Study Of Prepairng Ultra-fine/Nanocrystalline Grained Strip By Extrusion Machining In Severe Plastic Deformation

Ultra-fine/Nanocrystalline Grained materials have been used more and more widely inindustrial production because of the excellent thermal properties, chemical properties andmechanical properties. In particular, its mechanical properties have obvious advantages. Thematerials strength and hardness can significantly be improved if the grain was refined.Severe plastic deformation (SPD) is the most widely used method in PreparingUltra-fine/Nanocrystalline Grained materials. This paper presents a novelty method, extrusionmachining in severe plastic deformation, which apply more constraint based on severe plasticdeformation.Extrusion machining in severe plastic deformation is a process combining the cuttingwith extrusion which prepare strip by extruding the chip through the passage between theplate and the front edge of cutting tool. This process of cutting which is useful for variousmetals and alloys not only produces large deformation strain, it also can change the size andshape of the chip by controlling the parameters such as depth of cut and compression ratio.In this paper, the cutting theoretical model and finite element model have beenestablished and the important parameters which most probably influence the process havebeen determined by the analysis of parameters based on theory. This study have used copperto machined on lathes to obtain the continuous chip and analyses the influence ofcompression ratio, rake angle, cutting speed and depth of cut for cutting force and cuttingtemperature. In addition, a finite element analysis which can adjust parameters have beendeveloped by deform-2d to analyze the changes of the stress, strain, temperature and cuttingforce. The intention of this article hopes to indicate the effect of different parameters for theCutting process and verify correctness of the simulation model through the comparisons withresults of the industrial trials and the FEM numerical experiment. The results show that thecutting force is small and steady when the compression ratio is equal to1.2. Shear strain canbe readily varied by changing the tool rake angle and the stain increases with the decrease ofrake angle. Cutting speed gives a notable effect on cutting temperature so that it should be under control to prevent grain growth coarsening. While decreasing the depth of cut, both thecutting force and the cutting temperature are decreased, however, the value of depth of cut isdetermined by the production needs and the compression ratio.