A study of cooling process in bulk metallic glasses fabrication

Yang, Guannan; Shao, Yang; Yao, Kefu; Chen, S. Q.

doi:10.1063/1.4935440

Cited by 16 publications

(5 citation statements)

References 47 publications

(48 reference statements)

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“…The final state of the cast rod depends on a number of factors, including casting temperature T cast , mold temperature T mold , rod diameter, thermal conductivity and thickness of the mold material, and the heat transfer coefficient between the cast rod and the mold. − For the same Zr-based composition, it was confirmed that the formation of a number of eutectoid phases or a fully amorphous structure depends only on T cast . In our case, increasing T cast leads to the formation of two martensitic CuZr phases ( Cm and P 2 1 / m ) and CuZr 2 crystals in rods of 2 and 3 mm diameter (Figure S6).…”

Section: Discussionsupporting

confidence: 55%

Cryo-Casting for Controlled Decomposition of Cu–Zr–Al Bulk Metallic Glass into Nanomaterials: Implications for Design Optimization

Sarac

Kim

Ivanov

et al. 2021

ACS Appl. Nano Mater.

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Cryo-cooled copper-mold suction casting reveals an unexpected phase separation (PS) in Cu46Zr46Al8 bulk metallic glass (BMG) by controlled atomic diffusion. The decomposed alloy cryo-cast to 193 K exhibits a remarkably lower free volume than the alloy cast to room temperature manifested by dilatometry. An unusual endotherm after the onset of relaxation registered by differential scanning calorimetry and compositional homogenization occurring on long time scales upon post-heat treatment even above the glass-transition temperature confirm the stability of the decomposed state against crystallization. As revealed by scanning transmission electron microscopy and energy-dispersive X-ray analysis, single-stage PS (cryo-cast to 193 K) results in distinct and evenly dispersed nanoscale Cu- and Zr-rich regions, whereas two-stage PS (cast to 298 K) involves further decomposition of existing Cu- and Zr-rich regions on a finer scale. Notably, PS accounts for macroscopic compressive plasticity at no expense of fracture strength. This study opens opportunities for the design optimization of homogeneously dispersed amorphous nanostructures of controllable size and composition in BMGs by single- or multistage decomposition through mold temperature control.

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Section: Discussionsupporting

confidence: 55%

Cryo-Casting for Controlled Decomposition of Cu–Zr–Al Bulk Metallic Glass into Nanomaterials: Implications for Design Optimization

Sarac

Kim

Ivanov

et al. 2021

ACS Appl. Nano Mater.

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“…The cooling rate of a plate can be estimated from the finite element modeling of the BMG ingots fabricated by the copper mold casting, where the obtained cooling rates of samples were in a linear agreement with the variation of sample diameter [66]. For the plate geometry, the equation to obtain the cooling rate was slightly modified as:…”

Section: Discussionmentioning

confidence: 99%

Influence of sub-glass transition heat-treatment on physical and structural properties of Cu46Zr44Al8Hf2 metallic glass

Sarac¹

2020

Res. Eng. Struct. Mater.

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The metastability of metallic glasses (MGs) can be altered via post-heat treatment around its glass transition temperature. Here, the influence of the short-term heat treatment slightly below the glass transition on the thermal, thermomechanical, and structural properties are investigated. The water-cooled copper mold casting is used to produce the Cu46Zr44Al8Hf2 MGs under argon gas. Heat treatment was performed by continuous heating at 20 °C/min to 400 °C, followed by immediate cooling. Samples were characterized by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) via continuously heating through its and (crystallization temperature) and by X-ray diffraction (XRD) in Bragg-Brentano (− 2) geometry. Main findings observed are (1) an increase in the thermal stability, − , registered by DMA and DSC, (2) a remarkable drop of the relaxation enthalpy in the DSC trace calculated from the change in specific heat before , (3) appearance of a third broad peak after heat-treatment in XRD, and (4) steady profile of ′ below correlated to the-relaxation in DMA. The unexpected increase in ∆ is linked to the release of the residual stresses accumulated during fast-quenching of the molten ingot down to room temperature. This stress can be estimated as 240 MPa on the outer surface and 100 MPa in the center of the cast CuZr-MG plates, which can be eliminated by the introduced heat-treatment method. Overall, this study suggests a direct and practical way to enhance the thermal stability and high strength retention of CuZr-based metallic glasses at elevated temperatures.

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“…These parameters are temperature dependent. The thermodynamic parameters of the copper mold were set as 400 W/(m•K) for k, 8.9 g/cm 3 for ρ, and 0.39 J/(g•K) for C p , respectively [24]. According to the Archimedes principle, ρ of the Fe-based BMG was about 7.461 g/cm 3 .…”

Section: Numerical Modelmentioning

confidence: 99%

Phase Evolution and Glass Formation in an Fe-Based Alloy

Huang

Shi

Zhang

et al. 2023

Acta Metall. Sin. (Engl. Lett.)

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The understanding of phase competing is of pretty importance in designing high glass-forming systems. In this work, it has been investigated experimentally and theoretically the phase evolution and glass formation of a wedge-casting Fe-based alloy. The results indicated that the phase formation was sensitive to the wedge position, i.e., there were amorphous phase, Fe 2 P, {Fe, Ni} and α-Fe precipitates as well as M 23 B 6 phase at the distances of 3, 10 and 20 mm away from the wedge-tip, respectively. These were closely connected with the variation of cooling rate, embodied in the heat transfer at the solidification process. Furthermore, we constructed the time-temperature-transformation (TTT) diagrams of the iron-based alloy and these crystal phases through calculating R c -related functions. Finally, the glass-forming features of the wedge-shaped Fe-based alloy have been elucidated in accordance with a crystallization kinetics analysis of the recorded temperature data and the phase selection competition. This research provides us an insight into in-depth understanding bulk metallic glass from the perspective of kinetics competition of crystallization phases.

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A study of cooling process in bulk metallic glasses fabrication

Cited by 16 publications

References 47 publications

Cryo-Casting for Controlled Decomposition of Cu–Zr–Al Bulk Metallic Glass into Nanomaterials: Implications for Design Optimization

Cryo-Casting for Controlled Decomposition of Cu–Zr–Al Bulk Metallic Glass into Nanomaterials: Implications for Design Optimization

Influence of sub-glass transition heat-treatment on physical and structural properties of Cu46Zr44Al8Hf2 metallic glass

Phase Evolution and Glass Formation in an Fe-Based Alloy

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