中文摘要：

采用光学显微镜、场发射扫描电镜及室温拉伸试验等研究了β-Mg17Al12相对AZ31B镁合金铸轧板边裂行为的影响。结果表明：β-Mg17Al12相在AZ31B镁合金铸轧板的表层及边部主要分布于晶界处且密度较大、构成网状，而在板坯的中心及中部呈球状弥散在α-Mg基体中，构成层片状；网状β-Mg17Al12相对AZ31B镁合金铸轧板塑性有恶化作用，而层片状β-Mg17Al12相有利于合金塑性；位于晶界处的β-Mg17Al12相与基体α-Mg结合力较差且表现为脆性，铸轧变形时首先与基体分离，造成裂纹在晶界处萌生和扩展；轧制压力和摩擦力使轧制区域拉伸应变积聚，由此传递到液态区两侧的凝固硬壳内（即板坯边部），使晶粒破碎或沿晶界β-Mg17Al12相撕裂并向纵深扩展，形成边裂。

英文摘要：

The effects of β-Mg17Al12 on the edge crack behavior of twin-roll casting AZ31B magnesium alloy plate were studied by opticalmicroscope, field emission scanning electron microscope and tensile testing. The results indicate that in the surface and the edge ofAZ31Bmagnesium alloy cast-rolling plate, β-Mg17Al12 phase mainly distributes at the grain boundary and its density is big, forming net-shape;and in the center and the middle of the plate, spherical β-Mg17Al12 phase disperses in α-Mg matrix, and forms lamellar-shape; thenet-shaped β-Mg17Al12 phase in the plate can decrease the mechanical properties, while the lamellar-shaped β-Mg17Al12 phase improve itsductility. The bonding force between the β-Mg17Al12 phase and the α-Mg matrix in the grain boundary is bad and characterized bybrittleness. In the deformation of roll casting process, first of all, β-Mg17Al12 phase separates from the α-Mg matrix, resulting in crackinitiation and propagation in grain boundary; rolling pressure and friction produces tensile strain accumulation in the rolling region, andpasses to the solidification shell which is on the both sides of liquid region （i.e. the slab edge）, making grains break or tear along the grainboundary β-Mg17Al12 phase to deepen longitudinally and as a result the edge crack forms.