Crystallization of Supercooled Zr41Ti14Cu12Ni10B23 Melts During Continuous Heating and Cooling

1998 ◽  
Vol 554 ◽  
Author(s):  
Jan Schroers ◽  
Andreas Masuhr ◽  
Ralf Busch ◽  
William L. Johnson
Keyword(s):  
Cooling Rate ◽  
Bulk Sample ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Continuous Heating ◽  
Glass Forming ◽  
Heating And Cooling ◽  
Diffusion Limited ◽  
Surface Nucleation ◽  
The Difference

AbstractThe crystallization behavior of the bulk glass forming Zr41Ti14Cu12Ni10Be23 liquid was studied under different heating and cooling rates. Investigations were performed in high purity graphite crucibles since heterogeneous surface nucleation at the container walls does not effect the crystallization of the bulk sample. A rate of about 1 K/s is sufficient to circumvent crystallization of the melt while cooling from the equilibrium melt. In contrast, upon heating a rate of more than 150 K/s is necessary to avoid crystallization of Zr41Ti14Cu12Ni10Be23 samples. The difference between the critical heating and cooling rate is discussed within classical nucleation theory and diffusion limited crystal growth. The calculated difference of the critical heating and cooling rate can be explained by the fact that nuclei formed during cooling and heating are expose to different growth rates.

scholarly journals Nucleation Behavior of a Single Al-20Si Particle Rapidly Solidified in a Fast Scanning Calorimeter

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2920
Author(s):  
Qin Peng ◽  
Bin Yang ◽  
Benjamin Milkereit ◽  
Dongmei Liu ◽  
Armin Springer ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Rapid Solidification ◽  
Heterogeneous Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Solidification Behavior ◽  
Nucleation Kinetics ◽  
Nucleation Behavior ◽  
Nucleation Undercooling ◽  
Primary Si

Understanding the rapid solidification behavior characteristics, nucleation undercooling, and nucleation mechanism is important for modifying the microstructures and properties of metal alloys. In order to investigate the rapid solidification behavior in-situ, accurate measurements of nucleation undercooling and cooling rate are required in most rapid solidification processes, e.g., in additive manufacturing (AM). In this study, differential fast scanning calorimetry (DFSC) was applied to investigate the nucleation kinetics in a single micro-sized Al-20Si (mass%) particle under a controlled cooling rate of 5000 K/s. The nucleation rates of primary Si and secondary α-Al phases were calculated by a statistical analysis of 300 identical melting/solidification experiments. Applying a model based on the classical nucleation theory (CNT) together with available thermodynamic data, two different heterogeneous nucleation mechanisms of primary Si and secondary α-Al were proposed, i.e., surface heterogeneous nucleation for primary Si and interface heterogenous nucleation for secondary α-Al. The present study introduces a practical method for a detailed investigation of rapid solidification behavior of metal particles to distinguish surface and interface nucleation.

Phase Selection in Sub-Rapidly Solidified Au-20Sn Alloys

2015 ◽  
Vol 817 ◽  
pp. 325-330
Author(s):  
Yu Hai Qu ◽  
Kai Jin Yang ◽  
Yan Tian Zhou ◽  
Yong Mao ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Copper Mold ◽  
Cooling Rates ◽  
Phase Selection ◽  
Graphite Mold ◽  
Injection Casting ◽  
Rapidly Solidified ◽  
Ausn Phase

The sub-rapidly solidified Au-20Sn eutectic alloys were prepared by four different solidification pathways, such as, graphite mold conventional casting, graphite mold injection casting, copper mold injection casting, and water-cooled copper mold suction casting. The precipitating sequences of competing primary phases of sub-rapidly solidified Au-20Sn alloys with four different cooling rates were investigated. The results show that phase selection process is related to the cooling rates during sub-rapid solidification process. The primary ζ'-Au5Sn phase with developed dendrites precipitate at low cooling rate (2.4×10−4.2×102K/min) and the morphologies of the primary ζ'-Au5Sn change to rosette-like at higher cooling rate (9.0×103K/min). While the cooling rate reaches to 3.5×104K/min, the primary ζ'-Au5Sn phase can be suppressed but δ-AuSn phase will precipitate prior to the ζ'-Au5Sn phase. On the basis of the classical nucleation theory and transient nucleation theory, the process of competitive nucleation between the ζ'-Au5Sn phase and the δ-AuSn phase were analyzed for sub-rapid solidified Au-20Sn alloy. The theoretical calculations are consistent with the experimental investigations.

Metastable Phase Equilibria in Co-Deposited Ni1−xZrx Thin Films

1991 ◽  
Vol 230 ◽  
Author(s):  
J. B. Rubin ◽  
R. B. Schwarz
Keyword(s):  
Thin Films ◽  
Cooling Rate ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Amorphous Structure ◽  
Nucleation Theory ◽  
Glass Forming ◽  
Constant Heating

AbstractWe determine the glass forming range (GFR) of co-deposited Ni1−xZrx (0 < x < 1) thin films by measuring their electrical resistance during in situ constant-heating-rate anneals. The measured GFR is continuous for 0.10 < x < 0.87. We calculate the GFR of Ni-Zr melts as a function of composition and cooling rate using homogeneous nucleation theory and a published CALPHAD-type thermodynamic modeling of the equilibrium phase diagram. Assuming that the main competition to the retention of the amorphous structure during the cooling of the liquid comes from the partitionless crystallization of the terminal solid solutions, we calculate that for dT/dt = 1012 K s−1, the GFR extends to x = 0.05 and x = 0.96. Better agreement with the measured values is obtained assuming a lower ‘effective’ cooling rate during the condensation of the films.

Hysteresis of Long-Range Ordering in CuAu

1995 ◽  
Vol 398 ◽  
Author(s):  
B. Chalupa ◽  
F. Chmelik ◽  
V. Sima ◽  
B. Sprusil ◽  
M. Spanl ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Cooling Rate ◽  
Long Range ◽  
Long Range Order ◽  
Expected Effect ◽  
Linear Heating ◽  
Glass Forming ◽  
Heating And Cooling ◽  
Small Influence ◽  
Long Range Ordering

ABSTRACTThe effect of heating and cooling on the long-range order transformation in stoichiometric CuAu is investigated by several complementary measuring methods. Measurements of heat flow, resistometry and acoustic emission are done dynamically by linear heating/cooling. It is shown that measuring dynamically yields the expected effect of undercooling, which decreases with decreasing cooling rate. The dependence of undercooling on cooling rate is compared with the concept of continuous cooling for glass forming. A small influence of heating rate on disordering temperature is reported (retro-effect).

scholarly journals Voronoi diagram based simulation and experimental validation of austenite in C22 and C35 steels

10.30544/482 ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 31-42
Author(s):  
Sanchu S ◽  
Biju N ◽  
V. N.N. Namboothiri
Keyword(s):  
Heat Treatment ◽  
Voronoi Diagram ◽  
Experimental Validation ◽  
Maximum Error ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Continuous Heating ◽  
Microstructure Modeling ◽  
Geometrical Features ◽  
Simulation Results

This paper examines the ability of power Voronoi diagram assisted simulation in microstructure modeling during heat treatment. A model is developed for predicting fraction of austenite evolved during continuous heating of steel to austenite range, by integrating geometrical features of power Voronoi diagram and classical nucleation theory. From the simulation results, it is possible to predict the transformed fraction. The simulation results are validated using experiments conducted on two varieties of steels. The maximum error obtained is 2.08%. Thus, power Voronoi assisted simulation can be considered as an effective tool in modeling microstructure evolution during austenitization.

Nucleation of Framboids

2021 ◽  
pp. 222-234
Author(s):  
David Rickard
Keyword(s):  
Growth Phase ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Lag Phase ◽  
Surface Energies ◽  
Diffusion Limited ◽  
Critical Supersaturation ◽  
Unlimited Growth ◽  
Major Route ◽  
Framboid Formation

Framboid microcrystals, which are intrinsically similar in size and habit within any individual framboid, must have all nucleated and grown at the same time. The formation of many thousands of equidimensional and equimorphic microcrystals in framboids is the fundamental evidence for burst nucleation. This is conventionally described by the LaMer model, which is characterized by (1) a lag phase before nucleation becomes significant; (2) burst nucleation where the rate of nucleation increases exponentially and may be completed in seconds; and (3) a short growth phase where nucleation becomes again insignificant. The growth phase is limited by the diffusion of Fe and S in stagnant, diffusion limited environments. By contrast, individual pyrite crystals evidence isolated nucleation and unlimited growth in advecting systems. The reaction with surface =FeS provided by sulfidized iron oxyhydroxides may a major route for producing individual pyrite crystals, rather than framboids, especially in sediments. Framboid formation by the nucleation of pyrite in solution can be described by classical nucleation theory (CNT), which leads to results consistent with observed critical supersaturation ranges, critical nucleus radius, and surface energies.

scholarly journals Molecular dynamics simulations of liquid silica crystallization

2018 ◽  
Vol 115 (21) ◽  
pp. 5348-5352 ◽  
Author(s):  
Haiyang Niu ◽  
Pablo M. Piaggi ◽  
Michele Invernizzi ◽  
Michele Parrinello
Keyword(s):  
Free Energy ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Free Energy Surface ◽  
X Ray Diffraction ◽  
Collective Variables ◽  
Atomic Simulations ◽  
The Difference ◽  
Dynamics Simulations ◽  
Good Agreement

Silica is one of the most abundant minerals on Earth and is widely used in many fields. Investigating the crystallization of liquid silica by atomic simulations is of great importance to understand the crystallization mechanism; however, the high crystallization barrier and the tendency of silica to form glasses make such simulations very challenging. Here we have studied liquid silica crystallization to β-cristobalite with metadynamics, using X-ray diffraction (XRD) peak intensities as collective variables. The frequent transitions between solid and liquid of the biased runs demonstrate the highly successful use of the XRD peak intensities as collective variables, which leads to the convergence of the free-energy surface. By calculating the difference in free energy, we have estimated the melting temperature of β-cristobalite, which is in good agreement with the literature. The nucleation mechanism during the crystallization of liquid silica can be described by classical nucleation theory.

Microstructural evolution during decomposition and crystallization of the Cu60Zr20Ti20 amorphous alloy

2004 ◽  
Vol 19 (2) ◽  
pp. 505-512 ◽  
Author(s):  
A. Concustell ◽  
Á. Révész ◽  
S. Suriñach ◽  
L.K. Varga ◽  
G. Heunen ◽  
...  
Keyword(s):  
Amorphous Matrix ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Continuous Heating ◽  
Liquid Region ◽  
Scanning Calorimetry ◽  
Isothermal Heat Treatments ◽  
Crystallization Stage

The effect of continuous heating and isothermal heat treatments on ductile Cu60Zr20Ti20 amorphous ribbons was monitored by differential scanning calorimetry, x-ray diffraction, synchrotron radiation transmission, and high-resolution transmission electron microscopy. Upon continuous heating, the alloy exhibited a glass transition, followed by a supercooled liquid region and two exothermic crystallization stages. Decomposition of the amorphous phase was also observed. The first crystallization stage resulted in the formation of a nanocomposite structure with hexagonal Cu51Zr14 particles embedded in the amorphous matrix, while in the second crystallization stage hexagonal Cu2TiZr-like phase was precipitated. The released enthalpies were 19 J/g and 30 J/g for each crystallization stage. Crystallization kinetics was studied by the classical nucleation theory. Deviations from the Johnson–Mehl–Avrami–Kolmogorov theory may be explained by the contribution of the decomposition of the amorphous matrix.

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