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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 high temperature mechanical properties of reciprocating extrusion Mg-4Al-2Si alloy were studied. The results show that the microstructure of Mg-4Al-2Si alloy can be remarkably refined by reciprocating extrusion. With the increase of extrusion pass, the matrix grains and Mg2Si phase grains are refined continuously. The matrix grains are finely grained by dynamic recrystallization The When extruded for 8 passes, the average grain sizes of matrix grains and Mg2Si grains decreased from as-cast 45μm and 20μm to 1.5μm and 1.3μm, respectively. However, when the extrusion pass was 11, the average grain sizes of matrix grains and Mg2Si phase Particles appear roughening phenomenon. Reciprocating extrusion can greatly improve the mechanical properties of the alloy at high temperature, the maximum yield strength is 197 MPa at 8 times of extrusion, and the maximum tensile strength is 256 MPa at 11 times of extrusion, Compared with the high temperature strength, respectively, increased by 163.9% and 239.7%. The high-temperature strengthening mechanism of the alloy is the dispersion strengthening effect of the Mg2Si particles, and the high-temperature tensile fracture mode is microporous polymeric ductile fracture.