Effect of hot-isostatic pressing on deep cryogenic thermal conductivity in additively manufactured CoCrNi medium-entropy alloy

Abstract

This study investigates the correlation between microstructural evolution and thermal conductivity in additively manufactured CoCrNi medium-entropy alloy (MEA). Specifically, the thermal conductivity of as-built CoCrNi MEA was compared with that of post-processed CoCrNi MEA subjected to hot isostatic pressing (HIP). HIP treatment was used to reduce microstructural defects such as pores and dislocations. The measured thermal conductivity of HIP-processed CoCrNi exhibited higher values of ∼12.24 W/m·K and ∼3.28 W/m·K at room temperature and deep cryogenic temperatures (300 K and 20 K), compared to as-built CoCrNi (∼8.85 W/m·K and ∼2.46 W/m·K for 300 K and 20 K). This improvement in thermal conductivity for HIP-processed CoCrNi is attributed to reduced electron scattering caused by fewer lattice defects after post-processing. These findings emphasize the fundamental relationship between microstructural defects and thermal properties in both additively manufactured and post-processed MEAs with exceptional cryogenic thermal conductivity.