Study On Microstructure,Texture Evolution And Properties Of 6016 Aluminum Alloy For Automobile Body

6016 aluminum alloy for automobile body is the significant material of lightweight in automobile,which is of great benefit to energy saving and environmental protection.However,the high-performance 6016 aluminum alloy body sheet has high production technology and complicated processes,and its microstructure and properties need to be further studied.In general,process parameters are important factors affecting the microstructure,texture and properties of aluminum alloys.In this paper,the evolution of microstructure and texture of 6016 aluminum alloy for automobile body in three different processes were systematically studied,and the relationship between microstructure and properties was also analyzed.The main results are as follows:(1)The textures of the hot-rolled and cast-rolled samples consist of Copper,S,Brass and Goss orientations.The hot-rolled grains are highly elongated along the rolling direction(RD),and a large number of fine second-phase particles are uniformly distributed along the RD.The cast-rolled grains are slightly elongated and inclined along the RD,and there are serious microsegregation and central segregation in this matrix.(2)After annealing at 350? for 2 hours,the annealed textures of the hot-rolled and castrolled sheets are still Copper,S,Brass and Goss orientation,but their strength and volume fraction decrease.The annealed microstructure states of the two sheets are not significantly different from those before annealing.After annealing at 540? for 8 hours,the initial texture of the cast-rolled sheet disappears completely,and the textures of Cube,CubeND and P are formed.The annealed grain of this alloy becomes very coarse,and the microsegregation in the matrix is basically eliminated,but the central segregation is not improved.(3)After cold rolling deformation at 83.3%,the textures of the three groups of sheets are mainly composed of Copper,S and Brass,while the cast-rolled sheet annealed at 540? for 8 hours has additional Cube and Goss orientations.A large number of second-phase particles are uniformly distributed in the cold-rolled matrix of the hot-rolled sheet,and there are no microcracks on the surface of this hot-rolled sheet.There are many broken coarse phases in the cold-rolled matrix of the cast-rolled sheet annealed at 350? for 2 hours,and these particles are distributed along the RD.And there are many microcracks on the surface of this cast-rolled sheet.The cold-rolled matrix of the cast-rolled sheet annealed at 540? for 8 hours contains fine broken phase,and there are only a few microcracks on the edge of this rolled surface.(4)After solution treatment at 560? for 10 minutes,the texture type of the hot-rolled sheet is mainly Cube,Goss and R orientation,and there are many coarse Al(Fe,Mn)Si particles left in the matrix.The texture type of the cast-rolled sheet annealed at 350 ? for 2 hours is mainly Cube,Goss,CubeND and P orientation,and a large number of coarse eutectic phases are concentrated on the matrix.The texture type of the cast-rolled sheet annealed at 540? for 8 hours includes Cube,Goss,CubeND and H orientation,and the size and number of residual eutectic phase in the matrix are small.The recrystallized grain structures of the three groups of sheets are equiaxed grains,and the average grain sizes are 25.2,16.9 and 18.1 ?m,respectively.The yield strength in the T4P state of the cast-rolled sheet annealed at 350? for 2 hours is not much different from that of the other two sheets.And this alloy sheet has the highest average r value and the lowest ?r value,but its tensile strength and elongation are the lowest.(5)The content of Copper,S and Brass components of the hot-rolled sheet decreases after annealing at 350? for 2 hours,and increases after cold rolling,but the content of Goss component decreases until it disappears after cold rolling.During solution treatment,the hotrolled sheet has cube-band nucleation and grain-boundary nucleation mechanisms,resulting in the highest content of Cube texture,as well as a small amount Goss and R textures,which leads to the lowest average r value of this alloy sheet.After annealing at 350? for 2 hours and cold rolling,the content changes of Copper,S,Brass and Goss components are the same as those of the hot-rolled sheet;however,after annealing at 540? for 8 hours,strong orientations such as Cube,CubeND,and P are formed in the cast-rolled sheet,and weak orientations such as Copper,S,Brass,Cube,and Goss are formed after cold rolling.During solution treatment,particle stimulated nucleation(PSN)and cube-band nucleation mechanisms occur in these two sets of cast-rolled sheets,which produces lower Cube and Goss textures,as well as strong CubeND and P or H orientation.As a result,the two groups of cast-rolled sheets have higher average r values.