挤压态Mg-1.2Zn-0.8Y合金组织及高应变速率下的力学行为

通过显微组织观察、X射线及电子衍射结构分析对挤压态Mg98Zn1.2Y0.8合金的第二相结构及分布,以及Mg基固溶体组织形态进行了研究,并对其100/s~667/s应变速率下的力学行为及断裂机制进行了分析.结果表明:Mg98Zn1.2Y0.8合金在300℃、挤压比为16的热挤压过程中发生了完全的动态再结晶;挤压态组织为晶粒细小的镁基固溶体、其上弥散分布的化合物H相,以及沿晶界分布的Z相.室温下随着应变速率从100/s提高到667/s,挤压态Mg98Zn1.2Y0.8合金的屈服强度及抗拉强度明显升高,延伸率也从9.2%提高到13%.室温下应变速率为100/s~667/s时挤压态M g98Zn1.2Y0.8合金的拉伸断裂方式是以韧性断裂为主并伴有脆性断裂的混合断裂.

Microstructure and Mechanical Behavior at High Strain Rates of As-extruded Mg-1.2Zn-0.8Y Alloy

The structure of compounds and the microstructure of as-extruded Mg₉₈Zn_1.2Y_0.8 alloy were investigated through OM， SEM， TEM and XRD. The dynamic behavior at high strain rate conditions of as-extruded Mg₉₈Zn_1.2Y_0.8 alloy was also researched through the tensile test and fracture surface observation. The results show that the complete dynamic recrystallization occurs in the Mg₉₈Zn_1.2Y_0.8 alloy during extruding process at a temperature of 300℃ and a reduction ratio of 16∶1. The fine particles of compound H-phase dispersively distribute in the Mg-based solid solution with fine grain size， and the particles of Z-phase mainly distribute along the grain boundaries. At room temperature， the yield strength and the tensile strength rise with the increase of strain rates from 100/s to 667/s， and the elongation also increases from 9.2% to 13%. Ductile fracture with some proportion of brittleness fracture occurs in the as-extruded Mg₉₈Zn_1.2Y_0.8 alloy at room temperature and strain rate 100/s -667/s.