•Fe–B amorphous alloys are designed with a cluster-plus-glue-atom model.•Best thermal stability and glass-forming ability are reached at the model compositions.•Double cluster model is proposed to describe the structure of Fe–B amorphous alloys.•Local structural similarity between metastable Fe3B and stable Fe2B is discussed.Fe–B binary alloys constitute the basis of many Fe-based metallic glasses with superior glass forming abilities and soft magnetic properties. The present work is devoted to understanding the composition rule of Fe–B binary amorphous alloys using the cluster-plus-glue-atom model and the relevant composition formula theory. According to this model, an ideal metallic glass is based on a chemical building block composed of a first-neighbor coordination polyhedral cluster plus one or three glue atoms, and the total number of valence electrons per unit formula is close to 24. For the Fe–B system, the principal cluster [B–B2Fe8], which enters into the composition formula for metallic glasses, is derived from the eutectic phase BFe2 (Al2Cu-type). This cluster, after being glued with one Fe atom, produces a cluster formula [B–B2Fe8]FeB3Fe9Fe75B25 that presents nearly 24 valence electrons. Experimental verification was then carried out, and at the anticipated composition, the crystallization temperature and glass-forming ability indicator α was the highest, indicating the best thermal stability and glass-forming ability. The crystallization behavior and structure characteristics of Fe–B binary amorphous alloys were also discussed.

•Fe–B–Si–Zr metallic glasses are designed with a cluster-plus-glue-atom model.•Bulk glassy rods with diameters 1.5–2.5 mm are reached at the model compositions.•These glassy alloys show wide supercooled liquid regions exceeding 30 K.•These glassy alloys exhibit fracture strengths of 3800–3900 MPa.•These glassy alloys exhibit high Ms (1.26–1.48 T) and low Hc (1.6–6.7 A/m).The present work is devoted to fabrication of Fe–B–Si–Zr multi-component bulk glassy alloys with good mechanical and soft magnetic properties. Glass formation in Fe–B system is first considered with an empirical cluster-plus-glue-atom model. A basic composition formula [B–B2Fe8]Fe is proposed as the framework for multi-component alloy design. Considering the structural stability of the model glass, Si and Zr are introduced to the [B–B2Fe8] cluster to replace the center B and shell Fe atoms, from which a series of Fe–B–Si–Zr alloys with composition formulas [Si–B2Fe8−xZrx]Fe (x = 0–0.6) are derived. Copper mold casting experiment shows that bulk glassy alloys are formed within the Zr content range of x = 0.2–0.6, and the largest glass-forming ability appears at [Si–B2Fe7.6Zr0.4]Fe with a critical size of 2.5 mm. The bulk glassy alloys exhibit high fracture strength as large as 3850 MPa. Magnetic property measurement indicates that these alloys exhibit good magnetic softness with high saturation magnetization (1.26–1.48 T) and low coercive force (1.6–6.7 A/m). The alloying effects of Si and Zr on bulk glass formation, thermal glass stability and magnetic softness are discussed with the empirical model.

The composition characteristics of maraging stainless steels were studied in the present work investigation using a cluster-plus-glue-atom model. The least solubility limit of high-temperature austenite to form martensite in basic Fe–Ni–Cr corresponds to the cluster formula [NiFe12]Cr3, where NiFe12 is a cuboctahedron centered by Ni and surrounded by 12 Fe atoms in FCC structure and Cr serves as glue atoms. A cluster formula [NiFe12](Cr2Ni) with surplus Ni was then determined to ensure the second phase (Ni3M) precipitation, based on which new multi-component alloys [(Ni,Cu)16Fe192](Cr32(Ni,Mo,Ti,Nb,Al,V)16) were designed. These alloys were prepared by copper mould suction casting method, then solid-solution treated at 1273 K for 1 h followed by water-quenching, and finally aged at 783 K for 3 h. The experimental results showed that the multi-element alloying results in Ni3M precipitation on the martensite, which enhances the strengths of alloys sharply after ageing treatment. Among them, the aged [(Cu4Ni12)Fe192](Cr32(Ni8.5Mo2Ti2Nb0.5Al1V1)) alloy (Fe74.91Ni8.82Cr11.62Mo1.34Ti0.67Nb0.32Al0.19V0.36Cu1.78 wt%) has higher tensile strengths with YS=1456 MPa and UTS=1494 MPa. It also exhibits good corrosion-resistance in 3.5 wt% NaCl solution.

Crystallization of Ni60Ta40 and Ni60Nb40 metallic glasses at temperatures well below their respective calorimetric glass transition temperatures has been studied by differential scanning calorimetry, nanodiffraction, and electron microscopies. Nanometer-scaled metastable FCC phases were found to grow out from the glass structures. The Z-contrast images reveal that the nanocrystals are enriched in Ta or Nb in comparison with the surrounded amorphous structures. The experimental evidence is suggestive of the decoupled cooperative diffusion of Ni atoms in these fragile glasses.

The present work is devoted to the development of Fe-(B-Si)-Zr amorphous alloys with high glass-forming ability and good magnetic properties. Using the cluster-plus-glue-atom model proposed for ideal amorphous structures, [FeFe11B3Si](Fe1−xZrx) was determined as the cluster formula of Fe-(B-Si)-Zr alloys. The glass formation and thermal stability of the serial alloys, namely, [FeFe11B3Si](Fe1−xZrx) (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.75, and 1.0), were studied by the combination of copper mold casting, X-ray diffraction, and differential thermal analysis techniques. The maxima of glass-forming ability and thermal stability were found to occur at the compositions of [FeFe11B3Si](Fe0.6Zr0.4) and [FeFe11B3Si](Fe0.5Zr0.5). The alloys can be cast into amorphous rods with 1.5 mm diameter, and upon reheating, the amorphous alloys exhibit a large undercooled liquid span of 37 K. The saturation magnetization of the [FeFe11B3Si](Fe0.5Zr0.5) amorphous alloy was measured to be 1.4 T.

Six series of alloys, namely, Ni3Zr6Alx, Ni3Zr7Alx, Ni4Zr9Alx, Ni3Zr8Alx, Ni3Zr9Alx and Ni3Zr10Alx (x=1, 1.5, 2, 3) were designed in this work and the bulk metallic glass (BMG) formation of these compositions was investigated by copper mold suction casting. A centimeter-scale BMG sample was obtained for the Ni4Zr9Al2 (Al13.3Ni26.7Zr60 in atomic percent) composition. The thermal glass parameters for this BMG were determined to be ΔTx = 68 K, Trg = 0.579, and γm = 0.689. Using the ‘cluster-resonance’ model for glass formation an optimal BMG composition was determined using the cluster formula [Ni3Zr9](Al2Ni1).

The formation of Ni-based ternary Ni-Nb-Ta bulk metallic glasses (BMGs) is explored in this work. Alloy compositions are designed by the cluster-plus-glue atom model based on a eutectic-related binary cluster Ni-Ni6Nb6, which is derived from the binary eutectic crystalline phase NiNb (Fe7W6 type). According to the cluster-plus-glue atom model, the well-known binary BMG-forming composition Ni62Nb38 can be described by a composition formula [Ni-Ni6Nb6]Ni3 = Ni62.5Nb37.5. With an aim to further improve the glass-forming ability of the Ni-Nb alloy, Ta is selected as an alloying addition to partially replace Nb in the [Ni-Ni6Nb6]Ni3 composition formula. The experimental results verified that BMGs with a critical size of 3 mm can be achieved at compositions [Ni-Ni6Nb6−xTax]Ni3 (x = 0.9 ∼ 1.1). Thermal and mechanical properties of the obtained BMG alloys are also investigated.

The present paper reports on the thermal stability and activation energy of crystallization of bulk metallic glasses (BMGs) (Cu61.8Zr38.2)1−xAlx. The (Cu61.8Zr38.2)1−xAlx composition series, prepared by copper mould suction casting into bars with a diameter of 3 mm, form BMGs with an e/a range of 1.24–1.3. These BMGs manifest increased thermal stability with increased e/a ratios. The activation energies (ΔE) of crystallization as derived from thermal analysis at different heating rates follow a similar tendency to that of the thermal stability, indicating stronger short-range ordering with increasing e/a ratios. The optimum BMG Cu58.1Zr35.9Al6 exhibits the highest thermal stability and the largest ΔE.

The present paper reports on the thermal stability and activation energy of crystallization of bulk metallic glasses (BMGs) (Cu61.8Zr38.2)1−xAlx. The (Cu61.8Zr38.2)1−xAlx composition series, prepared by copper mould suction casting into bars with a diameter of 3 mm, form BMGs with an e/a range of 1.24–1.3. These BMGs manifest increased thermal stability with increased e/a ratios. The activation energies (ΔE) of crystallization as derived from thermal analysis at different heating rates follow a similar tendency to that of the thermal stability, indicating stronger short-range ordering with increasing e/a ratios. The optimum BMG Cu58.1Zr35.9Al6 exhibits the highest thermal stability and the largest ΔE.