Effects of solution heat treatment on the microstructure and hardness of Mg–5Li–3Al–2Zn–2Cu alloy

The microstructure and hardness of Mg–5Li–3Al–2Zn–2Cu alloy were investigated both in the as-cast condition and after solution heat treatment at 330–390 °C for 5 h. The as-cast alloy contains a microstructure consisting of α-Mg matrix, AlLi phase, AlCuMg phase and Al2Cu phase. After the solution heat treament, the AlLi phase was dissolved into the matrix, however, the AlCuMg and Al2Cu phases were not dissolved. With the increase of solution temperature, almost all the AlLi phase was dissolved, and the effects of solution strengthening of Al and Li atoms in the alloy increase, which results in the gradual increase of the Brinell hardness of the solution-treated alloy.