Martensite Transformation Start Temperature During Quench and Austempering in Fe-8Ni-0.2C Alloys

Hiroyuki Kawata, Kunio Hayashi, Chisato Wakabayashi, Naoki Yoshinaga, Manabu Takahashi

Research output: Contribution to journalArticlepeer-review

Abstract

It is important for the improvement of mechanical properties of quenching and partitioning (QP) steels to control the martensite transformation behavior and the stability of untransformed austenite. In this study, we evaluated the martensite transformation restart temperature (Mr) via a dilatometer during the reheat austempering pattern. This heat pattern corresponding to the typical heat treatment for QP steel involves quenching to TQ, a temperature between the martensite transformation start temperature (Ms) and the finish temperature, and austempering above Ms. In Fe-8Ni-0.2C alloy, Mr equals TQ, regardless of the progress of bainite transformation during austempering at 673 K (400 °C). In Fe-8Ni-1Si-0.2C alloy, Mr decreases parabolically from TQ with the progress of bainite transformation, and this behavior corresponds to the assumed carbon concentration by bainite transformation. These results indicate that the self-stabilization of the entire untransformed austenite during the first quench from Ms to TQ was preserved, regardless the bainite transformation. Moreover, the stabilization by the carbon concentration in untransformed austenite was added to this self-stabilization.

Original languageEnglish
Pages (from-to)1395-1408
Number of pages14
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume52
Issue number4
DOIs
Publication statusPublished - Apr 2021

All Science Journal Classification (ASJC) codes

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

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