Structure and properties of AA7075-SiC composite parts produced by cold spray additive manufacturing

In this work, the cold spray additive manufacturing technology was applied for producing composite AA7075 deposits reinforced by silicon carbide particles. It was found that ceramic content in the composite did not exceed 21-25 %vol. Different heat treatments and capsule-free hot isostatic pressing (HIP) were performed to homogenise the structure of the AA7075-SiC composite. The microstructure of the composite before and after heat treatments was analysed using SEM and TEM analysis and compared with bulk AA7075. The analysis showed that the presence of SiC in the composite influenced the distribution of hardening phases in AA7075 during heat treatment. The presence of uniformly distributed SiC particles accelerated the decomposition of the supersaturated aluminium solid solution during ageing. The decomposition process blocked the formation of large hardening precipitates at the grain boundaries generally observed at the bulk metallic alloy AA7075. The compressive strength tests revealed the improvement of the strain at failure of the composite deposits after heat treatment and HIP. At the same time, the compressive strength slightly decreased. The thermal expansion coefficient (TEC) of AA7075-SiC20% composite was lower than for the base bulk AA7075. The dilatation behaviour of the composite during TEC tests could be approximated using the simple rule of mixture.

Automated summary

In this study, cold spray additive manufacturing technology was used to produce composite AA7075 deposits reinforced by silicon carbide particles. Different heat treatments and capsule-free hot isostatic pressing were used to homogenize the structure of the composite. The presence of SiC in the composite influenced the distribution of hardening phases in AA7075 during heat treatment.