TY - JOUR

T1 - Microstructural insights into the coarse‑grained heat‑affected zone of a high‑strength all‑weld metal

T2 - Development of a continuous cooling transformation diagram

AU - Schrittwieser, Daniel

AU - Marin Morales, David

AU - Pahr, Hannes

AU - Lumper-Wimler, Lea

AU - Glushko, Oleksandr

AU - Schnitzer, Ronald

N1 - Publisher Copyright: © The Author(s) 2024.

PY - 2024/12/18

Y1 - 2024/12/18

N2 - The present study deals with the development of a continuous cooling transformation diagram corresponding to the coarse-grained heat-affected zone of a high-strength all-weld metal with a minimum yield strength of 1100 MPa fabricated via gas metal arc welding. Dilatometry tests were conducted to determine the transition temperatures. High-resolution imaging methods, such as transmission electron microscopy and atom probe tomography, as well as nanoindentation, were employed to resolve the microstructural constituents. At fast cooling rates (t 8/5 from 1.4 to 25 s), the microstructure comprises a mixture of martensite and coalesced bainite, with a slight increase in the content of coalesced bainite with faster cooling. This demonstrates that coalesced bainite cannot be avoided in the coarse-grained heat-affected zone of the current alloy by increasing the cooling rate. With slower cooling (t 8/5 ≥ 50 s), the microstructure becomes increasingly bainitic, accompanied by a marginal drop in Vickers hardness. At t 8/5 times of 500 s and 1000 s, the all-weld metal consists of granular bainite with significant amounts of retained austenite and different shaped martensite-austenite constituents. The coarser massive-type constituents contain body-centered cubic grains, sized in the hundreds of nanometers, with a hardness approximately twice as high as that of the surrounding bainitic matrix.

AB - The present study deals with the development of a continuous cooling transformation diagram corresponding to the coarse-grained heat-affected zone of a high-strength all-weld metal with a minimum yield strength of 1100 MPa fabricated via gas metal arc welding. Dilatometry tests were conducted to determine the transition temperatures. High-resolution imaging methods, such as transmission electron microscopy and atom probe tomography, as well as nanoindentation, were employed to resolve the microstructural constituents. At fast cooling rates (t 8/5 from 1.4 to 25 s), the microstructure comprises a mixture of martensite and coalesced bainite, with a slight increase in the content of coalesced bainite with faster cooling. This demonstrates that coalesced bainite cannot be avoided in the coarse-grained heat-affected zone of the current alloy by increasing the cooling rate. With slower cooling (t 8/5 ≥ 50 s), the microstructure becomes increasingly bainitic, accompanied by a marginal drop in Vickers hardness. At t 8/5 times of 500 s and 1000 s, the all-weld metal consists of granular bainite with significant amounts of retained austenite and different shaped martensite-austenite constituents. The coarser massive-type constituents contain body-centered cubic grains, sized in the hundreds of nanometers, with a hardness approximately twice as high as that of the surrounding bainitic matrix.

KW - CCT diagram

KW - Coalesced bainite

KW - Granular bainite

KW - High-strength weld metal

KW - Martensite-austenite constituent

KW - Weld metal HAZ

UR - http://www.scopus.com/inward/record.url?scp=85212397500&partnerID=8YFLogxK

U2 - 10.1007/s40194-024-01904-4

DO - 10.1007/s40194-024-01904-4

M3 - Article

VL - 2024

JO - Welding in the world

JF - Welding in the world

SN - 0043-2288

IS - ??? Stand: 7. Jänner 2025

ER -