CoCrFeNiMn high entropy alloy additively manufactured via cold spray: microstructure and mechanical properties of as-deposited and heat-treated

The application of cold spray for additive manufacturing (CSAM) of structural components using metallic materials has recently attracted much attention. However, there is little work on developing thick deposits or components with high entropy alloys (HEAs) via CSAM and investigating the microstructural evolution and mechanical properties after deposition and subsequent annealing heat treatment. This work investigated the microstructure and mechanical properties of as-deposited and heat-treated 5-mm thick CoCrFeNiMn HEA deposit fabricated via CSAM. The microstructure of the HEA deposit characterised using scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), and x-ray diffraction (XRD) reveals bimodal grain size distribution with ultrafine grains at the particle-particle interfacial regions and coarse grains at the particle interiors. Heat treatment at different temperatures of the HEA deposit was investigated; increasing the temperature increases grain sizes resulting from static recovery and recrystallisation, with annealing twin formed at higher temperatures. Most notably, phase transformation of the deposit microstructure occurs at 600 ºC, with Cr-rich phase particles formed at regions of high dislocations and grain boundaries. Nano-and micro-hardness and tensile testing of micro-flat dogbones samples were performed on the as-deposited and heat-treated samples. The residual stress of the thick as-deposited sample was measured using the contour method.