Effect of combined lean additions of isomorphous and eutectoid beta stabilisers on the properties of titanium

Abstract

Reduction of the manufacturing cost of titanium and the development of new alloys are crucial to effectively harvest the benefits derived by the use of titanium in industrial applications. Therefore, we considered the creation of new Ti-2X-2Z alloys via the combined lean additions of isomorphous (i.e. Nb) and eutectoid (i.e. Cu, Mn, and Fe) beta stabilisers, and systematically analysed their effect on the manufacturability and mechanical response of titanium produced via powder metallurgy. It is found that the addition of the alloying elements reduces the compressibility of the powder blend but enhances the densification. The microstructure of titanium is transformed into a Widmanst€atten structure composed of a grain boundaries and aþb lamellae where the stronger the beta stabilisers the more refined the microstructural features, and no intermetallic phases are precipitated despite the use of eutectoid stabilisers. Consequently, the combined addition of isomorphous and eutectoid beta stabilisers has a significant effect on the mechanical response with the material becoming stronger, harder and less tough with the increment of the potency of the added beta stabilisers; however, the Ti-2X-2Z alloys share similar strengthening mechanisms. A more accurate theoretical equation for developing titanium alloys through the molybdenum equivalent parameter should be developed