The interaction between in situ grain refiner and ultrasonic treatment and its influence on the mechanical properties of Mg–Sm–Al magnesium alloy

This work investigated the interaction between in situ grain refiner and ultrasonic treatment (UT) and its influence on the mechanical properties of Mg–Sm–Al magnesium alloy. The grain size is reduced with the increasing of Al content, which is attributed to the enhancement of heterogeneous nucleation by Al2Sm particles. The ultrasonic melt treatment also refines grains via increasing the number of nucleation sites by ultrasonic cavitation. There is a maximum grain refinement efficiency on a certain solidification circumstance. The alloying method (generation the in situ grain refiner) and UT have a positive interaction, which increases the number of potential nucleation particles in melt, while the number of activated nucleation particles is decided by solidification condition. The increase of Al content and UT improve both yield strength and ultimate tensile strength due to grain refinement strengthening and the second phase strengthening. The UT significantly improves the elongation of each alloy with an increasing range of up to 312%. The de-agglomeration of second particles and increased diversity of grain orientation respond to such improvement.