The Phase Equilibria Of The Co-Cu-Mo Ternary System

As a new multifunctional metal matrix composite,Mo–Cu alloy has a good application prospect.It has been widely used in the fields of electrical contacting,heat dissipating,electronic packaging,and high-temperature aerospace.Mo–Cu alloy combines the high melting point and excellent corrosion resistance of Mo with the excellent electrical and thermal conductivity of Cu.However,Cu and Mo are insoluble with each other and their wetting properties are extremely poor,so a pseudoalloy is formed and it is difficult to obtain high density under conventional sintering process.Studies have shown that chemically activated sintering and adding trace metals such as Ni,Co,and Fe to Mo–Cu alloy can improve the sintering process of Mo–Cu alloy and increase the degree of densification.Among these added active elements,Co is one of the most commonly used elements.Therefore,The accurate knowledge of phase equilibria in the Mo–Cu-based alloy systems is helpful to the composition design and process optimization of the Mo–Cu alloy.At present,the phase equilibria information of the Co–Cu–Mo ternary system is very vacant.The present work aims to construct the isothermal sections of the Co–Cu–Mo ternary system at 900 and 1100?,respectively.In my research,the main experimental methods for the determination of the liquidus projection and isothermal sections of Co-Cu-Mo ternary system were the alloys method and equilibrated alloys method.What's more,the main experimental instruments that used for this work were the SEM?the electron microscopy?,EDS?the energy-dispersive spectrometry?and XRD?X-ray diffraction?.In this work,the microstructures of all alloy samples were observed and analyzed to determine the compositions of all phases in the microstructures.Finally,the experimental data were used to construct the liquidus projection and the isothermal sections of the Co–Cu–Mo ternary system at 900 and 1100?.In the 900? isothermal section,three three-phase fields have been detected,i.e.,?Cu?+?-Co3Mo+?-Co9Mo2,.?Cu?+?-Co3Mo+?Co,?-Co9Mo2+?Cu?+?Mo?.And three two-phase regions have been detected,i.e.,?-Co7Mo6+?Mo?,?-Co7Mo6+?-Co3Mo,?Cu?+?Co.O There are five three-phase regions in 1100? isothermal section,i.e.,L+?Mo?+?-Co₇Mo₆,L+?-Co₇Mo₆+?-Co₉Mo₂,L+?-Co₉Mo₂+?Co,L+?Cu?+?Co,?Mo?+?-Co2Mo3+?-Co7Mo6.Besides,two two-phase regions?Cu?+?Co and?-Co7Mo6+?-Co9Mo2 have been detected in this isothermal section.In addition,there were three primary phases in the liquidus projection,i.e.,?-Co7Mo6,?-Co9Mo2 and?Co.Four reactions were found in the process of solidification,i.e.,L??-Co7Mo6+?Co,?-Co7Mo6+?Co??-Co9Mo2,?-Co9Mo2??Co+?-Co3Mo,L+?Co??Cu?.