Applicability of As-Cast on beta Type Titanium Alloys Proposed in the Compositional Region with Different Tensile Deformation Types

摘要

Three beta type titanium alloys were proposed for as-cast applications in practical fields on the basis of the d-electrons parameters with both bond order (Bo(t)) and d-orbital energy level (Md-t). Ti-5.5Cr-5.4Mn-5.1Zr-2.8Fe with the lowest Md-t, Ti-4.5Cr-2.5Mn-1.1Al with the lowest Bo(t) and Ti-10.8Mo-2.3Sn-1.0Al with the highest Md-t were designed by using ubiquitous elements in the predicted regions showing the slip, twin and martensite dominant deformation behaviors in the Bo(t)-Md-t diagram, respectively. Their ingots were produced by the cold crucible levitation melting technique. Ti-5.5Cr-5.4Mn-5.1Zr-2.8Fe showed mono beta 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 beta and a small amount of alpha '' phases, and the stress-strain curves with stress-induced alpha '' martensite at both conditions, which corresponded to the twin dominant deformation. Ti-10.8Mo-2.3Sn-1.0Al consisted of beta and large amounts of alpha '' 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 Bo(t)-Md-t 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.