Redistribution and refinement of the dendrites in a Mg-Y alloy by laser surface remelting and its influence on mechanical properties

Laser surface remelting (LSR) was performed on a Mg-6.2Y (at.%) magnesium alloy to enhance mechanical properties of its surface. The results show that both grains and secondary phase were greatly refined by LSR. The epsilon phase (Mg24+xY5) was redistributed from alpha-Mg grain boundaries to interior of the grains. The Y content of epsilon phase decreased from 14.3 to 9.3 at.% due to the LSR. Some metastable Y-rich nano particles were formed on the epsilon phase due to the rapid solidification. Mechanical properties of treated surface were significantly improved due to grain refinement and phase redistribution. Compressive strength of the treated region was increased to 606 MPa and exhibited a moderated ductility compared to the initial material. The increase of ductility by LSR is related to the uniformed redistribution of epsilon phase, which led to a homogeneous distribution of strain.