Formability of titanium alloy sheets by friction stir incremental forming

This paper investigates the behavior of titanium formability when forming under localized friction heating, caused by high tool rotation. In accordance with planned experiments, different process conditions at various tool rotations, feed rates, and step-down sizes were investigated. The experiments were carried out on 1 mm thick Ti6Al4V alloy sheets, using an 11 mm diameter, ball-ended tooltip. The rotational speeds were designed to create sufficient thermal effect, while maintaining high lubricity at the forming interface. Moderate tool rotational speed (2000 rpm) tends to improve formability, reduce the forces, and lower the rate of tool wear. The experimental procedures are presented, and an extensive discussion of the results is reported.