An analysis of the lamellar transformation in TiAl alloys containing boron

A new titanium biomaterial was fabricated by hot press sinter-bonding of titanium/hydroxyapatite composite surface-coated layer to pure bulk titanium. The distribution of the hydroxyapatite particles in the composite surface-coated layer was mainly influenced by the hydroxyapatite volume fraction (Vha) of the composite surface-coated layer. When the Vha was less than 15%, it was uniform. At the temperature of 1023 K, no interfacial reaction layer was observed at the interface between the hydroxyapatite and titanium matrices in the composite surface-coated layer. The tensile strength of the new titanium biomaterial was influenced both by the ratio of thickness of the composite surface-coated layer to the total thickness of the titanium biomaterial and the Vha. Three tensile damage phenomena associated with microstructure of the titanium biomaterial were observed after tensile test. (1) Cracks with small crevice appeared in the composite surface-coated layer and the tensile strength was almost equal to that of pure titanium. (2) Cracks with large crevice appeared in the composite surface-coated layer and the tensile strength was lower than that of pure titanium. (3) No crack appeared in the composite surface-coated layer and the tensile strength was much lower than that of pure titanium. The results of bone conductivity test showed that hydroxyapatite had an ability to improve the bonding between the titanium biomaterial and bone.