Shah, Naishalkumar and Rahul, M R and Bysakh, Sandip and Phanikumar, Gandham (2021) Microstructure stability during high temperature deformation of CoCrFeNiTa eutectic high entropy alloy through nano-scale precipitation. Materials Science and Engineering A-Structural Materials Properties Microstructure and Processing, 824. Art No-141793. ISSN 0921-5093

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Dual-phase microstructures arising out of eutectic reactions offer several advantages: ease of casting, composite properties and tunable characteristic length scale of the phases. Eutectic high entropy alloys (EHEA) with a multi-component solution phase and a hard intermetallic phase are candidate materials to identify alternate high-temperature materials. Alloying elements can be chosen to improve the resistance to lamellar microstructure degradation and coarsening. In this work, we present the CALPHAD guided design of a hypo-eutectic high entropy alloy CoCrFeNiTa0.395 with primary dendritic FCC phase and fine eutectic (FCC solution + Laves phase) microstructure possessing good high-temperature mechanical properties. The primary FCC phase fraction is 0.42 +/- 0.02. The interlamellar spacing of the eutectic is 0.69 +/- 0.12 mu m. The alloy exhibited a balanced yield strength of 1303 +/- 18 MPa, a fracture strength of 2237 +/- 23 MPa and a fracture strain of 0.3 under mom temperature compression testing. The mechanism for change in the lamellar morphology during deformation at temperatures beyond 0.8 T-E is explained schematically. Strain field distribution obtained by FEM simulation correlates well with the observed microstructure gradients in the deformed samples. The formation of nano-scale precipitates in the low strain rate deformation is attributed to thermal effects. High-temperature precipitation of two types of precipitates (L1(2) ordered and Ni3Ta type) in the FCC-solution phase extended the useable temperature range of this alloy.

Item Type: Article
Subjects: Engineering Materials
Depositing User: Bidhan Chaudhuri
Date Deposited: 22 Dec 2021 10:08
Last Modified: 22 Dec 2021 10:08

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