电流辅助压弯成形对Mg-2.5Nd-0.5Zn-0.5Zr合金微观组织和力学性能的影响

Effect of electrically-assisted bending forming on microstructure and mechanical properties of Mg-2. 5Nd-0. 5Zn-0. 5Zr alloy

采用金相和透射电镜等技术系统研究了电流密度和保压时间对Mg-2.5Nd-0.5Zn-0.5Zr合金压弯成形“几”字型零件微观组织演变和成形性能的影响。结果表明,随着电流密度的增加(33.5~51.5 A·mm^(-2)),压弯“几”字型零件成形性能逐渐提高,回弹逐渐减小。随着保压时间的延长(0~20 s),回弹逐渐减小。当电流密度为51.5 A·mm^(-2),保压时间为20 s时,压弯成形的“几”字型零件表面质量良好、尺寸精度较高、基本无回弹,表现出良好的力学性能,硬度为63.8~71.3 HV。脉冲电流可以促进Mg-2.5Nd-0.5Zn-0.5Zr合金压弯成形过程中位错的滑移和攀移,减小位错塞积和缠结,同时释放残余应力,减小零件的回弹,进而提高Mg-2.5Nd-0.5Zn-0.5Zr合金的塑性变形能力和成形零件的精度。

The effects of current density and holding time on the microstructure evolution and formability of bending formed cap-shape parts of Mg-2.5Nd-0.5Zn-0.5Zr alloy were systematically studied by means of metallographic microscope and transmission electron microscopy.The results show that with the increase of current density(33.5-51.5 A·mm-2),the formability of the bending formed capshape parts improves gradually,and the springback reduces gradually.With the extension of the holding time(0-20 s),the springback reduces gradually.When the current density is 51.5 A·mm-2 and the holding time is 20 s,the surface quality of bending formed capshape parts is good,dimensional accuracy is high,and basically no springback,showing good mechanical properties,and the hardness is 63.8-71.3 HV.Pulsed current can promote the sliping and climbing of dislocations and reduce the dislocation plugging and entangling during the bending forming process of Mg-2.5Nd-0.5Zn-0.5Zr alloy,meanwhile,release the residual stress and reduce the springback of parts.And then the plastic deformation ability of Mg-2.5Nd-0.5Zn-0.5Zr alloy and the accuracy of the formed parts are improved.