Study On Preparation Method Of Titanium Foams Made By Gas Entrapment

With the development of structure integration light and function, foam metal which is study gradually become the hotspot. Titanium foam has wide application prospect because of its characteristic of lightweight, good mechanical performance and corrosion resistance, etc. However, at present, Titanium foam cannot meet the requirements of industrial application because of most of titanium foam preparation methods were not very ideal, and the foaming process and pore size morphology is difficult to control.Foaming process was studied by using powder metallurgy technology, through gas trapping method. Within the scope of the 830-1010℃, titanium foam porosity increases first and then decreases with foaming temperature increases, and when the temperature is 950℃, the maximum porosity is 32%. Titanium foam porosity increase gradually with foaming time, but after 10 hours, porosity almost no longer increases. The optimal parameters of porosity in the largest was foaming 10 hours under 950 ℃ by optimizing the process parameters. The microscopic characteristics of the titanium foams were observed by optical microscopy and scanning electron microscopy, and the variations of isothermal creep foaming process porosity and microstructure holes were studied. The results show that:pore morphology of titanium foams was sphere and pore distribution was dispersed, the biggest pore was 170μm. What caused the pore wall morphology different under different foaming temperature is the accommodated creeping deformation mechanism.950℃ and below is the grain boundary sliding. Above 950 ℃ is intragranular slip.The foaming dynamics equation of Titanium foams was deduced through analyzing the foaming process of Titanium foams produced by Gas trapping method. The main factors affecting titanium foam porosity are foaming temperature and creep resistance of the matrix. The relation curves of between the porosity and the foaming time, and their kinetic curves under different temperature conditions are built by experimental results. The microstructure of Titanium foams matrix was analyzed by metallurgical microscope. It is found that the foaming rate is proportional to the foaming temperature and inversely proportional to the matrix material creep resistance, but with the temperature increases, the foaming rate does not increase continuously. This phenomenon can be explained by the microstructure change of the matrix material whose creep resistance decreases first and then increases with temperature increases. And this proves the reasonable of the kinetic curve.The main factors is porosity which affecting compression performance titanium foam. Under the action of stress in 800MPa, with the increase of titanium foam porosity, dependent variable should be increased gradually which result in there is a wide flat area about the stress-strain curve in compression test of titanium foam, and causing titanium foam absorbing energy is increased.30% porosity of titanium foam absorbing energy is 7 times than its preform body. Through the study on titanium foam thermal performance, With the increase of porosity, the thermal conductivity of titanium foams gradually decline; With the increase of temperature, the same porosity of thermal conductivity of titanium foam is declining. However, the impact of temperature on titanium foam thermal conductivity compared to the porosity is tiny. Under the condition of,400 ℃, the thermal conductivity of the original billet is 5.68W/(m*K), the thermal conductivity of 30% porosity of titanium foam is 3.2 W/(m*K) which almost reduced to half of their original cost. In addition, compare to the thermal conductivity of titanium foam core material, titanium foam sandwich structure is low.