Effects of B and Sn additions on the microstructure and mechanical property of Mg-3Al-1Si alloy

Abstract

The commercially used Mg-3Al-1Si (AS31) alloy was modified with B and Sn, and subjected to hot rolling. The microstructure and mechanical property of as-cast and hot-rolled alloys were investigated and compared. For the as-cast alloys, single addition of B or Sn refined the grains of AS31 alloy. The B addition could modify the network shaped Mg2Si phase into fine particles while the modification effect of Sn was not obvious. It was found that simultaneous addition of B and Sn resulted in large grains and coarse Mg2Si phase in the as-cast alloy. The as-cast AS31-2Sn alloy showed the highest tensile strength of 231 MPa and ductility of 19.5%. For the hot-rolled alloys, B or Sn addition distinctly refined the grains of AS31 sheet, while their combination severely retarded dynamic recrystallization, leading to much un-recrystallized structure. The AS31-2Sn sheet exhibited the best yield strength of ∼260 MPa with desirable ductility of ∼15%. Such desirable strength can be attributed to solid solution strengthening, grain boundary strengthening, texture strengthening and dislocation strengthening.