Process parameter optimisation and the effect of oxygen on porosity and thermal conductivity in HIPed laser powder bed fused Al7075

The thermal performance of Al7075, a high-strength aluminium alloy, remains constrained in laser powder bed fusion (L-PBF) due to processing-induced porosity and microstructural inhomogeneities. This study investigates the effect of build chamber oxygen content (100 ppm vs. 1000 ppm) and hot isostatic pressing (HIPing) on the porosity and thermal conductivity of L-PBF Al7075 components. Process parameters were optimised using predictive modelling to minimise defect formation, yielding dense builds with laser power of 350 W, scan speed of 1200 mm/s, and hatch distance of 0.14 mm. Quantitative analysis showed that lower oxygen content reduced as-built porosity and significantly improved post-HIP thermal conductivity, with the 100 ppm samples achieving 51.65 W/m·K compared to 35.63 W/m·K for 1000 ppm. Although HIPing reduced porosity in all cases, the conductivity remained below that of wrought Al7075, highlighting persistent limitations in thermal transport. These results demonstrate the coupled role of oxygen control and post-processing in governing the defect landscape and functional thermal properties in L-PBF-fabricated Al7075, offering guidance for improved thermal management in high-performance applications.