Microstructure And Tensile Properties Of Friction-Stir-Processed Al-Li-Cu-Zr-Sc Alloy

Microstructure evolution and its influence on the tensile properties of a high-strength cast Al-3Li-1.5Cu-0.15Zr-0.15Sc alloy during friction-stir processing (FSP) are investigated in this paper. It is found that the coarsening of alpha-Al dendrites in an as-cast alloy is insignificant after a solid-solution treatment. Most of the Al2Cu and Al6CuLi3 phases are dissolved into the matrix while the Al-3(Li, Sc, Zr) phase remains intact. During FSP, a complete dynamic recrystallization takes place in the stir zone and fine equiaxed grains are obtained. Residual intermetallic particles are also broken into fine particles and distributed uniformly in the matrix. The microstructure distribution in the stir zone is inhomogeneous and a strong {111} texture and a weak {110} texture are formed. After FSP, the tensile strength is significantly improved owing to the interaction of the grain refinement, breaking up of intermetallic phases and formation of texture.