Effects of ultrasonic rolling on the surface integrity of in-situ TiB2/2024Al composite

Mechanical surface modification is of great significance to the final engineering applications of particles reinforced aluminum matrix composites (PRAMCs) as structural materials. In the present study, in-situ 6 wt% TiB2/2024Al composite was surface-modified by ultrasonic rolling (UR). The surface integrity of the modified composite was comprehensively analyzed and assessed in terms of surface morphology, topography, microstructure, residual stress (RS), strain hardening (SH), and microhardness. Results showed that a single pass of UR treatment with a set of preselected parameters can directly improve the surface finish of the fine-turned samples by 1.5 orders of magnitude. The grain structure in the superficial layer can be effectively refined. High-level and profound compressive residual stress (RSc) and SH were introduced into the sample surface, which can be beneficial for the composite to resist multiple modes of mechanical failures. Besides, a sophisticated finite element (FE) simulation was conducted, which described the UR process fairly well from a numerical viewpoint. It is worth noting that the newly observed discretization mechanism of TiB2 clusters indicates the feasibility of modifying the surface distribution of the reinforcements, which brings about a brand-new and low-cost way to enhance the surface comprehensive mechanical properties of PRAMCs.