Exploring the impact of rolling temperature on interface microstructure and mechanical properties of steel–bronze explosive welded bilayer composite sheets

In this study, the microstructure evolution and mechanical properties of the explosive welded (EXWed) steel–bronze bilayer composite sheets before and after rolling are presented. Dissimilar welding was performed at two stand-off distances with various charge thicknesses. The welded bilayer sheets were rolled at ambient and 300 °C with a 33.3% thickness reduction. A feasibility welding window based on the process parameters was developed, and the samples were fabricated accordingly. Steel–bronze interfaces were divided into four distinct categories based on changes in microstructure and elemental distribution. After rolling, the initially formed wavy interface was stretched and flattened, and the vortex zones were compressed and, in some cases, submerged inside the steel part. Despite the proper connection in most parts of the interface, some parts suffered from local discontinuities. By implementing rolling, depending on the force and the rolling temperature, the diffusion barriers were partially removed, separate boundaries were brought closer, and a metallic bond was established at the bronze/steel interface. In addition, shrinkage cavities and pores were compressed and compacted. EXW and subsequent cold rolling increased the hardness since hot rolling diminished the interface hardness.