New biocompatible low modulus and high strength β Ti-Fe-Nb-Sn ultrafine eutectic composites

Abstract

High strength β Ti–Fe–Nb–Sn ultrafine eutectic composites are promising in structural and functional applications exhibiting high fracture strength with large plasticity. The present work aims to develop new biocompatible β Ti–Fe-based ultrafine eutectic composites using biocompatible elements (Ti, Fe, Sn and Nb) and avoiding and/or controlling the formation of metastable ω phase also known as Laves phase. Five new compositions (Ti64Fe22Nb14, Ti66Nb18Fe16, Ti63Fe23Nb8Sn6, Ti60Fe23Nb8Sn9 and Ti44Fe34Nb16Sn6 (at.%) were produced using Cu-mold suction casting and the evolution of phases and microstructure with the cooling rate and their mechanical properties were investigated. In this sense, was observed a decreasing in the melting point by the addition of eutectoid β-stabilizing elements (Fe and Sn), which leads to values down to Tl = 1215 °C. The samples were characterized by X-ray diffraction, differential scanning calorimetry, scanning and transmission electron microscopy, Young's modulus measurements by the ultrasonic method, microhardness and compression tests. Thus, in this paper are shown promising results on new biocompatible metallic alloys of the TiFeNbSn system with high strength and low Young's modulus due to the adequate combination of a microstructure formed by micrometer-sized β-Ti dendrites with ultrafine eutectics between soft β-Ti phase and hard Ti–Fe and Ti3Sn intermetallics, highlighting alloys Ti64Fe22Nb14 and Ti63Fe23Nb8Sn6. Their yield and fracture strength measured by compression and Young's Modulus measured by ultrasound were 1810 MPa, 2160 MPa and 45 GPa for alloy Ti64Fe22Nb14 and 1915 MPa, 2240 MPa and 59 GPa for alloy Ti63Fe23Nb8Sn6 (at.%)

Keywords

• β Ti–Fe–Nb–Sn alloys
• Ultrafine eutectic composites
• Microstructural characterization
• Mechanical properties