Research On Preparation, Pore Characteristic And Mechanical Properties Of Porous Ti-39Nb-6Zr Biomedical Alloys

Titanium and its alloys have been widely used as implants replacing hard human tissues in biomedical fields due to their superior biocompatibility, good corrosion resistance, high strength and low elastic modulus. Ti-Nb-Zr alloys are new P-type titanium alloys and become one of the hotspots in medical titanium field in recent years. In order to further reduce the Young’s modulus of titanium alloys and obtain a good match to human bones, powder metallurgy is applied to fabricate porous titanium alloys. Scanning electron microscope (SEM) and image analysis technology were adopted to analyze the characteristic and morphology of pores. Compressive tests and bending tests were employed to evaluate the mechanical properties of the porous titanium alloys. The main results are as follows:Press pressure affected the density and the original pores morphology of compacts. With the increase of pressure, the porosity, the mean pore size and the mean roundness of pores in different ranges decreased, while the compressive strength and Young’s modulus increased.The sintering procedure affected the porous structures and mechanical properties of the alloys greatly. With the increase of sintering temperature and time, the porosity, the mean pore size decreased, the mean roundness of pores in different ranges increased, and the compressive strength and Young’s modulus increased.Without space holder, the pore sizes of the porous titanium alloys were mostly under 50μm, and the pores in the range of 10μm～30μm had the most contribution on porosity of the alloys, and the porosity were less than 25%. The compressive strength and Young’s modulus were between 200MPa～355MPa and 4.7GPa～10.4GPa respectively. After adding space holder, the morphology and distribution of pores changed greatly. The pore sizes were mostly centered in 10μm～50μm, and those big pores above 100μm had the most contribution to porosity of the alloys. With the content of space holder increasing, the compressive strength and Young’s modulus of the alloys decreased greatly, and the decrease trend nearly kept linear relationship with the content of space holder. Different kinds of space holder had different effects on porous alloys. The compressive strength of porous alloys added with NH4HCO3 was higher than that added with CO(NH2)2, while the Young’s modulus of them had little difference. When adding with NH4HCO3, the porosity of porous was between 29.5%～46.4%, and compressive strength and Young’s modulus were 70MPa～325MPa and 1.7GPa～8.1GPa respectively. While after adding with CO(NH2)2, the data were 29.8%～46.7%,40MPa～245MPa and 2.2GPa～8.5GPa separately.The macro photograph of porous alloys and the process of the fracture showed the alloys had brittle fracture and plastic fracture characteristics. The results showed that the compression fracture mechanism was a mixture of brittle fracture and plastic fracture. In the bending test, the fractures of samples without space holder showed a large sum of dimples, which belonged to dimples fracture, while the fractures of samples added with space holder showed the characteristics of quasi-cleavage fracture, which belonged to brittle fracture.