Microstructures and Phase Transformations of Ti-50.9at%Ni Alloy Processed by Equal Channel Angular Extrusion at Medium Temperature

2007 ◽  
Vol 561-565 ◽  
pp. 877-880 ◽  
Author(s):  
Chao Ying Xie ◽  
Zhi Guo Fan
Keyword(s):  
Phase Transformation ◽  
Phase Transformations ◽  
Equal Channel Angular Extrusion ◽  
Martensitic Transformations ◽  
Optical Microscope ◽  
Medium Temperature ◽  
Thermal Peak ◽  
Ni Alloy ◽  
Coarse Grains ◽  
Angular Extrusion

Submicron-grained Ti-50.9at%Ni alloy was prepared by Equal Channel Angular Extrusion (ECAE) at medium temperature(500°C). Microstructure evolution and phase transformations of Ti-50.9at%Ni alloy after ECAE processes at medium temperature have been investigated by optical microscope, TEM and DSC tests. It is found that the initial coarse grains of Ti-50.9at%Ni alloy were refined into submicron grains, smaller than 0.5 um in size, after eight passes ECAE at 500°C. Martensitic transformation temperatures decreased remarkably after one pass ECAE and more gently with increasing the pass number of ECAE. R phase transformation was stimulated after ECAE processes and underwent within a larger temperature range with an ambiguous thermal peak. The reverse R phase and reverse martensitic transformations, during heating, were separated eventually after eight passes ECAE.

Recrystallization Characteristics of Ti-50.9at%Ni Alloy Processed by Equal Channel Angular Extrusion

2007 ◽  
Vol 26-28 ◽  
pp. 385-388 ◽  
Author(s):  
Zhi Guo Fan ◽  
Chao Ying Xie
Keyword(s):  
High Temperature ◽  
Optical Microscopy ◽  
Equal Channel Angular Extrusion ◽  
Recrystallization Process ◽  
Recrystallization Behavior ◽  
Ni Alloy ◽  
Coarse Grains ◽  
Angular Extrusion

The initial coarse grains of Ti-50.9at%Ni alloy were refined into submicron grains, small than 0.5 um in size, after eight passes Equal Channel Angular Extrusion (ECAE) at 500°C. Optical microscopy and high temperature DSC tests were applied to investigate recrystallization behavior. It is found that the recrystallization start (Rs) and recrystallization peak (Rp) temperatures of Ti-50.9at%Ni specimens processed by eight passes ECAE are lower than that of the samples processed by one pass ECAE. Ti-50.9at%Ni specimens processed by eight passes ECAE with submicron grains are characterized by higher stability and need less energy to finish recrystallization process.

Phase Transformations and Super-Elasticity of a Ni-Rich TiNi Alloy with Ultrafine-Grained Structure

2010 ◽  
Vol 667-669 ◽  
pp. 1137-1142 ◽  
Author(s):  
Zhi Guo Fan ◽  
Jie Song ◽  
Xiao Ning Zhang ◽  
Chao Ying Xie
Keyword(s):  
Phase Transformations ◽  
Equal Channel Angular Extrusion ◽  
Martensitic Transformations ◽  
Tini Alloy ◽  
Solution Treated ◽  
Ultrafine Grained ◽  
Treated Sample ◽  
Ni Alloy ◽  
Loading And Unloading ◽  
Elasticity Characteristics

A Ni-rich Ti-50.7.at%Ni alloy was processed by Equal Channel Angular Extrusion (ECAE) at 500°C. After 8 passes ECAE, microstructure was refined to sub-micron scale, approximately 0.2 μm～0.3 μm. TEM observation reveals that Ti3Ni4 phase precipitated in Ni-rich Ti-50.7.at%Ni alloy during the preheating treatment before each ECAE pass, but re-dissolved during sequent ECAE processes. After ECAE treatment, the B2R transformation occurred within a larger temperature range. Comparing with the solution-treated TiNi specimen, the martensitic transformations start (Ms) and peak temperatures (Mp) of TiNi specimens ECAEed were dramatically lowered. Super-elasticity characteristics of TiNi alloy were tested by tensile loading and unloading cycles. The results reveal that at a tensile strain of 4% or smaller, ultrafine-grained (UFG) TiNi alloy processed by 4 passes ECAE shows better super-elasticity than solution-treated sample. Microstructure evolution and its effect on phase transformations and super-elasticity characteristics have been discussed.

Shape Memory Behavior of Ti-50.9at%Ni Alloy after ECAE Processes

2007 ◽  
Vol 561-565 ◽  
pp. 2313-2316 ◽  
Author(s):  
Zhi Guo Fan ◽  
Chao Ying Xie
Keyword(s):  
Phase Transformation ◽  
Shape Memory ◽  
Initial Solution ◽  
Transformation Behavior ◽  
Shape Memory Behavior ◽  
Solution Treated ◽  
Ni Alloy ◽  
Coarse Grains ◽  
Shape Memory Properties ◽  
Before And After

The initial coarse grains of Ti-50.9at%Ni were obviously refined after eight ECAE processes. Effects of pressing number on the transformation behavior have been investigated in detail. Comparing with the initial solution-treated Ti-50.9at%Ni, the R-phase transformation was stimulated and the martensitic temperature Ms decreased with ECAE processes at 773K. The shape memory properties of Ti-50.9at%Ni alloy before and after ECAE processes at 773K have been measured. Good one way shape memory and superelasticity were obtained for the submicron-grained Ti-50.9at%Ni alloy.

Investigation on Microstructure and Phase Transformation of La Added Ti49.3Ni50.7 Shape Memory Alloy

2012 ◽  
Vol 557-559 ◽  
pp. 1041-1044 ◽  
Author(s):  
Jia Wen Xu ◽  
Ai Lian Liu ◽  
Bing Yu Qian ◽  
Wei Cai
Keyword(s):  
Phase Transformation ◽  
Room Temperature ◽  
Optical Microscope ◽  
X Ray Diffraction ◽  
Transformation Behavior ◽  
Phase Transformation Behavior ◽  
Ni Alloys ◽  
Ni Alloy ◽  
The Matrix ◽  
La Addition

The effect of La addition on the microstructure and phase transformation behavior of Ti 49.3Ni50.7 alloy is investigated by optical microscope (OP), scanning electron microscope (SEM), X-ray diffraction analysis (XRD) and differential scanning calorimeter (DSC). The results show that the microstructure of Ti-Ni alloy is changed obviously with La addition, and the microstructure of Ti-Ni alloy containing La at room temperature is made up of the matrix and LaNi phase. La addition firstly increases the martensitic transformation temperatures evidently and the increase of Ms is about 62°C with 1at.% La. Secondly Adding La changes the type of phase transformation behavior of Ti-Ni alloys, and R phase transformation with Rs temperature about room temperature occurs in La added Ti-Ni alloy.

Grain Refinement and Texture Evolution during Equal Channel Angular Extrusion of Pure Cu and Cu-Zn Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 1215-1218
Author(s):  
Hai Hong Chen ◽  
Sai Yi Li ◽  
Dong Hong Zhang ◽  
Xin Huang
Keyword(s):  
Grain Refinement ◽  
Equal Channel Angular Extrusion ◽  
Texture Evolution ◽  
Shear Bands ◽  
Optical Microscope ◽  
X Ray Diffraction ◽  
Zn Content ◽  
Angular Extrusion ◽  
Pure Cu ◽  
Stacking Fault Energies

Equal channel angular extrusion (ECAE) experiments were conducted on as-cast pure Cu, Cu–10%Zn, and Cu–30%Zn, using a 90 die for up to 4 passes. The stacking fault energies (SFEs) of the three materials decrease with increasing Zn content. The microstructures and textures of the processed billets were analyzed using optical microscope and X-ray diffraction, respectively. The results show that the structures of the three materials were all significantly refined after ECAE and a lower SFE led to a finer microstructure with a higher density of shear bands. The textures were considerably weakened after 4 passes, more apparent in the material with a lower SFE. It is concluded that the SFE has significant influences on both the grain refinement and texture evolution during ECAE deformation.

Microstructure and Wear Properties of GCr15 Alloy Produced by Equal Channel Angular Extrusion

2011 ◽  
Vol 211-212 ◽  
pp. 661-665
Author(s):  
Guo Quan Xiang ◽  
Min Xin Zheng ◽  
Lian Qing Ji
Keyword(s):  
Grain Size ◽  
Mass Loss ◽  
Grain Refinement ◽  
Equal Channel Angular Extrusion ◽  
Optical Microscope ◽  
Wear Properties ◽  
Gcr15 Steel ◽  
Angular Extrusion

GCr15 alloy produced by hot-forged is subjected to equal channel angular extrusion (ECAE) process at 950°C. The microstructure of GCr15 steel via ECAE and annealed is studied by an optical microscope. The effect of ECAE and annealing on the wear properties of the alloy is also investigated. The results show that the grain size reduced from 50 mm to 10 mm via one pass ECAE, and the hardness of the alloy is increased. The wear mass loss of the alloy is greatly reduced due to the grain-refinement after ECAE and annealing.

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