Study On The Mechanism And Sintering Properties Of Preparation Of Ultrafine Molybdenum Rhenium Alloy Powders By Hydrocarbon Synergistic Reduction

Molybdenum-rhenium alloy has excellent thermal conductivity,conductivity and corrosion resistance,as well as high hardness and high temperature strength.It is widely used in the manufacturing of key components such as high-temperature aviation industry,electronics,nuclear power reactors,etc.In addition,due to its good biocompatibility,it has also made considerable progress in new medical materials in recent years.Therefore,it is an important research direction to prepare Mo-Re alloy with good properties.In this paper,ultra-fine Mo-Re pre-alloy powder was prepared by step reduction of hydrocarbon,and Mo-Re alloy was prepared by vacuum spark plasma sintering.The preparation process,properties and mechanism of ultra-fine Mo-Re pre-alloy powder and Mo-Re alloy have been studied.The main conclusions are as follows:（1）The phase transition and mechanism of the preparation of ultra-fine Mo-Re alloy powder by hydrocarbon stepwise reduction were studied.By comparing the effects of different reduction temperatures and different carbon content on the powder properties,the process parameters were adjusted,and the phase and morphology of the powder obtained by reduction were characterized by XRD and SEM.The results showed that when the carbon content was too low,the powder could not be fully reduced once,resulting in coarse particles and poor dispersion of the reduction products,When the carbon content is too high,there are more C and Mo₃C₂ in the product.When the carbon content remains unchanged,the calcination reduction effect becomes better with the increase of temperature.Finally,the best powder preparation process was determined as follows:carbon addition C/（Mo+Re）=0.7,calcination temperature of400℃,secondary reduction temperature of 950℃,and holding time of 120 min.The average particle size of the obtained Mo-Re alloy powder is 172.96 nm,with good dispersion.（2）The high performance Mo-Re alloy was prepared by vacuum spark plasma sintering.The effects of different sintering temperature and holding time on the microstructure,mechanical properties and electrical conductivity of Mo-Re alloy were studied.The results showed that with the increase of plasma sintering temperature and holding time,the density and average grain size of Mo-Re alloy increased.The electrical conductivity and mechanical properties of Mo-Re alloy were closely related to the relative density and grain size;Too high sintering temperature will lead to abnormal growth of grains,more internal defects in grains,and lower mechanical properties and electrical conductivity.The optimum sintering process of Mo-Re alloy is as follows:sintering temperature 1650℃,holding time 5min,the relative density of the prepared Mo-Re alloy can reach 97.915%,the average grain size is 862.3 nm,the conductivity is 77.26%,its Vickers hardness is 1781.9 kg?mm^-2,and the fracture toughness is 16.6 MPa?mm ^1/2 at this time.