流变挤压铸造制备LPSO结构增强Mg-Zn-Y-Zr合金及其组织性能

采用流变挤压铸造工艺制备了含有LPSO结构的Mg99.9-3xZnxY2xZr0.1(x=0.5、1、2,摩尔分数,%)合金,研究了合金的微观组织特征及力学性能。结果表明,流变挤压铸造能有效细化合金的微观组织。合金的基体组织由尺寸较大的α1-Mg和尺寸较小的α2-Mg晶粒组成,LPSO结构呈细小的网状结构均匀地分布在晶界处,LPSO结构的含量越低,其细化效果越明显。随着挤压压力增大,合金中LPSO结构的厚度越来越小,当压力达到100MPa后,厚度变化趋缓。与常规重力铸造相比,流变挤压铸造能有效提高合金的力学性能,特别是伸长率。在400MPa下的流变挤压铸造Mg96.9Zn1Y2Zr0.1合金的抗拉强度和伸长率较重力铸造下分别提高了19%和170%。

Microstructure and Mechanical Properties of Rheo-squeeze Casting LPSO Structure Reinforced Mg-Zn-Y-Zr Alloys

Mg99.9-3xZnxY2xZr0.1(x=0.5,1,2,molar fraction,%)alloys reinforced with LPSO structure was prepared by rheo-squeeze casting.Microstructure and mechanical properties of the alloys prepared were investiagted.The results reveal that rheo-squeeze casting can refine effectively the microstructure of the alloys.The matrix structures of the alloys are composed of largerα1-Mg and smallerα2-Mg grains.The LPSO structure is distributed uniformly in the grain boundary.The lower the content of LPSO structure is,the more obvious the refining effect is.With the increase of squeeze pressure,the thickness of LPSO structure in the alloys is decreased.After the squeeze pressure reaches 100 MPa,the thickness is changed slowly with increasing in pressure.Compared with conventional gravity casting,rheo-squeeze casting can improve effectively the mechanical properties of the alloys,especially for the elongation,where the tensile strength and elongation of the rheo-squeeze casting Mg96.9Zn1Y2Zr0.1 alloy under 400 MPa are improve by 19%and 170%,respectively.