Fine colonies promote twinning-induced large plasticity in cast Ti-64 alloy

Ti-6Al-4 V (Ti-64) alloy specimens were prepared using two distinct casting methods, gravity casting and centrifugal casting. The room-temperature tensile results demonstrate that the strength of the alloys prepared by the two casting methods is comparable, but the plasticity of the latter (16 %) is twice as great as that of the former (8 %). Microstructural analysis reveals that the α colony size within the centrifugally casting alloy was smaller, which promoting the formation of {10–12} < -1011 > tensile twins. It in turn favors the plasticity of casting Ti-64 alloy. Basal dislocations are generated within the twin, which decompose at the interface at the tip of the twin causing the interface to shift forward. This is not only indicative of the twin's role in coordinating deformation but also serves as a mechanism for the further growth of the twin.