Effect of aging treatment on microstructure and mechanical properties of Al matrix composite reinforced by in-situ intragranular Al2O3

Age-hardening Al matrix composites (AMCs) exhibit great potential for developing advanced metal structural materials, while reinforcement configuration-dependent aging behaviors are still largely unclear. To gain an indepth fundamental understanding of the effect of in-situ generated intragranular reinforcement on precipitation response, a systematical heat-treatment was applied for the in-situ generated Al2O3 reinforced Al-Cu composite prepared via powder metallurgical Al-5 wt% CuO (Al-5CuO) system. Results show that the nano-scale intragranular Al2O3 activates the dislocation-assisted bulk diffusion pattern to promote the precipitation response, thus effectively shortening the peak-aging time of the composite as compared to the referenced Al-4 wt% Cu alloy matrix (Al-4Cu). The adequate precipitation within grains in the early-aging stage endows the peak-aged Al5CuO composite with homogeneous size distribution of & theta;' phase, contributing to the impressive mechanical properties. The mechanical analyses reveal that precipitation strengthening accounts for the prominent elevation of yield strength, while the enhanced ductility is achieved by decreasing the size and number density of precipitates segregated along reinforcement-matrix interface and grain boundary. This work yields new insights into intragranular reinforcement-driven precipitation response, which is crucial for designing age-hardening AMCs with high mechanical performance.

Automated summary

Through a systematic heat treatment, the effect of in-situ generated nano-scale Al2O3 reinforcement on the precipitation response of an Al-Cu composite was studied. The results showed that the nano-scale reinforcement activated a dislocation-assisted bulk diffusion pattern, promoting precipitation and shortening the aging time. Adequate precipitation within grains in the early-aging stage resulted in a homogeneous distribution of θ' phase, contributing to impressive mechanical properties. Precipitation strengthening and the control of precipitate size and number density were found to be key factors in improving both strength and ductility.