Influences of solid solution parameters on the microstrucuture and hardness of Mg–9Li–6Al and Mg–9Li–6Al–2Y

• The Y addition restrains the formation of lamellar AlLi and spheroidizes the α-Mg.
• During the solid solution at 340 °C, MgLi2Al is dissolved, and AlLi precipitates.
• During the solid solution at 440 °C, AlLi is dissolved and MgLi2Al precipitates.
• The Y addition improves the hardness and makes the hardness become stable.

The microstructure evolution of Mg–9Li–6Al and Mg–9Li–6Al–2Y with the variation of solid solution parameters was investigated. Results show that, in Mg–9Li–6Al, under the condition of 340 °C × 0.5 h, the MgLi2Al phase is dissolved in the phase of β-Li, and the AlLi phase precipitates from α-Mg phase. With the holding time being prolonged to 1 h, the precipitated AlLi distributes in the whole phase of α-Mg. Under the condition of 440 °C × 0.5 h, the AlLi phase is dissolved in the matrix, and MgLi2Al phase precipitates from β-Li. The addition of 2 wt.% Y in Mg–9Li–6Al can promote the precipitation of MgLi2Al phase and restrain the precipitation of AlLi phase, causing the increase of hardness of the alloy.