Study On Preparation And Properties Of Porous Titanium Matrix Composites

Porous titanium matrix composites have the excellent properties of both porous metal materials and titanium matrix composite.They can not only reduce the weight of materials on the basis of ensuring comprehensive mechanical properties,but also have stronger toughness,corrosion resistance and high temperature resistance.As a result,porous titanium matrix composites have a very wide range of applications and prospects.For further research,the preparation process of porous titanium composites was optimized,and then the effects of TiC and SiC on the porosity,pore structure,microstructure,macrostructure and mechanical properties of porous titanium matrix composites were studied.In this experiment,metal powder metallurgy method is used,and needle-shaped urea is used as the pore former.The porous titanium matrix composites are obtained by vacuum sintering at 1200 ? for 2h.After a series of preparation and examination of sintered samples,the following conclusions are drawn:(1)The mixed powder of Tiand TiC/SiC powder in different proportions was pretreated by grinding for 30 minutes,and then the mixed raw material powder is refined,the surface roughness of which was also increased,and the surface activation energy became higher,which can promote sintering.After XRD analysis,no new phase was produced in the mixed material.No other phase diffraction peaks were found in the sample after sintering,which indicated that no other substances or contamination were generated in the blank during the sintering process and subsequent cutting,grinding,polishing and other processes.(2)The porous titanium matrix composites prepared by pretreatment of grinding have smoother linear cutting surface and denser tissue,and the size of microscopic pores in the composites tends to be the same.The porosity of prepared porous titanium matrix composite material showed a trend of slow decline,but the overall change was little,which was about 50% of the original setting.In addition,the porosity of the pre-treated group without grinding showed no pattern.The trend of shrinkage and porosity of the composites is basically consistent.(3)The porous titanium matrix composites with different TiC contents were observed by metallographic microscope and SEM electron microscope.Which results show that the number of micropores on the pore wall was gradually closed,and the macropores was obviously reduced,while the change of macropores is little.The sintering neck inside the material became more clear,compact and uniform.However,with the increase of TiC addition,the sintering neck becomes too coarse and the melting becomes more obvious.The micro-Vickers hardness measurement shows that the addition of TiC can significantly improve the hardness value of the composite,especially when the addition of TiC is 6wt.%,the Vickers hardness value reaches 566.74,which is 165.32%higher than that of porous pure titanium.At the same time,the compressive stress of the porous titanium matrix composites reaches the maximum of 156.45 MPa.The hardness and compressive strength of the porous titanium matrix composites decrease gradually with the increase of TiC content.(4)The porous titanium matrix composites with porosity ranging from 36.02% to50.87% were prepared by adding different contents of SiC under the same preparation conditions.The Vickers hardness of the pore wall of the composites is between246.2?624.03,and the compressive strength of which is between 36.89 ?191.1 MPa.The addition of SiC can promote the densification of the composites and the reduction of the number of microscopic pores on the pore wall,and the sintering neck was gradually thick and uniform.These phenomena indicate that the addition of SiC promoted the sintering of the composites,and finally promoted the improvement of the comprehensive mechanical properties.The fracture morphology of pure porous titanium was analyzed by compressive mechanical test,and it was found that it was in accordance with the characteristics of brittle fracture.While the characteristics of compression fracture morphology of composites with SiC added mainly belongs to plastic fracture accompanied by brittle fracture,and the failure stress of which is larger.