Tuning the mechanical properties of powder bed fusion printed CoCrFeNiMn high-entropy alloys by annealing and hot isostatic pressing

Abstract

Powder bed fusion (PBF) and other additive manufacturing (AM) techniques show good potential for research and the processing industry. The reinforcement on the microstructure and mechanical properties is a practical necessity of additive manufacturing (AM) processed high-entropy alloy (HEA), which has structural and performance defects for application. Two post thermal treatment approaches based on annealing and hot isostatic pressing (HIP) for PBF technology printed CoCrFeNiMn HEA are proposed to enhance mechanical properties. No additional phase is detected by X-ray diffraction when the printed alloy undergoes post thermal processing, in addition to the face-centred-cubic crystalline phase. Both approaches give rise to almost fully dense arrangement structure with relative density exceeding 98%. Post treatments can significantly enhance the plasticity of PBF printed HEAs; in particular, they can lead to considerable increment in elongation and tensile properties, which can be attributed to the main mechanism of the synergistic effect of dislocation and nano-twin crystal deformation. In summary, both post thermal treatments are of great significance to the development of HEA with excellent mechanical properties. In particular, HIP leads to optimal structure and performance.