Evolution of microstructure and performance of n-type BiTeSe thermoelectric materials fabricated by multi-path equal channel angular extrusion

Equal Channel Angular Extrusion (ECAE) has become a very popular tool for studying the evolution of microstructure and properties under severe plastic deformation. It is believed that the stress-strain characteristics are uniform in a cross-section of the billet and this uniformity of the stress-strain distribution ensures the uniformity of microstructure and mechanical properties in ECAE processed billet. However, some experimental data such as the fracture of the extruded billet, which is initiated at the inner surface of the sample, has caused doubts about uniformity of stress-strain distribution. This non-uniformity has been proved recently by Finite Element Simulation. In this paper the studies of the positive role of the applied back-pressure during ECAE are reviewed and the influence of a back-pressure on the uniformity of the stress-strain distribution, strain localisation, die corner filing, and the prevention of fracture is shown. The effect of back-pressure on grain refinement and improvement in mechanical properties is emphasized. The paper summarises our results from over seven years of work using a unique machine for ECAE with computer-controlled back-pressure and velocity of the backward punch.

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Evolution of Microstructure and Texture during Annealing of a Copper Processed by ECAE

Materials Science Forum ◽

10.4028/www.scientific.net/msf.495-497.845 ◽

2005 ◽

Vol 495-497 ◽

pp. 845-850 ◽

Cited By ~ 4

Author(s):

Anne Laure Etter ◽

Denis Solas ◽

Thierry Baudin ◽

Richard Penelle

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Grain Size ◽

Equal Channel Angular Extrusion ◽

Transmission Electron ◽

Average Grain Size ◽

Angular Extrusion ◽

Evolution Of Microstructure ◽

Electron Back Scattered Diffraction

A submicron-grained (SMG) microstructure, with an average grain size of ~0.4 µm was produced by equal channel angular extrusion (ECAE). The SMG microstructure was composed of large dynamic recrystallized grains within a matrix of deformed elongated cells. Samples were annealed for various times at 473 K and then examined using transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD). The results specify that a large recovery takes place during the first annealing times. Moreover, MET investigations show nucleation of grains which orientations are found in the recrystallized texture. The EBSD measurements established that, after 7min30s at 473 K, the microstructure is equiaxed and stable with an average grain size of about 2 µm.

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Evolution of Microstructure and Crystallographic Texture in AA2014 Aluminium Alloy during Equal Channel Angular Extrusion

Materials Science Forum ◽

10.4028/www.scientific.net/msf.702-703.97 ◽

2011 ◽

Vol 702-703 ◽

pp. 97-100 ◽

Cited By ~ 1

Author(s):

Sivaswamy Giribaskar ◽

K.S. Suresh ◽

Gouthama ◽

Satyam Suwas

Keyword(s):

Aluminium Alloy ◽

Crystallographic Texture ◽

Room Temperature ◽

Equal Channel Angular Extrusion ◽

Al Alloy ◽

Microstructural Changes ◽

Angular Extrusion ◽

Initial Texture ◽

Evolution Of Microstructure ◽

2014 Al Alloy

Present work addresses the evolution of texture and microstructure of equal channel angular extrusion (ECAE) processed AA 2014 Al alloy upto four passes at room temperature by adopting route BC. TEM is used to assess the microstructural changes during each ECAE pass. Texture measurements on samples of each pass were carried out by XRD technique. The evolution of texture components after each ECAE pass are analyzed and the changes are discussed with respect to the initial texture.

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