Effect of Restraint Intensity on Microstructure and Mechanical Properties of Gigapascal-Grade Deposited Metal

To clarify the effects of restraint conditions on the microstructure and mechanical properties of Gigapascal-grade deposited metal, this study conducted a self-designed weld restraint test using a flux-cored wire designed for Gigapascal-grade deposited metal. Simulation software was employed to calculate the uniform loading restraint intensity at different locations of the weld on the test plates, followed by corresponding welding experiments. Samples were extracted from areas with varying restraint intensities for microstructure characterization and mechanical property testing. The results indicate that as the restraint intensity decreases, the retained austenite content, dislocation density, proportion of low-angle grain boundaries, and kernel average misorientation value in the deposited metal increase, while the grain size progressively refines. As the restraint intensity decreases, the tensile strength and elongation of the deposited metal showed no significant variation. However, the yield strength gradually increased, reaching 978 ± 19 MPa, 1079 ± 24 MPa, and 1141 ± 25 MPa, while the hardness gradually decreased, with values of 433 ± 16 HV10, 371 ± 13 HV10, and 362 ± 10 HV10. The room-temperature impact absorbed energy increased gradually, recorded as 31.2 ± 1.3 J, 38.5 ± 0.9 J and 42.3 ± 1.5 J. Furthermore, the fracture morphology under the restraint intensity of 2.9 × 105 N/mm2 exhibited cleavage facets with river patterns, which are typical characteristics of quasi-cleavage fracture.