Effects of rare-earth, strontium and titanium additions on mechanical properties and corrosion behaviors of AZ91 magnesium alloys
The effects of RE, Sr and Ti additions on microstructures and tensile properties of AZ91 alloys were studied by XRD, SEM, tensile test, electrochemical polarization tests and salt-spray corrosion tests. The results show that new phases as Al11Ce3, Al2Y, Al4Sr and compound Al10Ce2Mn7 phase were observed with RE and Sr additions, and small amounts of titanium did not cause the formation of any new phase in the microstructure. With RE and Sr additions, the mechanical properties of AZ91D alloy was improved. The best properties of which has been shown is AZ91+RE+Sr alloy. The ultimate tensile strength is 208 MPa, yield tensile strength is 93 MPa, and elongation of alloys is 6.5%. With the increase of Ti addition, mechanical properties of the alloys decrease. After exposed in NaCl salt spray, the whole surface of test alloy suffers from heavy corrosion while its corrosion resistance improved significantly with RE+Sr+Ti additions.