Structural stability of Mg-6Al-2Sr magnesium alloy

The Mg-6Al-2Sr magnesium alloy containing 6.15 at.% of aluminium, 2.1 at.% of strontium and 0.42 at.% of manganese was investigated at sand casting state performed at 700°C and after annealing treatment at 180°C, 250°C and 350°C during 500÷5000h with cooling in air. In the as-cast conditions the Mg-6Al-2Sr alloy consisted of α-Mg grains with intermetallic phases: (Al,Mg)4Sr, Al₈Mn₅ and Al ₃Mg₁₃Sr. Annealing at 180°C resulted in the precipitation of the Mg₁₇Al₁₂ phase in the aluminium enriched area and the beginning of decomposition of the Al₃Mg ₁₃Sr phase. Annealing at 250°C causes further decomposition of the Al₃Mg₁₃Sr phase while no precipitates of the Mg ₁₇Al₁₂ phase could be observed. After exposure at 350°C the total decomposition of the Al₃Mg₁₃Sr phase into a mixture of the Al₄Sr and α-Mg phases has been observed.