BENDING OF AMORPHOUS-ALLOYS

Fe-based and Ni-based amorphous foils with thicknesses of 25-30 mum have been used for bending experiments. First, the mechanical and physical properties of the foils were measured, after which bending experiments were carried out by four bending methods, i.e., conventional V-bending, L-bending with a lateral force, multi-stage V-bending and V-bending with a soft metal. SEM observations have been made to look for shear bands and crack initiation along the bend lines. The maximum strain caused by bending is greater than that of the uniaxial tension test, the temperature rise being effective in suppressing crack initiation. The relationship between the bending condition and the bend angle has been obtained for each bending method. As a result, the superiority of multi-stage V-bending and V-bending with a soft metal to the two other methods is established, crack initiation is prevented, and the minimum spring-back angles for these methods are 4-degrees and 6-degrees, respectively, in the case of Ni-based amorphous bending (alpha=90-degrees). As for V-bending with a soft wire, the bending mechanism is elucidated by computer simulation. The high accuracy bending of this method can be attributed to the application of hydrostatic pressure through the soft metal and the bending deformation occurring under the stress state of tension.