Nucleation behaviour and microstructure of single Al-Si12 powder particles rapidly solidified in a fast scanning calorimeter

AbstractThe understanding of rapid solidification behaviour, e.g. the undercooling versus growth velocity relationship, is crucial for tailoring microstructures and properties in metal alloys. In most rapid solidification processes, such as additive manufacturing (AM), in situ investigation of rapid solidification behaviour is missing because of the lack of accurate measurement of the cooling rate and nucleation undercooling. In the present study, rapid solidification of single micro-sized Al-Si12 (mass%) particles of various diameters has been investigated via differential fast scanning calorimetry employing controllable cooling rates from 100 to 90,000 K s−1 relevant for AM. Based on nucleation undercooling and on microstructure analysis of rapidly solidified single powder particles under controlled cooling rates, two different heterogeneous nucleation mechanisms of the primary α-Al phase are proposed. Surface heterogeneous nucleation dominates for particles with diameter smaller than 23 μm. For particles with diameter larger than 23 μm, the nucleation of the primary α-Al phase changes from surface to bulk heterogeneous nucleation with increasing cooling rate. The results indicate that at large undercoolings (> 95 K) and high cooling rates (> 10,000 K s−1), rapid solidification of single particle can yield a microstructure similar to that formed in AM. The present work not only proposes new insight into rapid solidification processes, but also provides a theoretical foundation for further understanding of microstructures and properties in additively manufactured materials.

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

Materials ◽

10.3390/ma14112920 ◽

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.

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Microstructure evolution and plastic deformation of Ni47Co53 alloy under tension

CrystEngComm ◽

10.1039/d1ce01446c ◽

2022 ◽

Author(s):

ruibo ma ◽

Lili Zhou ◽

Yong-Chao Liang ◽

Ze-an Tian ◽

Yun-Fei Mo ◽

...

Keyword(s):

Molecular Dynamics ◽

Plastic Deformation ◽

Rapid Solidification ◽

Microstructural Evolution ◽

Microstructure Evolution ◽

Cooling Rates ◽

Solidification Processes ◽

Molecular Dynamics Methods

To investigate microstructural evolution and plastic deformation under tension conditions, the rapid solidification processes of Ni47Co53 alloy are first simulated by molecular dynamics methods at cooling rates of 1011, 1012...

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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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Microstructural Characterization of Rapidly Solidified Ultrahigh Strength Aluminum Alloys

Microscopy and Microanalysis ◽

10.1017/s1431927600020614 ◽

1998 ◽

Vol 4 (S2) ◽

pp. 98-99

Author(s):

D. H. Ping ◽

K. Hono ◽

A. Inoue

Keyword(s):

Rapid Solidification ◽

Microstructural Characterization ◽

Atom Probe ◽

Probe Field ◽

Amorphous Phases ◽

Ultrahigh Strength ◽

Icosahedral Phases ◽

Transmission Electron ◽

Solidification Processes ◽

Rapidly Solidified

Recently, Inoue et al. succeeded in fabricating ultrahigh-strength Al-based alloys consisting of a nanoscale mixture of α-Al and amorphous phases or a mixture of a-Al, amorphous and icosahedral phases in Al-TM-Ce, Al-TM-Ln (TM: transition metals) and Al-Cr-Co-Ce systems by rapid solidification [1-3]. In order to understand the mechanism of the nanoscale microstructural evolution during the rapid solidification processes in these nanocomposite alloys, we have characterized the microstructures of rapidly solidified Al94.5Cr3Co1.5Ce1 and Al96V4Fe2 alloys by atom probe field ion microscopy (APFIM) and high resolution transmission electron microscopy (HREM).TEM investigations have revealed that the as-quenched Al94.5Cr3Co1.5Ce1 alloy is composed of a nanoscale mixture of amorphous and α-Al. A typical TEM bright field micrograph is shown in Fig. 1. The microdiffraction patterns taken at various locations in the darkly contrasted region have shown that the region consists of a few interconnected α-Al grains and many localized amorphous regions which are trapped within the Al grains.

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Microstructure and Properties of Rapidly Solidified Al-Zn-Mg-Cu Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.993.203 ◽

2020 ◽

Vol 993 ◽

pp. 203-207

Author(s):

Wei Min Ren ◽

Zi Yong Chen ◽

Zhi Lei Xiang ◽

Li Hua Chai

Keyword(s):

Aluminum Alloy ◽

Aluminum Alloys ◽

Cooling Rate ◽

Rapid Solidification ◽

Second Phase ◽

Alloy Strip ◽

Roller Speed ◽

Microstructure And Properties ◽

Cu Alloy ◽

Rapidly Solidified

Refining grain plays an important role in improving the mechanical properties of aluminum alloys. However, the conventional casting method with a slow cooling rate can be easy to cause coarseness of the microstructure and serious segregation. In this paper, the rapid solidification of Al-Zn-Mg-Cu alloy was prepared by the single-roller belt method. The alloy strip was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and hardness test to study the microstructure and properties of the rapidly solidified aluminum alloy. The results show that the roller speed was an important parameters affecting the formability of the alloy. When the roller speed was 15 m/s, the aluminum alloy produced a thin bandwidth of 5 mm and a thickness of 150 um. As the rotation speed of the roller increased, the cooling rate of the melt increased, and the microstructure of the rapidly solidified Al-Zn-Mg-Cu aluminum alloy strip improved in grains refinement. Compared with the conventionally cast Al-Zn-Mg-Cu aluminum alloys, the Al-Zn-Mg-Cu aluminum alloys prepared by rapid solidification showed much finer crystal grains, and enhanced solid solubility of alloying elements with less precipitation of second phase and high hardness.

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A STEM Microstructural Analysis of Rapidly Solidified High-Sulfur Austenitic Steel

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600001677 ◽

1980 ◽

Vol 38 ◽

pp. 394-395

Author(s):

Thomas F. Kelly

Keyword(s):

Rapid Solidification ◽

Average Particle Size ◽

Microstructural Analysis ◽

Scanning Transmission Electron Microscope ◽

Average Particle ◽

Cooling Rates ◽

Scanning Transmission ◽

High Cooling Rates ◽

Carpenter Technology Corporation ◽

Rapidly Solidified

Rapid solidification processing (RSP) has been viewed as a means of obtaining better properties from (crystalline) metal alloys where the improvements are a result of the various effects of high cooling rates (> 105°K/sec) on the “as solidified” structure. Described herein are the results of an investigation into the microstructural and microchemical nature of a rapid solidification processed high sulfur, 303 stainless steel using a dedicated scanning transmission electron microscope (STEM). The RSP material of this study was prepared by forced convective cooling, in helium, of centrifugally atomized metal droplets to achieve cooling rates on the order of 105°K/sec. The resultant powder, of n 50 ym average particle size, was consolidated to a fully dense state. Equivalent conventionally processed 303 SS material was obtained from Carpenter Technology Corporation. The 303 SS material of this investigation was therefore studied in three processed states:the rapidly solidified powder, the rapidly solidified and consolidated bar stock, and the conventionally processed material.

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Rapidly Solidified Al-6Si-3Cu Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.570.103 ◽

2008 ◽

Vol 570 ◽

pp. 103-108 ◽

Cited By ~ 2

Author(s):

C. Triveño Rios ◽

Claudemiro Bolfarini ◽

Walter José Botta Filho ◽

Claudio Shyinti Kiminami

Keyword(s):

Rapid Solidification ◽

X Ray Diffraction ◽

Type Alloy ◽

X Ray ◽

Optical Scanning ◽

Transmission Electron ◽

Al2cu Phase ◽

Solidification Processes ◽

Dendritic Arm Spacing ◽

Rapidly Solidified

Rapid solidification processes, RSP, are powerful tools to induce microstructural modifications, which may improve mechanical properties of alloys. In this paper the influence of rapid solidification on the formation of the undesirable brittle intermetallic compounds promoted by Si and Fe in Al-6Si-3Cu (A319-type) alloy have been investigated. The alloy have been casted using both conventional method and water-cooled wedge-copper mould. The microstructures have been evaluated by using a combination of X-ray diffraction, optical, scanning and transmission electron microscopy, and by Vickers microhardness. By increasing the cooling rate the length of the intermetallic β-Al5FeSi phase decreased, accompanying the same tendency of the secondary dendritic arm spacing. These results are accompanied by an increasing in hardness. Moreover, the formation and growth of the Al2Cu phase have been suppressed. These microstructural and hardness changes with the rapid solidification might be attributed to the increased solid solution content of the elements in the Al matrix.

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The Effect of Cooling Rate During Rapid Solidification on the Structure and Texture of NiTi

MRS Proceedings ◽

10.1557/proc-74-185 ◽

1986 ◽

Vol 74 ◽

Cited By ~ 1

Author(s):

A. J. Pedraza ◽

M. J. Godbole ◽

E. A. Kenik ◽

D. F. Pedraza ◽

D. H. Lowndes

Keyword(s):

Cooling Rate ◽

Rapid Solidification ◽

Heat Extraction ◽

X Ray Diffraction ◽

Rapid Solidification Technique ◽

Melted Layer ◽

Monoclinic Distortion ◽

Small Distortion ◽

B2 Phase ◽

Rapidly Solidified

AbstractA study has been conducted on the effects of increasing cooling rate during rapid solidification of NiTi upon the phases that are produced. The hammer and anvil rapid solidification technique and laser melting with a nanosecond excimer laser were used, which allow the cooling rate to be varied by three to four orders of magnitude. Although 1/3 {110} superlattice reflections are seen in the selected area diffraction (SAD) patterns of the splat quenched (SQ) specimens, x-ray diffraction analyses show the presence of only B2 phase and martensite. On the other hand, laser treatment (LT) of the specimens produces a layer that has a L10 structure with a slight monoclinic distortion. This phase can be envisaged as a small distortion of a B2 unit cell with a volume per atom ~3.3% lower than the equilibrium B2 phase. Also martensite is present in the layer. SQ alloys exhibit a marked {200} texture due to columnar growth opposite to the direction of heat extraction, while LT produces epitaxial regrowth of the melted layer. No substantial disordering is obtained in NiTi rapidly solidified alloys.

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Microstructure Evolution in Rapidly Solidified Immiscible Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.508.37 ◽

2006 ◽

Vol 508 ◽

pp. 37-44 ◽

Cited By ~ 2

Author(s):

Michael Reuß ◽

Lorenz Ratke ◽

Jiu Zhou Zhao

Keyword(s):

Cooling Rate ◽

Nucleation Rate ◽

Particle Diameter ◽

Casting Process ◽

Average Particle ◽

Cooling Rates ◽

Gravity Casting ◽

The Difference ◽

Rapidly Solidified ◽

Mould Casting

We prepared Al-Bi alloys with our new aerogel counter gravity casting facility and Al-Pb alloys by simple mould casting with variable cooling rates. By counter gravity casting, it is possible to have directional solidification with flat isotherms and without forced melt flow during the casting process. Both methods allow studying the nucleation rate in liquid-liquid decomposition. The most important result is that a separation between monotectic and hypermonotectic particles is possible by using suitable cooling rates. The difference of the frequency maxima is a function, depending on cooling rate and starting composition. By casting experiments with variable cooling rates, we found that the average particle diameter is a function of the cooling rate, according to the theory of Ratke and Zhao, but the nucleation rate is higher than assumed in their theory.

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The Thermodynamics of Intracellular Ice Nucleation in the Freezing of Erythrocytes

Journal of Heat Transfer ◽

10.1115/1.3450374 ◽

1975 ◽

Vol 97 (3) ◽

pp. 326-332 ◽

Cited By ~ 28

Author(s):

W. M. Toscano ◽

E. G. Cravalho ◽

O. M. Silvares ◽

C. E. Huggins

Keyword(s):

Cooling Rate ◽

Heterogeneous Nucleation ◽

Numerical Solutions ◽

Ice Nucleation ◽

Nucleation Temperature ◽

Extracellular Medium ◽

Cooling Rates ◽

Intracellular Ice ◽

High Cooling Rates ◽

Analytical Expressions

A theoretical model describing the thermodynamics of intracellular ice nucleation is developed for red blood cells as a model biomaterial. Analytical expressions based on current theories of ice nucleation by both homogeneous and heterogeneous nucleation processes are coupled with a thermodynamic model for the loss of intracellular water during freezing. Numerical solutions for both modes of nucleation identify two cooling regions—high cooling rates and low cooling rates—separated by a sharp demarcation zone. The nucleation temperature for high cooling rates is approximately 20° K higher than the nucleation temperature for low cooling rates and is essentially independent of cooling rate in each region. The nucleation temperatures for heterogeneous nucleation are approximately 30° K higher than the nucleation temperatures for homogeneous nucleation in the two regions. For the case of heterogeneous nucleation, it is possible to increase the nucleation temperature by packing of catalysts via the concentration polarization effect. If the cell suspension is allowed to supercool before nucleation occurs in the extracellular medium, the sharp transition from low cooling rates to high cooling rates for heterogeneous nucleation shifts to much lower cooling rates. The dependence of the transition cooling rate on the degree of supercooling has been established for a typical freezing situation.

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