Constitutive properties of dissimilar metal laser welds

Digital image correlation (DIC) methods have been developed and used to determine the constitutive tensile stress-strain response in laser welds between PH13-8 Mo and 304L stainless steels. Both continuous-wave (CW) and pulsed laser welds were examined. Testing was conducted in the transverse (cross-weld) orientation and samples were ground smooth to eliminate geometric effects (weld root notch) and lightly bead blasted to provide image speckling. The DIC method provided quantitative 2-dimensional strain maps of the deformation field throughout tensile testing, and local stress-strain response was extracted from various weld regions. As expected, steep strain gradients were observed in the test welds, but constitutive relationships could nevertheless be extracted from the important weld zones. Metallographic analysis, electron backscattered analysis, and hardness testing were used to further quantify the microstructure and its relationship to the constitutive properties. Mixing in the CW weld appeared to be less complete than in the pulsed weld, and the CW weld likely contained both martensitic and ferritic regions as well as austenite, while the pulsed weld appeared to be predominantly ferritic with some residual austenite. Although additional refinement of the technique is needed to fully characterize the differences between these CW and pulsed welds, DIC has been shown to be a powerful technique for assessing the mechanical behavior of dissimilar metal laser welds. Copyright © 2009 ASM International® All rights reserved.