Thermal Deformation Behavior Of Cu-2.7Be Alloy For Photomultiplier Electrode

Cu-2.7Be alloy has excellent secondary electron emission properties and is the key raw material for high-performance photomultiplier tubes.With the increase of Be content,Cu-Be alloy produce the hard and brittle second phase,leading to stress concentration and cracking of the material.The difficulty in machining and forming the material limits the application of Cu-Be alloy in photomultiplier tubes.The study of the evolution law of thermoplastic deformation behavior of Cu-2.7Be alloy was of great theoretical significance for the formulation of processing and forming technology of Cu-2.7Be alloy for photomultiplier electrode.In this paper,the hot compression deformation behavior and microstructure evolution of Cu-2.7Be alloy were taken as the research object,and the main conclusions are as follows:（1）The evolution of hot compression flow stress of Cu-2.7Be alloy at different temperatures and strain rates was studied:When the strain rate was constant,the flow stress of the alloy decreased with the increase of deformation temperature;When the deformation temperature was constant,the higher the strain rate is,the greater the flow stress is.At low temperature and high strain rate(923 K/10 s^-1),the maximum stress reaches about 270 MPa,and at high temperature and low strain rate(1073 K/0.01 s^-1),the minimum stress reaches about 20 MPa.（2）The modified J-C model,Arrhenius model and ANN model were used to predict the flow behavior,the results showed:the modified J-C model was more suitable for high strain rate conditions,and the Arrhenius model performed better at high temperature.Compared with the other two models,the ANN model performed the best,but it need a lot of experimental data as the basis,and the calculated amount were large.The Arrhenius model was the best constitutive model for predicting the hot compression flow stress of Cu-2.7Be alloy,considering the calculation amount and prediction ability.（3）Based on DMM model,thermal processing diagram was drawn,and the ideal thermal processing region was obtained:the temperature range was 1023 K-1073 K,and the logarithmic range of strain rate was-1.25s^-1 to-0.25s^-1.（4）The microstructure evolution of Cu-2.7Be alloy after thermoplastic deformation has been studied.In the region with high power dissipation(1073 K/0.1s^-1),the microstructure was completely recrystallized.Cracking and flow localization were observed at 923 K/10 s^-1 and 1073 K/10 s^-1respectively,which should be avoided in the process of machining.Based on SEM and TEM,the softening mechanism of the alloy under different deformation conditions was revealed:Dynamic recovery（DRV）at low temperature,Continuous dynamic recrystallization（CDRX）at high temperature,and Discontinuous dynamic recrystallization（DDRX）at high temperature（1073 K）and high strain rate(10 s^-1).