异径轧制对AZ31镁合金薄带微观组织的影响

考虑到轧制镁合金薄带板形的控制精度要求,采用小辊径同径轧制和异径轧制工艺分别制备了0.5,1.0 mm的AZ31镁合金薄带,研究不同工艺过程中板材内部晶粒微观组织的变化规律以及同径轧制与异径轧制在轧制过程中的对称性问题.结果表明:0.5 mm异径轧制和同径轧制板带的晶粒尺寸分别为8.8和10.1μm,1.0 mm的分别为13.6和16.7μm.0.5 mm的异径轧制与同径轧制的单元等效塑性应变最大值分别为0.42和0.29,1.0 mm的分别为0.75和0.66,与实验结果相符.0.5 mm同径轧制的特征节点在板带上中下部的等效米塞斯应力和剪切应力分布对称,异径轧制的分布非对称.0.5 mm板带经过250,300,350℃退火1 h后,异径轧制的晶粒长大较缓慢,同径轧制的晶粒长大较快.350℃下,异径轧制的晶粒尺寸为9.8μm,同径轧制的为24.9μm.

Effect of Asymmetric Rolling on Microstructure of AZ31 Magnesium Alloy Sheets

To fullfill the demand of rolling accuracy of magnesium alloy sheets, the symmetric problem during rolling process and the microstructural evolution of the AZ31 sheets with the thickness of 0.5 and 1.0mm, which made by symmetric and asymmetric rolling process using small rollers, were investigated. The results showed that the average grain size in the 0.5mm sheets by symmetric and asymmetric rolling was 10.1 and 8.8μm, respectively, that of the 1.0mm was 16.7 and 13.6μm, respectively. The element equivalent strain of the 0.5mm sheet was up to 0.42 by asymmetric rolling and 0.29 by symmetric rolling and that of the 1.0mm was 0.75 and 0.66, respectively. In symmetric rolling, the distributions of the nodal equivalent Mises stress and shear stress in the 0.5mm sheet were more symmetric by symmetric rolling process, in contrast with those by asymmetric rolling. Grain growth in the 0.5mm sheet by asymmetric rolling was much slower than that by symmetric rolling during annealing for 1h at 250, 300 and 350℃. At 350℃, the average grain size in the 0.5mm sheet by asymmetric rolling was 9.8μm and that by symmetric rolling was 24.9μm.