摘要：
The effects of β-Mg17Al12on the edge crack behavior of twin-roll casting AZ31B magnesium alloy plate were studied by optical microscope, field emission scanning electron microscope and tensile testing. The results indicate that in the surface and the edge of AZ31B magnesium alloy cast-rolling plate, β-Mg17Al12phase 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-Mg17Al12phase disperses in α-Mg matrix, and forms lamellar-shape; the net-shaped β-Mg17Al12phase in the plate can decrease the mechanical properties, while the lamellar-shaped β-Mg17Al12phase improve its ductility. The bonding force between the β-Mg17Al12phase and the α-Mg matrix in the grain boundary is bad and characterized by brittleness. In the deformation of roll casting process, first of all, β-Mg17Al12phase separates from the α-Mg matrix, resulting in crack initiation and propagation in grain boundary; rolling pressure and friction produces tensile strain accumulation in the rolling region, and passes 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 grain boundary β-Mg17Al12phase to deepen longitudinally and as a result the edge crack forms.
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