Thermo Mechanical Treatment of Nickel and Titanium Aluminides

2005 ◽  
Vol 237-240 ◽  
pp. 653-658
Author(s):  
Vijaya Agarwala ◽  
Joanna Karwan-Baczewska
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Nickel Aluminide ◽  
High Performance ◽  
Titanium Aluminides ◽  
Flow Behavior ◽  
Tensile Tests ◽  
Arbitrary Parameter ◽  
Average Grain Size ◽  
Structural Applications

Polycrystalline Ni3Al and TiAl are attractive materials for high temperature structural applications due to their stability in oxidizing and sulphidizing environment upto700 0 C. They possess significantly higher specific stiffness and similar specific strength as that of super alloys. Hence, these materials can replace super alloys for high temperature applications (~900°C). TiAl has lesser density and can be used for reducing component weight up to 50% and suitable for aerospace and automobile (high performance vehicles) sectors. The major difficulty for putting Ni3Al for engineering applications is its extremely low ductility and inter-granular fracture at ambient temperatures. TiAl, apart from the said brittleness it also suffers from high temperature corrosion. However the brittleness of these aluminides can be reduced by micro-alloying and by subjecting them to Thermo Mechanical Treatments, TMT. This paper deals with the recrystallization studies on nickel aluminides, deformed to different extents by rolling. The average grain size dependence with the % elongation is evaluated in the grain size range of 10-35micron. For the nickel aluminide deformed for 50% by rolling, the variation of resistivity and hardness with annealing time is determined. The homogenized TiAl samples were cold worked and annealed at 1000 0 C. Since the aluminide suffers from low ductility at room temperature, an arbitrary parameter, electrical resistivity, was chosen. Corresponding hardness values were also obtained. Finally a qualitative determination of ductility was made by studying the flow behavior of alloy around the hardness indentation. Thus a correlation was developed between resistivity, hardness and ductility values. It was then to some extent possible to investigate the TMT cycles on the microstructure and hence on the ductility of the TiAl without going for the actual tensile tests.

B2 Alulinides for High Temperature Applications

1986 ◽  
Vol 81 ◽  
Author(s):  
K. Vedula ◽  
J.R. Stephes
Keyword(s):  
High Temperature ◽  
Nickel Aluminide ◽  
Titanium Aluminides ◽  
Research Center ◽  
Nasa Lewis Research ◽  
Aerospace Materials ◽  
Composite Systems ◽  
Reinforced Composite ◽  
Structural Applications ◽  
Titanium Nickel

The B2 aluminides are currently being investigated for potential high temperature structural applications. Although they are not being as actively pursued as the titanium aluminides or the L12 nickel aluminide, the B2 aluminides are very attractive from density gonsiderations. Several recent reviews of the potential for aluminides are available in literature [e.g Ref. 1,2]. Table I is a comparison of the titanium, nickel and iron aluminides of interest and shows that B2 NiAl and FeAl have the major advantage of lower densities than Ni3Al and Fe3Al. In addition, the melting point of NiAl is over 200K higher than convetitional nickel based superalloys. Hence, although low density is the prime driving force, at least in NiAl a temperature advantage is also possible. Both of these aluminides have the advantage of containing very inexpensive elements. In fact, the thrust towards the B2 aluminides evolved from a program aimed at conserving strategic aerospace materials at NASA Lewis Research Center. A recent thrust at NASA Lewis Research Center has been to consider these aluminides as matrix materials for fiber reinforced composite systems.

scholarly journals Development of Al–Mg–Si alloy performance by addition of grain refiner Al–5Ti–1B alloy

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110294
Author(s):  
Khaled Abd El-Aziz ◽  
Emad M Ahmed ◽  
Abdulaziz H Alghtani ◽  
Bassem F Felemban ◽  
Hafiz T Ali ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Corrosion Resistance ◽  
Testing Machine ◽  
Dendritic Structure ◽  
Grain Refiner ◽  
Corrosion Properties ◽  
Average Grain Size ◽  
Structural Applications ◽  
Alloy Addition

Aluminum alloys are the most essential part of all shaped castings manufactured, mainly in the automotive, food industry, and structural applications. There is little consensus as to the precise relationship between grain size after grain refinement and corrosion resistance; conflicting conclusions have been published showing that reduced grain size can decrease or increase corrosion resistance. The effect of Al–5Ti–1B grain refiner (GR alloy) with different percentages on the mechanical properties and corrosion behavior of Aluminum-magnesium-silicon alloy (Al–Mg–Si) was studied. The average grain size is determined according to the E112ASTM standard. The compressive test specimens were made as per ASTM: E8/E8M-16 standard to get their compressive properties. The bulk hardness using Vickers hardness testing machine at a load of 50 g. Electrochemical corrosion tests were carried out in 3.5 % NaCl solution using Autolab Potentiostat/Galvanostat (PGSTAT 30).The grain size of the Al–Mg–Si alloy was reduced from 82 to 46 µm by the addition of GR alloy. The morphology of α-Al dendrites changes from coarse dendritic structure to fine equiaxed grains due to the addition of GR alloy and segregation of Ti, which controls the growth of primary α-Al. In addition, the mechanical properties of the Al–Mg–Si alloy were improved by GR alloy addition. GR alloy addition to Al–Mg–Si alloy produced fine-grained structure and better hardness and compressive strength. The addition of GR alloy did not reveal any marked improvements in the corrosion properties of Al–Mg–Si alloy.

scholarly journals Structural Transformations and Mechanical Properties of Metastable Austenitic Steel under High Temperature Thermomechanical Treatment

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 645
Author(s):  
Igor Litovchenko ◽  
Sergey Akkuzin ◽  
Nadezhda Polekhina ◽  
Kseniya Almaeva ◽  
Evgeny Moskvichev
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
High Temperature ◽  
Austenitic Steel ◽  
Structural Transformations ◽  
Initial State ◽  
Twin Boundaries ◽  
Metastable Austenitic Steel ◽  
Average Grain Size ◽  
Heating Up

The effect of high-temperature thermomechanical treatment on the structural transformations and mechanical properties of metastable austenitic steel of the AISI 321 type is investigated. The features of the grain and defect microstructure of steel were studied by scanning electron microscopy with electron back-scatter diffraction (SEM EBSD) and transmission electron microscopy (TEM). It is shown that in the initial state after solution treatment the average grain size is 18 μm. A high (≈50%) fraction of twin boundaries (annealing twins) was found. In the course of hot (with heating up to 1100 °C) plastic deformation by rolling to moderate strain (e = 1.6, where e is true strain) the grain structure undergoes fragmentation, which gives rise to grain refining (the average grain size is 8 μm). Partial recovery and recrystallization also occur. The fraction of low-angle misorientation boundaries increases up to ≈46%, and that of twin boundaries decreases to ≈25%, compared to the initial state. The yield strength after this treatment reaches up to 477 MPa with elongation-to-failure of 26%. The combination of plastic deformation with heating up to 1100 °C (e = 0.8) and subsequent deformation with heating up to 600 °C (e = 0.7) reduces the average grain size to 1.4 μm and forms submicrocrystalline fragments. The fraction of low-angle misorientation boundaries is ≈60%, and that of twin boundaries is ≈3%. The structural states formed after this treatment provide an increase in the strength properties of steel (yield strength reaches up to 677 MPa) with ductility values of 12%. The mechanisms of plastic deformation and strengthening of metastable austenitic steel under the above high-temperature thermomechanical treatments are discussed.

Recent Advances in Development and Processing of Titanium Aluminide Alloys

2000 ◽  
Vol 646 ◽  
Author(s):  
Fritz Appel ◽  
Helmut Clemens ◽  
Michael Oehring
Keyword(s):  
High Temperature ◽  
Titanium Aluminide ◽  
Titanium Aluminides ◽  
Environmental Stability ◽  
Physical Metallurgy ◽  
Specific Strength ◽  
Wide Range ◽  
Structural Applications ◽  
Strength And Stiffness ◽  
Nickel Base

ABSTRACTIntermetallic titanium aluminides are one of the few classes of emerging materials that have the potential to be used in demanding high-temperature structural applications whenever specific strength and stiffness are of major concern. However, in order to effectively replace the heavier nickel-base superalloys currently in use, titanium aluminides must combine a wide range of mechanical property capabilities. Advanced alloy designs are tailored for strength, toughness, creep resistance, and environmental stability. Some of these concerns are addressed in the present paper through specific comments on the physical metallurgy and technology of gamma TiAl-base alloys. Particular emphasis is placed on recent developments of TiAl alloys with enhanced high-temperature capability.

Superplastic Behavior of a Cu-Cr-Zr Alloy Subjected to ECAP

2016 ◽  
Vol 838-839 ◽  
pp. 404-409
Author(s):  
Roman Mishnev ◽  
Iaroslava Shakhova ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Strain Rate ◽  
Temperature Interval ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Superplastic Behavior ◽  
Average Grain Size ◽  
Gauge Section ◽  
Zr Alloy

A Cu-0.87%Cr-0.06%Zr alloy was subjected to equal channel angular pressing (ECAP) at a temperature of 400 °C up to a total strain of ~ 12. This processing produced ultra-fine grained (UFG) structure with an average grain size of 0.6 μm and an average dislocation density of ~4×1014 m-2. Tensile tests were carried out in the temperature interval 450 – 650 °C at strain rates ranging from 2.8´10-4 to 0.55 s-1. The alloy exhibits superplastic behavior in the temperature interval 550 – 600 °C at strain rate over 5.5´10-3 s-1. The highest elongation-to-failure of ~300% was obtained at a temperature of 575 °C and a strain rate of 2.8´10-3 s-1 with the corresponding strain rate sensitivity of 0.32. It was shown the superplastic flow at the optimum conditions leads to limited grain growth in the gauge section. The grain size increases from 0.6 μm to 0.87 μm after testing, while dislocation density decreases insignificantly to ~1014 m-2.

scholarly journals Influence of Vibration Treatment and Modification of A356 Aluminum Alloy on Its Structure and Mechanical Properties

Metals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 87 ◽  
Author(s):  
Vladimir Promakhov ◽  
Marina Khmeleva ◽  
Ilya Zhukov ◽  
Vladimir Platov ◽  
Anton Khrustalyov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Titanium Diboride ◽  
Tensile Tests ◽  
A356 Aluminum Alloy ◽  
Vibration Treatment ◽  
Complex Effect ◽  
Average Grain Size ◽  
Master Alloys ◽  
A356 Aluminum

A series of casting experiments was conducted with A356 aluminum alloys by applying vibration treatment and using Al-TiB2 composite master alloys. The main vibration effects include the promotion of nucleation and a reduction in as-cast grain size. Using composite master alloys with titanium diboride microparticles allows further reduction in the average grain size to 140 µm. The reasons for this behavior are discussed in terms of the complex effect on the melt, considering the destruction of dendrites, and the presence of additional crystallization centers. Tensile tests were performed on the samples obtained during the vibration treatment and with titanium diboride particles. The tensile strength increased from 182 to 227 MPa after the vibration treatment for the alloys containing titanium diboride.

Status and Development of Nickel Aluminide (NiAl) Composites

1994 ◽  
Vol 350 ◽  
Author(s):  
R. A. Amato ◽  
J.-M. Yang
Keyword(s):  
High Temperature ◽  
Mechanical Behavior ◽  
Nickel Aluminide ◽  
Matrix Alloy ◽  
Fiber Development ◽  
Continuous Fiber ◽  
Alloy Development ◽  
New Class ◽  
Structural Applications ◽  
Key Issues

AbstractNiAl-based composites are a new class of engineering materials being developed for high temperature structural applications in oxidizing and aggressive environments. This paper discusses some of the recent advances in developing continuous fiber-reinforced polycrystalline NiAl-based composites. Several key issues including matrix alloy development, fiber development, fabrication development and mechanical behavior will be addressed.

The effect of thermal exposure on precipitation of Ti3Al(C,N) in Ti-48Al-IV-0.2C

1992 ◽  
Vol 50 (1) ◽  
pp. 22-23
Author(s):  
W.T. Donlon ◽  
W.E. Dowling ◽  
C.E. Cambell ◽  
J.E. Allison
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Titanium Aluminides ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
Weight Ratio ◽  
Thermal Exposure ◽  
Treatment Temperature ◽  
Field Samples ◽  
Structural Applications

Titanium aluminides are attractive candidates for high temperature structural applications because of their high strength to weight ratio at elevated temperatures. The microstructure of these alloys consists of γ-TiAl (distorted L10 structure) , plus α2-Ti3Al (ordered DO19 structure). Varying the heat treatment temperature and cooling rate of these alloys alters the volume fraction and distribution of the γ and α2 phases. This has significant effects on the room temperature ductility. In addition, precipitation of carbides has been observed during high temperature exposure. The effect of these precipitates on the mechanical properties has yet to be determined.Figure 1 shows the general microstructure that was used for this investigation. TEM foils were prepared by electropolishing using 5% perchloric, 35% 1-butanol, 60% methanol at -40°C. No precipitates were found following heat treatment in the γ+α phase field. Samples approximately 20 mm square were thermally exposed to temperatures between 625° and 1000°C for times between 1 and 2000 hours.

In Situ Observation of Grain Growth and Recrystallization of Steel at High Temperature

2010 ◽  
Vol 638-642 ◽  
pp. 1077-1082 ◽  
Author(s):  
Yasuhiro Yogo ◽  
Kouji Tanaka ◽  
Koukichi Nakanishi
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Grain Growth ◽  
In Situ Observation ◽  
Initial Structure ◽  
Grain Sizes ◽  
Dynamic Observation ◽  
Average Grain Size ◽  
Observation Method

An in-situ observation method for structures at high temperature is developed. The new observation device can reveal grain boundaries at high temperature and enables dynamic observation of these boundaries. Grain growth while maintaining microstructure at high temperature is observed by the new observation device with only one specimen for the entire observation, and grain sizes are quantified. The quantifying process reveals two advantages particular to the use of the new observation device: (1) the ability to quantify grain sizes of specified sizes and (2) the results of average grain size for many grains have significantly less errors because the initial structure is the same for the entire observation and the quantifying process. The new observation device has the function to deform a specimen while observing structures at high temperature, so that enables it to observe dynamic recrystallization of steel. The possibility to observe recrystallization is also shown.

Effects of Starting Materials on Preparation and Properties of Pure SiC Ceramics via the HTPVT Method

2019 ◽  
Vol 889 ◽  
pp. 3-9
Author(s):  
Yu Chen Deng ◽  
Nan Long Zhang ◽  
Ya Ming Zhang ◽  
Bo Wang ◽  
Jian Feng Yang
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Gas Phase ◽  
Vapor Transport ◽  
Nucleation Density ◽  
Flexure Strength ◽  
Nucleation Stage ◽  
Sic Ceramics ◽  
Initial Nucleation ◽  
Average Grain Size

The method of high temperature physical vapor transport (HTPVT) is an available approach to prepare silicon carbide (SiC) ceramics with high density and high purity. In the present work, α-SiC (6H-SiC) and β-SiC (3C-SiC) powders were used as starting materials respectively to fabricate SiC ceramics with HTPVT process, and the effects of starting materials on nucleation, density, microstructure and mechanical properties of SiC ceramics were investigated. It showed that at high temperature, the decomposition rate of β-SiC was higher than that of α-SiC, and at the initial nucleation stage, the average grain size of SiC crystal obtained with β-SiC starting materials was smaller than that with α-SiC starting materials, because higher vapour pressure of gas phase which decomposed by β-SiC starting materials facilitated nucleation and growth of SiC grains. Density of the resulted SiC ceramics using α-SiC and β-SiC as starting materials was 3.16 g·cm-3 and 3.17 g·cm-3, indicating close values, while, using β-SiC as the starting materials, the grain size was smaller, consequently, the flexure strength was higher. Increasing growth temperature from 2200°C to 2300°C, the densities and the flexure strength of the SiC ceramics using either α-SiC or β-SiC were decreased.

Sign in / Sign up

Export Citation Format

Share Document