Extreme rejuvenation and softening in a bulk metallic glass

Abstract

Rejuvenation of metallic glasses, bringing them to higher-energy states, is of interest in improving their plasticity. The mechanisms of rejuvenation are poorly understood, and its limits remain unexplored. We use constrained loading in compression to impose substantial plastic flow on a zirconium-based bulk metallic glass. The maximum measured effects are that the hardness of the glass decreases by 36%, and its excess enthalpy (above the relaxed state) increases to 41% of the enthalpy of melting. Comparably high degrees of rejuvenation have been reported only on microscopic scales at the centre of shear bands confined to low volume fractions. This extreme rejuvenation of a bulk glass gives a state equivalent to that obtainable by quenching the liquid at ~1010 K s–1, many orders of magnitude faster than is possible for bulk specimens. The contrast with earlier results showing relaxation in similar tests under tension emphasizes the importance of hydrostatic stress.

Aging and rejuvenation during elastostatic loading of amorphous alloys: A molecular dynamics simulation study

“…Thus, it was demonstrated experimentally that the elastostatic compression of Zr-based bulk metallic glasses leads to a significant increase in enthalpy, which is comparable with the states produced upon very fast quenching from the liquid state or by severe plastic deformation [15]. Furthermore, upon increasing stress, a transition from relaxation to rejuvenation in metallic glasses subjected to elastostatic compression was observed [14].…”

“…Alternatively, in cases when the shape change due to flow is not important, higher energy states can be attained by reheating amorphous alloys above the glass transition temperature followed by suitably fast cooling back to the glass state [4][5][6][7]. Somewhat unexpectedly, a convenient and efficient method to enhance the potential energy of a glass is to simply apply a static stress in the elastic range and let the system accumulate irreversible structural transformations [8][9][10][11][12][13][14][15][16].…”

Heat Effects Occurring in the Supercooled Liquid State and Upon Crystallization of Metallic Glasses as a Result of Thermally Activated Evolution of Their Defect Systems

“…Besides that, any physical impact (thermal cycling, plastic deformation, irradiation, etc.) leads to certain additional heat effects in MGs [2][3][4].…”

Accelerated relaxation in disordered solids under cyclic loading with alternating shear orientation

“…There are a number of experimental techniques that can be used to increase the stored energy; namely, high pressure torsion, ion irradiation, wire drawing, and shot peening. Moreover, it was shown that prolonged static loading below the yield stress can induce either irreversible structural rearrangements or the formation of nanocrystals in the metallic glass matrix, leading to improved plasticity [5][6][7][8][9][10][11]. Alternatively, aged glasses can be rejuvenated by recovery annealing above the glass transition temperature and then cooled down with a suitably fast rate [12][13][14][15][16].…”