Development of High Strength Alloys in the Mg-Ni-Y-RE System

The microstructural and mechanical characterization of two alloys within the Mg-Ni-YRE system prepared by casting and subsequent hot extrusion at 400ºC have been carried out. The microstructure of both materials consists of a fine-grained magnesium matrix embedding a high volume fraction of second phases; coarse Mg12RE and long period ordered stacking structure (LPS phase) and fine Mg2Ni particles. Both alloys show high strength values up to 250ºC. The yield stress values at room temperature are 295 and 405 MPa for low- and high-alloyed magnesium alloy, respectively. Load transfer from the magnesium matrix to coarse Mg12RE and LPS particles account for the high strength of both alloys at temperatures below 250ºC. Above this temperature both alloys exhibit a superplastic behaviour at low stresses with elongations of 700 and 450 % for the low and high-alloyed magnesium alloy, respectively.