Microscale bonding strength of Cu-Fe-Al transferred lamellar microstructure formed by copper-coated seel fine particle peening

Fine particle peening（FPP）is a surface modification process in which fine hard metallic particles project onto the substrate. During this process, shot particles that remain transfer to the substrate and form a complex and multi-layered lamellar structure in which transferred fragments are distributed in the depth direction and several tens of micrometers from the surface. Because the bond strength at each interface of this structure and its generation mechanism are unclear, the local bond strength of the laminated interface was evaluated in this study by a microscale tensile test conducted by focus ion beam facilities. In the transferred lamellar modified region, the hardness was considerably higher than that of as-received materials, and the microscopic bonding strength between the transferred copper or iron and the aluminum matrix was 300 MPa or greater. When steel particles were used with FPP, iron oxide was mainly transferred to the aluminum matrix. However, copper plating on the particles suppressed the oxidation of the steel composing the particles and, as a result, the metallic steel was transferred. The bonding strength was improved by oxidation-controlled steel particles.