Mechanical properties of structural amorphous steels: Intrinsic correlations, conflicts, and optimizing strategies

Abstract

Communication: Correlation of the instantaneous and the intermediate-time elasticity with the structural relaxation in glassforming systemsAmorphous steels have demonstrated superior properties and great potentials for structural applications since their emergence, yet it still remains unclear about how and why their mechanical properties are correlated with other factors and how to achieve intended properties by designing their compositions. Here, the intrinsic interdependences among the mechanical, thermal, and elastic properties of various amorphous steels are systematically elucidated and a general trade-off relation is exposed between the strength and ductility/toughness. Encouragingly, a breakthrough is achievable that the strength and ductility/toughness can be simultaneously improved by tuning the compositions. The composition dependences of the properties and alloying effects are further analyzed thoroughly and interpreted from the fundamental plastic flow and atomic bonding characters. Most importantly, systematic strategies are outlined for optimizing the mechanical properties of the amorphous steels. The study may help establish the intrinsic correlations among the compositions, atomic structures, and properties of the amorphous steels, and provide useful guidance for their alloy design and property optimization. Thus, it is believed to have implications for the development and applications of the structural amorphous steels. V C 2013 AIP Publishing LLC. [http://dx.

Synthesis of CoCrMoCB bulk metallic glasses with high strength and good plasticity via regulating the metalloid content

“…On the other hand, it has been pointed out that electrons could transfer from the metalloid atom to fill the "d" shells of transition metal atom, then s-d hybrid bonding is formed [4,26]. Because C owns one more bonding electron and higher electronegativity than B (2.55 for C, 2.04 for B), the character of transition metal-C bonding is stronger than that of transition metal-B bonding [12,13]. So the transition metal-C bonding will reinforce the amorphous structure.…”

“…The results (not shown) reveal that the metalloid dependence of σ y is analogous to that of σ c (mainly depends on C C ), and the metalloid dependence of E or K is analogous to that of G (mainly depends on C B ). A general view is that amorphous structure can be approximately described as the stiff solute-centered clusters (short-range order) or superclusters (medium-range order) embedded in the solvent atoms with relatively loose bonding [12,30,32]. Therefore, it is expected that the amorphous structures of the present alloys are regarded as B/C-centered clusters and metal solvent atoms.…”

“…The atomic bonding character between metalmetalloid atoms is more covalent-like [2,10]. This has a strong influence on the activation energy barrier of the fundamental flow units or the global bonding strength [11,12], and additionally, affects the GFA and macroscopic mechanical properties of BMGs [13][14][15][16][17]. On the other hand, both the GFA and mechanical properties are also influenced by the degree of dense randomly packed atomic configuration [4,[16][17][18].…”

Intrinsic factor controlling the deformation and ductile-to-brittle transition of metallic glasses

“…In a similar manner, here, the detailed shearing modes of various MGs are also classified into different types depending on the parameter δ. For the Fe-and Co-based MGs which usually display a typical δ in the range 1\d\ve=2, the shearing, although still prevailing over cracking, can be regarded as crack-like as it tends to develop through sparse shear bands with low stability and a high cavitation trend [16,34]. In contrast, for MGs with a high value of δ (d [ e) such as those based on noble metals, the shearing typically advances through uniformly distributed multiple shear bands with high stability [2,11].…”

Effect of Boron Additions on Glass Formation and Magnetic Properties of Fe-Co-Ti-Zr-B Amorphous Ribbons

“…In general, it is well known that the contents of metalloid elements, such as P, C, Si, and B, play a significant role in the formation of metallic glasses in the Fe-based amorphous alloys [10][11][12][13]. In particular, due to atomic interaction and large atomic size differences between B and transition metals, the suitable ratios of B to transition metals, such as Fe, Co, and Ni, lead to the enhancement of its GFA and thermal stability of amorphous alloys.…”