Influence Of Hot Rolling On Microstructure,Texture And Mechanical Properties Of 7n01 Aluminium Alloy

As the rapid development of high-speed rail,the demending of 7N01 aluminum alloy which is necessary is increasing.Thermoplastic forming is the main processing technology of 7N01 aluminum alloy in the high-speed train body,except casting.This thermoplastic forming(hot rolling or hot extrusion)process plays a key role in the end use properties of 7N01 aluminum alloy sheets and sections,however,in the past few studies on the thermal deformation of 7N01.With the continuous speeding of high-speed rail,7N01 aluminum alloy,requirements of thermoplastic deformable material are getting higher.In order to improve the controll ability of the 7N01 aluminum alloy thermoplastic deformation material production process,further to improve the quality and performance of the alloy material,the law of microstructure and texture evoluted from hot rolling process to the final solution treatment is necessary.In this paper,the influence of hot-working deformation system on the structure and properties of plate was studied through microstructure,texture and mechanical properties,which provided experimental basis for controlling the microstructure uniformity of hot-rolled plate in 7N01 aluminum alloy in China.The results show that:(1)The 7N01 semi-continuous flat cast ingot homogenized in factory has more obvious {100} plane texture.Second homogenization treatment eliminated further the segregation phenomenon and plane texture,and enhanced copper and cube texture slightly.(2)Middle layer of sheet hot rolled at lower temperature(390℃)was more prone to deforming,resulting in R textures and deformed textures,including brass,goss and S.After the solution treatment,small grains appeared on the original grain boundary and second phase,with weakened deformation texture.Deformation was prone to focus on the 1/4 layer rather than middle layer of plate.There appeared less small grains on the middle layer when rolled at higher temperature,with increasing strength of R texture and deformation texure(brass、goss and S).(3)As single-pass reduction rate enhanced,deformation gradually penetrated to the middle layer.Obvious deformation appeared on middle layer with reduction 40%at lease.Weak deformation textures were formed only on 1/4 layer of the plate,including brass,copper,copper and S,and middle layer had no obvious a fiber,including goss,brass and {110}<110>,and copper in addition.The goss texture enhanced with increasing reduction.After the solution treatment,the middle layer of the plate produced a significant recovery,with small grains occurring at the second phase on the original grain boundary,and the a fiber,especially goss component,enhanced,with near-copper texture weakness.(4)Total reduction rate and pass reduction rate played synergy to alloy plate structure and texture.When the total reduction was 50%,the grain deformation was more uniform with more obvious deformation band.on the middle layer of plate rolled with the high pass reduction rate,with overall stronger a fiber,without obvious peak.There was no deformation band rolled with low pass reduction rate,Stronger brass,S and R textures all appeared on the middle layer of plate,without remaining components of a fiber(goss and {110}<110>)and R.After solution treatment,a recovery occurred.The ｛110}<110>increased on the middle layer of both plate.Other components of a fiber(goss and brass)enhanced with high pass reduction rate.The other hand,other textures did not change significantly except copper texture decreasing slightly with low pass reduction rate.Continued to increase the total reduction to 85%,the microstructure on the middle layer seriously deformed into fibrous,shear bands appeared in high pass reduction rate.Increasing the total reduction rate also made the texture enhanced,and peak moved to goss and copper,which was stronger with low reduction rate.Increasing the total reduction rate also made stronger R and S orientation then rolled with 50%,and a lot shear band,with high pass reduction rate.After solution treatment,both had recrystallization obviously,the recrystallization was mainly equiax-shaped without elongated,around the second phase with low pass reduction rate,and weakened goss and copper textures.The enlongated recrystallization distributed along the rolling direction accompanied by equiax-shaped recrystallization gathering around the second phase particles with high pass reduction rate,with increasing the texture of goss and copper textures.(5)After solution and aging treatment multi-pass hot-rolled 3mm sheet appeared a lot of cross-shear band,and texture nearby brass,nearby copper,nearby goss,deformation texture S and R were visible,and nearby copper was weaker with high pass reduction rate.The grain deformation gradually increased,and the shear band gradually increased with total reduction from 57%to 91%.When the total reduction reached 84%,it was difficult to distinguish between the various grains,and appeared significat fibrous tissue.The low pass reduction rate happened to more equiax-shaped recrystallization grains.Only goss decreased when the reduction increased to 84%,other textures had no obvious change.Overall increasing of nearby brass,nearby copper and nearby goss happened with reduction increasing to 91%.Increasing pass reduction happened to appear more elongated recrystallization grains except equiax-shaped recrystallization grains,and increasing texture except R or S.Goss was weaker with reduction of 91%.The longitudinal strength of the alloy sheet slightly decreased with the total reduction increasing,opposite to reach to 91%with high pass reduction rate.