Optimizing the Microstructure of Implant Alloy TiA15Fe2.5 by Microprobe Analysis

Abstract

The (α + β)-titanium alloy TiAl5Fe2.5 was developed mainly for medical applications¹⁻⁵. With this (α + β)-alloy the microstructure and simultaneously the mechanical properties can be optimized by deformation temperature and/or by heat treatment in the (α + β)-temperature range below the β/(α + β)-transition temperature. This temperature increases with oxygen content and was found to be 960 °C with 0.05% O¹. In the (α + β)-temperature range the amount of the β- and of the α-phase and the chemical composition of both phases depends on temperature. According to the ternary diagram Al-Fe-Ti with decreasing temperature the amount of the β-phase is diminished and the iron content of the β-phase is increased. It was shown that in the temperature region of 500–600 °C after the transformation of the β-phase to (α + β) the iron content in the β-phase can reach an amount which is sufficient to precipitate the intermetallic compound TiFe and an age-hardening effect can be observed⁶. In order to optimize the microstructure of the (α + β)-alloy TiA15Fe2.5 and to investigate the transformation behaviour of the α- and β-phase during aging it was intended to analyze by microprobe analysis of Al and Fe the α- and the β-phase of different microstructures obtained by deformation and heat treatment in the (α + β)-region.