研究AZ31镁合金异步铸轧板坯沿厚度方向的显微组织分布。结果表明,板坯组织沿厚度方向具有较明显的不均匀性。在板坯的上表面附近存在较多的流线型变形带组织;在中心处观察不到变形带组织,枝晶臂较粗大;在板坯下表面附近枝晶组织较细密。板坯上表面附近的流线型变形带是由上、下铸轧辊表面线速度差产生的剪切应变而引起的。Al、Zn和Mn在枝晶晶界处发生偏聚,Si均匀分布在α-Mg固溶体内。 The microstructure distribution along the thickness of AZ31 magnesium alloy as-cast slab was studied. The results show that the slab has obvious inhomogeneity along the thickness. In the vicinity of the upper surface of the slab, there are many streamline deformation bands; the deformation band structure is not observed in the center, and the dendrite arm is coarse; the dendrite structure is finer near the lower surface of the slab. The streamline deformation zone near the upper surface of the slab is caused by the shear strain caused by the difference in linear velocity between the upper and lower casting rolls. Al, Zn and Mn segregate at the dendrite boundaries, and Si is uniformly distributed in the α-Mg solid solution.