Microstructural and microhardness investigations of welded advanced high-strength steels

This work provides a comparative understanding of how welding affects the microstructural and microhardness behavior of advanced high-strength steels (AHSS), mainly Domex 650 and DP1000. It highlights the differing responses of these steels, which are governed by variations in alloy composition and microstructural evolution, helping engineers better predict performance and optimize welding processes for AHSS. The alloy composition affects heat-affected zone (HAZ) softening, microstructural changes, and microhardness in welded joints. The thermal cycles introduced during welding lead to distinct microstructural responses in the HAZ of each steel. Domex 650 tends to soften due to the formation of quasi-polygonal ferrite, which results in a noticeable drop in hardness to a minimum of 200 HV1 during welding in the coarse-grain HAZ. In contrast, DP1000 shows localized hardening in the HAZ, with hardness values reaching 346–349 HV1 due to martensite formation and grain refinement. These findings offer new insight into how alloy composition influences the microstructural evolution and mechanical behavior of AHSS during welding.