Sintering Machanism Of Titanium Wire Based On Double Cylinder Model

Sintering mechanism is a core scientific question of titanium wire sintering porous titanium, at present the related sintering mechanism is set up on the basis of powder sintering process, it does not apply to titanium wire sintering process, which seriously restricted the development process of titanium wire sintering porous titanium products, Therefore, the research on the sintering mechanism of titanium wire is of great theoretical significance and application value. In this paper, theoretical analysis and experimental research are used to study the sintering mechanism between titanium wires. The results are as follows:A double cylinder model was established for the sintering process of titanium wire, and the geometric structure of the sintering neck growth process was analyzed based on the double cylinder model. The thermodynamic analysis of the model was carried out to determine the critical value of the sintered neck of titanium wire without phase transition.Based on the double cylinder model, five kinds of possible control neck growth substance migration mechanism includes: viscous flow mechanism, evaporation condensation mechanism, volume diffusion mechanism, surface diffusion and grain boundary diffusion mechanism and the corresponding was disscucced,and the corresponding neck growth formula was obtained. By using the formula of neck growth and the performance parameters of titanium wire, the sintering diagram of titanium wire was established, and the results shows that: As the sintering temperature increases, the main material migration mechanism of the sintering neck growth is changed. At the early stage of sintering neck formation(The ratio of sintered neck radius to Ti wire radius is less than 0.1),with the increase of sintering temperature, the sintering mechanism is transformed from grain boundary diffusion into evaporation condensation mechanism, then changed into surface diffusion mechanism. With the sintering neck growing up, the sintering control mechanism will also change. When the sintering temperature is 850 degrees Celsius, the sintering mechanism of sintering neck is transformed into the mechanism of evaporation and condensation from the surface diffusion when the ratio of the sintered neck radius to the radius of the titanium wire is 0.1. When the ratio of the sintered neck radius to the radius of the titanium wire is 0.5, the mechanism of sintering is changed into the grain boundary diffusion mechanism from the evaporation condensation mechanism. When the sintering temperature is 950 degrees Celsius, the sintering mechanism of sintering neck is transformed into the mechanism of evaporation and condensation from the surface diffusion when the ratio of the sintered neck radius to the radius of the titanium wire is 0.2. When the ratio of the sintered neck radius to the radius of the titanium wire is 0.6, the mechanism of sintering is changed into the volume diffusion mechanism from the evaporation condensation mechanism.The sintering neck of Ti wires with the diameter of 50,100,150μm sintered at 850,950,1000℃ for 0.5h, 1h and 2h was compared and analyzed. Arrhenius curve fitting was used to get the three sizes of Ti wires in the first two hours of sintering, the dominated diffusion mechanism is evaporation and condensation mechanism. The corresponding sintering mechanism is basically consistent with the theoretical sintering diagram. The correctness of the theoretical sintering diagram is verified.