Direct observations of the α → γ transformation at different input powers in the heat-affected zone of 1045 C-Mn steel Arc welds observed by spatially resolved X-ray diffraction

T. A. Palmer, J. W. Elmer

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Spatially resolved X-ray diffraction (SRXRD) experiments have been performed during gas tungstenarc (GTA) welding of AISI 1045 C-Mn steel at input powers ranging from 1000 to 3750 W. In-situ diffraction patterns taken at discreet locations across the width of the heat-affected zone (HAZ) near the peak of the heating cycle in each weld show regions containing austenite (γ), ferrite and austenite (α + γ), and ferrite (α). Changes in input power have a demonstrated effect on the resulting sizes of these regions. The largest effect is on the γ phase region, which nearly triples in width with increasing input power, while the width of the surrounding two-phase α + γ region remains relatively constant. An analysis of the diffraction patterns obtained across this range of locations allows the formation of austenite from the base-metal microstructure to be monitored. After the completion of the α → γ transformation, a splitting of the austenite peaks is observed at temperatures between approximately 860°C and 1290°C. This splitting in the austenite peaks results from the dissolution of cementite laths originally present in the base-metal pearlite, which remain after the completion of the α → γ transformation, and represents the formation of a second more highly alloyed austenite constituent. With increasing temperatures, carbon, originally present in the cementite laths, diffuses from the second newly formed austenite constituent to the original austenite constituent. Eventually, a homogeneous austenitic microstructure is produced at temperatures of approximately 1300 °C and above, depending on the weld input power.

Original languageEnglish (US)
Pages (from-to)3353-3369
Number of pages17
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume36
Issue number12
DOIs
StatePublished - Dec 2005

All Science Journal Classification (ASJC) codes

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

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