ORALS

SESSION: MagnesiumFriPM2-R4	Intl Symp. on Next Generation Magnesium Alloys and Their Applications for Sustainable Development
Fri Oct, 25 2019 / Room: Adonis
Session Chairs: TBA Session Monitor: TBA

15:55: [MagnesiumFriPM209] Invited
Activities of Non-basal Slips in Mg-Y and Mg-LI alloy Single and Poly Crystals
Shinji Ando¹ ; Keisuke Takemoto¹ ; Hiromoto Kitahara¹ ; ¹Kumamoto University, Kumamoto, Japan;
Paper Id: 296 [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.

References:
[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\n[2] Hiroaki Rikihisa1, Takashi Mori, Masayuki Tsushida, Hiromoto Kitahara and Shinji Ando, Materials Transactions, 58(2017) 1656-1663.

SESSION: MagnesiumFriPM2-R4	Intl Symp. on Next Generation Magnesium Alloys and Their Applications for Sustainable Development
Fri Oct, 25 2019 / Room: Adonis
Session Chairs: TBA Session Monitor: TBA

16:45: [MagnesiumFriPM211]
Local Deformation Behavior of Mg Alloy Single Crystals using Ball Indenter
Hiromoto Kitahara¹ ; Momoka Watanabe¹ ; Shinji Ando¹ ; ¹Kumamoto University, Kumamoto, Japan;
Paper Id: 295 [Abstract]

A steel ball indenter was impressed on low index planes in Mg alloy single crystals with different CRSSs: Mg-Al, Mg-Zn, and Mg-Y alloy single crystals. Effects of alloying elements on indentation behavior and roles of slip and twins on indentation size were investigated. Pure Zn single crystals, whose loading direction causing {10-12} twins is opposite to pure Mg, were also prepared. Indentations showed a circular shape on (0001) in the Mg alloys and pure Zn single crystals. Also, slip lines and twins were hardly observed around (0001) indentations. On the other hand, (10-10) and (1-210) indentations showed an elliptical morphology which elongated to [0001]. Basal slip lines and {10-12} twins were observed around (0001) indentations in Mg-Al and Mg-Zn alloys. Twins, however, were hardly observed in Mg-Y alloy single crystals. Indentation sizes of (0001) of the Mg alloys were smaller than that of pure Mg. Also, indentation sizes of pure Mg and Zn were nearly the same. Indentation sizes decreased with increasing CRSS for the basal slip. Therefore, the size would be determined by CRSS for the basal slip. CRSSs for the basal slip of pure Mg and Zn were nearly the same. Therefore, the size gap would be caused by the presence of {10-12} twins. In Mg alloys, indentation sizes decreased as alloy elements were added. The size differences between pure Mg and the Mg alloys would be determined by ratios of basal slip and twinning activities.