Effects of Changes in Chemistry on Flex Bending Fatigue Behavior of Al-Based Amorphous Alloy Ribbons

The effects of changes in composition on the flow behavior and flex bending fatigue behavior of a series of Al-Gd-Ni-X (X = Fe or Co) amorphous alloy ribbons have been determined at 1 Hz at room temperature. It has been shown that the addition of Fe, Co, and Fe/Co combination into these materials increases the strength, T _g, and T _x1 in addition to the activation energy for crystallization. The lowest strength (i.e., 880 MPa) base alloy Al₈₇Gd₆Ni₇ exhibited the best low-cycle fatigue (LCF) and worst high-cycle fatigue (HCF) behavior, whereas the higher strength alloys (~1100 MPa) Al₈₅Gd₆Ni₇Fe₂ and Al₈₅Gd₆Ni₇Fe₁Co₁ exhibited worse LCF and better HCF behavior. The ratio of the stress amplitude at the fatigue limit at 1 × 10⁶ cycles to uniaxial failure strength ranged from 0.25 to 0.37 (240 to 397 MPa), much higher than conventional aluminum alloys. These results are also compared with those obtained on other amorphous alloy ribbons.