The effect of increased HIP temperatures on bifilms and tensile properties of A206-T71 aluminum castings

The effects of hot isostatic pressing (HIP) temperatures on bifilms and tensile properties of A206-T71 castings were investigated. Castings were: (i) non-HIPed, and HIPed at (ii) typical HIP temperature, (iii) solution heat-treat temperature and (iv) eutectic melting temperature. Tensile strength and elongation data were analyzed using Weibull statistics. In all cases, HIP was found to increase the threshold tensile properties. Also, average and maximum tensile properties, as well as variability in elongation were increased by HIP. This was attributed to HIP's ability to heal porosity and thin bifilms more effectively than thicker bifilms. The mechanism for healing bifilms by HIP appeared to be the fracture of thin bifilms and partial bonding across their surfaces. The effect of increased HIP temperature was masked by the presence of spinel bifilms, which resisted the healing effect of HIP.