Deformation behaviour of chromium sheets in mechanical and laser bending

Chromium is known to have limited room-temperature ductility but to exhibit apparent ductile-to-brittle transition behaviour at temperatures ranging from 150 to 300 °C. In this paper, the deformation behaviour of a chromium sheet was investigated in roll-compression and laser bending. Tensile tests and three-point bending tests were performed also to determine the basic mechanical properties of the chromium sheet. The ductile-to-brittle transition temperature of the chromium determined by the tensile test was found to be 180 °C. While the sheet could be bent to 90° at a temperature of 130 °C in three-point bending, it was possible to bend the sheet to the same bending angle at a lower temperature (100 °C) in roll-compression bending, the presence of compressive stress in roll-compression bending being considered to be the reason for the difference in the temperatures. A finite element stress analysis was also conducted to reveal the stress distribution of the chromium sheet in roll-compression bending. Laser bending was demonstrated to be a possible process to deform chromium sheets. A threshold laser power of 40 W is observed, below which bending is unlikely to occur. The bending angle was found to increase with increasing laser power and number of irradiations, and decreasing scanning velocity.