In-Situ Study of Deformation Mechanisms in a Bi-Layered Bronze/Steel Sheet

Enhancing ductility is a crucial concern within metal matrix composites. Cu-Pb bronze alloy is a commonly utilized copper-based bearing alloy, and it demands superior mechanical properties and service safety. While copper and lead exhibit excellent ductility, Cu-Pb bronze alloys experience a substantial reduction in ductility due to plastic deformation being concentrated within the low-strength Pb phase. To address this issue, we employed the solid-liquid continuous casting (SLC) method to overlay the Cu-Pb alloy onto a mild steel substrate, significantly enhancing overall ductility. We conducted an in-situ tensile test using a scanning electron microscope (SEM) in conjunction with Digital Image Correlation (DIC) and Electron Back-scattered Diffraction (EBSD) to elucidate the underlying mechanisms. Localized strain is distributed uniformly in the steel layer but concentrated in the Pb phase within the bronze layer. However, this localization is effectively mitigated by the layered structure, as evidenced by the high compressive strain observed in the affected zone at the bronze/steel interface. Larger misorientation angles near the copper grain boundaries indicate that the deformation of copper grains is influenced by the localized strain within the lead phase. The layered structure effectively reduces strain concentration throughout the material and accommodates the deformation incompatibility inherent in Cu-Pb bronze alloys.