Cyclic cryogenic pretreatments influencing the mechanical properties of a bulk glassy Zr‐based alloy

Abstract

In this study, cryogenic thermal cycling was applied to bulk glassy Zr52.5Cu17.9Al10Ni14.6Ti5 (Vitreloy 105) bending samples. After that, significantly improved plasticity and better fatigue properties at three‐point bending as well as higher impact toughness were measured in dependence of the duration and the cooling rate of the thermal cycling process. This improved material behaviour is caused by reinforced shear banding, visible in scanning electron microscopy at the side faces of the specimens after fracture. A comprehensive analysis of the fracture surfaces of both quasi‐static and cyclic bent specimens revealed intense crack propagation along major shear bands and increased fatigue fracture regions, respectively. It is supposed that there is a structural rejuvenation due to the local variations of the thermal expansion coefficients within the multicomponent alloy affecting the mechanical properties.

The effect of cryogenic thermal cycling on aging, rejuvenation, and mechanical properties of metallic glasses

“…Remarkably, recent experimental studies on metallic glasses have demonstrated that cryogenic thermal cycling can induce rejuvenation that leads to less relaxed states of higher energy and improved plasticity [4][5][6][7][8]. It was argued that atomic-scale structural rejuvenation upon thermal cycling might be caused by internal stresses that arise due to spatially heterogeneous thermal expansion of the amorphous material [9].…”

Potential energy states and mechanical properties of thermally cycled binary glasses

“…In recent years, a number of methods were proposed to enhance plasticity of metallic glasses, such as addition of chemical heterogeneities [5,6] or a soft second phase [7]. A less intrusive way to tune the amorphous structure is to apply cryogenic thermal cycling that can induce rejuvenation due to heterogeneity in the local thermal expansion and therefore improve plasticity [8][9][10][11][12][13]. Using atomistic simulations, it was recently shown that internal stresses due to thermal expansion can in principle trigger a plastic event in sufficiently large systems [14].…”

Modulating fatigue property of in situ Ti‐based metallic glass composites by changing dendrite composition

“…The long‐range disordered structure in the molten liquid will be preserved, and accordingly, no microdefects like dislocations and grain boundaries can be formed 1 . This unique structure renders that the highly strain‐localized shear bands become the main mechanism dominating the plastic deformation and also play a key role in the fatigue crack initiation and propagation in MGs 2–4 . The fast propagation and failure of the individual shear band usually deteriorate the mechanical properties such as the nearly zero global tensile plasticity and low fatigue resistance, which severely restricts the potential applications as structural materials 5–7 …”

“…1 This unique structure renders that the highly strain-localized shear bands become the main mechanism dominating the plastic deformation and also play a key role in the fatigue crack initiation and propagation in MGs. [2][3][4] The fast propagation and failure of the individual shear band usually deteriorate the mechanical properties such as the nearly zero global tensile plasticity and low fatigue resistance, which severely restricts the potential applications as structural materials. [5][6][7] One intrinsic method of overcoming these problems is to develop the MG composites (MGCs) by introducing a "microstructure" (such as crystalline dendrites, particles, and fibers) into the MG matrix, which can interact with the shear banding behaviors and constrain the propagation of the individual shear band.…”