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In this work, the influences of ultrasonic surface rolling process (USRP) on the surface integrity and wear resistance of 300M steel samples were comprehensively studied. The effects of processing pass on the surface integrity were analyzed in term of surface topography, surface roughness (Ra), superficial microstructure, microhardness, and residual stresses. The results indicated that 10-pass USRP treatment can generate a highly smooth surface with Ra ≈ 7 nm. Nanocrystalline and ultrafine crystalline structures were produced in the surface layer. Significant compressive residual stress with a maximum value of about −950 MPa and a depth of about 800 μm was introduced into the sample surface. The comprehensive effects of grain refinement, work hardening, and compressive residual stress improved the surface hardness by about 30.9%, which obviously enhanced the wear resistance of 300M steel. It is noteworthy that the improvements of surface integrity and wear resistance of 300M steel brought about by USRP tend to be saturated along with the increase of processing passes.

Surface modification of 300M steel induced by ultrasonic surface rolling process (USRP) was studied regarding surface topography, microstructure, the distribution of shear strain, microhardness, and residual stress profiles. The effects of USRP on the tensile and fatigue properties were finally discussed. The results indicated that one pass of USRP can reduce the surface roughness (Ra) by more than one order of magnitude (from 0.30 μm to 0.025 μm). Besides, a severe plastic deformation layer was noticed at the top surface, which led to an increase of surface microhardness by about 17% and an elevation of compressive residual stress by about 190%. In USRP, a high plastic shear strain of ~3 and shear strain rate of ~105 s−1 can be induced into the topmost surface, which motivates the dislocation activities in the form of dislocation tangles, dislocation walls, and dislocation cells. Dislocation slip supplemented by mechanical twinning dominates the microstructural evolution pattern of the USRP sample. The excellent surface finish, high microhardness, and high compressive residual stress result in an obvious increase in the resistance of high-cycle fatigue behavior. Besides, the tensile strength was improved by 3.8%, whereas the corresponding yield strength and elongation were reduced by 5.9% and 24.3%, respectively.

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.