The Effect of Molybdenum on the Creep Behavior of Orthorhombic Titanium Aluminides

2002 ◽  
Author(s):  
Dominique A. Shepherd ◽  
Vijay K. Vasudevan
Keyword(s):  
Creep Behavior ◽  
Titanium Aluminide ◽  
Creep Resistance ◽  
Titanium Aluminides ◽  
Tensile Creep ◽  
Atomic Fraction ◽  
Beta Transus ◽  
Creep Properties ◽  
Orthorhombic Titanium ◽  
Transus Temperature

The effect of molybdenum additions on the creep properties of two orthorhombic titanium aluminide materials, Ti-22Al-26Nb and Ti-22Al-24.5Nb-1.5Mo (% atomic fraction), has been investigated. Heat treatments below the beta transus temperature followed by a 16-hour ageing treatment produced similar microstructures. Using the similar microstructures (consisting of O laths in a B2 matrix with α2 dispersed at B2 grain boundaries) for the two compositions, tensile creep testing was conducted under stresses of 68 MPa, 160 MPa, and 197 MPa at temperatures of 590 °C and 760 °C. The creep results demonstrated the favorable effects of Mo on creep resistance in these orthorhombic titanium aluminides. Due to similar microstructures, results also suggested that improvements have been substructural, rather than purely microstructural, in nature.

Microstructure and Creep Properties of AJ62 and AE44 Die-Casting Magnesium Alloys

2010 ◽  
Vol 638-642 ◽  
pp. 1546-1551 ◽  
Author(s):  
Andrzej Kiełbus ◽  
Tomasz Rzychoń
Keyword(s):  
Magnesium Alloys ◽  
Creep Resistance ◽  
Cell Structure ◽  
Creep Behaviour ◽  
Die Casting ◽  
Tensile Creep ◽  
Creep Properties ◽  
Die Cast ◽  
Subgrain Formation ◽  
Good Creep Resistance

Microstructure and tensile creep behaviour of the die-cast AE44 and AJ62 magnesium alloys has been studied at temperatures between 175°C and 200°C and at stresses in the range from 60 to 75 MPa. At the 175°C the AJ62 and AE44 alloys exhibit good creep resistance after 120h creep deformation. At 200°C the AE44 alloy shows still good creep resistance, whereas in the case of AJ62 alloy the rapid decreasing of creep resistance has been observed. TEM observations reveal dislocations cell structure in AE44 alloy after creep test. In AJ62 alloy subgrain formation and decreasing the dislocation density have been observed.

Characterization of the Microstructure, Tensile and Creep Behavior of Powder Metallurgy Processed and Rolled Ti-6Al-4V-1B Alloy

2010 ◽  
Vol 436 ◽  
pp. 195-203 ◽  
Author(s):  
Wei Chen ◽  
Carl J. Boehlert
Keyword(s):  
Elevated Temperature ◽  
Powder Metallurgy ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Deformation Behavior ◽  
Creep Resistance ◽  
Tensile Creep ◽  
Duplex Microstructure ◽  
Α Phase

This work investigated the microstructure and elevated-temperature (400-475oC) tensile and tensile-creep deformation behavior of a powder metallurgy (PM) rolled Ti-6Al-4V-1B(wt.%) alloy. The PM rolled Ti-6Al-4V-1B alloy exhibited a duplex microstructure, and it did not exhibit a strong α-phase texture compared with the PM extruded Ti-6Al-4V-1B alloy. The PM rolled Ti-6Al-4V-1B alloy exhibited greater creep resistance than the PM extruded Ti-6Al-4V-1B alloy as well as the as-cast Ti-6Al-4V-1B alloy.

Improved tensile creep properties of yttrium- and lanthanum-doped alumina: a solid solution effect

2001 ◽  
Vol 16 (2) ◽  
pp. 425-429 ◽  
Author(s):  
Junghyun Cho ◽  
Chong Min Wang ◽  
Helen M. Chan ◽  
J. M. Rickman ◽  
Martin P. Harmer
Keyword(s):  
Solid Solution ◽  
Steady State ◽  
Creep Behavior ◽  
Solubility Limit ◽  
Steady State Creep ◽  
Tensile Creep ◽  
Creep Properties ◽  
Uniform Microstructure ◽  
Equiaxed Grains ◽  
Rare Earth Doped

The tensile creep behavior of yttrium- and lanthanum-doped alumina (at dopant levels below the solubility limit) was examined. Both compositions (100 ppm yttrium, 100 ppm lanthanum) exhibited a uniform microstructure consisting of fine, equiaxed grains. The creep resistance of both doped aluminas was enhanced, compared with undoped alumina, by about two orders of magnitude, which was almost the same degree of improvement as for materials with higher dopant levels (in excess of the solubility limit). In addition, measured creep rupture curves exhibited predominantly steady-state creep behavior. Our results, therefore, verified that the creep improvement in these rare-earth doped aluminas was primarily a solid-solution effect.

Improved creep resistance in anisotropic silicon nitride

2001 ◽  
Vol 16 (8) ◽  
pp. 2182-2185 ◽  
Author(s):  
Naoki Kondo ◽  
Yoshikazu Suzuki ◽  
Manuel E. Brito ◽  
Tatsuki Ohji
Keyword(s):  
Silicon Nitride ◽  
Creep Rate ◽  
Tensile Stress ◽  
Creep Behavior ◽  
Creep Resistance ◽  
Elevated Temperatures ◽  
Tensile Creep ◽  
Grain Alignment ◽  
Remarkable Improvement ◽  
Order Of Magnitude

Tensile creep behavior of silicon nitride with aligned rodlike grains (anisotropic silicon nitride), fabricated by superplastic forging, was investigated at elevated temperatures. Creep rate of the anisotropic silicon nitride was about 1 order of magnitude lower than that of the isotropic one (without forging). The stress sensitivities for the isotropic and anisotropic specimens at 1200 °C were 2.1 and 2.6, respectively, and that for the anisotropic specimen at 1250 °C was 3.6. The grain alignment should cause a remarkable improvement in the creep resistance when a tensile stress is applied along the alignment direction.

The Effect of Heat Treatments on Microstructure and Creep Properties of Powder Metallurgy Beta Gamma Titanium Aluminide Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 500-503 ◽  
Author(s):  
Trevor Sawatzky ◽  
Dong Yi Seo ◽  
H. Saari ◽  
D. Laurin ◽  
Dae Jin Kim ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Titanium Aluminide ◽  
Room Temperature ◽  
Tensile Creep ◽  
Air Cooling ◽  
Gamma Titanium Aluminide ◽  
Creep Properties ◽  
Gamma Titanium ◽  
Titanium Aluminide Alloys ◽  
Lamellar Interfaces

The microstructure and creep properties of two powder metallurgy (PM) ‘beta gamma’ titanium aluminide alloys are presented. Alloy powders with nominal compositions of TiAl-4Nb-3Mn (G1) and TiAl-2Nb-2Mo (G2) were produced by gas atomization and consolidated by a two-step hot isostatic pressing (HIP) process (1250 °C/200 MPa/1 hour + 1100 °C/200 MPa/3 hours + slow cooling to room temperature). After HIP, the materials were given a step cooled heat treatment (SCHT) of 40 min at 1400 °C, furnace cooling to 1280 °C, and air cooling to room temperature. Selected specimens were aged at 900 °C for 6 or 24 hours. The SCHT yielded similar fully lamellar microstructures for both alloys, with a lamellar spacing of 0.04 m, but with different grain sizes averaging 80 m (G1) and 40 m (G2). The aging treatments generated  precipitates along lamellar colony boundaries in both alloys, but along lamellar interfaces only in alloy G2. Constant load tensile creep tests were performed at 760 °C and 276 MPa. Alloy G2 exhibited superior creep performance compared to alloy G1, due to the quantity and size of  precipitate particles at the lamellar interfaces.

scholarly journals Tensile Creep Properties of Cr-Si Alloys at 980 °C in Air—Influence of Ge and Mo Addition

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1072
Author(s):  
Petra Pfizenmaier ◽  
Anke Silvia Ulrich ◽  
Mathias C. Galetz ◽  
Uwe Glatzel
Keyword(s):  
Creep Behavior ◽  
Alloy Composition ◽  
Constant Load ◽  
Ternary Alloys ◽  
Tensile Creep ◽  
Chromium Nitride ◽  
Creep Properties ◽  
Alloying Additions ◽  
Nitride Formation ◽  
The Impact

The tensile creep behavior of Cr-Si alloys with Cr ≥ 91 at.% was investigated in air at 980 °C with a constant load of 50–100 MPa. Additionally, the influence of substitutional alloying additions of 2 at.% Ge and Mo, leading to ternary alloys was studied. The addition of Ge or Mo results in an improvement in creep strength, with the highest strength achieved with addition of Mo. For longer creep exposure times a strong effect is observed, because of severe nitrogen uptake from the air, depending on alloy composition. Based on the results a novel mechanism for the impact of chromium nitride formation on the creep behavior is proposed.

scholarly journals Influence of α-Phase Field Heat Treatment on the Tensile and Primary Creep Resistance of a Powder Metallurgical Processed Ti-45Al-5Nb-0.2B-0.2C Titanium Aluminide Alloy

2017 ◽  
Vol 899 ◽  
pp. 418-423
Author(s):  
Rafael Paiotti Marcondes Guimarães ◽  
Juliano Soyama ◽  
Thomas Ebel ◽  
Márcio C. Fredel ◽  
Florian Pyczak
Keyword(s):  
Heat Treatment ◽  
Colony Size ◽  
Titanium Aluminide ◽  
Creep Resistance ◽  
Titanium Aluminides ◽  
Primary Creep ◽  
Heat Treatments ◽  
Titanium Aluminide Alloy ◽  
Metallurgical Processing ◽  
Microstructure Parameters

In powder metallurgical processing the sintering process, as well as heat treatments, can drastically influence microstructure formation. In the case of γ-titanium aluminides, it is critical to achieve certain microstructure parameters, such as colony size, porosity and grain boundary morphology in order to obtain appropriate mechanical properties. In this study, the effect of a heat treatment implemented after sintering with the objective of varying the colony size was investigated. Specimens of Ti-45Al-5Nb-0.2B-0.2C prepared by metal injection moulding and uniaxial pressing of feedstock were used to evaluate the tensile and creep properties. Heat treatments conducted at 1350 and 1400 °C for 3 h led to colony sizes of approximately 100 and 200 μm, respectively. Classically, there is an inverse relationship between grain size and creep resistance, nonetheless, for γ-titanium aluminides, the morphology of the colony boundaries was also found to play a role. The larger colony sizes achieved with the heat treatments did not improve the primary creep resistance, which was explained by the change in the morphology of the colony boundaries as they became larger.

A Physically Consistent Method for the Prediction of Creep Behavior of Metals

1979 ◽  
Vol 46 (4) ◽  
pp. 800-804 ◽  
Author(s):  
G. J. Weng
Keyword(s):  
Single Crystals ◽  
Creep Behavior ◽  
Pure Shear ◽  
Tensile Creep ◽  
Polycrystalline Materials ◽  
Steady Creep ◽  
Creep Properties ◽  
Consistent Method ◽  
Latent Hardening ◽  
Good Agreement

A physically consistent method, which considers the deformation mechanisms, the active and latent hardening in single crystals, and their transient and steady creep, is proposed to predict the creep behavior of polycrystalline materials. This method consists of two steps: first, the material constants of single crystals are determined from the tensile creep data of the polycrystal, and then these constants are used to predict the creep properties of the same polycrystal under required loading conditions. This method simultaneously satisfies the requirements of equilibrium and compatibility over the grain boundaries, and is self-consistent. The proposed method was applied to calculate the creep strains of a 2618-T61 Aluminum alloy under pure shear, combined stress and nonradial loading; the results obtained were in good agreement with the test data.

The Microstructure and Creep Behavior of a Boron-Modified Ti-15Al-33Nb (at%) Alloy

2006 ◽  
Vol 15-17 ◽  
pp. 976-981 ◽  
Author(s):  
C.J. Cowen ◽  
Carl J. Boehlert
Keyword(s):  
Creep Behavior ◽  
Creep Resistance ◽  
Constant Load ◽  
Tensile Creep ◽  
Stress Range ◽  
Monolithic Alloy ◽  
Temperature Range ◽  
Normal Constituent

The affect of boron (B) on the microstructure and creep behavior of a Ti-15Al-33Nb (at%) alloy was investigated. In addition to the normal constituent phases present in the monolithic alloy, the B-modified alloy contained borides enriched in titanium and niobium. These borides were present in the form of needles/laths up to 50 μm long and 10 μm wide which took up 5-9% of the volume. Constant load, tensile-creep experiments were performed in the stress range of 150-340 MPa and the temperature range of 650-710°C, in both air and vacuum environments. An addition of 0.5 at% B did not improve the creep resistance of the monolithic alloy, while the addition of 5 at% B significantly improved the creep resistance.

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