Effects of Substitution of Cu with Ni on Microstructure and Mechanical Properties of Mg-Er-Cu Alloy

Mg-RE-TM alloy exhibits excellent mechanical properties, due to its long period stacking ordered (LPSO) phase. In this work, the effects of substitution of Cu with Ni on microstructure and mechanical properties of Mg97Er2Cu1 alloy, has been systematically examined. Results showed that the as-cast Mg97Er2Cu1 alloy was mainly composed of α-Mg matrix, LPSO phase and Mg2Cu phase, while the Ni-substitution alloys mainly consisted of α-Mg matrix and LPSO phase. By substituting Cu with Ni, the grains of the as-cast alloys were refined, and the mechanical properties were improved. The as-cast Mg97Er2Cu0.25Ni0.75 alloy with 75% Ni substituted for Cu had a maximum ultimate tensile strength of 236 MPa, a yield tensile strength of 147 MPa, and an elongation of 8.1%. The improvement of alloy mechanical properties was related to the increase of the volume fraction of LPSO. The detailed strengthening mechanism was discussed based on the grain refinement mechanism and the second phase strengthening mechanism.