Surface Porous Materials Rapid Preparation By High Current Pulsed Electron Beam Of And Characterization

A Nadezhda-2 type High Current Pulsed Electron Beam (HCPEB) was used for surface treating in multi-crystal pure copper,304L austenite stainless steel and single-crystal Si in this present work. Surface morphologies and microstructures were characterized by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and surface profiler. The corrosion resistance and hardness of 304L austenite stainless steel were characterized by chemical immersion and microhardness testing.Numerical simulation was conducted to evaluate the surface temperature field of the pure copper induced by HCPEB. The results show that the temperature of near-surface had exceeded the melting point of pure copper, the melt occurred in sub-surface first at 0.4μs, the depth of heat-affected zone was about 40μm, the heating and cooling rate were approximately 109 and 107 K/s, respectively.Numbers of volcan-like craters and micropores formed on the surface of the three types samples irradiated by the HCPEB. When the samples were irradiated by the HCPEB, the melting occurred in sub-surface at first. With the accumulation of energy, the volume expansion happened, then the eruption took place, resulting in the formation of the crater. The diameter of crater was related with the density of energy, but not relationship with the pulse number, its diameter increased with the increase in energy of beam. However, the density of crater was related with both of them, its density first increased and then decreased with the increasing pulse number. Under the condition of multi-pulses, its density decreased with the increasing energy. Due to the polishing effect of electron beam, a part of craters were polished, thus the density of crater decreased.X-ray diffraction analyses show that lots of residual stress generated in sub-surface of 304L stainless steel induced by HCPEB irradiation, which resulted in a large amount of vacancies, vacancy clusters, dislocations and stacking faults. Under the effect of the temperature field, these vacancies moved to the surface along with the defects such as dislocation and boundary and accumulated, leading the formation of micropores.Texture coefficients and the TEM analysis show that (220) plane had a preferred orientation. With the increasing pulse number, the (220) planes decreased, but the (111) planes increased.The hardness of 304L stainless steel increased after HCPEB treatment, grain refinement and dislocation strengthening were the main reason for the increase in hardness of the sample surface. Meanwhile, the corrosion resistance of stainless steel also improved, purification may be one reason.