Abstract: BACKGROUND: At present, the traditional powder sintering method is easy to introduce impurities in the process of preparing porous titanium, and the manufacturing of porous titanium still faces two major problems: impurity pollution and difficult control of the material forming process.
OBJECTIVE: To prepare pure porous titanium with certain porosity, and analyze the microstructure evolution and properties of the porous titanium. 
METHODS: Porous titanium was prepared at a low energy density by selective laser melting technology. The parameter range of porous titanium with large porosity was obtained by measuring the porosity of the formed specimen, and the evolution of the microstructure and mechanical properties of the specimen in the range were analyzed.
RESULTS AND CONCLUSION: (1) With the increase in energy density, the porosity of the porous titanium specimen decreased gradually. When the energy density was between 10.61 and 27.78 J/mm3, porous titanium with a porosity of 11.23%-33.67% could be formed. When the energy density was between 27.78-37.88 J/mm3, the forming parts were relatively dense. (2) The phase composition of porous titanium formed was mainly α titanium. With the increase in energy density, the porosity gradually decreased, and the pore morphology changed from irregularly connected pores to closed nearly spherical pores. The powder particles changed from a slightly sintered neck to a continuous fuse. The CT scan results revealed that there were a large number of connected pores in the forming specimen with a large specific surface area and the pore radius was roughly distributed between 2-6 μm at the energy density of 10.61 J/mm3. Simultaneously, porous titanium with compressive strength of 188-1 000 MPa could be obtained at the energy density of 10.61-27.78 J/mm3, which could meet the requirements of biomedical applications. (3) These results have confirmed that the selective laser melting technology can overcome the problems of impurity pollution and long manufacturing cycle caused by the traditional preparation process, and provide an effective solution for the preparation of porous titanium with excellent mechanical properties.

Key words: low energy density, selective laser melting, porous titanium, microstructure, porosity, mechanical property