Influence of Al-Si additions on mechanical properties and corrosion resistance of Mg-8Li dual-phase alloys

Sheet samples of Mg-8Li, Mg-8Li-3Al, Mg-8Li-3AlSi and Mg-8Li-5AlSi alloys were obtained by hot rolling. Optical microscope, microhardness tester, nanoindentor, X-ray diffractometer and electrochemical analyzer were adopted to investigate the microstructures, micro-mechanical properties and corrosion resistance. Roller was preheated to 150 °C before rolling process, and rolling reduction designed was about 20% per pass with a total rolling reduction of 84%. The rolled plates were annealed at 200 °C for 120 min. The tensile tests were performed at room temperature. Experimental results showed that both the strength and corrosion resistance of the α + β dual-phase of Mg-Li alloy were significantly improved with adding Al-Si elements. The strength enhancement was attributed to the solid solution of Al into the α-Mg matrix and into the β-Li matrix as well as to the precipitation strengthening of Mg2Si particles. Besides, the dendrite grains of α-Mg transformed to equiaxed ones with addition of Al into alloy Mg-Li.