from the conferences organized by TANGER Ltd.
In this study, a commercially acquired Ni-rich (50.0~50.8at% Ni) Ni-Ti shape memory alloy sheet having the thickness of 0.9 mm was cut in the shape of a circle with a diameter of 36 mm and placed in a heated chamber at 800°C for one hour and then quenched in water, which served as a solid solution process affiliated to an annealing process. This sheet blank was then stretch formed with a hemispherical punch of 30 mm in diameter to a stroke 1 mm, 2 mm, 3 mm, and 4 mm, respectively. After removing the punch, the formed part was then put into a furnace for aging treatment at 300°C for one hour and subsequently quenched in water. As a result, for smaller punch strokes the sheets could not be well formed, because the maximum strain presented in the alloy was little bit over the elastic region. After the aging process, the heights of the formed sheets were extra shortened because of a further springback. The springback after stretch forming and during aging can be compensated by modifying the punch radius, so that a tolerable shape with shape memory effect can be achieved with only one die set. Furthermore, if the sheet part was immersed in liquid nitrogen basin to have its martensitic phase and compressed into a flat shape, the original shape of the part can be fully recovered by returning to room temperature.
Keywords: Ni-Ti Shape Memory Alloy, Sheet Metal Forming, Stretch Forming, Shape Memory© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.