Microstructural and microhardness variation of amorphous Fe₇₈Si₉B₁₃ alloy during bend stress relaxation

The amorphous Fe₇₈Si₉B₁₃ ribbons were bend stress relaxed at various temperature well below the crystallization temperature (T_x) for different time. The effect of pre-annealing on the subsequent bend stress relaxation was examined. The variation of the microstructure and microhardness during bend stress relaxation process was studied using X-ray diffraction (XRD), atomic force microscopy (AFM) and Vickers microhardness test, respectively. Curvature radius of the amorphous Fe₇₈Si₉B₁₃ ribbons decreased with increase bend stress relaxation temperature and time. The microhardness of the stress relaxed specimens increased with time at 300°C due to the forming of nanocrystals during bend stress relaxation. The pre-annealing reduced the decrease rate of the curvature radius of stress relaxed specimens.