超高强度钢热场-超声复合滚压表层微观组织强化机制

To deal with the problems of poor cold plastic deformation ability and difficult surface deformation strengthening of ultra-high strength steel, a thermal assisted ultrasonic rolling surface strengthening method is proposed. The surface thermal assisted ultrasonic rolling test of 45CrNiMoVA steel was carried out. The evolution and strengthening mechanism of surface microstructure were characterized and analyzed by SEM, EBSD, and TEM, combined with the residual stress distribution results of the surface layer. It is found that under the coupling effect of acoustic softening and thermal softening, the plastic deformation degree of 45CrNiMoVA steel surface material is intensified, the depth of plastic deformation layer is increased, the grain refinement of surface material occurs, and the microstructure with gradient distribution of grain size along the depth direction is formed. Fine-grain strengthening and dislocation strengthening are the main strengthening mechanisms. The effectiveness of the thermal assisted ultrasonic rolling method is proved, which is of great significance to the development of surface strengthening technology of ultra-high strength steel parts.