往复挤压Mg-4Al-2Si合金的显微组织与高温力学性能

Microstructure and elevated temperature mechanical properties of Mg-4Al-2Si alloy by reciprocating extrusion

研究了往复挤压Mg-4Al-2Si合金的显微组织与高温力学性能。结果表明,往复挤压可显著细化Mg-4Al-2Si合金的组织,随着挤压道次的增加,基体晶粒与Mg2Si相颗粒不断细化,其中,基体晶粒由于动态再结晶而细化。挤压8道次时,基体晶粒和Mg2Si颗粒的平均尺寸分别由铸态的45μm和20μm减小至1.5μm和1.3μm;但是,当挤压道次为11时,基体晶粒与Mg2Si相颗粒均出现粗化现象。往复挤压可使合金的高温力学性能大幅度提高,挤压8道次时,高温屈服强度最高,为197 MPa;挤压11道次时,高温抗拉强度最高,为256 MPa,与铸态高温强度相比,分别提高了163.9%和239.7%。合金的高温强化机制为Mg2Si颗粒的弥散强化作用,高温拉伸断裂形式为微孔聚合型韧性断裂。

The microstructure and elevated temperature mechanical properties of Mg-4Al-2Si（AS42）alloy by reciprocating extrusion（RE）were studied.The results show that the RE is an effective method to refine grain and Mg2Si particles of AS42 alloy.As the number of RE passes is increased,the grain and particles become finer.The α-Mg grain refinement is mostly due to dynamic recrystallization.The grain sizes of as-cast α-Mg and Mg2Si particles decrease from 45 μm and 20 μm to 1.5 μm and 1.3 μm after 8 passes RE,respectively.The grain and particles begin to coarse due to high temperature from 11 passes RE.The elevated temperature mechanical properties of AS42 alloy is improved significantly by RE.RE-8 passes,yield strength shows maximum,197 MPa.RE-11 passes,the maximum ultimate tensile strength 256 MPa is approached.The yield strength and ultimate tensile strength increase by 163.9% and 239.7% compared with as-cast AS42 at 150 ℃ respectively.Elevated temperature strengthening mechanism of RE-AS42 alloy is Mg2Si particles dispersion strengthening.RE-AS42 alloy usually shows flexible fracture at 150 ℃.