Effects of Nd and Ag additions on the microstructures and mechanical properties of Mg-8 mass% Li alloys

Mg-8 mass%Li-Nd-Ag alloys with compositions of 0, 3, 6 mass%Nd and 0, 2 mass%Ag were melted in a mild steel crucible by a fluxless method. The effects of neodymium and silver additions on the microstructures and mechanical properties of the Mg-8 mass%Li alloy was investigated. The increase in neodymium resultes in the increased amount of Mg3Nd compounds and the decreased amount of the primary α phase. Silver is soluble in both the primary β phase and Mg3Nd compounds and, therefore, causes no microstructural change for ternary alloys. Work hardening of the Mg-8 mass%Li alloy is degraded by the neodymium addition because of decrease in the primary α phase, whereas it is upgraded by the silver addition. A hot-rolled binary alloy softens by isochronal annealing at temperatures above 373K. The recrystallization temperature is raised up to 423K by the addition of neodymium. Age hardening phenomena are observed for all alloys T6 heat-treated after hot-rolling. The increase in hradness is caused by the precipitation of the α phase from the supersaturated β solid solution and also due to the oxidation or loss oflithium. Tensile strengh of all hotrolled alloys decreased exponentially with increasing test temperature from room temperature to 573K. No clear improvement of both mechanical strength and heat resistance is observed by the additions of neodymium and silver. This is due to the fact that the fraction of the α phase decreases with increasing neodymium, although the amount of the Mg3 Nd compounds increases.