Study On The Mutual Diffusion Behavior Of Cu, Se, Bi And Phase Transition

With the rapid development of modern science and technology, the requirement of industrial materials were also unceasingly increasem, so the physical and mechanical properties of the alloy should be gradually improved, at the same time the alloy became more difficult on the processing. Our team have been to study the environmental friendly free-cutting brass alloy recently, the Cu-Se-Bi alloy was prepared which had small hot cracking tendency, good polishing performance and welding performance,but the stability of the material was deviation. A large number of experiments showed that the performance of environmental friendly free-cutting alloy was not stable, mainly because the phase is instability in the alloys, at the same time all the alloy material properties is not clear, so it is very important for the single phase to study on physicochemical properties.This topic studied the transformation of phase for perfaring the stable performance of Cu-Se-Bi alloy by the way of diffusion coupling method and mechanical alloying method. To summary and analysis phase transformation process and phase transformation rule in the Cu, Se, Bi system, and to provide the basis of the Cu, Se, Bi phase between the physical and chemical properties,at the same time it prepared the phase of Cu2Se, CuSe2, Cu3Se2, CuSe, Bi2Se3, BiSe. Fannally it was provided the basis of theory for preparing a more excellent performance of Cu-Se-Bi alloy.It studied the influence of phase by changing the diffusion time and diffusion temperture,the time and rotating speed of ball milling,the composition ratio of process,the following conclusions:In the Cu/Se diffusion,when the temperature was150℃, it formed a single phase which was CuSe2diffusion layer; when the diffusion temperature was200℃, it formed two layer diffusion phase which were Cu2Se, CuSe2respectively, and the result was consistent with the thermodynamic calculation results;For Cu/SeBi diffusion, when the temperature was150℃, the diffusion reaction was slow and was not clear to formed the diffusion layer, when the temperature was250℃, it was a priority to form Cu2Se, and was consistent with the thermodynamic calculation results.In the Cu-Se binary system of ball milling,when the distribution ratio was2:1, it was not occur phase transition in the milling speed of150r/min; it formed Cu3Se2and CuSe phase in the milling speed of250r/min; the Cu2Se phase was generated by mechanical alloying in the milling speed of350r/min.Under the milling speed of350r/min, the CuSe phase was generated in the distribution ratio of1:1; the phase was CuSe and CuSe2phase in the distribution ratio of1:2. CuSe phase was first formed in the process in the milling process, the rloe of CuSe phase was a transition phase in milling process, in the case of Copper enough further would generate Cu3Se2 phase and formed CuSe2phase in the case of Selenium enough.For Se-Bi binary system,the powder Selenium have been alloyed completely in the process of ball milling and formed Bi2Se3phase and BiSe phase. When the ball mill speed was350r/min, the grain refinement and lattice distortion was more serious.In Cu-Se-Bi ternary system of ball milling, the ball mill speed was250r/min and the ball milling time was30h, the Cu-Se-Bi ternary system alloyed completely, it generated the new phase which were Cu3Se2phase, Bi2Se3phase, and BiSe phase.Under the ball milling speed was350r/min, when the ball milling time was40h, the metal compounds occured amorphous transition; For Cu-Se-Bi ternary system of ball milling, the diffraction peaks of Copper and Selenium powder disappeared with the ball milling time,but the diffraction peak of Bismuth powder was always exist, and Cooper and Selemium alloyed priorly in ball milling process.