Pure Copper Upsetting Squeeze Deformation Of The Grain Refinement / Nano Process

A lot of properties of metal material are in contact with their grain size, for instance, mechanical strength and hardness of material increase as the grain size of material minishes, plastic and ductility become intensive. Therefore, grain refinement of material is always an efective method that people improve comprehensive performance of metal material. But to many materials, the grain size is so hard to refine below submicrometer in the past, due to all kind of restrictions about technology and process. Plastic deformation is a method which was developed in the 1990's, it can refine grain by plastic yield. This method can refine to nanometer, so it attracts many people's attention. But the researches on mechanics of grain refinement and regularity are still in the intial stage.The Preparation of ultrafined/nanostructured material by forging method has been studied in this article, super-fine grain size can be gained through alternate load. In room-temperature, microscope structure, crystal shape and size of Cu sample extruded for different times are analyzed by adopting the analysis tech including optical microscope, scan electric microscope, AFM and X radial diffraction. Meanwhile, mechanical property is primarily analyzed by means of fathoming hardness of sample. The refining mechanism of the extruding sample was also discussed.The results shows: Repeated extrusion can prepare the pure copper block materials with ultra-fine grain, with the increasing deformation, the extent of grain refinement becomes notable, single extruded quantify, quantify of deformation and direction of deformation are the key factors to prepare ultra-fine grain materials. Extrusion in three-dimensional direction, single extruded quantify is 25%. When the three-dimensional orientation of the accumulated deformation reaches 3000%, the grain size drives to stabilization and the hardness drives to saturation, microhardness increases from the 72HV of original state to 158HV; when single extruded quantify is 47%, the three-dimensional orientation of the accumulated deformation reaches 1880%, the grain size is about 80nm, microhardness increases from 72HV of the original state to 162HV, yield strength increases from 300.357MPa of annealed to73.876MPa with an increase of 306.6% . Extrusion in two-dimensional direction, there is a great difference between the extruded surface and the non-deformation surface, grain refinement is not obvious.In a word, rpeated extruding deformation can refine grain size and improve comprehensive performance of metal material. It is a feasible method that can produce ultrafined/nanostructured material by severe plastic deformation.