Tension-compression asymmetry in an extruded Mg alloy AM30: temperature and strain rate effects

Zachariah, Z and Tatiparti, Sankara Sarma V and Mishra, SK and Ramakrishnan, N and Ramamurty, U (2013) Tension-compression asymmetry in an extruded Mg alloy AM30: temperature and strain rate effects. In: Materials Science and Engineering: A, 572 . pp. 8-18.

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Abstract

The effect of strain rate, (epsilon) over dot, and temperature, T, on the tension-compression asymmetry (TCA) in a dilute and wrought Mg alloy, AM30, over a temperature range that covers both twin accommodated deformation (below 250 degrees C in compression) as well as dislocation-mediated plasticity (above 250 degrees C) has been investigated. For this purpose, uniaxial tension and compression tests were conducted at T ranging from 25 to 400 degrees C with (epsilon) over dot varying between 10(-2) and 10 s(-1). In most of the cases, the stress-strain responses in tension and compression are distinctly different; with compression responses `concaving upward,' due to {10 (1) over bar2} tensile twinning at lower plastic strains followed by slip and strain hardening at higher levels of deformation, for T below 250 degrees C. This results in significant levels of TCA at T < 250 degrees C, reducing substantially at high temperatures. At T=150 and 250 degrees C, high (epsilon) over dot leads to high TCA, in particular at T=250 degrees C and (epsilon) over dot=10 s(-1), suggesting that twin-mediated plastic deformation takes precedence at high rates of loading even at sufficiently high T. TCA becomes negligible at T=350 degrees C; however at T=400 degrees C, as (epsilon) over dot increases TCA gets higher. Microscopy of the deformed samples, carried out by using electron back-scattered diffraction (EBSD), suggests that at T > 250 degrees C dynamic recrystallization begins between accompanied by reduction in the twinned fraction that contributes to the decrease of the TCA.

Item Type:	Journal Article
Publication:	Materials Science and Engineering: A
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	Magnesium Alloy; Yield Strength; Tension-Compression Asymmetry; Temperature; Strain Rate
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	11 Jun 2013 07:56
Last Modified:	11 Jun 2013 07:56
URI:	http://eprints.iisc.ac.in/id/eprint/46628

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