Effect of growth orientation of columnar crystals on tensile and compressive properties of directionally solidified Mg-Gd alloy
Mg-6.3Gd alloy with growth orientation concentrated in<2(1)(1)0>and Mg-8.2Gd alloy with growth orientation concentrated in<3(2)(1)4>were prepared by directional solidification,and the relation between crystal orientation and mechanical properties under tension load and compression load was studied.For the Mg-6.3Gd alloy subjected to tensile load,the Schmid factor(Fs)of basal<a>slip of columnar crystals with<2(1)(1)0>orientation is less than 0.051,and{10(1)1}contraction twinning in columnar crystals is activated to coordinate strain,so the alloy has higher yield strength(σs=176 MPa),but the plasticity is only 8％.In the case of the Mg-8.2Gd alloy subjected to tensile load,Fs of basal<a>slip of columnar crystals with<3(2)(1)4>orientation is higher than 0.46,and{10(1)2}extension twinning in columnar crystals is activated to coordinate strain,thus the Mg-8.2Gd alloy has lower yield strength(σs=57 MPa),but the plasticity is only 22％.Under compression load,both{11(2)1}and{10(1)2}extension twinning are activated in two alloys,and the compressive strength of the two alloys are much greater than their yield strength,showing distinct work hardening.Meanwhile,the two alloys also have good compressive plasticity.
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