interfacial reaction but improved the final wettability. The role of the Si addition on the wetting was presumably attributed to its segregation at the interface and the formation of strong chemical bonds with the SiC surface.

Cong, Xiao-Shuang; Shen, Ping; Wang, Yi; Jiang, Qichuan

2014-10-01

433

High quality AlGaN grown on ELO AlN/sapphire templates  

NASA Astrophysics Data System (ADS)

The defect structure and the homogeneity of 1-3 µm thick AlxGa1-xN layers grown on epitaxially laterally overgrown (ELO) AlN on patterned AlN/sapphire templates have been investigated in dependence on the miscut direction of the c-plane sapphire substrates, the etching depth into the sapphire and the Al concentration. It was found that shallowly etched AlN/sapphire templates with a 0.25° miscut toward the a-plane provide a smooth surface of ELO AlN and therefore a good Al homogeneity in the overgrown Al0.8Ga0.2N layer. The threading dislocation density in these layers is as low as 5×108 cm-2.

Zeimer, U.; Kueller, V.; Knauer, A.; Mogilatenko, A.; Weyers, M.; Kneissl, M.

2013-08-01

434

Stress relaxation of an AISI 1080 steel  

Microsoft Academic Search

Stress relaxation is a simple test which offers means for evaluating the deformation dynamics of materials. The principal\\u000a advantage of this method is that it scans a broad range of strain rates while straining the specimen by only a small amount.\\u000a Therefore, it is possible to assume that the substructure of the material remains approximately constant during the test in

Ricardo E. Medrano; Peter P. Gillis

1989-01-01

435

AISI Direct Steelmaking Program. Final technical report  

SciTech Connect

This final report deals with the results of a 5-yr project for developing a more energy-efficient, environmentally friendly, less costly process for producing hot metal than current coke ovens and blast furnaces. In the process, iron ore pellets are smelted in a foamy slag created by reaction of coal char with molten slag to produce CO. The CO further reacts with oxygen, which also reacts with coal volatile matter, to produce the heat necessary to sustain the endothermic reduction reaction. The uncombusted CO and H{sub 2} from the coal are used to preheat and prereduce hematite pellets for the most efficient use of the energy in the coal. Laboratory programs confirmed that the process steps worked. Pilot plant studies were successful. Economic analysis for a 1 million tpy plant is promising.

Aukrust, E.

1994-08-01

436

Fretting fatigue in AISI 1015 steel  

Microsoft Academic Search

A small oscillatory movement between two contacting surfaces is termed as fretting and on many occasions it acts as the crack\\u000a initiation site leading to catastrophic failure of the overall structure. The occurrence of fretting is observed in many engineering\\u000a structures such as shaft flanges, gas turbines, steel ropes etc. An experimental facility, which can simulate the fretting\\u000a fatigue in

R. Gnanamoorthy; R. Rosi Reddy

2002-01-01

437

Calcium platinum aluminium, CaPtAl  

PubMed Central

A preliminary X-ray study of CaPtAl has been reported previously by Hulliger [J. Alloys Compd (1993), 196, 225–228] based on X-ray powder diffraction data without structure refinement. With the present single-crystal X-ray study, we confirm the assignment of the TiNiSi type for CaPtAl, in a fully ordered inverse structure. All three atoms of the asymmetric unit have .m. site symmetry. The structure features a ? 3[AlPt] open framework with a fourfold coordination of Pt by Al atoms and vice versa. The Ca atoms are located in the large channels of the structure. PMID:22064850

Kenfack Tsobnang, Patrice; Fotio, Daniel; Ponou, Simeon; Fon Abi, Charles

2011-01-01

438

Nominalization in Q'anjob'al (Maya)  

E-print Network

Q’anjob’al typically makes a rigid distinction between transitive and intransitive verb inflections. Transitive verbs cross-reference their subjects with an ergative prefix while intransitive verbs cross-reference their ...

Mateo, Pedro

2010-01-01

439

COMMUNICATION MatthiasTreier et al.  

E-print Network

COMMUNICATION MatthiasTreier et al. Anaromaticcouplingmotiffor two-dimensionalsupramolecular architectures ISSN1359-7345 www.rsc.org/chemcomm Number38|14October2008|Pages4509­4648 Chemical Communications

Hone, James

440

12th Annual ALS Users' Association Meeting  

SciTech Connect

Science took the front seat as 219 Advanced Light Source (ALS) users and staff gathered on Monday and Tuesday, October 18 and 19 for the twelfth annual users' meeting. The bulk of the meeting was dedicated to reports on science at the ALS. Packed into two busy days were 31 invited oral presentations and 80 submitted poster presentations, as well as time to visit 24 vendor booths. The oral sessions were dedicated to environmental science, chemical dynamics, biosciences, magnetic materials, and atomic and molecular science. In addition, there was an ALS highlights session that emphasized new results and a session comprising highlights from the young scientists who will carry the ALS into the future.

Robinson, Arthur L.

1999-12-17

441

Analysis of al-2 Mutations in Neurospora  

PubMed Central

The orange pigmentation of the fungus Neurospora crassa is due to the accumulation of the xanthophyll neurosporaxanthin and precursor carotenoids. Two key reactions in the synthesis of these pigments, the formation of phytoene from geranylgeranyl pyrophosphate and the introduction of ? cycles in desaturated carotenoid products, are catalyzed by two domains of a bifunctional protein, encoded by the gene al-2. We have determined the sequence of nine al-2 mutant alleles and analyzed the carotenoid content in the corresponding strains. One of the mutants is reddish and it is mutated in the cyclase domain of the protein, and the remaining eight mutants are albino and harbor different mutations on the phytoene synthase (PS) domain. Some of the mutations are expected to produce truncated polypeptides. A strain lacking most of the PS domain contained trace amounts of a carotenoid-like pigment, tentatively identified as the squalene desaturation product diapolycopene. In support, trace amounts of this compound were also found in a knock-out mutant for gene al-2, but not in that for gene al-1, coding for the carotene desaturase. The cyclase activity of the AL-2 enzyme from two albino mutants was investigated by heterologous expression in an appropriately engineered E. coli strain. One of the AL-2 enzymes, predictably with only 20% of the PS domain, showed full cyclase activity, suggesting functional independence of both domains. However, the second mutant showed no cyclase activity, indicating that some alterations in the phytoene synthase segment affect the cyclase domain. Expression experiments showed a diminished photoinduction of al-2 transcripts in the al-2 mutants compared to the wild type strain, suggesting a synergic effect between reduced expression and impaired enzymatic activities in the generation of their albino phenotypes. PMID:21818281

Diaz-Sanchez, Violeta; Estrada, Alejandro F.; Trautmann, Danika; Limon, M. Carmen; Al-Babili, Salim; Avalos, Javier

2011-01-01

442

Analysis of al-2 mutations in Neurospora.  

PubMed

The orange pigmentation of the fungus Neurospora crassa is due to the accumulation of the xanthophyll neurosporaxanthin and precursor carotenoids. Two key reactions in the synthesis of these pigments, the formation of phytoene from geranylgeranyl pyrophosphate and the introduction of ? cycles in desaturated carotenoid products, are catalyzed by two domains of a bifunctional protein, encoded by the gene al-2. We have determined the sequence of nine al-2 mutant alleles and analyzed the carotenoid content in the corresponding strains. One of the mutants is reddish and it is mutated in the cyclase domain of the protein, and the remaining eight mutants are albino and harbor different mutations on the phytoene synthase (PS) domain. Some of the mutations are expected to produce truncated polypeptides. A strain lacking most of the PS domain contained trace amounts of a carotenoid-like pigment, tentatively identified as the squalene desaturation product diapolycopene. In support, trace amounts of this compound were also found in a knock-out mutant for gene al-2, but not in that for gene al-1, coding for the carotene desaturase. The cyclase activity of the AL-2 enzyme from two albino mutants was investigated by heterologous expression in an appropriately engineered E. coli strain. One of the AL-2 enzymes, predictably with only 20% of the PS domain, showed full cyclase activity, suggesting functional independence of both domains. However, the second mutant showed no cyclase activity, indicating that some alterations in the phytoene synthase segment affect the cyclase domain. Expression experiments showed a diminished photoinduction of al-2 transcripts in the al-2 mutants compared to the wild type strain, suggesting a synergic effect between reduced expression and impaired enzymatic activities in the generation of their albino phenotypes. PMID:21818281

Díaz-Sánchez, Violeta; Estrada, Alejandro F; Trautmann, Danika; Limón, M Carmen; Al-Babili, Salim; Avalos, Javier

2011-01-01

443

Semiconducting Al transition-metal quasicrystals  

NASA Astrophysics Data System (ADS)

We report on a class of icosahedral aluminum transition-metal (Al-TM) alloys with true semiconducting behavior. Our description of the structure of these icosahedral quasicrystals is based on the six-dimensional Katz-Gratias-Boudard (KGB) model of the face-centered-icosahedral (fci) quasicrystal and its rational approximants. The shell structure of the atomic surfaces in perpendicular space defines the chemical order of aluminum and transition-metal (TM) atoms leading to semiconducting transport properties. In transition-metal aluminides the hybridization between the Al(s,p) and transition-metal d orbitals is responsible for the formation of a semiconducting gap in the electronic spectrum. We have analyzed the electronic charge distribution and observed an enhanced charge density along the Al-TM bonds that is characteristic of covalent bonding. The existence of an energy gap in the electronic spectrum at or in the vicinity of the Fermi level is explicitly demonstrated for several low-order approximants in the hierarchy of Fibonacci approximants which converges to the icosahedral quasicrystals of the fci class, to which also the i-AlPdRe belongs. We predict existence of truly semiconducting quasicrystalline 1/1-approximants. Our results also lead to the prediction of the existence of new semiconducting quasicrystals with specified Al-TM compositions. The possibility of the existence of a semiconducting band gap suggests an explanation for the anomalously high resistivity of the icosahedral AlPdRe quasicrystals. We demonstrate that substitutional defects violating the ideal Al-TM ordering predicted by the KGB model lead to the formation of localized states in the band gap. A real sample of i-AlPdRe thus seems to be a semiconductor with a band gap filled by the localized states.

Kraj?í, M.; Hafner, J.

2003-10-01

444

Modeling of precipitation in Al alloys  

SciTech Connect

Objective was the development of a computational model of precipitation from a supersaturated alloy solid solution. The model is based on the formalism of chemical-reaction-rate theory combined with classical descriptions of precipitate thermodynamic properties and a mean-field treatment of diffusion-limited growht and coarsening. For the case of precipitation of Al{sub 3}Sc in supersaturated Al-Sc alloys, it is demonstrated how the model can be used to calculate number densities and size distributions of precipitates as a function of aging time and temperature, including effects of continuous cooling and thermally generated point defects. Application of the model to a specific alloy system requires knowledge of diffusion data, point defect energetics, and thermodynamic properties for bulk phases and interphase interfaces. For interfaces and point defects, thermodynamic data can be difficult to measure and reliable values of defect free energies are often unavailable. For this reason, part of the efforts were devoted to applying semiempirical and first-principles atomistic techniques to the calculation of interfacial and point-defect thermodynamic properties. This report discusses applications for interphase interfaces in the Al-Ag, Al-Sc, and Al-Li alloy systems. We also describe atomistic work aimed at understanding the energetics of vacancy clusters in Al. These clusters serve as sinks for isolated vacancies during aging and their growth can lead to more complex defects, such as dislocation loops, that act as heterogeneous nucleation sites.

Asta, M.; Foiles, S.M.; Wolfer, W.G. [Sandia National Labs., Livermore, CA (United States)] [and others

1996-10-01

445

Air blast characteristics of laminated al and NI-AL casings  

NASA Astrophysics Data System (ADS)

Air blast characteristics of Al and Ni-Al laminated materials were experimentally investigated in a 23 m3 closed chamber. Ni and Al foils, 50 to 100 micrometers in thickness, were rolled and compacted to form a cylindrical casing with a density of 95% TMD through an explosive formation technique. Charges were prepared using 2 kg C4 explosive packed in the laminated casing to a metal-explosive mass ratio of 1.75. The blast pressure history measured on the chamber wall showed a double-shock front structure with a precursor shock followed by the primary blast. The front peak pressure for the Ni-Al cased charge reaches 1.5-2 times that of the Al cased, consistent with the larger fireball recorded for the Ni-Al cased. The long time quasi-static explosion pressure (QSP) from the Ni- Al cased charge is 0.8 of that of the Al cased, due to half of Al mass in the Ni-Al.

Zhang, Fan; Ripley, Robert; Wilson, William

2012-03-01

446

Formation and large cryogenic magnetocaloric effect of HoAl2/Al2O3 nanocapsules  

NASA Astrophysics Data System (ADS)

HoAl2/Al2O3 nanocapsules with a core of HoAl2 and a shell of amorphous Al2O3 have been synthesized. The formation of the rare-earth compound nanocapsules can be ascribed to the different melting points and the optimal proportions of Ho and Al atoms during the arc-discharging process. Furthermore, the formation of the Al2O3 shell protects the rare-earth atoms from serious oxidation. The HoAl2/Al2O3 nanocapsules display superparamagnetic properties between the blocking temperature of 6 K and the Curie temperature of 26 K. The absolute value of the magnetic-entropy change in the HoAl2/Al2O3 nanocapsules rapidly increases with the decrease in temperature and reaches 14.7 J kg-1 K-1 at 3 K for a magnetic-field change from 0 to 70 kOe. As a result, this new type of nanocapsule may be applied, in the temperature range studied, in cryogenic magnetic-refrigerator devices.

Liu, X. G.; Li, B.; Geng, D. Y.; Shi, C. X.; Yang, F.; Kang, D. J.; Zhang, Z. D.

2009-02-01

447

Optical microcavities and enhanced electroluminescence from electroformed Al-Al2O3-Ag diodes  

NASA Astrophysics Data System (ADS)

Electroluminescence (EL) and electron emission into vacuum (EM) occur when a non-destructive dielectric breakdown of Al-Al2O3-Ag diodes, electroforming, results in the development of a filamentary region in which current-voltage (I-V) characteristics exhibit voltage-controlled negative resistance. The temperature dependence of I-V curves, EM, and, particularly, EL of Al-Al2O3-Ag diodes with anodic Al2O3 thicknesses between 12 nm and 30 nm, has been studied. Two filters, a long-pass (LP) filter with transmission of photons with energies less than 3.0 eV and a short-pass (SP) filter with photon transmission between 3.0 and 4.0 eV, have been used to characterize EL. The voltage threshold for EL with the LP filter, VLP, is ˜1.5 V. VLP is nearly independent of Al2O3 thickness and of temperature and is 0.3-0.6 V less than the threshold voltage for EL for the SP filter, VSP. EL intensity is primarily between 1.8 and 3.0 eV when the bias voltage, VS ? 7 V. EL in the thinnest diodes is enhanced compared to EL in thicker diodes. For increasing VS, for diodes with the smallest Al2O3 thicknesses, there is a maximum EL intensity, LMX, at a voltage, VLMX, followed by a decrease to a plateau. LMX and EL intensity at 4.0 V in the plateau region depend exponentially on Al2O3 thickness. The ratio of LMX at 295 K for a diode with 12 nm of Al2O3 to LMX for a diode with 25 nm of Al2O3 is ˜140. The ratio of EL intensity with the LP filter to EL intensity with the SP filter, LP/SP, varies between ˜3 and ˜35; it depends on Al2O3 thickness and VS. Enhanced EL is attributed to the increase of the spontaneous emission rate of a dipole in a non-resonant optical microcavity. EL photons interact with the Ag and Al films to create surface plasmon polaritons (SPPs) at the metal-Al2O3 interfaces. SPPs generate large electromagnetic fields in the filamentary region of the electroformed Al-Al2O3-Ag diode, which then acts as an optical microcavity. A model is proposed for electronic processes in electroformed Al-Al2O3-Ag diodes.

Hickmott, T. W.

2013-12-01

448

Tin/Al sub 2 O sub 3 /TiAlOn composite  

SciTech Connect

The present invention pertains to novel improved density ceramic composites of TiN/Al2O3/TiAlON in which there is no spinel and no AlN, but alpha-alumina, titanium nitride, and titanium aluminum oxynitride. In general, the improved density TiN/Al2O3/TiAlON ceramic composites of the invention are prepared by: adding aluminum isobutoxide (Al(O-iBu)3) to a refluxing mixture of deionized water and formic acid at elevated temperatures to obtain an aluminum sol; casting the slurry in molds; drying the cast material and calcining it at about 600 C; screening the calcined material to minus 200 mesh; pressing pellets at about 10 KPsi, isostatically pressing them at about 40 KPsi; and sintering the pellets below 1,700 C to obtain sintered bodies having densities greater than about 4.2 g/cc.

Han, K.

1990-04-02

449

Effects of Al(III) and Nano-Al13 Species on Malate Dehydrogenase Activity  

PubMed Central

The effects of different aluminum species on malate dehydrogenase (MDH) activity were investigated by monitoring amperometric i-t curves for the oxidation of NADH at low overpotential using a functionalized multi-wall nanotube (MWNT) modified glass carbon electrode (GCE). The results showed that Al(III) and Al13 can activate the enzymatic activity of MDH, and the activation reaches maximum levels as the Al(III) and Al13 concentration increase. Our study also found that the effects of Al(III) and Al13 on the activity of MDH depended on the pH value and aluminum speciation. Electrochemical and circular dichroism spectra methods were applied to study the effects of nano-sized aluminum compounds on biomolecules. PMID:22163924

Yang, Xiaodi; Cai, Ling; Peng, Yu; Li, Huihui; Chen, Rong Fu; Shen, Ren Fang

2011-01-01

450

Analog resistive switching behavior of Al/Nb2O5/Al device  

NASA Astrophysics Data System (ADS)

Resistive switching effects in metal–insulator–metal (MIM) structures are strongly influenced by the electrode materials. In this work a platinum-free symmetric Al/Nb2O5/Al device is compared to a device with platinum bottom electrode. For the device with the platinum bottom electrode, filamentary based resistive switching with good data retention was observed up to 125 °C. For the Al/Nb2O5/Al device, an area dependent pure electronic based resistive switching was observed. Electron trapping at the bottom electrode interface is responsible for the observed analog switching behavior which makes an Al/Nb2O5/Al device suitable for neuromorphic applications.

Mähne, H.; Wylezich, H.; Hanzig, F.; Slesazeck, S.; Rafaja, D.; Mikolajick, T.

2014-10-01

451

Theoretical studies of Ni/sub 3/Al and NiAl with impurities  

SciTech Connect

Intermetallic compound has been extensively studied because of their superior properties in strength, low creep rate, and high melting point. But most of the systems have room temperature ductility problems, like Ll/sub 2/ and B2 compounds. Both Ll/sub 2/ Ni/sub 3/Al and B2 NiAl exhibit intergranular fracture mode. Understanding grain boundaries in these materials is of particular importance since intergranular fracture limits the applicability of these otherwise promising material. In an effort trying to understand the fracture mechanism, we have used embedded atom potentials to study the properties of Ni/sub 3/Al and NiAl. We also consider the effect of boron, sulfur, and nickel segregation on the strength of grain boundaries in Ni/sub 3/Al and NiAl. 22 refs., 2 figs.

Chen, S.P.; Voter, A.F.; Boring, A.M.; Albers, R.C.; Hay, P.J.

1988-01-01

452

?-phase formation in NiAl and Ni2Al alloys  

NASA Astrophysics Data System (ADS)

The phase stability of bcc-like NiAl and Ni2Al with respect to phase transformations into the ? phase is examined by first-principles, full-potential, linear muffin-tin orbital method (FPLMTO), band-structure calculations. In agreement with experiment we find that bcc-like NiAl is stable, whereas Ni2Al is unstable. We have also performed some calculations in slightly disordered phases, and find that the disordering tends to inhibit the transformation. This supports the suggestion that a combined displacive/ordering transformation mechanism is involved in the phase transformations of the Ni2Al system. Calculated lattice parameters and the degree of internal shuffling of atoms for the ordered Ni2Al phase were found to be in excellent agreement with the experiment

Sanati, M.; Albers, R. C.; Pinski, F. J.

2001-06-01

453

The lowest ionization potentials of Al2  

NASA Technical Reports Server (NTRS)

Potential curves for the lowest two electronic states (X 2 sigma g + and A 2 pi u) of Al2(+) were computed using complete active space SCF/multireference CI wave functions and large Gaussian basis sets. The lowest observable vertical ionization potential (to Al2(+) X 2 sigma g +) of the Al2 X 3 pi u ground state is calculated to occur around 6.1 eV, in excellent agreement with the experimental range of 6.0 to 6.42 eV obtained in recent cluster ionization studies by Cox and co-workers. The second vertical ionization potential (to Al2(+) A 2 pi u) occurs near 6.4 eV, also within the experimental range. The adiabatic IP of 5.90 eV is in good agreement with the value of 5.8 to 6.1 eV deduced by Hanley and co-workers from the difference in thresholds between collision induced dissociation processes of Al3(+). The computed IP values are somewhat larger than those deduced from branching ratios in cluster fragmentation experiments by Jarrold and co-workers. The observation of an ionization threshold below 6.42 eV is shown to be incompatible with an Al2 ground electronic state assignment of 3 sigma g -, but the separation between the two lowest states of Al2 is so small that it is likely that both are populated in the experiments, so that this does not provide unambiguous support for the recent theoretical assignment of the ground state as 3 pi u.

Bauschlicher, Charles W., Jr.; Barnes, Leslie A.; Taylor, Peter R.

1988-01-01

454

The Stability of Al 11Sm3 (Al4Sm) Phases in the Al-Sm Binary System  

SciTech Connect

The relative stability of Al{sub 11}Sm{sub 3} (Al{sub 4}Sm) intermetallic phases was experimentally investigated through a series of heat treatments followed by microstructural, microchemical, and X-ray diffraction (XRD) analyses. The principal findings are that the high-temperature tetragonal phase is stable from 1655 to 1333 K and that the low-temperature orthorhombic phases, {alpha} and {gamma}, have no range of full stability but are metastable with respect to the crystalline Al and Sm reference states down to 0 K. Thermodynamic modeling is used to describe the relative energetics of stable and metastable phases along with the associated two-phase mixtures. Issues regarding transition energetics and kinetics are discussed.

S.H.Zhou; R.E. Napolitano

2007-06-01

455

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

456

The embrittlement of Al-Zn-Mg and Al-Mg alloys by water vapor  

Microsoft Academic Search

Al4.5Zn1.5Mg and Al5Mg were reacted in water-vapor saturated air (WVSA) at 120°C and tensile tested. After an initial loss of ductility with exposure time, probably caused by hydrogen embrittlement of the grain boundaries, between 15 hours and 25 hours exposure the mechanical properties of Al4.5Zn1.5Mg improved, this effect being due both to a reduced corrosion activity of the grain boundaries

C. D. S. Tuck

1985-01-01

457

Martensitic transformation in CVD NiAl and (Ni,Pt)Al bond coatings  

Microsoft Academic Search

The martensitic phase transformation in single-phase ?-NiAl and (Ni,Pt)Al coatings was investigated. After isothermal exposure to 1150 °C for 100 h, the ? phase in both types of coatings was transformed to a martensite phase during cooling to room temperature. Martensitic transformation was also observed in the (Ni,Pt)Al bond coat with and without a YSZ top layer after thermal cycling

Y Zhang; J. A Haynes; B. A Pint; I. G Wright; W. Y Lee

2003-01-01

458

Third-order elastic moduli of polycrystalline Al-Mg and Al-Cu alloys  

Microsoft Academic Search

The third-order elastic moduli of polycrystalline Al-rich Al-Mg and Al-Cu alloys are determined by measuring the changes in ultrasonic wave velocities under applied uniaxial stress. A solid-state pulse interferometer sensitive to a few parts per million for the relative velocity measurement was used. Pressure derivatives of elastic moduli and Gruneisen gamma are evaluated from the measured second- and third-order moduli.

V. K. Raju; P. J. Reddy

1981-01-01

459

Plasma spray processing of Al 2O 3\\/AlN composite powders  

Microsoft Academic Search

A novel method is proposed to prepare Al2O3\\/AlN composite powders. The composite powders were synthesized by direct nitridation of Al2O3 powders in Ar\\/N2 plasma. The processing characteristics were studied. The results show that the particle size of the initial materials, the nitrogen plasma gas flow rate and the power of the plasma generator are important factors that influence the phase

L. H Cao; K. A Khor; L Fu; F Boey

1999-01-01

460

77 FR 73732 - In the Matter of Amendment of the Designation of al-Qa'ida in Iraq, aka Jam'at al Tawhid wa'al...  

Federal Register 2010, 2011, 2012, 2013

...Front, aka Jabhat al-Nusrah, aka Jabhet al-Nusra, aka The Victory Front, aka Al Nusrah Front for the People of the Levant...the Secretary of State hereby amends the 2004 designation of al-Qa'ida in Iraq as a foreign terrorist...

2012-12-11

461

High temperature deformation of NiAl and CoAl  

NASA Technical Reports Server (NTRS)

The high temperature mechanical properties of the aluminides are reviewed with respect to their potential as high temperature structural materials. It is shown that NiAl and CoAl are substantially stronger than the pure metals Ni and Co at high temperatures and approach the strength of some superalloys, particularly when those superalloys are tested in "weak" directions. The factors that limit and control the high temperature strengths of NiAl and CoAl are examined to provide a basis for the development of intermetallic alloys of this type.

Nix, W. D.

1982-01-01

462

Deformation microstructures of [gamma]-TiAl in the Ti-46Al-2V alloy  

SciTech Connect

The intermetallic compound [gamma]-TiAl (L1[sub 0]) is potentially useful for elevated temperature structural applications. It has significant strength and reasonable ductility at high temperatures, but its applications are seriously affected by poor room temperature ductility. The deformation mechanisms of [gamma]-TiAl have been the topics of several papers in recent years. The effect of V addition on the deformation microstructures of [gamma]-TiAl in the two-phase ([alpha][sub 2] + [gamma]) Ti-46Al-2V (at.%) alloy at various temperature is reported in this paper.

Das, S.; Chaudhuri, K. (Univ. of Wisconsin, Madison, WI (United States). Dept. of Materials Science and Engineering)

1995-01-15

463

HYDROGEN ADSORPTION ON ?-TiAl (001) AND Ni/TiAl (001) SURFACES  

NASA Astrophysics Data System (ADS)

In this paper, we present first principles calculations of the energetic, electronic and magnetic properties of the variant termination of TiAl (001) and Ni/TiAl (001) surfaces with and without hydrogen atoms. The calculations have been performed within the density functional theory using full-potential linearized augmented plane wave method. The generalized gradient approximation (GGA) is utilized as the exchange-correlation energy. The octahedral site is the stable absorption site of H atom in the ?-TiAl system. This absorption reduces the cohesive energy of ?-TiAl system due to increase in the lattice constant. The surface energy for both TiAl (001) terminations is calculated. The stable adsorption site of H atoms on the variant termination of TiAl (001) surface is performed. The adsorption energy of hydrogen on Ti is more energetic than that on Al. The adsorption of H atom on both terminations of H/Ni/TiAl (001) is more preferable at the bridge site. The adsorption energies are enhanced on Ni atom due to the contraction between d-Ni bands and TiAl substrate band.

Mubarak, A. A. Karim; Alelaimi, Mahmoud

2014-04-01

464

Microsample testing of single crystalline Ti-52 at% Al and Ti-55.5 at% Al  

SciTech Connect

Dislocation activity in two-phase commercial TiAl alloys occurs most readily in the {gamma}-TiAl phase, and measurements of the CRSS of single crystalline {gamma}-TiAl provides a solid foundation for understanding the mechanical performance of these alloys. Single crystals of {gamma}-TiAl with greater than 54.5 at% Al have been grown using the optical float zone crystal growing technique, but single crystals with lower Al content, closer to that of commercial alloys, have not. In the present study, polycrystalline ingots of Ti-52 at% Al have been heat treated to form very large grains, and microsample tensile specimens, which have a nominal gage cross-section of 250{micro}m x 300{micro}m, a gage length of 250{micro}m and an overall length of 3 mm, have been machined from within single grains. Microsample high-temperature stress-strain curves for Ti-55.5 at% Al single crystals oriented along the [001] and [010] are presented. Tensile test results for Ti-52 at% Al tested at 1,073K along the[{bar 2}37], [{bar 1}73] and [{bar 3}44] orientations will also be discussed.

Zupan, M.; Dimiduk, D.M.; Hemker, K.J.

1999-07-01

465

Mechanical properties of Al and Al alloys and their relationship to interconnection reliability  

NASA Astrophysics Data System (ADS)

Pure Al, Al-3 wt %Si, and Al-15 at. % C films are characterized macroscopically in terms of yield stress and hardness and microscopically in terms of a grain structure to investigate the effects of Si and carbon additives to modify mechanical properties of the Al matrix. A theory is presented to estimate the yield stress of metal films. The experimental method is based on laser interferometer measurements of the varied substrate curvature involved with thermal treatment of a film-substrate composite. It is shown that carbon addition increases yield stress and hardness of Al, whereas Si addition decreases these properties. Carbon addition suppresses grain growth by 450 °C annealing as small as about 0.04 ?m. Reliability tests on Al and Al-alloy interconnects revealed that increased yield stress improves resistance against failures due to the stress at high temperatures and high current densities, but degrades resistance against cycled thermal shock. The double layered Al-C/Al structure was highly resistant against both thermal and current stress.

Ozawa, Kiyoshi

1993-01-01

466

Solid state reaction of Al and Zr in Al/Zr multilayers: A calorimetry study  

SciTech Connect

The exothermic, solid state reaction of Al and Zr has been studied in thick Al/Zr multilayers using Differential Scanning Calorimetry and X-ray diffraction. The multilayer samples were magnetron sputter deposited into highly textured alternate layers of Al and Zr with nominal composition Al{sub 3}Zr. The samples used in this study were 47{mu}m thick with a 427{Angstrom} period. When samples were isochronally scanned from 25 to 725C, a large exotherm at {approximately}350C was followed by one or two smaller exotherms at {approximately}650C. The first exotherm is dominated by a diffusion based reaction of Al and Zr that produces two phases in isochronal scans: amorphous Al-Zr and cubic Al{sub 3}Zr, and two additional phases in isothermal anneals: Al{sub 2}Zr and tetragonal Al{sub 3}Zr. The exothermic heat from this multi-phase reaction is measured using isochronal scans and isothermal anneals, and the heat flow is analyzed using a 1-D diffusion based model. An average activation energy and a diffusion constant are determined. In the isothermal scans, the total exothermic heat increases linearly with {radical}time, and layer thicknesses vary linearly with heat.

Blobaum, K.J.; Weihs, T.P.; Barbee, T.W. Jr.; Wall, M.A.

1995-04-14

467

Elastic and piezoelectric properties of AlN and LiAlO2 single crystals.  

PubMed

We have successfully grown high-quality AlN piezoelectric single crystal using the sublimation technique. Transparent crack-free boules of approximately 15 mm in diameter and 25 mm in length along the [0001] direction were obtained, with coloring from amber to dark brown depending on growth temperature. Full sets of material parameters of grown AlN and commercially available LiAlO(2) bulk crystals were measured at room temperature. Temperature coefficients of the material parameters of LiAlO(2) were also obtained in a temperature range from -70 to +50 degrees C. PMID:20378443

Sotnikov, Andrey; Schmidt, Hagen; Weihnacht, Manfred; Smirnova, Elena; Chemekova, Tatiana; Makarov, Yuri

2010-04-01

468

Possible Involvement of Al-Induced Electrical Signals in Al Tolerance in Wheat.  

PubMed Central

The relationship between Al-induced depolarization of root-cell transmembrane electrical potentials (Em) and Al tolerance in wheat (Triticum aestivum L.) was investigated. Al exposure induced depolarizations of Em in the Al-tolerant wheat cultivars Atlas and ET3, but not in the Al-sensitive wheat cultivars Scout and ES3. The depolarizations of Em occured in root cap cells and as far back as 10 mm from the root tip. The depolarization was specific to Al3+; no depolarization was observed when roots were exposed to the rhizotoxic trivalent cation La3+. The Al-induced depolarization occurred in the presence of anion-channel antagonists that blocked the release of malate, indicating that the depolarization is not due to the electrogenic efflux of malate2-. K+-induced depolarizations in the root cap were of the same magnitude as Al-induced depolarizations, but did not trigger malate release, indicating that Al-induced depolarization of root cap cell membrane potentials is probably linked to, but is not sufficient to trigger, malate release. PMID:12223834

Papernik, L. A.; Kochian, L. V.

1997-01-01

469

The PtAl- and PtAl2- anions: Theoretical and photoelectron spectroscopic characterization  

NASA Astrophysics Data System (ADS)

We report a joint photoelectron spectroscopic and theoretical study of the PtAl- and PtAl2- anions. The ground state structures and electronic configurations of these species were identified to be C?v, 1?+ for PtAl-, and C2v, 2B1 for PtAl2-. Structured anion photoelectron spectra of these clusters were recorded and interpreted using ab initio calculations. Good agreement between theory and experiment was found. All experimental features were successfully assigned to one-electron transitions from the ground state of the anions to the ground or excited states of the corresponding neutral species.

Zhang, Xinxing; Ganteför, Gerd; Bowen, Kit H.; Alexandrova, Anastassia N.

2014-04-01

470

Magnetron sputtered nc-Al/alpha-Al2O3 nanocomposite thin films for nonvolatile memory application.  

PubMed

In this paper, we developed nc-Al/a-Al2O3 nanocomposite thin films using magnetron sputtering. The nc-Al/a-Al2O3 films were sputtered on p-type Si substrates from pure Al target in gas mixture of Ar and O2. X-ray photoelectron spectroscopy and high resolution transmission electron microscope studies confirm that the nanocrystalline Al are embedded in amorphous Al2O3 matrix thus nc-Al/ a-Al2O3 nanocomposite forms. This nanocomposite thin film exhibits memory effect as a result of charge trapping. PMID:19916417

Li, Yibin; Zhang, Sam; Liu, Y; Chen, T P; Sritharan, Thirumany; Xu, Cong

2009-07-01

471

Sintering Behavior and Mechanical Properties of NiAl, Al2O3, and NiAl-Al2O3 Composites  

NASA Astrophysics Data System (ADS)

It is commonly known that the properties of sintered materials are strongly related to technological conditions of the densification process. This paper shows the sintering behavior of a NiAl-Al2O3 composite, and its individual components sintered separately. Each kind of material was processed via the powder metallurgy route (hot pressing). The progress of sintering at different stages of the process was tested. Changes in the microstructure were examined using scanning and transmission electron microscopy. Metal-ceramics interface was clean and no additional phases were detected. Correlation between the microstructure, density, and mechanical properties of the sintered materials was analyzed. The values of elastic constants of NiAl/Al2O3 were close to intermetallic ones due to the volume content of the NiAl phase particularly at low densities, where small alumina particles had no impact on the composite's stiffness. The influence of the external pressure of 30 MPa seemed crucial for obtaining satisfactory stiffness for three kinds of the studied materials which were characterized by a high dense microstructure with a low number of isolated spherical pores.

Chmielewski, M.; Nosewicz, S.; Pietrzak, K.; Rojek, J.; Strojny-N?dza, A.; Mackiewicz, S.; Dutkiewicz, J.

2014-08-01

472

Photoemission from Al Alloys during Tensile Deformation  

NASA Astrophysics Data System (ADS)

We report simultaneous measurements of strain and photoelectron emission intensity from high purity Al (1350), Al-Mg (5052), Al-Mn (3003), Al-Cu (2024) and Al-Mg-Si (6061) alloys under uniaxial tension due to pulsed excimer laser radiation (248-nm). The photoemission signals are sensitive to deformation-induced changes in surface morphology, including the formation of slip lines and slip bands. In the early stages of deformation (strain Â¡Ü 0.03), the photoemission intensity increases gradually in a nonlinear fashion. Depending on sample composition and heat treatment, the photoemission intensity subsequently grows linearly until the accumulated strain reaches about 0.20. Finally, the photoemission intensity increases parabolically until failure. The onset of strain localization corresponds to the transition from linear to parabolic growth. A constitutional model incorporating microstructure evolution and work-hardening during tensile deformation is proposed to qualitatively interpret the growth of the photoemission signals as a function of strain. The photoemission signals from the tested alloys are interpreted in terms of the effect of surface treatment, work function, microstructure, and composition on the development of dislocation structures during deformation.

Cai, Mingdong; Langford, Stephen; Levine, Lyle; Dickinson, Thomas

2004-03-01

473

First-principle study of adhesion, wetting and bonding on Al/Al3V(001) interface  

NASA Astrophysics Data System (ADS)

The adhesion, wetting, and bonding on fcc-Al(001)/D022-Al3V(001) interface were investigated using density functional calculations. Considering different terminations of Al3V(001) (Al- and Al + V-terminated) and stacking sites (center-, hollow- and top-sites), six Al/Al3V(001) models were calculated. For the models with same stacking site, Al + V-terminated model has larger work of adhesion (Wad) than the Al-terminated one. For the models with same termination, the work of adhesion decreases, and the interface energy (?int) increases as the order of top-, bridge- and center-sites. Al-terminated-center-sited and Al + V-terminated-center-sited models are more stable among six models. After complete structure relaxation, both models have the same epitaxial stacking style. Therefore, the both models can be regarded as of the same and most stable one (noted as CSI model), but separating along Al-Al and Al-Al+V inter-planes. Based on the perfect wetting and strong adhesion in CSI model, the heterogeneous nucleation of ?-Al on Al3V(001) was interpreted in terms of crystallography and thermodynamics. The interfacial bonding was discussed with analysis of valence electron density distribution and partial density of states (PDOS). The bonding is mainly contributed from AlV covalent bonds and AlAl metallic interactions.

Li, Jian; Qi, Yuning; Zhang, Ming; Zhou, Yong; Li, Xiao

2014-06-01

474

Early Solar Nebula Condensates with Canonical, Not Supracanonical, Initial 26Al/27Al Ratios  

NASA Astrophysics Data System (ADS)

The short-lived radionuclide 26Al existed throughout the solar nebula 4.57 Ga ago, and the initial abundance ratio (26Al/27Al)0, as inferred from magnesium isotopic compositions of calcium-aluminum-rich inclusions (CAIs) in chondritic meteorites, has become a benchmark for understanding early solar system chronology. Internal mineral isochrons in most CAIs measured by secondary ion mass spectrometry (SIMS) give (26Al/27Al)0 ~ (4-5) × 10-5, called "canonical." Some recent high-precision analyses of (1) bulk CAIs measured by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS), (2) individual CAI minerals and their mixtures measured by laser-ablation MC-ICPMS, and (3) internal isochrons measured by multicollector (MC)-SIMS indicated a somewhat higher "supracanonical" (26Al/27Al)0 ranging from (5.85 ± 0.05) × 10-5 to >7 × 10-5. These measurements were done on coarse-grained Type B and Type A CAIs that probably formed by recrystallization and/or melting of fine-grained condensate precursors. Thus the supracanonical ratios might record an earlier event, the actual nebular condensation of the CAI precursors. We tested this idea by performing in situ high-precision magnesium isotope measurements of individual minerals in a fine-grained CAI whose structures and volatility-fractionated trace element abundances mark it as a primary solar nebula condensate. Such CAIs are ideal candidates for the fine-grained precursors to the coarse-grained CAIs, and thus should best preserve a supracanonical ratio. Yet, our measured internal isochron yields (26Al/27Al)0 = (5.27 ± 0.17) × 10-5. Thus our data do not support the existence of supracanonical (26Al/27Al)0 = (5.85-7) × 10-5. There may not have been a significant time interval between condensation of the CAI precursors and their subsequent melting into coarse-grained CAIs.

MacPherson, G. J.; Bullock, E. S.; Janney, P. E.; Kita, N. T.; Ushikubo, T.; Davis, A. M.; Wadhwa, M.; Krot, A. N.

2010-03-01

475

ALS and Frontotemporal Dysfunction: A Review  

PubMed Central

Though once believed to be a disease that was limited to the motor system, it is now apparent that amyotrophic lateral sclerosis (ALS) may be associated with cognitive changes in some patients. Changes are consistent with frontotemporal dysfunction, and may range from mild abnormalities only recognized with formal neuropsychological testing, to profound frontotemporal dementia (FTD). Executive function, behavior, and language are the most likely areas to be involved. Screening helpful in detecting abnormalities includes verbal or categorical fluency, behavioral inventories filled out by the caregiver, and evaluation for the presence of depression and pseudobulbar affect. Patients with cognitive dysfunction have shortened survival and may be less compliant with recommendations regarding use of feeding tubes and noninvasive ventilation. Evolving knowledge of genetic and pathological links between ALS and FTD has allowed us to better understand the overlapping spectrum of ALS and FTD. PMID:22919484

Achi, Eugene Y.; Rudnicki, Stacy A.

2012-01-01

476

Textures of Ta/Al multilayer films  

NASA Astrophysics Data System (ADS)

Ta/Al multilayer films with a modulation wavelength of 7.0 nm were grown using magnetron sputtering. The Bragg ?-2? scan pattern and the plate film photograph of x-ray diffraction reveal that the sample has Ta(110) and A1(111) axial textures with a mosaic spread of about ±5° and coherency strains. The structure change of the multilayer sample after annealing at 550 °C for 2 h is determined by the plate film photography of x-ray diffraction to study the thermal stability. It is found that after annealing a large amount of Ta and Al atoms at the interfaces are combined into TaAl3 with [(202)+(002)] textures.

Yuan, X. Y.; Wu, Z. Q.; Hu, A.; Jiang, S. S.; Qiu, Y.; Khatanova, N. A.; Ilyushin, R. S.

1993-04-01