Effects of Ti addition on the microstructure and mechanical properties of Mg-Zn-Zr-Ca alloys

The effects of Ti additions ( 0, 0.4, 0.6, 0.8, 1.0, 1.2 wt.%) on the microstructure and mechanical properties of as- cast and aging Mg-0.4% Zn1.0% Zr-1.5% Ca (wt.%) alloys were investigated. The results indicated that minor Ti can effectively refine grains, while excessive Ti addition resulted in the grain coarsening. When the content of Ti was 0.8 wt.%, the as-cast alloy exhibited the finest grain size of 39 mm which contributed to the optimal mechanical properties with Brinell hardness of 57.9 HB, ultimate tensile strength of 145 MPa and elongation of 3.2%. After T6 heat treatment, the continuous net-like Mg2Ca and Mg6Zn3Ca2 phases changed to uniform massive T phases (ternary MgeZneCa phases) and dispersive halo-like precipitates (Mg2Ca and Mg6Zn3Ca2 phases). The ultimate tensile strengths of the alloy at room temperature (RT), 175 degrees C and 200 degrees C were correspondingly improved to 182 MPa, 169 MPa and 141 MPa, respectively. Copyright 2015, National Engineering Research Center for Magnesium Alloys of China, Chongqing University. Production and hosting by Elsevier B. V. All rights reserved.