Enhanced age-hardening behavior in Al–Cu alloys induced by in-situ synthesized TiC nanoparticles

Abstract

The influence of in-situ synthesized TiC nanoparticles on age-hardening behavior of Al–Cu alloys was investigated in Al–4.5Cu–1.5TiC alloy. It was found that TiC nanoparticles decrease the peak-age time effectively, from about 20 h for Al–4.5Cu alloy decreasing to about 12 h for the Al–4.5Cu–1.5TiC. Mechanical property test shows that the age-hardening effect has been improved by the TiC nanoparticles. The increment of yield strength before and after aging is about 84 MPa for Al–4.5Cu, while, it reaches to about 113 MPa for the Al–4.5Cu–1.5TiC. After aging heat treatment, precipitates have been observed both in matrix and around TiC nanoparticles. Due to the difference of coefficient of thermal expansion between TiC and Al, high density dislocations in the Al–4.5Cu–1.5TiC were generated during water quenching after solution. Dislocations play a role of diffusion path for Cu atoms during aging, which reduces the peak-age time. Alpha-Al lattice distortion resulted from lattice mismatch of TiC/Al interface induces the precipitation of θʹ phase around TiC nanoparticles, which increases the number density of θʹ and improves the age-hardening effect. This finding is supposed to be also applicable to alloy systems of Al–Cu–Mg, Al–Cu–Mg–Li, Al–Cu–Mg–Ag, etc.