Influence of heat treatment and deep cryogenic exposure on the properties of laser powder bed fusion-fabricated aluminium alloy

This study examines the effect of deep cryogenic treatment (DCT) duration on laser powder bed fusion (LPBF) fabricated and heat-treated (HT) AlSi10Mg alloy. Samples were built at 0° orientation with a volumetric energy density of 33.97 J/mm³ and solution heat-treated at 540°C for 30 minutes. Post-heat treatment, the samples are subjected to DCT for three (24 hours, 48 hours, and 72 hours) different exposure durations. The DCT significantly influenced the overall performance, with properties strongly dependent on exposure duration, and outcomes were assessed between as-built, HT+24hDCT, HT+48hDCT, and HT+72hDCT samples. The HT+48hDCT sample exhibited 56.16% and 89.46% higher ultimate tensile strength and yield strength, respectively, compared to the as-built condition. The HT+48hDCT sample shows 59.19% and 27.38% higher ultimate compressive strength and displacement, respectively, and 74.74% and 61.41% higher ultimate flexural strength and displacement compared to the as-built condition. These improvements are linked to microstructural refinement and better phase uniformity, which further enhanced load bearing capacity. The HT+48hDCT sample shows 88.37% lower wear rate and 99.99% lower corrosion rate due to increased hardness and reduced localized electrochemical activity. Microstructural analysis reveals a transition from fine cellular structures in the as-built state to more refined and uniform equiaxed grains after DCT, indicating that controlled DCT duration promotes structural uniformity. The HT+48hDCT sample also shows a 9.67% increase in hardness and an 84.09% reduction in tensile residual stress, improving mechanical stability and resistance to failure.