Preparation And Properties Of Powder/Fiber Porous Titanium By Spark Plasma Sintering

Titanium and titanium alloys have high specific strength,good corrosion resistance,wear resistance and biocompatibility,excellent tritium(hydrogen)storage properties,and their tritides have low equilibrium pressure at room temperature,so they are usually used as storage elements of reaction energy by thermonuclear fusion.Tritium is radioactive.When the helium concentration produced by decay exceeds the critical threshold,it weakens the tritium storage performance of titanium and leads to material failure.Tritium storage performance of titanium can be improved by constructing special porous structure,controlling pore parameters,refining grain size and increasing the number of internal grain boundary/phase boundary.In this paper,porous titanium with powders/powders,powders/fibers,fibers/fibers composite porous structure,micro-crystalline and super-large specific surface area was prepared by spark plasma sintering(SPS)using titanium powders and titanium fibers with different mass ratios as raw materials.The effects of different sintering temperatures,sintering pressures and fiber additions on the pore structure,microstructure,phase,compression properties and sintering behavior of the samples were investigated.The research results are as follows:Porous titanium with powder/fiber composite pore structure is prepared by SPS with a porosity ranging from 1.10 to 22.65%,and the pore diameter is mainly distributed in the range of 20?150?m.The porosity of the sample decreases with increasing sintering temperature,sintering pressure and fiber content.The main phase structure of the sample after sintering is close-packed ?-hcp Ti,and the sintering temperature and pressure have little effect on the phase composition.When the sintering temperature is 800?,the microstructure is mainly composed of equiaxed ? and acicular ?,and contains a small amount of twin crystals.Meanwhile the crystal grains on the fibers are finer than the powder;When the temperature is raised to 900?,the microstructure is also dominated by the equiaxed ?,but a small amount of acicular ? and lamellar ? tissue appear;At 1000?,the microstructure evolved into a serrated ? sheet and a layer of ? tissue.The sintered samples have good plasticity and high strength at the same time.The experimental results of pore structure,microstructure and compression properties under different parameters of the sample were synthesized.The optimum sintering process of SPS powder/fiber porous titanium is as follows: sintering temperature 900?,sintering pressure 15 MPa,fiber content 4%.The porosity,modulus of elasticity,yield strength and compressive strength are 5.91%,5.69 GPa,272.41 MPa and 700.75 MPa respectively.Porous porous titanium prepared by SPS has a porosity ranging from 1.13% to 7.58%,and the porosity of the sample decreases with the increase of sintering temperature and sintering pressure(within 20 MPa).When the pressure increases from 20 MPa to 25 MPa,the effect of continuous pressurization on material density is not significant.At a sintering temperature of 800?,the microstructure of the sample is mainly equiaxed ?;At 900?,it evolves into lamellar ? structure and a large number of small isometric primary ?,the equiaxed primary ? is mostly distributed at the original boundary of the fiber;At 1000?,the sample microstructure consists mainly of sheet ? and sheet ?,and contains a large number of ordered needle-like ?.