微量Y(0.2 wt.%)对铸造Mg-Sn合金热变形行为影响

Effect of Yttrium Addition (0.2 wt.%) on the Hot Compression Behavior of the As-cast Mg-Sn Alloy

摘要:

采用MTS-CMT5105电子万能试验机,在温度为250~400℃、初始应变速率为10_-4~10_-1s_-1,最大变形量为40%的条件下,对铸态Mg-2.5Sn(wt.%)和Mg-2.5Sn-0.2Y(wt.%)合金进行压缩变形。结合真应力-应变曲线、峰值应力、显微组织、本构方程、DMM加工图,研究了微量Y(0.2 wt.%)对铸造Mg-Sn合金热变形行为的影响。结果表明：微量Y的添加,在较低应变速率时,会使Mg-Sn合金热压缩峰值应力增加30%以上；但在较高应变速率时,却对其影响不大。会改变合金塑性变形机制的控制方式,即由扩散控制变为位错的滑移和攀移。会抑制动态再结晶。会降低功率耗散系数,扩大加工失稳区。

Abstract:

The uniaxial hot compression tests of casting Mg-2.5Sn (wt.%) and Mg-2.5Sn-0.2Y (wt.%) alloys were conducted on an MTS-CMT5I05 universal testing machine at temperatures ranging between 250~400℃ and the strain rate of 10_-4~10_-1 s_-1 with strain of 40%. The effect of yttrium (Y) addition content (0.2 wt.%) on the hot compression behavior of the casting Mg-Sn alloys were investigated by true stress-strain curves, peak stress, microstructures, constitutive equation, and DMM processing maps. Results showed that the Y addition increased the peak stress of 30% at low strain rate, but made any sense at high strain rate. Deformation mechanism was changed from the lattice diffusion to dislocation slip and climb. In addition, Y retarded the dynamic recrystallization, reduced the efficiency of power dissipation and expanded the flow instability area.