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.

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.

TEM and DSC Investigation of the Recovery of a Recycled Aluminum Processed by Equal Channel Angular Extrusion

2010 ◽  
Vol 667-669 ◽  
pp. 451-456 ◽  
Author(s):  
Atef Rebhi ◽  
Thabet Makhlouf ◽  
Jean Philippe Couzine ◽  
Yannick Champion ◽  
Nabil Njah
Keyword(s):  
Elevated Temperatures ◽  
Equal Channel Angular Extrusion ◽  
Substantial Effect ◽  
Recrystallization Process ◽  
Dislocation Loops ◽  
First Passage ◽  
Slip Mechanism ◽  
Significant Difference ◽  
Angular Extrusion ◽  
Dislocation Cells

TEM investigation was performed on a recycled aluminum processed by Equal Channel Angular Extrusion. The aluminum contains many inclusions which were identified to be rich in iron and silicon.This has a substantial effect in dragging recovery. ECAE was performed via routes B and C using a die formed by two channels characterized by the well defined angles =90° and  = 90°. The evolution of the microstructure seems to be similar whether using route B or C. a high dislocation density was introduced since the first passage together with a high density of Frank dislocation loops. The latter are due to a by-passing of inclusions by cross-slip mechanism. Weak beam experiments enable us to investigate the early stages of recovery consisting in the formation of dislocation walls and few dislocation cells. A partial arrangement of dislocations was observed since the first passage through the die. The formation of dislocation cells began already before annealing and progresses at more elevated temperatures. The substantive recovery seems to push recrystallization process to high temperatures. By contrast, DSC investigations show a significant difference: The amount of energy deduced from the area of the peak relative to recrystallization is higher when using route C.

scholarly journals EBSD Analysis of Deformed and Partially Recrystallized Microstructures in ECAE-Processed Copper

2012 ◽  
Vol 715-716 ◽  
pp. 825-830 ◽  
Author(s):  
O.V. Mishin ◽  
J.R. Bowen ◽  
Andrew Godfrey
Keyword(s):  
Uniform Distribution ◽  
Room Temperature ◽  
Equal Channel Angular Extrusion ◽  
Pure Copper ◽  
Sample Thickness ◽  
Ebsd Analysis ◽  
Recrystallization Behavior ◽  
Angular Extrusion

The deformed microstructure and recrystallization behavior of copper samples processed using equal channel angular extrusion (ECAE) have been investigated. The heavily deformed microstructure was found to be non-uniform through the sample thickness and to vary in a manner consistent with the non-uniform distribution of strain imposed by processing. The through-thickness heterogeneity of the deformed microstructure resulted in a different extent of recrystallization in different layers during annealing. Recrystallized grains were also observed in samples that were not annealed, but stored at room temperature, which indicates that the deformed microstructure of ECAE-processed pure copper is unstable even at room temperature. In each sample, recrystallization was found to initiate in regions containing predominantly large misorientations.

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