ECAP Die Design And Manufacture And The Effect Of ECAP On The Properties Of Copper

As is well-known,lots of properties of metal materials have relations with its grain size,For instance,mechanical strength and hardness are increasing with the grain size of material minishing.Therefore,grain refinement is always an effective method for improving comprehensive properties of metal materials. But for lots of materials,the grain size is too hard to refining below submicrometer in the past due to restrictions from preparation and process technology.With the development of material science and material preparation and processing technology,people began to study the materials with grain size below submicrometer from the 1980s,which is ultra-fine grain material.As an effective material preparation method for obtaining bulk submicron and nanometer materials,ECAP is attracting a great deal of attention and considered to be the most promising for the preparation of ultra-fine-structured materials.In this paper deforming force of pure copper was calculated by upper bound method,two sets of ECAP dies(a)inner angleΦ=120°,outer angleΨ=60°, (b)inner angleΦ=105°,outer angleΨ=60°are designed and manufactured repectively,and through which pure copper and single crystal copper were tested with ECAP.The single crystal copper was tested with ECAP through route A and B_C underΦ=105°,Ψ=37°,the results indicated that the effect of grain refinement through route A is better than route B_C.The tensile strength received maximum 420 MPa through route A and 412 MPa through route B_C after the seventh pass,so is the Vickers hardness maximum 156.6 HV and 153.5 HV for through route A and route B_C after the twelveth pass,and extension rate maximum 23%and 26.5% for through route A and route B_C,repectively.For pure copper ECAP through route B_C underΦ=120°,Ψ=60°andΦ=105°,Ψ=37°,it was found that the effect is better throughΦ=105°,Ψ=37°with tensile strength,Vickers hardness and elongation is up to 430MPa,167HV and 21% repectively.Moreover,the fatigue behavior of ultrafine-grained T2 copper processed by ECAP was tested and S-N curve was obtained,the microstructure and the mechanism of fatigue failure were studied and discussed by scanner electron microscope(SEM).