Strain Rate Induced Crystallization in Bulk Metallic Glass-Forming Liquid

Lohwongwatana, Boonrat; Schroers, Jan; Johnson, William L.

doi:10.1103/physrevlett.96.075503

Cited by 53 publications

(38 citation statements)

References 44 publications

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Section: Bonding Of Brittle Materialsmentioning

confidence: 99%

“…To verify this, one would need to work out the thermal history of the interfacial region [89,92], which is determined by the interplay between the heat conduction and the heat generation by deformation. Such an analysis is complicated becuase the incubation time for crystallization decreases drastically with increasing strain rate [94,95].Interestingly, the deposition efficiency of BMGs passes through a maximum by increasing the process gas temperature or pressure [87,96]. More severe process conditions lead to particle detachment and rebound [97,96].…”

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Cold spraying – A materials perspective

et al. 2016

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Cold spraying is a solid-state powder deposition process with several unique characteristics, allowing production of coatings or bulk components from a wide range of materials. The process has attracted much attention from academia and industry over the past two decades.The technical interest in cold spraying is twofold: first as a coating process for applications in surface technology, and second as a solid-state additive manufacturing process, offering an alternative to selective laser melting or electron beam melting methods. Moreover, cold spraying can be used to study materials behaviour under extremely high strain rates, high pressures and high cooling rates. The cold spraying process is thus considered to be relevant for various industrial applications, as well as for fundamental studies in materials science.This article aims to provide an overview of the cold spray process, the current understanding of the deposition mechanisms, and the related models and experiments, from a materials science perspective. IntroductionCold spraying (CS) is a solid-state material deposition technique, where micron-sized particles of a powder bond to a substrate as a result of high-velocity impact and the associated severe plastic deformation. Acceleration of particles to high velocities is obtained via expansion of a pressurised and (ironically) 'hot' gas through a diverging-converging nozzle.Despite heating the process gas -which is to provide higher acceleration of the gas and also to facilitate particle deformation through thermal softening -the feedstock remains in the solid state throughout the entire process; hence the name 'cold' spraying. This is to underline the contrast to conventional thermal spraying where particles are completely or partially molten upon impact onto the substrate. Alternative terminology includes cold gas spray, micro cold spray, cold gas dynamic spray, kinetic spray, supersonic particle deposition and metal powder application (MPA), all of which refer to the same principle of solid-state powder deposition as described above. CS is used for coating and repair. It is also used for additive manufacturing (AM) at relatively high deposition rates as compared to the methods based on selective laser or electron beam melting. The main advantage of CS is that it alleviates the problems associated with high temperature processing of materials, such as oxidation and unfavourable structural changes. It is possibly the only continuous method to produce bulk components of metastable materials that are available only in the powder form, e.g. as obtained from mechanical attrition or gas atomisation. The aim of the present paper is to provide an overview of CS from a materials perspective, particularly for a broader audience in materials research, e.g. with interest in dynamic phenomena, plasticity and phase transformations. In terms of application and properties, CS is perhaps best to be compared to thermal spraying processes, as in [24,25]. In view of relevant physical phenomena, however, CS is mos...

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Section: Bonding Of Brittle Materialsmentioning

confidence: 99%

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Cold spraying – A materials perspective

et al. 2016

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“…Crystallization is typically triggered by nucleation of a particular crystalline phase, followed by other competing phases, often catalyzed by the presence of the first phase. Crystal nucleation rates depend not only on temperature, pressure, and alloy composition, but also on extrinsic factors such as the presence of chemical impurities, trace crystalline debris (e.g., oxide inclusions), container wall effects, or shear flow conditions in the liquid, to name a few (3)(4)(5)(6)(7). Variations in these extrinsic factors often lead to inconsistent and nonreproducible GFA.…”

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Compositional landscape for glass formation in metal alloys

Na¹,

Demetriou

Floyd³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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A high-resolution compositional map of glass-forming ability (GFA) in the Ni-Cr-Nb-P-B system is experimentally determined along various compositional planes. GFA is shown to be a piecewise continuous function formed by intersecting compositional subsurfaces, each associated with a nucleation pathway for a specific crystalline phase. Within each subsurface, GFA varies exponentially with composition, wheres exponential cusps in GFA are observed when crossing from one crystallization pathway to another. The overall GFA is shown to peak at multiple exponential hypercusps that are interconnected by ridges. At these compositions, quenching from the high-temperature melt yields glassy rods with diameters exceeding 1 cm, whereas for compositions far from these cusps the critical rod diameter drops precipitously and levels off to 1 to 2 mm. The compositional landscape of GFA is shown to arise primarily from an interplay between the thermodynamics and kinetics of crystal nucleation, or more precisely, from a competition between driving force for crystallization and liquid fragility. T he glass-forming ability, or GFA, of a liquid metal alloy is not an intrinsic material attribute, but rather defined by the absence of a viable crystallization pathway as the liquid is undercooled below its thermodynamic melting temperature (1, 2). Crystallization is typically triggered by nucleation of a particular crystalline phase, followed by other competing phases, often catalyzed by the presence of the first phase. Crystal nucleation rates depend not only on temperature, pressure, and alloy composition, but also on extrinsic factors such as the presence of chemical impurities, trace crystalline debris (e.g., oxide inclusions), container wall effects, or shear flow conditions in the liquid, to name a few (3-7). Variations in these extrinsic factors often lead to inconsistent and nonreproducible GFA.The classical nucleation theory of crystals in undercooled liquids was originally developed by Turnbull (1) to account for the substantial undercooling observed in elemental liquid metals. He later extended his theory to explain metallic glass formation in rapidly cooled low melting eutectic Au-Si and Au-Ge-Si alloys (8,9). Below the liquidus temperature T L , the liquid viscosity, η(T), rises steeply with falling temperature. A liquid ultimately freezes at a glass transition temperature T g , where the viscosity reaches a solid-like value of ∼10 12 Pa·s. Turnbull considered the "reduced glass transition temperature" t rg = T g =T L as a characteristic material parameter. He argued that crystal nucleation rates should fall precipitously as t rg increases, becoming immeasurably small for t rg ≈ 2/3. This is widely referred to as Turnbull's criteria for bulk glass formation; it has been proven to be a valuable, albeit rough, guide in the development of bulk metallic glasses (10-12).In the present work, a systematic experimental approach is developed to quantify the intrinsic dependence of GFA on composition for near-eutectic multicomponent met...

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“…Shear-driven crystallization is equally relevant for simple fluids like bulk metallic glasses (9), molecular liquids (10), and atomic systems (11). The general understanding is that shear lowers the energy barrier for nucleation and accelerates the growth of a stable crystalline phase from a metastable, amorphous/ isotropic solution at Peclet number Pe = σa 3 kBT > 1, where σ is the shear stress, a is the characteristic length scale, and k B T is the thermal energy (12).…”

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Reversible shear-induced crystallization above equilibrium freezing temperature in a lyotropic surfactant system

Rathee

Krishnaswamy

Pal

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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We demonstrate a unique shear-induced crystallization phenomenon above the equilibrium freezing temperature ðT o K Þ in weakly swollen isotropic ðL i Þ and lamellar ðL α Þ mesophases with bilayers formed in a cationic-anionic mixed surfactant system. Synchrotron rheological X-ray diffraction study reveals the crystallization transition to be reversible under shear (i.e., on stopping the shear, the nonequilibrium crystalline phase L c melts back to the equilibrium mesophase). This is different from the shear-driven crystallization below T o K , which is irreversible. Rheological optical observations show that the growth of the crystalline phase occurs through a preordering of the L i phase to an L α phase induced by shear flow, before the nucleation of the L c phase. Shear diagram of the L i phase constructed in the parameter space of shear rate ð_ γÞ vs. temperature exhibits L i → L c and L i → L α transitions above the equilibrium crystallization temperature ðT o K Þ, in addition to the irreversible shear-driven nucleation of L c in the L i phase below T o K . In addition to revealing a unique class of nonequilibrium phase transition, the present study urges a unique approach toward understanding shear-induced phenomena in concentrated mesophases of mixed amphiphilic systems.shear-induced phase separation | strongly binding counterions | coagels S hear is known to assist crystallization below the equilibrium freezing temperature in complex fluids like colloidal glasses (1, 2), dense granular suspensions (3), polymer melts (4, 5), micellar solutions of block copolymers (6), and multicomponent surfactant systems (7,8). Shear-driven crystallization is equally relevant for simple fluids like bulk metallic glasses (9), molecular liquids (10), and atomic systems (11). The general understanding is that shear lowers the energy barrier for nucleation and accelerates the growth of a stable crystalline phase from a metastable, amorphous/ isotropic solution at Peclet number Pe = σa 3 kBT > 1, where σ is the shear stress, a is the characteristic length scale, and k B T is the thermal energy (12). The crystalline phase primarily induced by the effect of flow on the internal structure and ordering of the constituents does not revert to the starting fluid state when the imposed shear is removed, indicating that the phenomenon is not a dynamic phase transition. In the present study, we report a unique phenomenon, where under steady shear, crystallization occurs above the equilibrium crystallization temperature ðT o K Þ in an isotropic mesophase ðL i Þ consisting of bilayers formed in a lyotropic surfactant system. Notably, above T o K , when the imposed shear is removed, the crystalline phase melts back to the starting L i phase.The studies were carried out in a cationic-anionic mixed surfactant system formed by SDS and the strong binding counter-ion paratoluene hydrochloride (PTHC) in water. At equilibrium, the organic counter-ion PTHC has the tendency to remain at the micelle-water interface, decreasing the spontaneous curvat...

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Strain Rate Induced Crystallization in Bulk Metallic Glass-Forming Liquid

Cited by 53 publications

References 44 publications

Cold spraying – A materials perspective

Cold spraying – A materials perspective

Compositional landscape for glass formation in metal alloys

Reversible shear-induced crystallization above equilibrium freezing temperature in a lyotropic surfactant system

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