Study Of Deformatlion Uniformity Of Equal Channel Angular Pressing In Pure Al

Equal Channel Angular Pressing(ECAP)is one of severe plastic deformation grain refinement method.In addition to the advantages of large plastic deformation method,the composition and size do not change,so it is an effective method for the preparation of materials of ultrafine crystals.There are various factors which can influence grain refinement of ECAP technology,such as mold structure,pressing pass,and extrusion route and so on.In this paper the influence of extrusion route on grain refinement was mainly studied.According to the deformation distribution of route 135 which our studying team had studied,the traditional BC route is optimized and the effect of deformation distribution on grain size was studied.By the analysis of the grain refinement mechanism,a new route X is proposed.In the ECAP,the high purity aluminum and industrial aluminum with the size of ?15x60mm were processed by five routes(Bc?BC*?135?145.5?X),industrial pure aluminum of route Bc and BC*were annealed,the microstructure,hardness and TEM organization of the samples were observed to make comparative analysis.Finally,the new technology of the combination of multi forging and ECAP for the industrial pure aluminum is proposed.The samples after 6 passes multi-directional forging were used to do ECAP in route 4A,4C and 2A+2C,the annealing test was used after ECAP,and the microstructure and property were contrastively analyzed.The optimized test of Bc route shows that:after the extrusion of 8 passes,the grain size uniformity is better than the traditional Bc route,and the grain refinement effect has no obvious change.The annealing experiments of pure Al extrusion shows that the recrystallization temperature of the two routes is 300?,and the thermal stability of the BC*route is better.The results of the high purity aluminum X route show that the grain refinement of the route 145.5 is better than the route 135,For the mold of ?=90°,?=20°,in room temperature extrusion under the state route on the grain refinement effect from good to bad as follows:route X>route 145.5>route 135>route BC.For the route X,the grain refinement effect is obvious after each pass.The test of multi direction forging and ECAP for industrial pure aluminum shows that,ECAP improves the structure uniformity of the multi-directional forging deformation,and the multi forging has also reduced the passes of ECAP,the order of refinement effect after 4 passes is C>2A+2C>A;the annealing experiments after ECAP shows that,complete recrystallization was observed after 300?×1.5h annealing,the grain size is uniform,the uniformity of route C was the best,the grain size difference between 2 and 3 pass was not obvious,the grain size of fourth pass was the smallest which is 20?m.