The Extrusion And ECA(Route A) Integration Large Strain Technology And The Effect Of E-ECA(Route A) On The Microstructure And Properties Of Aluminum Alloy

The extrusion and equal channel angular(E-ECA)by route A large strain technology is a new kind of severe plastic deformation(SPD)that combines the advantages of traditional forward extrusion and twice ECA by route A.The technology can regulate the microstructure of material while effectively eliminating the loose and pore of materials.In this paper,the E-ECA die by route A is designed and manufactured by oneself.First of all,the pressing load and effective strain in E-ECA by route A were simulated by DEFORM-3D,thereby optimizating die parameters and using to design die,then design and manufacture die combines with the actual situation.Using two kinds of aluminium alloy(7075 aluminium alloy and Al-8.55Zn-2.29Mg-0.91Cu-0.21Zr-0.02 Sr aluminium alloy)for the experimental material.The effects of different deformation stages after route A of E-ECA processing on the structure and property of alloy were investigated by EBSD analysis,XRD analysis,micro-hardness test,electrical conductivity test,inter-granular and exfoliation corrosion resistance test.the research results are as follows:(1)In this paper,the DEFORM-3D is used to simulate the large strain deforming of E-ECA by route A.Through the analysis of the main parameters to guide the design of the die,the effects of alloy?s pressing load and effective strain has been analysised by changing“?”and“(37)”.The study found that with the increase of extrusion ratio“?” and the decrease of channel angle“(37)”,the effective strain of the workpiece is increased,the maximum pressing load increase linearly.Through analysis the simulation results and experimental conditions,The parameters of die are determined:?=2,(37)=135°.(2)The design of female die includes two parts: die cavity parameter design and external structure design.the main parameters are extrusion ratio(?=2),channel angle((37)=135?),curvature angle of outer arc(?=45°),the taper of variable diameter(?=120°)and inner arc radius(R=3mm).The overall shape of die is designed to be conical and the taper is 8°.A new mould-parting method of die is designed in this paper,this method combines the advantages of longitudinal parting and local partial module,not only the integrity of the maximum force part of die is guaranteed,but also reduces the processing difficulty of ECAP channel.The working condition is good after the mold is finished and the surface quality of material is good,it shows the mold design is reasonable.The shape and load of the experimental sample as same as simulated sample,it shows the numerical simulation is feasible.(3)The 7075 aluminum alloy is used as the experiment material,explored the effect of the large strain deforming of E-ECA by route A on the microstructure and properties of 7075 alloy.Results found that the grain size of the alloy decreases obviously after E-ECA by route A processing and solution treatment,the average grain boundary angle decreases from 32.72? to 26.81?,the grain boundary angle decreases due to the grain was elongated,the proporition of low angle grain boundary increases from 21% to 38%.The microhardness of the T6(121??24h)heat treated alloy increase from 184.1HV to 201.4HV.In terms of corrosion properties,the depth of intergranular corrosion decreases from 60.82?m to 21.17?m after deformation,intergranular corrosion grade increased from three to two,the route A of E-ECA technology reduced the exfoliation corrosion grade from PA to P B.(4)The aluminum alloy Al-8.55Zn-2.29Mg-0.91Cu-0.21Zr-0.02 Sr was used as the experiment material,explored the effect of the large strain deforming of E-ECA by route A on the microstructure and properties of the new aluminum alloy.Results shows that the E-ECA by route A processing and solution treatment can refine grain size obviously and change the morphology of grain,the average grain boundary angle decreases from 36.04? to 25.96?,the grain boundary angle decreases due to the grain was elongated,the proporition of low angle grain boundary increases from 12% to 36%.The microhardness of the T7X(121??5h+133 ??16h)heat treated alloy increase from 191.2HV to 203.8HV.The large strain processing technology can enhance the intergranular corrosion resistance of alloys,the depth decreases from 259.13?m to 100.48?m,the exfoliation corrosion grade dropped from PA to PC.