Research On Hot Deformation Behavior And Microstructure Property Of6082Aluminum Alloy Forging With Rib

Aluminum alloy forging with ribs has been widely used in automobile andaircraft. This kind of parts has complex shape and high precision. Moreover, therequiremets for microstructures and properties of these parts are increasinglyimproved. At present, the materical data of6082in forging process is scare, andthere is no profoundly research on occurring and evolvement of defects in formingprocess for forging with ribs. Therefore, in this dissertation, the hot deformationbehavior and defect mechanism of6082aluminum alloy forging with ribs werestudied and the influence of forming scheme as well as technical parameters onmicrosturctures and properties was precented.For6082aluminum alloy, the calculated activated energy Q was145.977kJ/mol. Stable flow state was entered before stain of0.1following flow stressdescending when strain rate bellow0.1^-1. The work hardening evidently affect onflow stress which entered in stable flow after stain of0.3and kept constant whenstrain rate above0.1^-1. The improved constitutive equation compensated by strain of4degree polynomial fit could predict flow stess more exact. Dynamic recovery was themain mechanism and grain size seemed coarse at lower strain rate which less than1;reversely, dynamic recrystallization was dominant at higher strain rate which morethan1. Lot of crash grains were obtained at350oC, the dislocation descended withincreasing temperature and equiaxial grain appeared at500oC.During hot deformation of roll forging, distribution of temperature as well asstress or strain was not homogeneous. The deference of temperature could be20oCas the deference of stress being30MPa. Deformation of45%for performing anddeference of sectional area between pre-forging and finish-forging within10%mayavoid folding, rib breaking and other defects. The angle increased2o after busting,which should be compensated for deformation matching in bending.When roll forged between440oC and490oC, the strength after heat treatmentincreased with increasing temperature which varied from310MPa to360MPa. Thepreformed blank should be cooled in water to retain fine microstructure while air coolingmay result in coarse and asymmetry grains. The coarse grain would be avoided when start forging as well as finish forgingtemperature was increased. The separated second phase particle increased withincreasing performing deformation, which made tension stress as well as yield stressincreased with maximum of350MPa and310MPa respectly.Upset extrusion results in confluent folding and enlarging radius could improvemetal flow state. Flow line turbulence and folding in rib was related with material exess,thus the mount of materal should be control strictly. The filling result seemed optimal attemperature of480oC, friction factor of0.3and slide velocity of5mm/s.