Shinji Ando

Abstract:

It is well known that the principle slip system of magnesium is a basal slip. Activation of non-basal slip systems, however, is necessary to show good ductility. Recently, the effect of yttrium on ductility of magnesium and discussion for activity of (c+a) pyramidal slips has been reported [1]. In this study, to investigate the effects of yttrium and lithium for non-basal slips, pure magnesium and magnesium alloy single crystals were stretched parallel to the basal plane in various temperatures, and polycrystalline magnesium alloys were also tested to estimate contribution of non-basal slips to their tensile deformation behavior.
In pure magnesium and Mg - (7-14)at%Li single crystals, second order pyramidal (c+a) slips (SPCSs) were observed at 77-298K as CRSS of the SPCS was decreased. Above room temperature, the first order pyramidal (c+a) slip (FPCS) was active in pure magnesium. In the Mg-(0.6-0.9) at%Y alloy single crystals, FPCS was observed at 77K to 298K while yield stress of the Mg-Y alloy single crystals was higher than that of pure magnesium [2]. In tensile tests of polycrystalline pure magnesium, Mg-(0.5-1.2)at%Y and Mg-(6-12)at%Li, slip lines of non-basal slip systems such as the SPCS, FPCS and prismatic slip were observed even at yielding in addition to basal slip lines. Among the non-basal slips, activities of FPCS and prismatic slips were increased with increasing strain in magnesium - yttrium and magnesium- lithium alloys. Our study suggested that the active non-basal slip system in tension parallel to the basal plane is a (c+a) pyramidal slip and enhanced ductility of magnesium alloys would be caused from increased activity of FPCS by alloying.

[1] S. Sandlobes, M. Friak, S. Zaefferer, A. Dick, S. Yi, D. Letzig, Z. Pei, L. -F. Zhu, J. Neugebauer, D. Raabe, Acta Materialia, 60(2012), 3011-3021
[2] Hiroaki Rikihisa1, Takashi Mori, Masayuki Tsushida, Hiromoto Kitahara and Shinji Ando, Materials Transactions, 58(2017) 1656-1663.