Towards Cryogenic Applications of Al/Ta Co-doped NiCoCr Medium Entropy Alloy Enabled by Selective Laser Melting

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High/medium entropy alloy (HEA/MEA) with multi-component elements is a novel alloy system developed beyond the traditional metallurgical design. The newly developed foreign-element-doped NiCoCr MEA has demonstrated greater potentials to achieve excellent mechanical performance at low temperatures due to the strengthening effect resulting from the foreign elements. As an important component of Industry 4.0, selective laser melting (SLM), as a branch of additive manufacturing, has become a major industry in EU and worldwide. However, to date, few to no efforts have been devoted into the investigation of NiCoCr MEA fabricated by SLM. Thus, the fundamental knowledge associated with the microstructures and properties of SLMed NiCoCr is still lacking. It is clear that such lack of critical knowledge is a hard barrier for the further development of NiCoCr parts used in cryogenic environment. Seeing this potential, this project proposes a novel alloy design strategy by incorporating nano-sized Al/Ti co-doped NiCoCr powder into the SLM process. This proposal will focus on: (1) Alloy composition design used for SLM; (2) Investigation of layer-by-layer twinning mechanism; (3) Temperature-induced mechanical response upon tension deformation; (4) Tailoring of cryogenic strength-ductility synergy. The combination of Al/Ti co-doping and SLM process create a possibility for SLMed NiCoCr to enable different microstructures and superior properties over its conventionally manufactured counterparts. It is expected that the new knowledge generated from this project will allow the 3D printing of complex MEA parts with excellent strength-ductility balance in cryogenic environment. This proposal includes both the transfer of knowledge to the host institution and the training of the candidate in new advanced techniques. Results have the potential capacity to increase the competitiveness and provide room for further studies at the fundamental and applied levels in additive manufacturing.