Microstructural insights into the coarse-grained heat-affected zone of a high-strength all-weld metal: Development of a continuous cooling transformation diagram
IF 2.4 4区 材料科学Q2 METALLURGY & METALLURGICAL ENGINEERING
Daniel Schrittwieser, David Marin Morales, Hannes Pahr, Lea Andrea Lumper, Oleksandr Glushko, Ronald Schnitzer
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引用次数: 0
Abstract
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 (t8/5 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 (t8/5 ≥ 50 s), the microstructure becomes increasingly bainitic, accompanied by a marginal drop in Vickers hardness. At t8/5 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.
期刊介绍:
The journal Welding in the World publishes authoritative papers on every aspect of materials joining, including welding, brazing, soldering, cutting, thermal spraying and allied joining and fabrication techniques.