Strength Of Bulk Metallic Glass Research Articles

Statistical weibull analysis of compressive fracture strength of (Zr55Cu30Al10Ni5)99Nb1 bulk metallic glass

The effect of sample size on the compressive strength of bulk metallic glass with nominal composition of (Zr55Cu30Al10Ni5)99Nb1 has been investigated. Ultrahigh strength ductile bulk metallic glass has been achieved in small dimensions. The variability of compressive strength is also analysed with the aim of weibull statistics. The weibull moduli of 25.5, 17.34 and 4.6 have been calculated for samples with 1, 3 and 5 mm in diameters, respectively. The results showed that the weibull moduli is strongly size dependent. The smaller sample exhibited more uniformity of compressive strength and more reliable in practical application as well.

Molecular dynamics simulation of mechanical characteristics of CuZr bulk metallic glasses using uni-axial tensile loading technique

In the present study, a three-dimensional molecular dynamics simulation is performed to elaborate the mechanical strength of bulk metallic glasses (BMGs). The radial distribution function (RDF) is used to predict the structural disorder that appeared during the quenching provided for BMGs processing. The mechanical behavior is investigated using uniaxial tensile loading through stress–strain curves. It is observed that during tensile loading, the yield strength of Cu50Zr50 increases with the increase in the strain rate, and it quickly attains the maximum value. Soon after the sample fractures without entering into the plastic region. To elucidate the effects of component concentration, we design BMGs with the following three configurations: Cu25Zr75, Cu50Zr50 and Cu75Zr25. It is revealed from the results that samples with a lower Cu concentration have a higher degree of short-range ordering and lower yield strength, and vice versa. To analyze the significance of crystalline–amorphous interfaces, we designed four cylindrical core–shell nanorods with Cu cores and BMGs shells. It is observed that the mechanical strength of the core–shell nanorod is significantly higher compared to the pure BMGs nanorod.

Inherent strength of zirconium-based bulk metallic glass

The polycluster morphology and inherent tensile strength of bulk metallic glass Zr 41Ti 14Cu 12.5Ni 10Be 22.5 in the as-cast state were determined by means of high-field mechanical loading using field ion microscopy. The two-level cluster structure with the length scale of the order of 2 and 10 nm was revealed. It was disclosed that the strength of this alloy is characterized by a strong size-effect in a nanometer scale range. It is shown that within this size region the Weibull distribution is not suitable to describe the scale effect. It is ascertained that the limit level of shear strength of the examined glass is 5.8 GPa, and shear strength of a separate cluster may be estimated as 6.7 GPa.

T0301-2-3 金属ガラスナノワイヤの力学的特性の分子動力学解析([T0301-2]金属ナノ材料の創製と展開(2))

It has recently been observed that metallic glass nanowires are formed during the breaking of bulk metallic glass. Metallic glass nanowires can easily been bent, and their strength is as extremely high as the strength of bulk metallic glass. In this paper, Cu-Zr metallic glass nanowires of amorphous structure are formed in the melt-quench simulations based on the molecular-dynamics method. The uniaxial tensions are imposed on these nanowires. Their Young's modulus and the deformation characteristics are examined.

Fractal network dimension determining the relation between the strength of bulk metallic glasses and the glass transition temperature

[Ma et al., Nat. Mater. 8, 30 (2009)] have uncovered the fractal dimension Df=2.31 associated with the medium-range order in a variety of bulk metallic glasses, reflected in the first sharp diffraction peak q1 determined from neutron and x-ray measurements. Here, based on the proposal in this journal of [Yang et al., Appl. Phys. Lett. 88, 221911 (2006)], which related the strength σy of bulk metallic glasses to the glass transition temperature Tg, we show that the product q1Dfσy is linear in Tg.

Unified equation for the strength of bulk metallic glasses

In the present study, a conceptual approach to evaluate the strength of metallic glass systems is proposed from a free volume point of view. Based on the physical analogy between the plastic deformation and glass transition, the strength of amorphous structures was found to depend on both the localized shear mechanism and the atomic cohesive energy. Interestingly, we find that the strength at the ambient temperature (T0) can be determined by the glass transition temperature (Tg) and molar volume (V), and can be specifically predicted by a unified parameter of (Tg−T0)∕V. The predicted strength was unambiguously verified from experimental data reported for a number of metallic glass systems.