高应变速率轧制对Mg-4Zn合金组织及性能的影响

Effects of High Strain-rate Rolling on Microstructure and Properties of the Mg-4Zn Alloy

采用光学显微镜、扫描电镜、浸泡质量损失和拉伸测试等手段研究了高应变速率轧制对Mg-4Zn合金微观组织、力学性能及耐腐蚀性能的影响。结果表明:固溶处理后进行高应变速率轧制,Mg-4Zn合金发生了均匀的动态再结晶,平均晶粒尺寸为4μm,力学性能明显改善,抗拉强度、屈服强度和伸长率分别为286 MPa、180 MPa和27.4%。固溶态、轧制态合金由于第二相含量及尺寸明显小于铸态,腐蚀方式为较均匀的丝状腐蚀,耐蚀性大大提高。Hank’s溶液中浸泡15 d实验表明,轧制态耐蚀性最佳,平均腐蚀速率为0.25 mg/(cm^2·d),约为铸态的1/5;其剩余抗拉强度最高为215 MPa,远高于铸态和固溶态。

Effects of high strain-rate rolling on microstructure, mechanical properties and corrosion resistance of Mg-4Zn alloy were investigated by optical microscope（OM）, scanning electron microscope（SEM）, mass loss of immersion test and tensile testing. Results show that high strain-rate rolling after solution treatment produces homogenous dynamic recrystallization（DRX） with final grain size of 4 μm, leading to a significant mechanical property improvement. The tensile strength, yield strength and elongation are 286 MPa, 180 MPa and 27.4%, respectively. The solutionized and the as-rolled alloys have better corrosion resistance than the as-cast alloy, exhibiting a uniform filiform corrosion due to the lower fraction and the finer size of the second phase. The as-rolled alloy presents the best corrosion resistance with the average corrosion rate of 0.25 mg/（cm^2.d）, about 1/5 of the as-cast alloy after soaking in Hank＇s solution for 15 d. It also shows the highest residual tensile strength（215 MPa）, far above the as-cast and the solutionized alloys.