Research On Mechanism Of Mechanical Alloying And Microwave Sintering Of Cu-Cr Alloy

For the excellent combination of high conductivity of Cu and high strength of Cr,Cu-Cr alloys are widely used in industry,especially the high-Cr contented Cu-Cr alloys are widely used in medium voltage vacuum circuit breaker.However,due to the large positive mixing heat of Cu-Cr alloys,they are difficult to dissolve even in the liquid phase.For the insoluble of Cu and Cr,micro segregation and macroscopic segregation are so easily observed in Cr phase.In response to these problems,the preparation and forming mechanism of Cu-Cr alloys by combining microwave sintering and mechanical alloying were studied in this paper.The research results of mechanical alloying process on Cu-Cr alloys showed that:?1?Mechanical alloying extent of Cu-Cr mixed powder increased with the extension of milling time.?2?With the increase of milling time,for the small particle and excellent ductility of Cu,large particle and bad ductility of Cr,and the first-occuring agglomeration of Cu,large-size lamellar particles of Cu-Cr mixed powder reduced and small-size lamellar particles of Cu-Cr mixed powder increased.The research on cold-strength experiment of Cu-Cr alloy powder showed that with the cold strength increased from 300MPa to 500Mpa,the microstructure and the dendity of cold-strength body of Cu₆₀Cr₄₀ alloy powder was refined,and the diffusion activation energy of sintering process required decreased.This indicated that increasing cold strength not only can benefit to increase the density of sintered samples,but also make the alloy microstructure refined.The research on Cu-Cr alloys microwave sintering process showed that:?1?By microwave sintering of Cu-Cr alloys with different compositions,the microstructure of alloys refined first,and then become rough with the increase of Cr content.?2?With the increase of the sintering temperature and pressure,the microstructure of the Cu₆₀Cr₄₀ alloy gradually homogenized,and the lamellar microstructure gradually transformed into a crystalline.This leaded to the increase of density,which can be up to98.8%.The most excellt density and optimal microstructure of Cu-Cr power can be obtained at the temperature between 960 and 980?.The reasons of this phenomenon were that the microwave that the Cu-Cr alloy absorbed can be converted to Cu-Cr alloys internal molecular kinetic and thermal energy,and the alloy material can be heated uniformly.Through this process,the temperature gradient in the high temperature sintering was reduced,and it can effectively improve the densification and alloying extent of the alloys.The research on mechanical alloying,cold pressure and microwave sintering of Cu₆₀Cr₄₀ alloy showed that,The optimum process conditions were 48h ball millig,500Mpa cold strength and 960⁹80?sintering temperature.