Research On Dynamic Softening Behavior And Thermal Processing Chart Of3003Aluminum Alloy Prepared By Different Melt-treatment Methods

Based on the preliminary studies, melt-treatment and thermal processing are consideredtogether through dynamic thermal-simulated technology in view of the relations betweeninternal metallurgical quality and hot deformation behavior of high-performance aluminumsheet and strip.Dynamic softening behavior and thermal processing chart of3003aluminumalloy prepared by different melt-treatment methods are studied by means of OM, SEM, EDS,TEM and Electron Backscattered Diffraction (EBSD) to provide theoretical and experiment’sbasis for the optimization of thermal processing parameter The main results are as follows:1.3003aluminum alloy is the sensitive material to positive strain rate or negativedeformation temperature,and characteristics of the flow stress curve are dynamic recovery,continuous dynamic recrystallization or discontinuous dynamic recrystallization.Thehyperbolic sine function is suitable to describe the relationships among strainspeed,deforming temperature and flow stress.The results of dual regression with hyperbolicsine function show that effects of different melt-treatment have obvious influence onthermally-activated energy Q,the highest of high-efficient comprehensive melt-treatment(150.03KJ/mol) and the lowest of no melt-treatment (189.14KJ/mol) respectively.Afterobtaining hot deformation material constants, flow stress equations containing the Zparameter during hot deformation as well as transition and softening stage are established.2.The better effects of melt-treatment are,the smaller primitive grain size andrecrystallization grain size are.Dynamic softening behavior of3003aluminum alloy includesdynamic recovery and dynamic recrystallization.The dynamic recovery mechanisms of3003aluminum alloy treated by no melt-treatment, normal purification and high purification aremainly escaping of three-dimensional dislocation net or the cross-slip of screw dislocation.Besides,the dynamic recovery mechanisms of normal comprehensive melt-treatment aremainly escaping of three-dimensional dislocation net or non-conservation movement ofcutting bands. The dynamic recovery mechanism of high-efficient comprehensivemelt-treatment is mainly the cross-slip of screw dislocation.Nucleation mechanism ofdynamic recrystallization of the alloy is primarily the subgrain congregation,and at the sametime there are nucleation mechanisms of dislocation tangling, crystal boundary bowing andshear zone.Under the condition of ε&=0.01～10.0s-1and lnZ≤27.26, continuous dynamicrecrystallization starts to appear in the high-efficient comprehensive melt-treated3003 aluminum alloy.With the condition of ε&=50.0s-1and27.26≤lnZ≤35.41, discontinuousdynamic recrystallization starts to appear.The lower the lnZ value is,the higher the appearancepossibility of dynamic recrystallization is. In the process of dynamic softening metallurgicaldefects such as inclusions and the second phases have significant impact on3003aluminumalloy. The second phases of3003aluminum alloy by no melt-treatment provide therecrystallization position and the second phases of3003aluminum alloy by high-efficientcomprehensive melt-treatment hinder the migration of the crystal boundary.3.Melt-treatment and thermal deformation conditions have important influence on grainboundary characteristic distribution of3003aluminum alloy. Under the condition of T=673Kand ε&=0.1s-1, the occupied proportion of low angle grain boundaries of no melt-treatment,normal comprehensive melt-treatment and high-efficient comprehensive melt-treatment is87.83%,85.55%and79.24%separately. Under the condition ofε&=0.1s-1or T=673K at thesame melt-treatment, dynamic recrystallization process carries on more fully separately withmedium and high deformation temperature or medium strain rate.4.Melt-treatment and thermal deformation conditions have obvious impact on spatialorientation distribution of3003aluminum alloy.With the condition of T=673K and ε&=0.1s-1,maximum density level of spatial orientation distribution by no melt-treatment is62.32%and55.65%higher separately than normal and high comprehensive melt-treatment,which showsvery strong intensity of texture. Under the condition of T=673K or ε&=0.1s-1, intensity oftexture is the lowest.5.During thermal deformation process of3003aluminum alloy,there are mainly Cubictexture, Gosse (G) texture,R texture, Brass (B) texture and Revolving cube texture, theintensity of which are related with melt-treatment, deformation temperature and strain rate.Under the condition of T=673K and ε&=0.1s-1, the relative volume content of texturecomponent by no melt-treatment, normal and high comprehensive melt-treatment is12.9%,0.9%and0.6%separately.6.The best processing region appears in the condition of medium or high deformationtemperature and strain rate for3003aluminum alloy by normal comprehensive orhigh-efficient comprehensive melt-treatment, the efficiency of power dissipation value ofwhich is39.28%and55.64%separately.But under the condition of low deformationtemperature and high strain rate,processing instable regions appear.The consistent of thermaldeformation organization by experimental observation and theoretical calculations of thermalprocessing char indicates that thermal processing chart based on DMM is reliable to analyzeunstable region and the best processing region of3003aluminum alloy.