Papers by Keyword: Be

Abstract: In order to provide the best technic parameter for hot pressing, the distributions of Fe and Be near the Be and 00Cr17Ni14Mo2 stainless steel (Be/SS) diffusion bonding interface under different technic parameter were simulated by the finite element method and measured by means of scanning auger microspectroy (AES). The simulated results were compared with experimental value, The distributions of Fe and Be near the Be/SS diffusion bonding interface and the relationships between the width of diffusion layer, the heating temperature, the holding time and the pressure were also discussed. The results indicate that under the condition of heating temperature 1323K and 1023K with diffusion pressure 60MPa and holding time 7200s, respectively, the simulated distributions of Fe and Be near the Be/SS diffusion bonding interface fit with the experimence values, and the width of diffusion layer at 1323K is about 2.5 times the one at 1023K. Under the condition of heating temperature 1023K with holding time 7200s, the width of diffusion layer measured at 30MPa, 40MPa, 50MPa and 60MPa is fit well with the simulated results and the relationship between the width of diffusion layer (x/μm) and the diffusion pressure (p/MPa) follows the eqution 0f x =-1.5×10^-2p² +2.8275p -0.1575. Under the condition of heating temperature 1023K with diffusion pressure 60MPa, the simulation curve between the width of diffusion layer (x/μm) and the holding time (t/s) follows the eqution 0f x=10t³-60.571t²+135.64t+0.2143.

Abstract: In order to provide the best technic parameter for hot pressing, the diffusion bonding temperature fields of Be/HR-1 stainless steel under different cooling methods were simulated by the finite element method. The results show that high temperature parts occur in stainless steel center zone in water cooling and air cooling, and the interface cooling rates follow respectively equation of T = 0.0297 t ² - 9.3223 t + 1017.6 and equation of T = 0.002 t ² - 0.7702 t + 1014.8. In funace cooling, high temperature part moves to beryllium center zone and the interface cooling rate follows equation of T = -0.0192 t + 1018.8. While the heat transfer coefficient (h) is taken as 5, the temperature distribution of both sides on the interface is symmetric and temperature gradient is the lowest, so the hot stress on the interface is reduced effectively to improve the diffusion bonding strength, which results fit with the experience ones well.

Abstract: A numerical analysis was performed to investigate the thermally-induced residual stress caused by the thermal expansion mismatch between Be and BeO. Models were constructed according to the real situation that the BeO particles embedded in grains or distributed at the grain boundaries, where the temperature-dependent materials properties, particle volume fraction and size and interparticle distance were taken into account. In simulation, it supposes particles inside grain no interacting with others, particles along the grain boundary being a period distribution. Be is modeled as elastic and elastic-plastic material with bilinear kinematic hardening model. BeO is modeled as isotropic and linear elastic. All simulations are performed by using ANSYS finite element code. Results show that the size, location and the volume fraction of particles influence on the residual stress (strain) to different extent during cooling process.

Abstract: Be and HR-I stainless steel with AgCu28 as an interlayer was diffusion bonded by hot pressing，The microstructure，distribution of composition and phase，mechanical properties of the joints were analyzed using scanning electron microscopy(SEM)，scanning auger microspectroy(SAM)，x-ray diffraction(XRD) and material testing machine，and the relationship between composition and structure and properties，and the effect of interlayer materials AgCu28 alloy were also discussed．The results show that good joint can be obtained using AgCu28 alloy as an interlayer material，because it can reduce the mutual diffusion between beryllium and stainless steel elements，the formation of brittle intermetallic compounds between beryllium and stainless steel elements are avoided effectively to improve the diffusion bonding strength and properties．