Study On The Temperature Field Of7050Al Alloy During Homogenization With The Application Of Electric Current

In order to assurance the stability and uniformity of the temperature field of7050during homogenization with electric current, the effects of heating parameters on the temperature distribution were investigated in present work. A model was established to simulate the temperature field homogenized with electric current, and was used to predict the temperature field of sample having large size. The dissolution and transformation of the constituent phase at grain boundaries during homogenization with electric current were also studied. The results are listed as follows:When the copper fixture without or with water cooling, the temperature differences between the rightmost and the leftmost positions are76℃and6℃, respectively, in sample heated at an air blowing frequency of lOHz and an electric current intensity of2000A, and becomes76℃and6℃, respectively, in sample heated at an electric current intensity of1500A and no air blowing. It can be seen that the copper fixture having water cooling can significantly decrease the temperature difference at the symmetric positions in sample.The times heated to470℃are507s and140s, respectively, in sample heated at no air blowing and current intensities of2000A and3000A, respectively, the heating speed increases with increasing current intensity. The temperature can not reach470℃and maintain at428℃when the sample heated at a current intensity of1500A.The pure electric current heating causes the inhomogeneous temperature distribution and inadequate temperature needed for homogenization when the current intensity is less than1500A. There is no error between center and surface with using compensation heating, air blowing and electric current, Therefore, the method using compensation heating, air blowing and electric current to realize the electric current homogenization of7050alloy.When the current intensity is2000A, the simulated and experimental results of temperature at the rightmost position are399.8℃and233℃, respectively, the error is0.6%. It can be seen that the simulated and experimental results are basically same.The area fraction of residual phase at grain boundaries of7050alloy after homogenized for2h at450℃/0A,450℃/1000A,465℃/0A,465℃/1000A, respectively, are2.82%,2.29%and2.44%,2.36%, respectively. When homogenized at450℃for24h, small amount of residual non-equilibrium eutectic phase AlZnMgCu remain, the area fraction of residual phase decreases to2.08%. When homogenized for24h at450℃/1000A,465℃/0A and465℃/1000A, respectively, the area fraction of residual phase reduces to1.68%,1.41%and0.80%, respectively. It can be seen that the electric current significantly accelerate the dissolution or transformation to S phase of AlZnMgCu phase.