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Title: In-Situ Phase Mapping and Direct Observations of Phase Transformations During Arc Welding of 1045 Steel

Abstract

In-situ Spatially Resolved X-Ray Diffraction (SRXRD) experiments were performed during gas tungsten arc (GTA) welding of AISI 1045 C-Mn steel. Ferrite ({alpha}) and austenite ({gamma}) phases were identified and quantified in the weld heat-affected zone (HAZ) from the real time x-ray diffraction data. The results were compiled along with weld temperatures calculated using a coupled thermal fluids weld model to create a phase map of the HAZ. This map shows the {alpha} {yields} {gamma} transformation taking place during weld heating and the reverse {gamma} {yields} {alpha} transformation taking place during weld cooling. Superheating is required to complete the {alpha} {yields} {gamma} phase transformation, and the amount of superheat above the A3 temperature was shown to vary with distance from the centerline of the weld. Superheat values as high as 250 C above the A3 temperature were observed at heating rates of 80 C/s. The SRXRD experiments also revealed details about the {gamma} phase not observable by conventional techniques, showing that {gamma} is present with two distinct lattice parameters as a result of inhomogeneous distribution of carbon and manganese in the starting pearlitic/ferritic microstructure. During cooling, the reverse {gamma} {yields} {alpha} phase transformation was shown to depend on the HAZ location.more » In the fine grained region of the HAZ, at distances greater than 2 mm from the fusion line, the {gamma} {yields} {alpha} transformation begins near the A3 temperature and ends near the A1 temperature. In this region of the HAZ where the cooling rates are below 40 C/s, the transformation occurs by nucleation and growth of pearlite. For HAZ locations closer to the fusion line, undercoolings of 200 C or more below the A1 temperature are required to complete the {gamma} {yields} {alpha} transformation. In this region of the HAZ, grain growth coupled with cooling rates in excess of 50 C/s causes the transformation to occur by a bainitic mechanism.« less

Authors:
;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
898032
Report Number(s):
UCRL-JRNL-215368
TRN: US200706%%208
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Metallurgical and Materials Transactions A, vol. 37A, N/A, July 1, 2006, pp. 2171-2182
Additional Journal Information:
Journal Name: Metallurgical and Materials Transactions A, vol. 37A, N/A, July 1, 2006, pp. 2171-2182
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ARC WELDING; AUSTENITE; CARBON; DISTRIBUTION; FERRITE; GRAIN GROWTH; HEATING; HEATING RATE; LATTICE PARAMETERS; MANGANESE; MICROSTRUCTURE; NUCLEATION; PEARLITE; PHASE TRANSFORMATIONS; STEELS; SUPERHEATING; TRANSFORMATIONS; TUNGSTEN; WELDING; X-RAY DIFFRACTION

Citation Formats

Elmer, J, and Palmer, T. In-Situ Phase Mapping and Direct Observations of Phase Transformations During Arc Welding of 1045 Steel. United States: N. p., 2005. Web.
Elmer, J, & Palmer, T. In-Situ Phase Mapping and Direct Observations of Phase Transformations During Arc Welding of 1045 Steel. United States.
Elmer, J, and Palmer, T. Tue . "In-Situ Phase Mapping and Direct Observations of Phase Transformations During Arc Welding of 1045 Steel". United States. https://www.osti.gov/servlets/purl/898032.
@article{osti_898032,
title = {In-Situ Phase Mapping and Direct Observations of Phase Transformations During Arc Welding of 1045 Steel},
author = {Elmer, J and Palmer, T},
abstractNote = {In-situ Spatially Resolved X-Ray Diffraction (SRXRD) experiments were performed during gas tungsten arc (GTA) welding of AISI 1045 C-Mn steel. Ferrite ({alpha}) and austenite ({gamma}) phases were identified and quantified in the weld heat-affected zone (HAZ) from the real time x-ray diffraction data. The results were compiled along with weld temperatures calculated using a coupled thermal fluids weld model to create a phase map of the HAZ. This map shows the {alpha} {yields} {gamma} transformation taking place during weld heating and the reverse {gamma} {yields} {alpha} transformation taking place during weld cooling. Superheating is required to complete the {alpha} {yields} {gamma} phase transformation, and the amount of superheat above the A3 temperature was shown to vary with distance from the centerline of the weld. Superheat values as high as 250 C above the A3 temperature were observed at heating rates of 80 C/s. The SRXRD experiments also revealed details about the {gamma} phase not observable by conventional techniques, showing that {gamma} is present with two distinct lattice parameters as a result of inhomogeneous distribution of carbon and manganese in the starting pearlitic/ferritic microstructure. During cooling, the reverse {gamma} {yields} {alpha} phase transformation was shown to depend on the HAZ location. In the fine grained region of the HAZ, at distances greater than 2 mm from the fusion line, the {gamma} {yields} {alpha} transformation begins near the A3 temperature and ends near the A1 temperature. In this region of the HAZ where the cooling rates are below 40 C/s, the transformation occurs by nucleation and growth of pearlite. For HAZ locations closer to the fusion line, undercoolings of 200 C or more below the A1 temperature are required to complete the {gamma} {yields} {alpha} transformation. In this region of the HAZ, grain growth coupled with cooling rates in excess of 50 C/s causes the transformation to occur by a bainitic mechanism.},
doi = {},
url = {https://www.osti.gov/biblio/898032}, journal = {Metallurgical and Materials Transactions A, vol. 37A, N/A, July 1, 2006, pp. 2171-2182},
number = ,
volume = ,
place = {United States},
year = {2005},
month = {9}
}