冷轧变形量对7A75铝合金组织性能的影响

Effect of cold rolling deformation on microstructure and properties of 7A75 aluminum alloy

研究了冷轧变形对7A75铝合金微观组织和力学性能的影响,并探讨了第二相粒子促进形核的机制。采用光学显微镜(OM)和透射电镜(TEM)观察了微观组织,采用万能拉伸试验机测试了力学性能,采用板材成形试验机测试了杯突值(IE)。结果表明:随冷变形量的增大,7A75铝合金的强度和伸长率均逐渐增大,且屈服强度的升高幅度大于抗拉强度。50%冷变形时屈服强度和抗拉强度分别达到435 MPa和460 MPa,与未经冷变形时相比分别提高了190 MPa和110 MPa,同时伸长率提高到14%。杯突IE值与伸长率的变化规律一致。30%、50%和70%的冷变形下,基体晶粒平均尺寸分别为31.5、13.5和13.0μm,冷变形量越大,基体晶粒尺寸越细小越均匀。过时效处理后,7A75铝合金中的MgZn2粒子尺寸大于0.5μm时,在冷变形后的固溶处理过程中为再结晶提供形核位置;而50~100 nm之间的粒子钉扎在晶界处,有效地抑制了再结晶晶粒的长大。

Effect of cold rolling deformation on microstructure and mechanical properties was investigated,the mechanism of second phase particles simulated nucleation was discussed.The microstructure was characterized by using OM and TEM.The mechanical properties were tested by using tension tester machine.The IE value was tested by using sheet forming test machine.The results indicate that the strength and elongation increases with the increase of deformation,and the increase rate of yield strength is higher than tensile strength.When the deformation is 50%,the yield strength and tension strength reach 435 MPa and 460 MPa respectively,which have an increase of 190 MPa and 110 MPa respectively compared to those without deformation.Meanwhile,the elongation increases to 14%,and the IE value also increases with the increase of deformation.When the deformation is 30%,50%and 70%,the average grain size is about 31.5,13.5 and 13.0μm respectively,which shows that the greater the deformation,the smaller and more uniform the matrix grain size.The precipitation phase MgZn2 lager than 0.5μm simulates the nucleation of recrystallization grain after cold rolling process during the solution treatment,while the ones which has the size of 50-100 nm pins the grain boundaries and inhibits the growth of recrystallization grains.