Interpretation of high-temperature tensile properties by thermodynamically calculated equilibrium phase diagrams of heat-resistant austenitic cast steels

Seungmun Jung, Seok S Sohn, Won Mi Choi, Byeong Joo Lee, Yong Jun Oh, Seongsik Jang, Sunghak Lee

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

High-temperature tensile properties of three heat-resistant austenitic cast steels fabricated by varying W, Mo, and Al contents were interpreted by thermodynamically calculated equilibrium phase diagrams of austenite, ferrite, and carbides as well as microstructural analyses. A two-step calculation method was adopted to cast steel microstructures below the liquid dissolution temperature because the casting route was not an equilibrium state. Thermodynamically calculated fractions of equilibrium phases were well matched with experimentally measured fractions. Ferrites existed at room and high temperatures in both equilibrium phase diagrams and actual microstructures, which has not been reported in previous researches on austenitic cast steels. In the W2Mo1Al1 steel, 38% and 12% of ferrite existed in the equilibrium phase diagram and actual microstructure, respectively, and led to the void initiation and coalescence at ferrites and consequently to the serious deterioration of high-temperature strengths. The present equilibrium phase diagrams, besides detailed microstructural analyses, effectively evaluated the high-temperature performance by estimating high-temperature equilibrium phases, and provided an important idea on whether ferrite were formed or not in the heat-resistant austenitic cast steels.

Original languageEnglish
Pages (from-to)43-53
Number of pages11
JournalMetals and Materials International
Volume23
Issue number1
DOIs
Publication statusPublished - 2017 Jan 1
Externally publishedYes

Keywords

  • heat-resistant austenitic cast steel
  • high-temperature tensile properties
  • microstructure
  • phase diagram
  • strength

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys
  • Materials Chemistry

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