In situ investigation of extension twinning-detwinning and its effect on the mechanical behavior of AZ31B magnesium alloy

Publication date: 15 October 2017
Source:Materials & Design, Volume 132
Author(s): B.L. Wu, G.S. Duan, X.H. Du, L.H. Song, Y.D. Zhang, M.J. Philippe, C. Esling
Magnesium alloys are usually dominated by the alternation of extension twinning and detwinning when subjected to cyclic plastic deformation. The twinning-detwinning process in AZ31B alloy was investigated by means of in situ observation under EBSD. It was shown that the activation of extension twinning is related to Schmid factor of a deformed grain, but twin variant selection is not directly linked to Schmid factor rank. Strain accommodation factor proposed on the concept of local Schmid factor (LSF) allows a good prediction for twin variant selection. A twin variant is favored when the strain accommodation factor is low. In addition, detwinning was found to induce Bauschinger effect in the alloy during compressive unloading. The completely detwinned twins are accommodated by the adjacent grains with very high strain accommodation factors. Extension twins can form and remain in both compression and tension processes of the cyclic deformation. Residual twins in the second cycle increase in number as compared with the first cycle. This was inferred to stimulate the cyclic strain hardening.

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