Embrittlement of Zr-based bulk metallic glasses

Shear transformation zone volume determining ductile–brittle transition of bulk metallic glasses

“…Tabachnikova et al [12] have shown that with the temperature decrease to 77 K from room temperature, both the compressive strength and plasticity of Zr 64. 13 225 at 77 K might also be ascribed to the decrease of the STZ volume due to low temperature, where nano-scaled "chevron" patterns rather than vein patterns on the low temperature fracture surface indicate an apparent decrease in the plasticity [7]. While for other BMGs [49][50][51][52][53][54][55] with both enhancements of yield strength and plasticity under compression when the test temperatures decrease from room temperature to liquid nitrogen temperature (77 K), a lower test temperature might introduce a brittle failure, i.e.…”

“…It is therefore expected that these materials should not undergo DBT process. However, the DBT phenomena, as first reported by Wu and Spaepen [6], have been widely observed in metallic glasses [7][8][9][10][11][12][13][14][15][16]. Due to the practical and scientific significance of this behavior, it has attracted much attention.…”

“…For example, Lewandowski et al [14,15] correlated the fracture energy of a number of different glasses with Poisson's ratio m and reported a sharp DBT at the critical m = 0.31-0.32. Kumar et al [13] argued that the embrittlement of BMGs subjected to annealing below and above the glass transition temperature was due to structural relaxation and crystallization, respectively. Very recently, the Ramamurty group [16] performed a series of impact toughness tests on as-cast and structurally relaxed Zr-based BMGs at various temperatures.…”

“…Due to the practical and scientific significance of this behavior, it has attracted much attention. Possible factors such as free volume [6], strain rate sensitivity [8], Poisson's ratio [14,15] and structural relaxation [11,13] have been thought to be responsible for it. For example, Lewandowski et al [14,15] correlated the fracture energy of a number of different glasses with Poisson's ratio m and reported a sharp DBT at the critical m = 0.31-0.32.…”

Thermal and soft magnetic properties of Co40Fe22Ta8B30 glassy particles: In-situ X-ray diffraction and magnetometry studies

“…The latter involves a long-range rearrangement of atoms associated with the redistribution and reduction of the excess free volume. 2 The decrease of the free volume upon annealing results in higher viscosity, 5 density, 6 and tensile strength, 7 lower plasticity, 7,8 and better soft magnetic properties. 9 Hence, characterization of the excess free volume is important for understanding the relationship between the atomic structure and properties of MGs.…”