Enhancing hoop strength of titanium alloy tube by cross spinning

There is an increasing demand for thin-walled long tubular workpieces of titanium alloys with excellent mechanical properties, which can be produced by power spinning owing to its specific advantages over other forming processes. In this paper, a novel spinning forming process, named cross spinning (CS), was proposed to tune the hoop properties of as-spun tubular workpieces. Traditional unidirectional spinning (UDS) and CS experiments were conducted to form the tubular workpieces of Ti-6Al-4V alloy, and their mechanical properties and microstructure evolution were analyzed and compared. The tensile test indicated that both axial and tangential strengths of the CS specimens were higher than that of the UDS specimens, which was more remarkable for the tangential strength. To clarify this phenomenon, crystal plasticity finite element method (CPFEM) coupled with spinning texture information was used to simulate the tensile test for the CS and UDS specimens. The results indicated that a more homogeneous texture was formed during CS, inducing lower average Schmid factor for prismatic slip system and larger activities of the pyramidal slip systems, was the major cause for enhancing the hoop mechanical properties of the as-spun workpieces compared with that during UDS.