时效处理对AZ81镁合金组织与力学性能的影响

通过对挤压坯预成形AZ81镁合金进行模压成形及随后的时效处理,研究了形变及时效过程中显微组织及力学性能的变化规律.结果表明:时效温度埘AZ81镁合金力学性能及显微组织的影响较大,随时效温度升高至200℃,第二相的析出速度加快,且析出相分布变得均匀,细小析出相呈弥散状态分布于晶界上;随时效时间的延长.β-Mg17Al12析出相逐渐增多,当时效温度为200℃、时效20h时,晶界大多被析出物所掩盖,晶粒内充满大量点针状析出相,合金显微组织的各向异性得以消除,成分较为均匀,进一步提高了模压成形镁合金的力学性能,经400℃模压成形及200℃×20 h的时效处理后,其抗拉强度可达358.5 MPa,屈服强度达到260.7 MPa,伸长率为9.8%.

Influence of Aging Treatment on Microstructure and Mechanical Properties of AZ81 Alloy

The change rules of microstructure and mechanical properties of AZ81 alloy during close-die hot-pressing of extruded preform and succedent aging were investigated.The results show that when the aging temperature goes to 200℃.the speed of second phase decomposition and precipitation goes up.The distribution of precipitated phase gets uniform,the precipitated phase distributes in grain boudary are in dispersed state;when aging time expanding,β-Mg17Al12 phase increases gradually;when aging at 200℃ for 20 h,the most and a majority of them are exiguous sheets,the component is uniform,it makes the mechanical properties of material getting best.Grain boundary is shielded by large quantity precipitate phases and gram inner distributes lots of spotted-niddle precipitate phases,but anisotropic property of AZ81 alloy are erased and its mechanical properties are improved.The tensile strength of AZ81 alloy by hot pressing forming at 400℃and aging at200℃ for 20 h is about 358.5 MPa,yield strength about 260.8 MPa,and elongation about 9.8%.