Effect of pore sizes and cholesterol-lipid solution on the fracture toughness of pure titanium sintered compacts

Abstract

Commercial pure titanium has been widely used as an implant material because of its excellent biocompatibility and good ductility. To determine the effect of pore size on the fracture resistance of porous titanium compacts, a series of fracture toughness (K(Q)) tests were performed on commercial pure titanium powder compacted to 017 and 0.62 GPa. Pore sizes ranged from 25 to 103 μm, with porosity between 8.5 and 35%. Two sets of fracture toughness tests using disc-shaped compacts (ASTM E 399-90) were performed, the first in air at 37°C and the second with compacts treated in cholesterol-lipid solution at 37°C. The K(Q) value of compacts with a smaller mean pore size (ca. 50 μm) was approximately twice that of the compacts with a larger mean pore size (100 μm). The effect of cholesterol-lipid solution treatment was detrimental, perhaps due to preferential lipid absorption by the titanium oxide and/or the presence of chlorides. For the smaller pore size compacts, the K(Q) values decreased by up to 20%. For the larger pore size compacts, the effect of cholesterol-lipid solution was less significant. Morphologically, compacts with smaller pore size had a predominantly ductile fracture with significantly higher dimple density than the larger pore size compacts.