Hot Torsional Deformation Behavior Of 7A04 Aluminum Alloy

In this paper,the high-temperature torsional deformation behavior of 7A04 aluminum alloy rods with fibrous grain structure was studied,the influence of deformation conditions on the flow stress was analyzed and the constitutive model was established;the evolution law of microstructure was explored;based on dynamic material model thermal processing map theory,thermal processing drawings was drawn,the microstructures in the different regions of the processing map were analyzed,the best deformation parameters were obtained.The main conclusions were as follows:（1）It can be concluded that the flow stress decrease with the increasing temperature,and increase with the increasing strain rate in the extruded 7A04 aluminum alloy bar at a deformation temperature of 360-480°C and a strain rate of 0.001-1s^-1,for extruded 7A04aluminumalloyrodsintheflowstressconstitutivemodelwas,（?）=082×10¹⁰[sinh（0.0195σ）]⁴²⁵exp（-155247/RT）.（2）The microstructure analysis showed that with increasing radius of the bar and the strains increase and the grain shape varied accordingly in torsion.The grains from the outer surface to the axis of the specimen can be divided into equiaxed grain zone,elliptical grain zone and fibrous grain zone in general.（3）The main softening mechanism of 7A04 aluminum alloy during hot torsion at high temperature was dynamic recrystallization.As the amount of strain increases,the more fully deformed,the more complete the recrystallization proceeds.Strain rate and deformation temperature,strain and Z parameters have an important influence on the dynamic recrystallization process:the grain size of equiaxed grain zone and the width of equiaxed grain zone gradually increased with the increase of temperature and the reduce of strain rate,however,the width of the elliptical grain zone gradually increases with the decrease of the temperature and the decrease of the strain rate.（4）There are two deformation conditions in the high-power dissipation region.The first one appears in the region with a deformation temperature of 480°C and a strain rate of 1 s^-1.The power dissipation efficiency reached 36%,and the second occurs at a deformation temperature of 360°C,the strain rate was 1s^-1,and the power dissipation efficiency can reach35%.The best hot deformation condition of 7A04 aluminum alloy at high temperature was360°C,0.001s^-11 and 480°C,0.001s^-1.