Synergistic strengthening of Al-SiC composites by nano-spaced SiC-nanowires and the induced high-density stacking faults

Aluminum alloys are widely used in engineering structures due to light weight and corrosion resistance but aluminum has low yielding and flow strengths. Here we reported super-strong Al-30 vol%SiC composites with a flow strength of about 1.18 GPa up to a uniform strain of 16.0%. Micromechanical tests revealed a flow strength of 0.73 GPa associated with the nano-spaced SiC nanowires strengthening, and additional flow strength of 0.45 GPa associated with high-density stacking faults (SFs) that are rarely formed and stabilized in Al due to high stacking fault energy (SFE). More surprisingly, SFs possess excellent thermal stability up to 320 degrees C and can be regained by thermal cooling even after they are eliminated during annealing at 600 degrees C. Microscopy characterizations and theoretical analysis revealed that thermal mismatch induced high stress during cooling promotes the formation of SFs, and the segregation of Si into SFs and dislocation cores enables the thermal stability of wide SFs. This work demonstrated an approach to creating high-density and thermo stable SFs in high SFE metals via microstructure-enabled thermal stress.

Automated summary

Aluminum alloys have low yielding and flow strengths, but a super-strong Al-30vol%SiC composite with a flow strength of 1.18 GPa and a uniform strain of 16.0% was reported. The alloy exhibited strengthening from nano-spaced SiC nanowires and high-density stacking faults (SFs) rarely stabilized in Al. SFs showed excellent thermal stability up to 320 degrees C and could be regained by thermal cooling even after elimination during annealing at 600 degrees C.