AZ31B宽幅镁合金铸轧板材热轧边裂原因分析

Analysis of Hot Rolled Cracks of Casting AZ31BMagnesium Alloy Plate

宽度150mm的AZ31B镁合金铸轧板材在轧制温度为350℃,轧制速度为0.5m/s,压下率分别为10%,20%,30%的不同工艺条件下进行了数值模拟和热轧实验研究。结果表明:同一温度条件下,随着轧制压下量的增大,镁板内部金属流动具有各向异性,其内部层片状结构的结合力随应变量的增大而减弱;在显微组织中,所产生的机械孪晶会随着轧制压下而压弯,甚至产生较小的次生孪晶,大小不一的孪晶组织会产生局部应力集中,从而产生微裂纹失稳扩展,边部的损伤因子随之增大。因此,减少长条形孪晶和第二相β-(Mg17Al12)的产生是控制边部裂纹的关键因素之一。

Using AZ31 Bmagnesium alloy sheet with the dimension of 150mm×150mm×7mm as the working material,hot rolling and corresponding numerical simulation were conducted by setting the rolling reduction of 10%,20% and 30%,the rolling temperature of 350℃ and rolling speed of 0.5m/s.It is found that material inside the magnesium sheet flows differently in different directions with the increase of rolling reduction under the same temperature.It implies that its flow has the characteristics of anisotropy.Because of increasing strain,the binding force of the inner layer of the sheet becomes weaker in this microstructure.Mechanical twins are bent with the increase of rolling reduction,and small secondary twins appear.Twins in different sizes will lead to local stress concentration,and edge cracks to propagate,which can cause unstable fatigue and increasing damage factor of edge portion.Therefore,reducing number of long strip twins and developing secondary phraseβ-（Mg17Al12）are critical to control edge cracks.