Influence of hot-working conditions on grain growth of superalloy 718

Chuya Aoki, Tomonori Ueno, Takehiro Ohno, Katsunari Oikawa

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

The grain growth behavior of superalloy 718 was investigated using high-temperature compression tests and subsequent heat treatment. Abnormal grain growth (AGG) induced by low plastic strains was observed during thermal processing, which included solution heat treatment, and annealing, causing the matrix grains to coarsen from ∼12 μm to 80 μm in diameter. Both the plastic strain and displacement rate during deformation had large influences on the occurrence of AGG, which was mainly observed in regions of low plastic strain; the plastic strain range where AGG occurred increased with decreasing displacement rate. In particular, deformation at low displacement rates (within the same range as dynamic recrystallization) easily produced grain growth during solution heat treatment. Such grain growth was referred to as irregular grain growth (IGG) to distinguish it from AGG. Both the AGG and IGG processes were initiated when the intragranular misorientation exceeded a critical level, causing an increase in the twin boundary ratio and a decrease in intragranular misorientation. The nuclei of AGG grains were the nucleation of newly recrystallized grains without dislocation.

Original languageEnglish
Pages (from-to)26-33
Number of pages8
JournalJournal of Materials Processing Technology
Volume267
DOIs
Publication statusPublished - 2019 May

Keywords

  • 718 superalloy
  • Abnormal grain growth
  • Kernel average misorientation

ASJC Scopus subject areas

  • Ceramics and Composites
  • Computer Science Applications
  • Metals and Alloys
  • Industrial and Manufacturing Engineering

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