1 School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China 2 School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004, Hebei, China 3 Qinhuangdao Key Laboratory of Advanced Metal Materials and Forming Technology, Qinhuangdao 066004, Hebei, China
Abstract: The Mg-6.38Gd-0.45Y alloy with columnar polycrystalline structure was prepared by directional solidification. The growth orientation of the columnar crystals was concentrated in [224-3], and the Schmid factor (SF) of basal 〈a〉 slip system of columnar crystals was greater than 0.4. Afterwards, the tensile deformation of the alloy at room temperature was studied. At the initial stage of deformation, {101-2} tensile twinning in columnar crystals in soft orientation were activated to coordinate strain. Thereafter, {101-2} tensile twin boundaries expanded rapidly and widely, and swallowed the matrix, which gradually changed the orientation of the matrix to [1-21-0] (SF＜0.15). As a result, {101-1} compression twinning and {101-1}-{101-2} double twinning were started to coordinate deformation. Compression twins and double twins were easy to form compression twin bands, and to run through the whole grain. Subsequently, the extended dislocations and tensile twin boundaries were intertwined with compression twin bands, and thus strain hardening occurs. However, the strengthening resulted in severe stress concentration in some regions, where microcracks would arise.
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2023, Vol. 37 
