Titanium-S23: A New Alloy with Ultra-High Tensile Toughness Directly from the Solid-State Processing of Recycled Ti–6Al–4V and Ti–5Al–5Mo–5V–3Cr Powders using Field Assisted Sintering Technology

Abstract

This article exploits field-assisted sintering technology (FAST) as a sustainable solid-state processing route for alloy design, to produce a novel β-rich, α + β titanium alloy, Ti–5.5Al–4.5V–2.5 Mo–1.5Cr, with exceptional tensile toughness properties. Surplus Ti–6Al–4V and Ti–5Al–5Mo–5V–3Cr powders, in size fractions that are outside the nominal particle size distribution range of additive manufacturing processes, are mixed and sintered with a range of FAST processing parameters. Microstructural analysis and Vickers hardness measurements optimize the processing parameters (to a maximum of 395 HV). Large-scale billets (250 mm diameter) are subsequently produced, allowing the extraction of tensile, Charpy, and microstructural analyses samples. Tensile testing reveals that this new synergistic alloy has an exceptional balance of strength–ductility (UTS = 1110 MPa, Elongation > 15%), that is, tensile toughness, in the as-FAST condition—exceeding the properties of the parent alloys. Microstructural analysis reveals the presence of fine-scale alpha precipitates to which the superior mechanical properties can be attributed. This study provides the basis for future investigations focused on this novel alloy, termed S23 by Rolls Royce plc, which can be produced from commercial surplus powder and scrap streams.