A Cu-25Cr alloy prepared by vacuum induction melting method was treated by the high current pulsed electron beam （HCPEB） with pulse numbers ranging from 1 to 100. Surface morphologies and microstructures of the alloy before and after the treatment were investigated by scanning electron microscopy and X-ray diffraction. The results show that significant surface modification can be induced by HCPEB with the pulse number reaching 10. Craters with typical morphologies on the Cu-25Cr alloy surface are formed due to the dynamic thermal field induced by the HCPEB. Micro-cracks, as a unique feature, are well revealed in the irradiated Cu-25Cr specimens and attributed to quasi-static thermal stresses accumulated along the specimen surface. The amount of cracks is found to increase with the pulse number and a preference of these cracks to Cr phases rather than Cu phases is also noted. Another characteristic produced by the HCPEB is the fine Cr spheroids, which are determined to be due to occurrence of liquid phase separation in the Cu-25Cr alloy. In addition, an examination on surface roughness of all specimens reveals that more pulses will produce a roughened surface, as a result of compromising the above features.
＜正＞Al-Zn-Mg-Cu super-high strength aluminum alloy is widely used in the aerospace and automotive industry.Howe...
Z.M.Zhou~(1,2,3,a),W.J.Huang~(4,b),Z.Zhao~(5,c),B.B.Lei~(6,d),C.Liu~(7,e) M.M.Cao~(8,f c) 1,4 Key Laboratory of Manufacture and Test Techniques for Automobile Parts,Ministry of Education, Chongqing,400054,China
A Cu-50Cr alloy was treated by the high current pulsed electron beam(HCPEB)at 20 and 30 ke V with pulse numbers ranging from 1 to 100.Surface morphologies and microstructures of specimens before and after the treatments were investigated by employing scanning electron microscopy and X-ray diffraction.Results show that the HCPEB technique is able to induce remarkable surface modifications for the Cu-50Cr alloy.Cracks in Cr phases appear even after one-pulse treatment and their density always increases with the pulse number.Formation reason for these cracks is attributed to quasi-static thermal stresses accumulated along the specimen surface.Craters with typical morphologies are formed due to the dynamic thermal field induced by the HCPEB and they are found to prefer the sites near cracks or boundaries between neighboring Cr phases.Another microstructural characteristic produced by the HCPEB is the fine Cr spheroids,which are determined to be due to occurrence of liquid phase separation in the Cu-50Cr alloy.Finally,a general microstructural evolution profile that incorporates various HCPEB-induced surface features is tentatively outlined.
