Microstructure evolution of casting Mg alloy AM60B subjected to compression deformation

In order to research the microstructure evolution of casting Mg alloy AM60B after compression,the isothermally compressive deformation of different compression ratios followed by metallographic observation was performed.The influence of grain boundaries and second phases on the deformation and recrystallization behavior of the alloy was investigated with optical microscopy,followed by transmission electron microscopy(TEM) to gain an insight into the interplay between the dislocations and microstructure features.The investigation results show that the deformation structure featured by refined grains forms first at as-cast grain boundary when the compression ratio is low,and then spreads throughout the whole cross-section of the casting when the deformation ratio approaches 70%.TEM observation indicates that,dislocations preferentially distribute in the region next to the grain boundaries and second phases,which leads first to the recrystallization occurring there and bounds the recrystallization process in later deformation.Therefore,the grain boundaries and second phases are beneficial to keeping the recrystallized microstructurc with fine grains,and may contribute to the formation of an inhomogeneous grain size distribution on the cross-section of the alloy.

In order to research the microstructure evolution of casting Mg alloy AM60B after compression, the isothermally compressive deformation of different compression ratios followed by metallographic observation was performed. The influence of grain boundaries and second phases on the deformation and recrystallization behavior of the alloy was investigated with optical microscopy, followed by transmission electron microscopy （TEM） to gain an insight into the interplay between the dislocations and microstructure features. The investigation results show that the deformation structure featured by refined grains forms first at as-cast grain boundary when the compression ratio is low, and then spreads throughout the whole cross-section of the casting when the deformation ratio approaches 70%. TEM observation indicates that, dislocations preferentially distribute in the region next to the grain boundaries and second phases, which leads first to the recrystallization occurring there and bounds the recrystallization process in later deformation. Therefore, the grain boundaries and second phases are beneficial to keeping the recrystallized microstructure with fine grains, and may contribute to the formation of an inhomogeneous grain size distribution on the cross-section of the alloy.