Preparation And Properties Of Nano To Submicron Porous β-TiMo Alloys

Beta phase titanium molybdenum(P-TiMo)alloys have low densities,high specific strength,strong impact resistance,good corrosion resistance and biocompatibility properties.Porous titanium alloys have attached much higher attention internationally for many years.However,there are few studies focusing on the fabrication,microstructures,properties and possible applications of micro-nano porous titanium alloy.In this thesis,the preparation,microstructure and properties of the micro-nano porous β-Ti15Mo alloy are investigated,in which the dense β-Ti15Mo alloy,submicron to nanoporous β-Ti15Mo alloy,and 3D hierarchical structured micro/nano β-Ti15Mo alloy are included.The dense(TiMo)1-xCux master alloys with homogeneous microstructures were successfully prepared by MA and SPS techniques.The nano to submicron porous TiMo alloy were prepared by dealloying of the master alloy in Mg powder at 600 for holding 30 min under pressureless condition of SPS.The results showed that the optimal SPS parameters for preparation of the(TiMo)1-xCux master alloy was at 830℃,50 MPa for 10 min.The solid dealloying in Mg powders is a diffusion dominated process.During the master alloy was emerging into the Mg powders,the Cu atoms were diffused into Mg powder compacts and at the same time some Mg atoms were diffused into the master alloy to occupy the vacancies left by the Cu atoms.The TiMoMg was formed by the reconstruction of atoms.Finally,nanoporous(3-TiMo alloy was obtained by etching in nitric acid to remove the Mg.The N2 adsorption experiments showed that the specific surface area is 28.96 m2..g-1 with the nano-pore size of 3.42-50 nm.The mercury intrusion results showed that it has submicron to micron sized pores with mean value of 1109 nm.By controlling the amounts of Cu(30-50 at%)of TiMoCu master alloy,the nano to submicron porous β-TiMo alloy were fabricated with the porosities from 34.47%to 55.12%.The nano-indentation tests showed that the Young’s modulus decreased linearly in the range of 10-30 GPa.In addition,3D hierarchical structured micro/nanoporous p-TiMo alloy was prepared by using of pore-forming agent of NaCl and the solid state dealloying.The results showed that the micro-porous TiMoCu master alloy was fabricated by the SPS at 700 ℃,50 MPa,10 min using NaCl(40-60 vol%NaCl)as the pore-forming agent.After the removal of the NaCl with water immersion,heat-treatment was performed at 850℃for 20 min to get the beta-Ti phase completely.At last,the Cu elements were removed from the master alloy via solid state dealloying.SEM results showed that there are 3-50 nm nanopores on the large pore walls of 200 μm.Finally,3D hierarchical structured micro/nano porous TiMo scaffolds were fabricated.Compression experiments showed that the highest compressive strength is 72.57 MPa for the hierarchical TiMo scaffolds with porosities greater than 50%.The simulated body fluid(SBF)immersion of the alkali treated hierarchical TiMo scaffolds showed that the hierarchical micro/nano porous structures is more effective to improve the apatite-formation ability with higher in vitro bioactivity due to the increased specific surface area and surface roughness.