冷轧率与退火工艺对汽车用5754铝合金组织演变的影响

Effect of Cold Rolling Rate and Annealing Process on Microstructure Evolution of the Automobile Used 5754 Aluminum Alloy Sheet

本文研究了汽车结构件用5754铝合金经不同冷轧变形量(冷轧率58%～75%,对应厚度2.5mm、2.0mm及1.5mm)后再进行H22、H111两种退火处理的整个生产过程中组织的演化。在冷轧变形以及后续退火过程中,5754合金中等效圆直径大于0.2μm的第二相分布不再发生改变,与热轧状态完全一致。热轧板芯部相比表层具有更多的轧制织构,存在沿厚度方向上的不均匀性。2.5mm厚5754铝合金在冷轧和H22状态下也存在组织不均匀性。然而不同的是,冷轧后,铝合金表层轧制织构增多;在不完全退火时,这种不均匀的方式再一次发生改变,芯部依然存在大量轧制织构,而表层的再结晶程度更高,立方织构明显增多;H111状态完全再结晶退火后,板材表层和芯部组织趋于均匀。随着冷轧率的增加,2.0mm及1.5mm厚的板材组织较为均匀,冷轧及H22、H111退火状态板材均未出现表层与芯部的组织差异。冷轧后,板材组织呈纤维状,立方织构较热轧板进一步减少;H22不完全再结晶退火状态时,可以观察到板材发生部分再结晶,轧制织构减少,立方织构增多;至H111完全再结晶状态时,组织呈等轴晶状,立方织构达到最大值。

The effects of cold rolling rate(58%—75%,the thickness of 2.5mm,2.0mm and 1.5mm)and annealing process(H22and H111temper)on microstructure evolution of 5754 aluminum alloy sheets,using in the automobile structural parts,were investigated.The secondary phases,equivalent circle diameter greater than 0.2μm,were not changed in the cold rolling and annealing process compared with the distribution of that in hot rolling state.In hot rolling state,the proportion of rolling textures in the core was higher than that in the surface,indicating that the heterogeneity existed along the normal direction.The distribution of grains and textures in the thickness of 2.5mm sheets were also heterogeneous in cold rolling and H22 temper process.But there were some differences that in the cold rolling process.The rolling textures in the surface were much higher than that in the surface.This phenomenon was reversed once again in incomplete recrystallization annealing process,i.e.H22 temper.The degree of the recrystallization was much higher in the surface and the cube textures were increased,whereas there were still plenty of rolling textures in the core of the sheets.After the sheets were fully recrystallized,the heterogeneous microstructure between core and surface was diminished.With the increase in cold rolling rate,the distribution of grains and textures in the thickness of 2.0mm and 1.5mm 5754 aluminum alloy were quite homogenous.There was no microstructure difference observed in cold rolling,H22 and H111state along the normal direction.After cold rolling process,the grains were fibrous,and the cube textures were decreased further compared with the state of hot rolling process.In the H22 temper state,the sheets were partial recrystallized,the rolling textures were reduced and cube textures were increased.After the sheets were fully recrystallized,grains become equiaxed and the cube textures reached maximum.