Effects of heat treatment on the microstructure and properties of cold-forged CoNiFe medium entropy alloy

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

  • X.L. An
  • H. Zhao
  • T. Dai
  • H.G. Yu
  • Z.H. Huang
  • C. Guo
  • C.L. Chu

Detail(s)

Original languageEnglish
Article number106477
Journal / PublicationIntermetallics
Volume110
Online published28 Apr 2019
Publication statusPublished - Jul 2019

Abstract

The effects of heat treatment on the microstructure and properties of cold-forged two-dimensional (2D) CoNiFe medium entropy alloy (MEA) are determined. Compared to the as-cast specimen with a columnar crystal structure, the cold-forged CoNiFe MEA has a heavily fragmented microstructure with deformation twins. As the annealing temperature is increased, the grain size becomes larger markedly. Annealing at 900 °C yields a fully recrystallized microstructure with a large population of annealing twins and the new orientation exhibits a first-order twin relationship (60° <111> rotation) during recrystallization. Moreover, the CoNiFe HEA annealed at 900 °C possesses excellent ductility (ε = 50%) and work-hardening ability (σUTSY = 246 MPa, σUTSY = 0.5), which depend on the annealing twins, dislocations, as well as micro-shear bands in the grains. Analysis of the fracture surface indicates that the main failure mechanism is ductile. Meanwhile, no phase separation occurs as the temperature is raised from 0 °C to 1000 °C as shown by the expansion rate versus temperature relationship, indicating that the materials have good stability at high temperature. The thermal expansion coefficient (CTE) of the sample annealed at 1100 °C for 1 h is 12.1 × 10−6 K−1 which is less than that of traditional metals (14.4–16 × 10-6 K−1).

Research Area(s)

  • Annealing, CoNiFe, MEAs, Two-dimensional (2D) forging, Work-hardening microstructure and properties

Citation Format(s)

Effects of heat treatment on the microstructure and properties of cold-forged CoNiFe medium entropy alloy. / An, X.L.; Zhao, H.; Dai, T.; Yu, H.G.; Huang, Z.H.; Guo, C.; Chu, Paul K.; Chu, C.L.

In: Intermetallics, Vol. 110, 106477, 07.2019.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review