Microstructure and Phase Selection of Undercooled Single-Phase Fe-Co Alloy

Fe-Co single-phase alloy melts with different Co contents were undercooled using fluxing method. The maximum undercooling DT = 457K (relative undercooling DT/Tm=0.259) was achieved in this work. At low undercooling (DT), single-phased microstructure was observed, but metastable bcc phase emerged in the as-solidified microstructure once DT exceeded a critical value, DTcrit. In the presence of classical nucleation theory, phase selection in the undercooled Fe-Co melt was investigated, and the theoretical calculation was coincided with the experimental result.

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Rapid-Quenching Investigation of the Nb-Pd-Ge System

MRS Proceedings ◽

10.1557/proc-205-313 ◽

1990 ◽

Vol 205 ◽

Cited By ~ 1

Author(s):

C. E. Krill ◽

W. L. Johnson

Keyword(s):

Phase Diagram ◽

Single Phase ◽

Rapid Quenching ◽

Nucleation Theory ◽

Classical Nucleation Theory ◽

X Ray Diffraction ◽

X Ray ◽

Solubility Range ◽

Fcc Phase ◽

Bcc Phase

AbstractThe structure of rapidly quenched Nb100-x-yPdxGey alloys has been investigated using x-ray diffraction. Niobium concentrations were varied between 100 and 45 at.% the remainder at each Nb concentration was composed of Pd and up to y = 15 at.% Ge. Germanium was found to suppress the nucleation rate of the fcc α-NbPd phase relative to that of the bcc α-Nb phase, thereby extending the single-phase bcc solubility range by ≈ 2 at.% Nb. High Ge content (y > 6) also induced quenching of the amorphous phase. These results can be understood from the standpoint of classical nucleation theory and from a consideration of the polymorphic phase diagram of Nb-Pd. The two approaches are consistent with Ge addition depressing the To line of the fcc phase more rapidly than it depresses the To line of the bcc phase.

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Phase-field modeling of grain evolutions in additive manufacturing from nucleation, growth, to coarsening

npj Computational Materials ◽

10.1038/s41524-021-00524-6 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Min Yang ◽

Lu Wang ◽

Wentao Yan

Keyword(s):

Additive Manufacturing ◽

Phase Field ◽

Field Model ◽

Three Dimensional ◽

Phase Field Model ◽

Nucleation Theory ◽

Experimental Result ◽

Classical Nucleation Theory ◽

Validation Experiment ◽

Powder Particles

AbstractA three-dimensional phase-field model is developed to simulate grain evolutions during powder-bed-fusion (PBF) additive manufacturing, while the physically-informed temperature profile is implemented from a thermal-fluid flow model. The phase-field model incorporates a nucleation model based on classical nucleation theory, as well as the initial grain structures of powder particles and substrate. The grain evolutions during the three-layer three-track PBF process are comprehensively reproduced, including grain nucleation and growth in molten pools, epitaxial growth from powder particles, substrate and previous tracks, grain re-melting and re-growth in overlapping zones, and grain coarsening in heat-affected zones. A validation experiment has been carried out, showing that the simulation results are consistent with the experimental results in the molten pool and grain morphologies. Furthermore, the grain refinement by adding nanoparticles is preliminarily reproduced and compared against the experimental result in literature.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.817.325 ◽

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.

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Application of classical nucleation theory to phase selection and composition of nucleated nanocrystals during crystallization of Co-rich (Co,Fe)-based amorphous precursors

Acta Materialia ◽

10.1016/j.actamat.2010.05.015 ◽

2010 ◽

Vol 58 (14) ◽

pp. 4804-4813 ◽

Cited By ~ 13

Author(s):

P.R. Ohodnicki Jr. ◽

D.E. Laughlin ◽

M.E. McHenry ◽

M. Widom

Keyword(s):

Nucleation Theory ◽

Classical Nucleation Theory ◽

Phase Selection

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Nucleation Behavior and Solid-Liquid Interfacial Energy of Polytetrahedral Phases

MRS Proceedings ◽

10.1557/proc-580-245 ◽

1999 ◽

Vol 580 ◽

Cited By ~ 2

Author(s):

Dirk Holland-Moritz

Keyword(s):

Interfacial Energy ◽

Orthorhombic Phase ◽

Nucleation Theory ◽

Classical Nucleation Theory ◽

Phase Selection ◽

Nucleation Behavior ◽

Σ Phase ◽

Selection Behavior ◽

Liquid Interfacial Energy ◽

Solid Liquid

AbstractAccording to classical nucleation theory the nucleation- and phase-selection behavior of undercooled meltallic melts is strongly dependent on the solid-liquid interfacial energy.A structural approach to the modelling of the interfacial energy for simple melt-crystal interfaces (fcc, hcp, bcc) was developed a number of years ago [1-4]. This approach is extended to polytetrahedral phases using numerical simulation. Results of these calculations are presented for different polytetrahedral structures: the tetragonal σ-phase in Ni-V, the monoclinic phase λ-Al13Fe4, the orthorhombic phase μ-Al5Fe2 and the icosahedral quasicrystalline I-phase in Al-Pd-Mn. The numerically estimated values for the solid-liquid interfacial energy are compared with results from experiments on the undercooling- and phase-selection behavior.

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Critical undercoolings for the formation of metastable phase and its morphologies solidified from undercooled Fe–Co melts

Journal of Materials Research ◽

10.1557/jmr.1999.0225 ◽

1999 ◽

Vol 14 (5) ◽

pp. 1679-1682 ◽

Cited By ~ 3

Author(s):

Li Mingjun ◽

Song Guangsheng ◽

Yang Gencang ◽

Zhou Yaohe

Keyword(s):

Phase Formation ◽

Metastable Phase ◽

Nucleation Theory ◽

Classical Nucleation Theory ◽

Solidification Behavior ◽

Metastable Phase Formation ◽

Bcc Phase ◽

Co Alloys ◽

Undercooled Melts

The maximum undercoolings of 304, 318, 308, and 296 K were achieved, respectively, in Fe-22, 26, 30, and 34 at.% Co alloys. The metastable bcc phase nucleated from melts when undercoolings exceeded critical ones. The critical undercoolings for the formation of metastable bcc phase from Fe-22, 26, 30, and 34 at.% Co melts were 104, 156, 204, and 248 K, respectively. The morphologies of as-obtained metastable bcc phase exhibited five typical patterns: dendrite cores with primary and second arms, well-developed second arms, and radiated, lath, and platelike structures. Based on the classical nucleation theory, the solidification behavior of the melts was analyzed with regard to the metastable phase formation when the melts were undercooled greater than critical undercoolings. The formation of various morphologies was also evaluated to consider the solidification behavior of the undercooled melts.

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Competitive Phase Selection in Fe-Ni Alloy Droplets

MRS Proceedings ◽

10.1557/proc-398-51 ◽

1995 ◽

Vol 398 ◽

Cited By ~ 1

Author(s):

F. Gärtner ◽

A. F. Norman ◽

H. Assadi ◽

A. L. Greer

Keyword(s):

Free Energy ◽

Interfacial Energy ◽

Kinetic Modelling ◽

Primary Phase ◽

Drop Tube ◽

Phase Selection ◽

Ni Alloys ◽

Ni Alloy ◽

Bcc Phase ◽

Selection Of

ABSTRACTIn the solidification of Fe-Ni droplets (≤ 30 at.% Ni), the selection of different microstructures is dominated by the competition between the bcc and ccp phases. In drop-tube experiments ccp is the primary phase in some dilute (up to 7at% Ni) alloys although the bcc phase is favoured by a lower free energy and by a lower interfacial energy with the liquid. Competitive dendrite growth is a possible explanation for the formation of primary ccp. Comprehensive thermodynamic (CALPHAD) and kinetic modelling is undertaken to understand the growth competition. The origin of the observed primary phases is discussed.

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PHASE FIELD SIMULATION OF EQUIAXED DENDRITIC GROWTH DURING NON-ISOTHERMAL POLYCRYSTALLINE SOLIDIFICATION

International Journal of Modern Physics B ◽

10.1142/s0217979210065593 ◽

2010 ◽

Vol 24 (15n16) ◽

pp. 2762-2767

Author(s):

J. J. LI ◽

J. C. WANG ◽

L. Y. WU ◽

G. C. YANG

Keyword(s):

Phase Field ◽

Dendritic Growth ◽

Field Model ◽

Phase Field Model ◽

Grain Structure ◽

Nucleation Theory ◽

Experimental Result ◽

Classical Nucleation Theory ◽

Cooling Conditions ◽

Heat Transition

The non-isothermal polycrystalline solidification of a binary alloy is simulated by employing a phase field model which takes into account the heat transition and the random crystallographic orientation. The stochastic nucleation is taken into account in the simulation through the Poisson seeding algorithm and a kinetic calculation for binary melts based on the classical nucleation theory. Different microstructures are obtained under various cooling conditions. It is found that the grain structure becomes finer with increasing the cooling rate, which agrees with experimental result.

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