铸态AZ81镁合金ECAP态组织与性能研究

摘要

采用自制的90°模具,经Bc路径在温度为300℃下研究对比了铸态及不同道次的等通道挤压（ECAP）态AZ81镁合金微观组织和力学性能.结果表明ECAP随着挤压道次的增加,AZ81镁合金显微组织和力学性能发生显著变化.当挤压到4道次,平均晶粒尺寸由原来铸态的145um细化为9.6um,拉伸断口韧窝明显增多;抗拉强度从180 MPa提高到306 MPa,延伸率和硬度分别达到15.8%和142HL.分析表明,AZ81镁合金在高温挤压过程中Mg17Al12相粒子被破碎,并部分溶入基体,α-Mg基体与β-Mg17Al12相互相阻碍其晶粒长大,获得细小晶粒组织.%The microstructure and mechanical of AZ81 magnesium alloys before and after equal channel angular pressing （ECAP） were investiagted using seIf- made 90°die at 300 ℃ in Be path. The results showed that there was a better grain refinement with the increasing of pass number, the grain was continuously refined and mechanicaI properties were improved after the pressing. When squeezed four passes, the average grain size were refined from 145 um to 9.6um, tensile fractures presented the increment of dimpIe structure, tensiIe strength were changed from 180 Mpa to 306 MPa, hardness was ofl42HL, elongation was of 15. 8%. The analysis showed that the grains were much smaller than that of the conventional alloys due to the β - Mg17 Al12 phase broken, and partially integrated into the α - Mg matrix during pressing at high temperature. The mutual restric- tion between the two phases greatly reduced the speed of the dynamic recrystallization.