Abstract
Three β type titanium alloys were proposed for as-cast applications in practical fields on the basis of the d-electrons parameters with both bond order (Bot) and d-orbital energy level (Mdt). Ti–5.5Cr–5.4Mn–5.1Zr–2.8Fe with the lowest Mdt, Ti–4.5Cr–2.5Mn–1.1Al with the lowest Bot and Ti–10.8Mo–2.3Sn–1.0Al with the highest Mdt were designed by using ubiquitous elements in the predicted regions showing the slip, twin and martensite dominant deformation behaviors in the Bot-Mdt diagram, respectively. Their ingots were produced by the cold crucible levitation melting technique. Ti–5.5Cr–5.4Mn–5.1Zr–2.8Fe showed mono β phase and similar stress-strain curves with highest tensile strength more than 1000 MPa at both as-cast and solution treated conditions, which corresponded to the slip dominant deformation. Ti–4.5Cr–2.5Mn–1.1Al showed β and a small amount of α′′ phases, and the stress-strain curves with stress-induced α′′ martensite at both conditions, which corresponded to the twin dominant deformation. Ti–10.8Mo–2.3Sn–1.0Al consisted of β and large amounts of α′′ martensite phases and showed the fracture strain more than 35% at both conditions, which corresponded to the martensite dominant deformation. Segregation degree in solidification process showed 4.8 times larger in the Ti–5.5Cr–5.4Mn–5.1Zr–2.8Fe position far from pure Ti position in the Bot-Mdt diagram, compared with that of Ti–10.8Mo–2.3Sn–1.0Al close to the pure Ti position. It was found that as-cast application possibility of both alloys of Ti–5.5Cr–5.4Mn–5.1Zr–2.8Fe and Ti–10.8Mo–2.3Sn–1.0Al could be promising in the view of tension behaviors.
