Microstructure,tensile properties and free bulge formability of Sr-and Y-containing AZ31 alloy sheet produced by twin-roll casting and sequential hot rolling

摘要

The effects of Sr and Y on microstructure,tensile property and free bulge formability of AZ31 alloy sheet produced by twin-roll casting and sequential hot rolling were investigated to improve the mechanical properties and formability of the AZ31 alloy.Sr and Y addition can form Al4 Sr,Al2 Y and Al3 Y phases which can impede dislocation movement and promote dynamic recrystallization during the rolling deformation and decrease the lattice resistance to dislocation motion by decreasing Al solubility in the alloy,resulting in finer grains,lower dislocation density and no twinning generating in the twin-roll casting and sequential hot rolling(TRC-HR)AZ31-1.3 Sr-1.0 Y alloy.The maximum stress and elongation of the alloy increase significantly after adding Sr and Y.The average cavity and grain sizes of the TRC-HR AZ31-1.3 Sr-1.0 Y alloy are smaller,resulting in higher elongation in the alloy.The addition of Y and Sr can effectively improve the free bulge formability and the thickness uniform of the alloy.The Al4 Sr,Al2 Y and A13 Y phases can inhibit the grain growth by obstructing dislocation motion or grain boundary slip,resulting in smaller grain size of AZ31-1.3 Sr-1.0 Y alloy bulge parts.