Cryogenic Tensile Strength of 1.6 GPa in a Precipitation-Hardened (NiCoCr)99.25C0.75 Medium-Entropy Alloy Fabricated via Laser Powder Bed Fusion
So-Yeon Park, Young-Kyun Kim, Hyoung Seop Kim, Kee-Ahn Lee
TL;DR
A new high-strength alloy was developed using laser printing and heat treatment, showing excellent performance at very low temperatures.
Contribution
A novel (NiCoCr)99.25C0.75 medium-entropy alloy with 1.6 GPa cryogenic tensile strength was fabricated via LPBF and heat treatment.
Findings
The alloy achieved a cryogenic tensile strength of 1.6 GPa at 77 K.
Precipitation of Cr-rich carbides stabilized the microstructure and enhanced mechanical properties.
Deformation mechanisms included twinning and dislocation interactions, leading to higher work hardening at low temperatures.
Abstract
A (NiCoCr)99.25C0.75 medium entropy alloy (MEA) was developed via laser powder bed fusion (LPBF) using pre-alloyed powder feedstock containing 0.75 at%C, followed by a precipitation heat treatment. The as-built alloy exhibited high density (>99.9%), columnar grains, fine substructures, and strong <111> texture. Heat treatment at 700 °C for 1 h promoted the precipitation of Cr-rich carbides (Cr23C6) along grain and substructure boundaries, which stabilized the microstructure through Zener pinning and the consumption of carbon from the matrix. The heat-treated alloy achieved excellent cryogenic tensile properties at 77 K, with a yield strength of 1230 MPa and an ultimate tensile strength of 1.6 GPa. Compared to previously reported LPBF-built NiCoCr-based MEAs, this alloy exhibited superior strength at both room and cryogenic temperatures, indicating its potential for structural…
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Taxonomy
TopicsHigh Entropy Alloys Studies · High-Temperature Coating Behaviors · Additive Manufacturing Materials and Processes