THE INFLUENCE OF AGGRESSIVE ENVIRONMENT AND ELECRO-IMPULSE IMPACT ON FATIGUE CHARACTERISTICS OF METALLIC GLASS

The authors carried out the fatigue tests for the tension of metallic glass tape samples by the load varying in time from some maximum value to minimum, in a constant-sign cycle with the frequency of 2 Hz. In the device construction, five sets of elastic elements with different stiffness coefficients are designed. For the elastic elements, the calibration graphs were constructed, according to which the stress in the sample was determined by the displacement value. Characteristic features of the development of fatigue cracks in the samples of cobalt-based amorphous alloys and iron-based nanocrystalline alloy were determined. The study determined the area of the fatigue crack nucleation, its growth and the break area. It is identified that the viscous destruction with the formation of densely spaced microtights takes place in the area of crack initiation, and in the area of the fatigue crack growth, its development similar to a cleavage with the formation of the developed “venous pattern” and the densely spaced shear bands formed when fatigue cracks stop occurs. The pop-in magnitude is 0.2-0.5 pm. In the break area, the crack propagates viscously, irregularly, with the formation of localized plasticity areas at the stops. For the samples, Weller curves are plotted and the fatigue limits are defined.

The authors carried out the investigations of the aggressive environments influence and the pulsed electric current preliminary impact on the fatigue properties of the amorphous metal alloys. It is determined that the samples, after the action of a pulsed current or an aggressive environment, are destroyed during fewer loading cycles relating to the initial samples. It is noted that the Co content in the samples under the study slightly influences the fatigue properties.