An experimental analysis of the dieless drawing process (Variant B) using ELI grade Ti-6AL-4V wire alloy

Dieless drawing is a novel forming process which enables a workpiece to be reduced in a cross-sectional area without using conventional multipass dies. This paper reports on a series of dieless drawing (Variant B) experiments on ELI grade Ti-6AL-4V. A sample of the titanium alloy wire was fixed at one end and loaded in tension by the application of a specific velocity, V₁, at the other end. Simultaneously, a heating and cooling device travelled along the longitudinal length of the sample with a velocity V₂. The deformation process utilized the mechanics of superplasticity to take advantage of the reduction in flow stress caused by the temperature increase. First, the suitability of ELI Ti-6AL-4V to the process of dieless wire drawing was considered by determining the materials strain rate sensitivity index m, the measure of a material's ability to deform in a superplastic manner. It was determined that this material had an m value of 0.45 within a narrow strain rate band of 10^-4-10^-2/s at a temperature of 950°C. Second, a comprehensive series of experiments was carried out to determine the dieless drawing variables of Variant B. Results indicated that the dieless drawing process is capable of producing up to 40 per cent reductions per pass but the process is dependent upon both the ratio of V₁/V₂ and the separation distance between the heating and cooling devices, S. It was also established that there was a direct relationship between the wire diameter variation (maximum-minimum wire-drawn diameter) and the V₁/V ₂ ratio. The experimentally determined results showed good agreement with a mathematical model proposed by Gliga and Canta. A mathematical analysis was undertaken to determine the temperature distribution within the heated sample.