Heat treatment method of magnesium-containing cast aluminum lithium alloy

The invention provides a heat treatment method of magnesium-containing cast aluminum lithium alloy. The heat treatment method comprises a ternary solution treatment step and a slow heating ageing treatment step which are carried out in sequence. By a reasonable optimized ageing treatment process and a method for slowly heating the alloy to the ageing temperature, the volume fraction, the size and the distribution of main strengthening phases (Al3Li, Al2CuLi and Al2Cu) of the alloy are controlled. Compared with the traditional ageing treatment process, the heat treatment method of the magnesium-containing cast aluminum lithium alloy has the characteristics that uniform growing of Al3Li and separation of an Al2Cu (theta') can be promoted, and heterogeneous nucleation and growing of a S(Al2CuMg) phase and a T1(Al2CuLi) phase are promoted; and by the slow heating ageing process, the plasticity of the magnesium-containing cast aluminum lithium alloy is greatly improved while the strength of the cast aluminum lithi