An analytical approach for the prediction of gamma-to-alpha phase transformation of aluminum oxide (Al2O3) particles in the Space ShuttleASRM and RSRM exhausts

1992 ◽  
Author(s):  
S. OLIVER ◽  
B.E. MOYLAN
Keyword(s):  
Phase Transformation ◽  
Aluminum Oxide ◽  
Analytical Approach ◽  
Alpha Phase ◽  
Al2o3 Particles

scholarly journals In-situ Experiments to Capture the Evolution of Microstructure During Phase Transformation of Titanium Under Dynamic Loading

2018 ◽  
Vol 183 ◽  
pp. 03020
Author(s):  
Benjamin M. Morrow ◽  
David R. Jones ◽  
Paulo A. Rigg ◽  
George T. Gray ◽  
Ellen K. Cerreta
Keyword(s):  
Phase Transformation ◽  
Dynamic Loading ◽  
Microstructural Analysis ◽  
Alpha Phase ◽  
Material Behavior ◽  
High Rate ◽  
Omega Phase ◽  
In Situ Experiments ◽  
Consistent Picture ◽  
Underlying Mechanisms

Under sufficient stresses, such as during dynamic loading, titanium experiences a phase transformation from hcp alpha phase to hexagonal omega phase. Omega phase is often retained in the microstructure after unloading, and has a strong influence on subsequent mechanical properties. Simulations suggest there are multiple pathways and underlying mechanisms for this transformation. Due to the incredibly short timescales involved, experimental measurements for model validation have been difficult. However, new capabilities at the Advanced Photon Source have enabled diffraction measurements during plate impact experiments to study the evolution of titanium during transformation. These high-rate data allow us to probe the mechanism and kinetics of phase transformations in new ways. Recent results will be presented and compared to post-mortem characterization of soft-recovered shocked specimens. Comparisons are made with previous tests where material was shock-loaded and soft recovered for microstructural analysis. Together these techniques create a consistent picture of material behavior during the shock-induced ff–! phase transformation in titanium.

Effect of Deposition Conditions on Intrinsic Stress, Phase Transformation and Stress Relaxation in Tantalum Thin Films

1991 ◽  
Vol 239 ◽  
Author(s):  
A. Mutscheller ◽  
L. A. Clevenger ◽  
J.M.E. Harper ◽  
C. Cabrai ◽  
K. Barmakt
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Phase Transformation ◽  
Stress Relaxation ◽  
Compressive Stress ◽  
Stress Relief ◽  
Beta Phase ◽  
Alpha Phase ◽  
Intrinsic Stress

AbstractWe demonstrate that the high temperature polymorphic tantalum phase transition from the tetragonal beta phase to the cubic alpha phase causes complete stress relaxation and a large decrease in the resistance of tantalum thin films. 100 nm beta tantalum thin films were deposited onto thermally oxidized <100> silicon wafers by dc magnetron sputtering with argon. In situ stress and resistance at temperature were measured during temperature-ramped annealing in purified He. Upon heating, films that were initially compressively stressed showed increasing compressive stress due to thermo-elastic deformation from 25 to 550°C, slight stress relief due to plastic deformation from 550 to 700°C and complete stress relief due to the beta to alpha phase transformation at approximately 700–800°C. Incomplete compressive stress relaxation was observed at high temperatures if the film was initially deposited in the alpha phase or if the beta phase did not completely transform into alpha by 800°C. This incomplete beta to alpha phase transition was most commonly observed on samples that had radio frequency substrate bias greater than -100 V. We conclude that the main stress relief mechanism for tantalum thin films is the beta to alpha phase transformation that occurs at 700 to 800°C.

Beta-alpha phase transformation in Ti and TiO alloys

1974 ◽  
Vol 34 (2) ◽  
pp. 181-189 ◽  
Author(s):  
M. Cormier ◽  
F. Claisse
Keyword(s):  
Phase Transformation ◽  
Alpha Phase

Evolution of Grain Boundary Texture in Zirconium Alloys

2011 ◽  
Vol 702-703 ◽  
pp. 710-713
Author(s):  
Karri V. Mani Krishna ◽  
Sudipto Mandal ◽  
Ankur Agrawal ◽  
Vijay Hiwarkar ◽  
Dinesh Srivastava ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Grain Boundary ◽  
Annealing Time ◽  
Considerable Increase ◽  
Direct Evidence ◽  
Texture Evolution ◽  
Zirconium Alloys ◽  
Alpha Phase ◽  
Variant Selection ◽  
Alpha Beta

Grain boundary texture evolution in case of two of the Zr based alloys (Zircaloy-4 and Zr-2.5\%Nb) was studied. In case of Zircaloy-4, grain boundary texture evolution during $\beta$ $\to$ $\alpha$ phase transformation was monitored. Direct evidence of variant selection during this transformation is presented. In case of Zr-2.5\%Nb alloy, considerable increase in $\alpha/\beta$ interfaces following Burger's orientation relationship was noticed with increasing annealing time at 700 \textdegree{}C.

Facile Synthesis of Ammonium Aluminum Carbonate Hydroxide Multilayered Nanofiber by Using Solid State Reaction

2011 ◽  
Vol 415-417 ◽  
pp. 580-584 ◽  
Author(s):  
Xiao Fu Hu ◽  
Yun Qi Liu ◽  
Chen Guang Liu
Keyword(s):  
Phase Transformation ◽  
Elevated Temperature ◽  
Solid State ◽  
Low Temperature ◽  
Aluminum Oxide ◽  
Solid State Reaction ◽  
Particle Sizes ◽  
Facile Synthesis ◽  
New Synthesis ◽  
Carbonate Hydroxide

In this paper, we make systematical investigation for the new synthesis pathway of AACH multilayered nanofiber, which has been prepared by a low-temperature solid-state reaction. The phase transformation sequence of AACH on heating is found that the precursor converts into γ-Al2O3at 700-900°C and elevated temperature results in the θ-Al2O3and α- Al2O3crystal phase formation at 1000°C. With a higher calcination temperature at 1100°C, α- Al2O3pattern appears. The specific surface area (SBET) of aluminum oxide specie calcined at 500°C for 4h is still in 420.2m2/g. Meanwhile, it suggests a partial change in particle sizes and morphology of sample calcined at 500°C for 4h.

scholarly journals Deformation and Phase Transformation of Disorder α Phase at (α+γ) two Phase Region in high Nb Containing TiAl alloy

2021 ◽  
Author(s):  
Haitao Zhou ◽  
Fantao Kong ◽  
Yanbo Wang ◽  
Xiangwu Hou ◽  
Ning Cui ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Microstructural Evolution ◽  
Microstructure Evolution ◽  
Tial Alloy ◽  
Temperature Drop ◽  
Alpha Phase ◽  
Phase Region ◽  
Two Phase ◽  
Α Phase ◽  
Assisted Decomposition

In this paper, the deformation and phase transformation of disorder &alpha; phase at (&alpha; + &gamma;) two phase region in as-forged Ti-44Al-8Nb-(W, B, Y) alloy are investigated by hot compression and hot packed rolling. Detailed microstructural evolution demonstrates that the as-deformed microstructure is significantly affected by deformation conditions. The mircrostructure differences are mainly due to temperature drop and strain rate. The evolution of &alpha; lamelae into &alpha; grains is detailed descripted. Moreover, the disorder &alpha; lamellae can also be decomposed into some new &alpha; grains by the assisted decomposition mechanism of &gamma; grains. Microstructure evolution model of current TiAl alloy at 1250 &deg;C during hot rolling is built.

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