Effects Of Homogenization Cooling Rates On Hot Deformation Behavior Of Al-Cu-Mg-Zr Alloy

Al-Cu-Mg alloys,heat-treatable aluminum alloys,are widely used in the transportation and aircraft industry.And the properties of finished products generally depend on homogenization and subsequent hot working processes.In present work,hot compression tests were performed on the Al-4.10Cu-1.42Mg-0.57Mn-0.12Zr alloy at strain rate of 0.01s-1 and deformation temperature of 300 ? and 450 ? on Gleeble-3500 system.The effects of cooling rate after homogenization on hot deformation behavior were studied by optical microscopy(OM),transmission electron microscopy(TEM),scanning electron microscopy(SEM)and X-ray diffraction(XRD)during hot deformation.The results are shown as follows:(1)The flow stress curve of Al-4.10Cu-1.42Mg-0.57Mn-0.12Zr alloy with higher cooling rate exhibits a peak stress at a critical strain,after which the flow stresses decrease monotonically until high strain,showing a obvious dynamic flow softening during deformation at 300 ?.While the flow stress increases with increasing strain and tends to be constant after a peak value,showing a steady state flow at 450 ?.While for the alloy with lower cooling rate,the flow stresses both show a steady state flow at 450 ? and 300 ?,but lower stress level is shown at 450 ? than that of 300 ?.The influence of cooling rate on hot deformation behavior of flow stress is much stronger at 300 ? than at 450 ?.(2)The cooling rate influences the hardness of Al-4.10Cu-1.42Mg-0.57Mn-0.12Zr alloy in subsequent hot deformation obviously.Hardness of sample with higher cooling rate is higher than that undergo lower cooling rate.The hardness values decrease at first and then increase during deformation at 450 8?,but an opposite tendency is shown at 300 ?.Correspondingly,the hardness value at 450 ? is higher than that at 300 ?.(3)Lots of dislocation rings exist in the matrix after high cooling rate,the dislocation rings evolve into grain boundary and the sub-grains are stretched and grow up during the subsequent hot compression deformation.Dislocations multipliy in early deformation for sample with lower cooling rate,which show dynamic recovery and dynamic recrystallization.The sub-grain increase during deformation as well.(4)Elements dissolve into the matrix adequately for the sample of higher cooling rate.Static precipitations happen and the particles coarsen rapidly when preheating at 450 ?.And the prime particles undergo a process of deforming,breaking and growing up at subsequent hot compressive deformation.When preheating at 300 ?,fine S(Al2CuMg)phase and 6(Al2Cu)phase precipitate along the dislocation ring,which resolve,re-precipitate and coarsen in later deformation.For sample with lower cooling rate,the prime coarse phases are broken and balled with increased strain during compressing.The process at 300 ? is similar with that at 450 ? but particles show more nodulizing at 300 ?.