Investigations on microstructures, mechanical and corrosion properties of Mg-5.5Zn-0.8Zr alloys with Sm addition

Abstract

The microstructure, mechanical and corrosion properties of as-cast Mg-5.5Zn-0.8Zr (ZK60) alloys with varying Sm contents were investigated. The microstructures of the ZK60 alloy mainly consisted of α-Mg grains and Mg7Zn3 particles in common. Addition of Sm to ZK60 alloy resulted in the formation of Mg41Sm5 and (Mg, Zn)3Sm phases, which changed the number, morphology and distribution of the second phase of the alloy, resulting in finer, more homogeneous grains and improved mechanical properties. The ultimate tensile strength (UTS), yield strength (YS) and elongation (EL) of the ZK60-0.8Sm alloy were increased by 19.8%, 25.3% and 31.7%, compared to those of ZK60 alloy, from 162 to 194 MPa, 74.4 to 93.2 MPa and from 6.0% to 7.9%, respectively. The corrosion mode of Sm-containing ZK60 alloys changed from serious local corrosion to uniform corrosion, and the corrosion resistance was improved. When the content of Sm was 1.6 wt%, the corrosion rate of the alloy was 1.7102 g · cm−2 · h−1, which was only 89% of the corrosion rate of ZK60 alloy. The improvement of the properties of ZK60-xSm alloys was attributed mainly to the interaction of solid solution strengthening, fine grain strengthening and precipitation strengthening.