Effect of extrusion temperature on microstructure, mechanical properties and corrosion resistance of Mg-6Sn-3Al-1Zn alloy

Abstract

The Mg-6Sn-3Al-1Zn (wt%) alloy was extruded at different extrusion temperatures, the microstructure was analyzed by XRD, EBSD, OM and SEM, the tensile properties were tested by a universal testing machine, corrosion resistance was tested by an electrochemical workstation. The results showed that with the increase of extrusion temperature, the volume fraction of Mg2Sn phase decreased, the average grain size of alloy increased, the filamentous fiber microstructure firstly increased and then decreased, and the yield strength and corrosion resistance of the alloy decreased. However, the elongation increased. After the alloy was extruded at 400 ℃, the Mg2Sn second phase and grains of α-Mg matrix of alloy distributed in the microstructure evenly, the average grain size was 11.9 µm, the comprehensive mechanical properties of alloy were the optimum, the tensile strength, yield strength and elongation were 312 MPa, 241 MPa and 10.7%, respectively. The corrosion mechanism of Mg-6Sn-3Al-Zn alloy was mainly based on electrochemical corrosion, chemical corrosion and obvious local corrosion. The lowest rate of hydrogen evolution of the alloy extruded at 300 °C in 3.5 wt% NaCl solution is 0.192 ml/h, the grain refinement helps to enhance the corrosion resistance of the alloy.