Study On The Preparation Process Of Integrated Aluminum Based Capillary Core For Flat Heat Pipe

Plate heat pipe has the characteristics of high heat transfer efficiency and light weight,which is the main component to solve the heat dissipation problem of multiple heat sources.Among them,aluminum-based plate heat pipe has the advantages of low cost and light weight,which is one of the current research hotspots.Capillary core is the core component of flat heat pipe.Powder sintered capillary core has the advantages of simple forming,good gravity resistance and small radial thermal resistance.The integrated aluminum-based capillary core prepared by combined sintering process can reduce the assembly process,contact thermal resistance and cost.Due to the high activity of aluminum,there is a dense oxide film on the surface of aluminum powder.At present,the preparation of powder sintered aluminum-based capillary core has the disadvantages of difficult sintering and large pore size.In this paper,pure aluminum powder was used as raw material,and potassium fluoaluminate and Al12Si were used as sintering additives to prepare mixed powder.Aluminum-based capillary core and integrated aluminum-based capillary core were prepared by loose sintering method.The effects of particle size of aluminum powder,content of sintering additives and sintering process on porosity,compression performance and welding performance of aluminum-based capillary core and aluminum plate were systematically studied,and the diffusion kinetics model of liquid phase sintering was established.The main research contents and conclusions are as follows:Through the composition design and experiment,the sintering additive system with potassium fluoride as the filler and Al12Si as the filler metal was determined,which was added to the aluminum powder with 10 wt.%and 5?15 wt.%,respectively.The porous materials with certain strength were prepared by loose sintering.Under the sintering conditions of 580? and 30 min,by adjusting the particle size of aluminum powder and the content of Al12Si,the porosity of the material can be controlled at 21.82?53.14%,the permeability is 4.3×10?13?4.74×10-11 m2,and the maximum pore diameter is 17.24?42.52 ?m.With the decrease of aluminum powder particle size,the porosity,maximum pore size and permeability of the material decrease,and the compressive strength increases gradually.With the increase of Al12Si content,the porosity and permeability of the material decrease,the compressive strength increases,and the maximum pore size decreases.A liquid phase sintering model was established to reveal the sintering process from liquid phase to solid phase.When the sintering temperature is 5 80?620? and the sintering time is 30?120 min,the aluminum-based capillary core material with porosity of 23.61?53.98%,maximum pore size of 15.94?53.15 ?m and permeability of 4.74×10-11?1.43×10-13 m2 can be prepared.With the increase of sintering temperature,the porosity decreases gradually,the permeability decreases gradually,and the maximum pore diameter increases first and then decreases.With the increase of sintering time,the overall porosity decreases gradually,the permeability decreases gradually,and the maximum pore diameter increases first and then decreases.In the sintering process,the porosity increases,and the Si-containing precipitates are distributed around the Al particles after sintering.Based on the preparation processs law of aluminum-based capillary core,the integrated aluminum-based capillary core with porosity of 49.12%and maximum pore size of 24.43 ?m was prepared by sintering-200/+325mesh aluminum powder,adding 5 wt.%Al12Si and 10 wt.%potassium fluoaluminate at 600? for 60 min,and forming metallurgical bonding with the bottom plate.