Study On The Softening Behavior Of Beryllium In Low Temperature(Less Than 450?) Deformation

Due to its excellent prcoperties,beryllium has been widely used in nuclear industry,weapon system,aerospace industry and other fields.However,owing to the lack of research on softening behavior of deformed beryllium,the development of pressure forming technology of beryllium in China is relatively backward Static recrystallization is an important means to soften cold deformed metals and obtain undistorted equiaxed grains.Modem recrystallization theory points out that the control of parameters in the recrystallization process has a profound influence on the recrystallization behavior and microstructure regulation of metals.In this paper,the static recrystallization behavior of hot pressed beryllium with low temperature(less than 450?)deformation during annealing is investigated,and the mechanism of static recrystallization is revealed.The Avrami equation is used to fit the static recrystallization process of beryllium metal,and the kinetic model of static recrystallization of beryllium is established.The results are as follows:(1)the main nucleation mode of static recrystallization of beryllium is mainly the nucleation of grain boundary bow out and twin,and a small amount of nucleation of second phase and intragranular.In terms of time sequence,the nucleation of grain boundary bow out and twin nucleation occur preferentially,and the development of other nucleation modes is relatively backward.(2)The static recrystallization rate of beryllium can be accelerated by increasing the annealing temperature.The recrystallization of beryllium can be completed in the range of 680? to 880?,and the recrystallization temperature range is wide.(3)During the plastic compression process of beryllium,the(0001)basal texture is significantly enhanced and concentrated with the increase of compression amount.Annealing recrystallization can efectively weaken the basal texture produced by compression.(4)The static recrystallization activation energy QR of deformed beryllium is about 115±11 kJ/mol.(5)Increasing strain can accelerate the static recrystallization process,shorten the completion time of static recrystallization,refine the recrystallization particles,and offer a positive effect on the fine-grained structure.The variation of static recrystallization volume fraction of deformed beryllium with time was fitted,and the power exponent parameter a=-0.804 was obtained.(6)The static recrystallization rate of beryllium can be effectively accelerated by increasing the deformation parameter Z.By fitting the volume fraction of static recrystallization of deformed beryllium with time under different hot deformation conditions,the power exponent parameter b=-0.041 and coefficient D=8.2×10-4 were obtained.(7)The parameters of the influencing factors in the Avrami exponent n-value equation are fitted and calculated.The coefficient is B=686.6.The power exponent parameter of Z value is ?=0.042.And the energy parameter is Q=64491 J/mol.(8)Based on the above fitting results,the constitutive model of static recrystallization of beryllium is obtained as follows (?).