Influence of cyclic loading on the structure and double-stage structure relaxation behavior of a Zr-Cu-Fe-Al metallic glass

The thermal and mechanical relaxation spectra of a Zr-Cu-Fe-Al bulk metallic glass were obtained before and after room-temperature cyclic loading up to 0.4% of elastic strain. The loading was performed using a dynamic mechanical analyzer at an oscillation frequency of 3 Hz to induce the structural changes within the glassy phase at room temperature. A double-stage structure relaxation behavior was monitored using the same dynamic mechanical analyzer at a lower strain on heating. These structure changes within the glassy phase were studied with X-ray diffractometry and high-resolution transmission electron microscopy. The cycling loading at room temperature lead to drastic changes in the atomic structure of the bulk metallic glassy samples. In particular, it caused partial nanocrystallization after 10,000 elastic cycles, which in turn influenced the relaxation behavior. The structural relaxation process of the Zr-Cu-Fe-Al bulk metallic glass monitored by thermal measurements is different from that observed by the dynamic mechanical analysis.