Study On Activated Sintering Technology Of Molybdenum Copper Alloy

Molybdenum copper alloy has excellent conductivity,thermal conductivity and thermal expansion coefficient adjustable,commonly used preparation method is powder sintering.In order to reduce the sintering temperature,sintering time and obtain the alloy with high density,the activated sintering technology of molybdenum-copper alloy was explored in this study.It mainly includes mechanical activation of powder,sintering of bimodal powder,accurate construction of submicron active layer,the effect of inducing copper and heat treatment on densification of molybdenum-copper alloy.XRD analyzer,optical microscope and SEM were used to analyze the activation effect and microstructure of the powder and Mo-Cu alloy.In this study,the activation treatment of coupling spiral mill was adopted,and the sintering process was divided into skeleton pre-sintering?850??and melt infiltration sintering?1160??.No copper strip was formed in the sintered samples,which was beneficial to improve the microstructure uniformity.The planet-coupled spiral mill can effectively break,activate and mix the powder aggregates by flowing shear stress.The existence of the screw thread on the coupling spiral axis makes the movement trajectory of the powder form a closed loop,while the addition of the planetary structure provides multiple motion systems for the movement of the powder,avoiding the blind area of the powder processing.With the increase of mechanical processing time,the loose density of powder increased and the degree of particle agglomeration decreased.At the same time,lattice distortion occurred on the particle surface,lattice distortion is characterized by cell volume,In order to further improve the pressing and sintering performance of the powder,the superfine powder was added to the coarse powder in a certain proportion to form a coating activation layer on the surface of the coarse powder.At the same time,the fluidity of powder and the uniformity of sintering structure were improved.he uniform thickness and complete activated layer are obtained by constructing the theoretical calculation formula of bimodal powder ratio.According to the size of fine and coarse powder,the optimal ratio of fine powder was 8 wt.%,and the sintered samples with fine powder content of 10 wt.%were used as the control group.The results showed that the thickness of the former fine powder layer was 0.25?0.75?m,while that of the latter was 1?1.5?m.In the sintering process,the cladding layer is first sintered to form a network connected structure.The shrinkage of fine powder layer provides pressure for coarse powder particles and promotes sintering.Sintering texture with orientation comes from two aspects:one is the left sintering formation of hard aggregate powder,the other is the formation of free sintering of particles.The sintered texture is proportional to the fine powder content,and the RTC value indicates that the?110?texture is formed preferentially.The inducing copper increased the sintering activity of powder and promoted the densification of sintering.Through the preparation process of skeleton pre-sintering and infiltration sintering,the alloy structure with uniform structure was obtained,and the copper element was evenly distributed in the molybdenum skeleton.Among them,the pores larger than 1?m are mostly connected pores,which is beneficial to copper infiltration and improve the infiltration ability.The pores smaller than 1?m are closed pores,and no liquid copper exists.In molybdenum-copper alloy,secondary diffraction occurs due to the superposition of the crystal lattice surface at the molybdenum-molybdenum interface,resulting in the formation of planetary diffraction spots.The molybdenum-copper interface formed an obvious transition layer,about 5 nm.There are phase relationship in interface of Mo-Cu alloy:?111?_Cu??110?_Mo,[110]_Cu?[111]_Mo?The densification heat treatment causes the sintering shrinkage to form micropores which further shrink or disappear.The results showed that the hardness of molybdenum-copper alloy increased about 57.69%at 0?900??4h?.At 700??0?6h?,the sintering hardness increased by about 42.31%.