Effects of aging precipitation and microstructure evolution on mechanical properties of TiB₂/Al-Cu-Li composites

The effects of microstructure evolution and aging precipitation during T6 process on the mechanical properties of TiB₂/Al-Cu-Li composites were investigated. The TiB₂/Al-Cu-Li composites were prepared by protective atmosphere melting. The results show that within the microstructure of as-cast alloys, TiB₂ particles and eutectic phases are mainly distributed around the grain boundaries. After homogenization treatment, the eutectic phase is mostly dissolved. After rolling deformation, TiB₂ particles are elongated along the rolling direction and a large number of dislocations are generated. The solid solution treatment weakens the Brass texture and S texture generated by the rolling and the precipitated phases generated by the rolling are resolved. Aging is performed at 175℃, δ'(Al₃Li)/β'(Al₃Zr) is the main precipitated phase during under-aging. With the increase of aging time, the T₁ phase is the main precipitation strengthening phase at 22 h peak aging. Through the combined effect of dislocation strengthening and precipitation strengthening, the yield strength and ultimate tensile strength increase and then decrease with increasing aging time, and the elongation continuously decreasing. The ultimate tensile strength, yield strength and elongation after peak aging reach 562.7 MPa, 475.9 MPa, and 4.5%, respectively.