Spatially resolved X-ray diffraction mapping of phase transformations in the heat-affected zone of carbon-manganese steel arc welds

Abstract

Phase transformations that occur in the heat-affected zone (HAZ) of gas tungsten arc welds in AISI 1005 carbon-manganese steel were investigated using spatially resolved X-ray diffraction (SRXRD) at the Stanford Synchrotron Radiation Laboratory. In situ SRXRD experiments were performed to probe the phases present in the HAZ during welding of cylindrical steel bars. These real-time observations of the phases present in the HAZ were used to construct a phase transformation map that identifies five principal phase regions between the liquid weld pool and the unaffected base metal: (1) ␣-ferrite that is undergoing annealing, recrystallization, and/or grain growth at subcritical temperatures, (2) partially transformed ␣-ferrite co-existing with ␥-austenite at intercritical temperatures, (3) single-phase ␥-austenite at austenitizing temperatures, (4) ␦-ferrite at temperatures near the liquidus temperature, and (5) back transformed ␣-ferrite co-existing with residual austenite at subcritical temperatures behind the weld. The SRXRD experimental results were combined with a heat flow model of the weld to investigate transformation kinetics under both positive and negative temperature gradients in the HAZ. Results show that the transformation from ferrite to austenite on heating requires 3 seconds and 158 ЊC of superheat to attain completion under a heating rate of 102 ЊC/s. The reverse transformation from austenite to ferrite on cooling was shown to require 3.3 seconds at a cooling rate of 45 ЊC/s to transform the majority of the austenite back to ferrite; however, some residual austenite was observed in the microstructure as far as 17 mm behind the weld.

In-situ phase mapping and direct observations of phase transformations during arc welding of 1045 steel

“…Spatially Resolved X-Ray Diffraction (SRXRD) has also been used to investigate phase transformations in the low carbon steel [7][8][9][10][11][12]. From these results, a map of the phases present in the HAZ was created for this steel that showed the locations of the γ and α phases during welding [7,8].…”

Observations of ferrite/austenite transformations in the heat affected zone of 2205 duplex stainless steel spot welds using time resolved X-ray diffraction

“…More detailed descriptions of the welding set-up are given in previous publications. [1][2][3][4][5][6][7][8][9][10] Quantitative metallographic (QTM) measurements have been made on samples taken from an as-received 2205 DSS forged bar. Etching of these samples has been performed using an electrolytic NaOH etch described in ASTM standard A 923-98.…”

“…It has been used to study phase transformations in commercially pure titanium, C-Mn steels, and stainless steels. [1][2][3][4][5][6][7][8] Unlike more conventional tools, such as metallography or dilatometry, SRXRD is able to provide a direct, in-situ, real-time monitoring capability for detecting and identifying the phases present at a particular location during welding. The resulting x-ray diffraction patterns can then be analyzed in order to determine the degree to which a phase transformation has progressed.…”

<I>In-Situ</I> Observation for Weld Solidification in Stainless Steels Using Time-Resolved X-ray Diffraction

“…So the solidification morphology of the weld metal has been estimated by the SEM observation of microstructure, using the liquid-tin quenching method. [10][11][12] In late nineties, Elmer et al [13][14][15] has been used a intense synchrotron radiation as a probe and directly revealed the phase mapping around the heat spot, during pure titanium welding. After that, Babu et al investigated the primary weld solidification in the Fe-C-Al-Mn weld steel [16][17][18] using the Time-Resolved X-Ray Diffraction (TRXRD) technique.…”

“…However, the dendrite growth due to movement of the heat source would be unable to catch using the established technique of stationary heat spot. [13][14][15][16][17][18] In this study, austenite stainless steels under welding conditions of a practical manufacturing process were investigated using the Spatially-Resolved X-Ray Diffraction (SRXRD) method for post weld characterization and TRXRD method for in-situ weld observation. The crystallographic information of the and phases in directional solidification was obtained.…”