Control of discontinuous and continuous precipitation of γʹ-strengthened high-entropy alloys through nanoscale Nb segregation and partitioning

L. Fan, T. Yang, J. H. Luan, Z. B. Jiao

Research output: Journal article publicationJournal articleAcademic researchpeer-review

2 Citations (Scopus)

Abstract

Control of discontinuous and continuous precipitation of L12-ordered γʹ precipitates is crucial for tailoring microstructure and mechanical properties of coherent precipitation-strengthened high-entropy alloys (HEAs). In this study, we show that the appropriate addition of Nb not only suppresses discontinuous γʹ precipitation through grain boundary segregation but also promotes continuous γʹ precipitation through nanoscale solute partitioning, leading to substantially improved mechanical properties of the HEAs. Specifically, we explore the effects of Nb on the discontinuous and continuous precipitation microstructures, grain boundary segregation, and mechanical properties of (CoCrFeNi)94-xAl3Ti3Nbx (x = 0, 0.4, 0.8, 1.6, and 2.3 at.%) HEAs. Atom probe tomography reveals that Nb exhibits preferential segregation at grain boundaries of HEAs, which substantially inhibits the grain boundary precipitation and migration due to the reduction of grain boundary energy and solute drag effect, thereby suppressing discontinuous γʹ precipitation at the grain boundaries. Moreover, Nb partitions to the continuous γʹ nanoparticles in grain interiors, which leads to a high chemical driving force for continuous γʹ precipitation. Because of these beneficial effects, Nb-modified HEAs with a uniform distribution of γʹ nanoparticles throughout the matrix were developed, and the correlation between the precipitate microstructure and mechanical properties of these HEAs is discussed.

Original languageEnglish
Article number154903
JournalJournal of Alloys and Compounds
Volume832
DOIs
Publication statusPublished - 15 Aug 2020

Keywords

  • Atom probe tomography
  • Grain boundary segregation
  • High-entropy alloy
  • Nanoscale precipitation
  • Precipitation strengthening

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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