Mechanical properties of ultra-fine grained strips under ultrasonic vibration extrusion cutting

Abstract

Ultrafine grained materials often have superior mechanical properties. In order to complement the advantages of other preparation methods of ultrafine materials, a new process of ultrasonic vibration extrusion cutting was proposed to induce severe plastic deformation of materials to prepare ultrafine grained strips with superior mechanical properties. The mathematical model, finite element simulation and cutting test were combined to validate each other. The mapping relationship and influence law among process parameters, physical field parameters, microstructures and mechanical properties were studied. After ultrasonic vibration extrusion cutting, average grain size of material was refined from tens of microns to ultra-fine grain level. With the decrease of extrusion ratio, thickness of nanocrystalline surface layer, degree of grain refinement, average microhardness and tensile strength of strip increase gradually. When extrusion ratio is 1.2, 1.5, 1.8 and 2.1, thickness of nanocrystalline surface layer is 52.9 μm, 44.1 μm, 26.5 μm and 22.8 μm, respectively. Compared with original matrix, average internal microhardness of strip is increased by about 39.9%, 37.6%, 32.8%, 24.1%, and tensile strength is increased by about 306.9%, 273.7%, 254.1%, 240.9%, respectively.