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Please use this identifier to cite or link to this item: http://repository.iitr.ac.in/handle/123456789/12744
Title: Effect of layered microstructure on the superplasticity of friction stir processed AZ91 magnesium alloy
Authors: Raja A.
Biswas P.
Pancholi V.
Published in: Materials Science and Engineering A
Abstract: Multipass friction stir processing (FSP) was performed in as-cast AZ91 Mg alloy (AC) to generate layered microstructure through the thickness and study its effect on superplasticity. The FSP tools with different tool pin length were used to develop three kinds of layered microstructured materials. A full thickness fine grained microstructure (FFG), a half thickness fine grained with remaining half in as-cast condition (HFG). The last variation was one third thickness modified into fine grain from both the surfaces and the middle section having as-cast microstructure (SFG). FSP was performed at a tool rotational speed of 720 rpm and at a transverse speed of 150 mm/min. The coarse α-Mg dendrites with large plate like interconnected β-Mg17Al12 interdendrites were the characteristics microstructure of as-cast AZ91 alloy. Fine grains and uniformly distributed precipitates were the characteristics of FSPed microstructure. High temperature tensile tests were carried out at 350 °C using three different initial strain rates i.e. 5 × 10−3 s−1, 1 × 10−3 s−1 and 5 × 10−4 s−1. The FFG material showed superplasticity at all strain rates and highest ductility of 680% was achieved at the strain rate of 5 × 10−4 s−1. The AC and HFG material displayed very low elongation while SFG material exhibited superplasticity of 388%. The superplastic behaviour in SFG was due to increase in the fraction of fine grained microstructure and modification of as-cast microstructure on both the surfaces. Microstructure and texture studies revealed that grain boundary sliding accommodated by grain boundary migration and grain rotation was responsible for superplasticity in FSPed region. © 2018 Elsevier B.V.
Citation: Materials Science and Engineering A (2018), 725(): 492-502
URI: https://doi.org/10.1016/j.msea.2018.04.028
http://repository.iitr.ac.in/handle/123456789/12744
Issue Date: 2018
Publisher: Elsevier Ltd
Keywords: AZ91 Mg alloy
EBSD and texture
Layered microstructure
Multipass FSP
Superplasticity
ISSN: 9215093
Author Scopus IDs: 57114501400
57196046390
14071738800
Author Affiliations: Raja, A., Department of Metallurgical and Materials Engineering, Indian Institute of Technology RoorkeeUttarakhand 247667, India
Biswas, P., Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology BombayMaharashtra 400076, India
Pancholi, V., Department of Metallurgical and Materials Engineering, Indian Institute of Technology RoorkeeUttarakhand 247667, India
Corresponding Author: Pancholi, V.; Department of Metallurgical and Materials Engineering, Indian Institute of Technology RoorkeeIndia; email: vivekfmt@iitr.ac.in
Appears in Collections:Journal Publications [MT]

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