Induction heating and cryogenic cooling in single point incremental forming of Ti-6Al-4V: process setup and evolution of microstructure and mechanical properties

Abstract

Hot single point incremental forming (SPIF) with induction heating and cryogenic cooling has been applied to form the Ti-6Al-4V sheets. The influence of both the forming temperature and the cooling rate after deformation, on microstructure evolution and microhardness of Ti-6Al-4V sheets, has been extensively studied. We propose the use and development of a new system of heating by induction. The system is composed of a medium–high frequency generator and a continuously water-cooled heating head, which is placed under the sheet and linked axially to the punch movement, heating the material locally by generating an eddy current within the material. Furthermore, a cooling system integrated with the movement of the forming punch allows us to apply a cryogenic fluid to the recently deformed sheet metal. Both localized heating and cooling systems are particularly suitable for such a process as SPIF, whose primary characteristic is the incremental forming of localized sheet zones. The meta-dynamic and static recrystallization processes have been suppressed in the sheet material, evident by the final microstructure and mechanical properties. Finally, a comparison between parts is made, both with and without cooling during hot SPIF.