Abstract
The mechanical behavior of metastable β Ti alloys can be controlled through heat treatments. Thus, the relationship between the precipitation of α phase and the mechanical properties of these alloys is of special interest. In this work, the microstructure evolution of Ti-30Nb-3Fe alloy during aging heat treatments was evaluated using optical microscopy, scanning electron microscopy and X-ray diffraction. Moreover, Vickers hardness and elastic modulus were measured as a function of aging time. Finally, the ultimate strength and ductility of the alloy aged at 500 °C was assessed by tensile tests. In comparison to a Ti-30Nb alloy, the addition of Fe lowered the β-transus temperature, decreased the martensite start temperature to a value below room temperature, increased the precipitation temperature and reduced the dissolution temperature of ω phase, and lastly, decreased the α phase precipitation temperature. Low heating rates enabled isothermal ω phase precipitation and growth, providing favorable conditions for α phase precipitation and increasing the amount of α phase precipitates. Compared to the solution heat-treated and water-quenched condition, aging heat-treated Ti-30Nb-3Fe alloy presented higher Vickers hardness and mechanical strength, without significant loss of ductility.
Highlights
Metastable β Ti alloys are widely used in the manufacturing of load-bearing components for aerospace and medical applications[1,2,3,4]
Besides their excellent corrosion resistance and improved biocompatibility, the extensive use of Ti alloys is strongly based on their mechanical behavior, which results from Ti allotropy combined with a range of alloying elements and suitable processing routes
The chemical compositions of arc melted and cold rolled samples were analyzed and the results indicated that the experimental composition matched the nominal composition
Summary
Metastable β Ti alloys are widely used in the manufacturing of load-bearing components for aerospace and medical applications[1,2,3,4]. Besides their excellent corrosion resistance and improved biocompatibility, the extensive use of Ti alloys is strongly based on their mechanical behavior, which results from Ti allotropy combined with a range of alloying elements and suitable processing routes. The addition of Nb to Ti has been investigated because it lowers the β-transus temperature, resulting in full β phase stabilization at room temperature and reducing the elastic modulus[7,8,9]. Ti-Nb-Fe alloys can potentially be used in the manufacture of devices for biomedical implants
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