Mg-7Sn-Zn(Y)合金的显微组织、时效硬化行为及力学性能

研究了Zn和Y合金化对Mg-7Sn合金显微组织、时效硬化行为和力学性能的影响.铸态Mg-7Sn合金主要由α-Mg和共晶(α-Mg+Mg₂Sn)相组成.Zn添加细化了Mg₂Sn相的尺寸,促进了Mg₂Sn相大量、均匀的弥散分布,同时诱导了Mg₂Sn相的非基面析出,增强了合金时效硬化效果.合金时效峰值硬度从64.6 HV增大到69.7 HV,峰值时效时间从166 h缩小至142 h.Zn和Y元素共同添加形成了针状MgSnY相,有效缩短了合金的时效峰值时间(由166 h缩短至120 h),但合金的峰值硬度略有降低,Mg-7Sn-1Zn合金具有最佳的力学性能,其高力学性能主要归结为细小、高体积分数Mg₂Sn相的析出强化.

Microstructure,age-hardening behavior and mechanical properties of Mg-7Sn-Zn(Y) alloy

The microstructure, age-hardening behavior and mechanical properties of Mg-7Sn-Zn(Y) alloy were investigated. The as-cast Mg-7Sn alloy was mainly composed of α-Mg and eutectic(α-Mg+Mg₂Sn) phase. The addition of Zn refines Mg₂Sn phase, increases volume fraction of Mg₂Sn phase and promotes precipitation of Mg₂Sn phase on non-basal plane, and thus enhances the ageing hardening capacity of the alloy. The peak-ageing hardness of the Mg-7Sn-1Zn alloy increases from 64.6 HV to 69.7 HV, and the peak-ageing time decreases from 166 h to 142 h. The addition of Zn and Y elements forms the needlelike MgSnY phase. Although the peak-ageing time of the alloy is effectively decreased(166 h to 120 h), the peak-ageing hardness of the alloy reduces.The Mg-7Sn-1Zn alloy exhibits the best mechanical properties,Which was mainly attributed to the precipitation strengthening of fine Mg₂Sn phasewith high volume fraction.