Competition between stable and metastable eutectic growth in Sn-Ni alloys

Hou, Ning; Belyakov, S. A.; Pay, L; Sugiyama, A.; Yasuda, Hideyuki; Gourlay, C.M.

doi:10.1016/j.actamat.2018.02.034

Cited by 19 publications

(8 citation statements)

References 42 publications

(48 reference statements)

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“…3(b)]. We shall mention the striking similarity of our observations with those obtained by synchrotron x-ray radiography in a metallic f/nf eutectic alloy (Ni-Ni3Sn4) [17]. Two-phase fingers.…”

Section: Melissupporting

confidence: 75%

Decoupled versus coupled growth dynamics of an irregular eutectic alloy

et al. 2020

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We present an experimental study of irregular growth patterns observed in real time during thin-sample directional solidification of a faceted/nonfaceted eutectic alloy, namely, the transparent 2-amino-2-methyl-1,3-propanediol (AMPD)-succinonitrile (SCN) system. The body-centered cubic SCN crystals are nonfaceted, while monoclinic AMPD crystals grow as faceted needles. At low velocities (<0.3 µms -1 ), a decoupled growth regime is observed, during which the tip of the AMPD crystals grows ahead of the SCN-liquid interface. At intermediate velocities, an unsteady coupled-growth regime takes place, with intermittent pinning of triple SCN-AMPD-liquid junctions, and frequent noncrystallographic branching. At higher velocities (>1 µms -1 ), two-phase fingers form.Many irregular eutectic alloys of industrial importance are such that one of the solid phases is faceted (e.g., silicon, germanium, graphite), while the other one (e.g., aluminum, austenite)is nonfaceted [1][2][3]. In spite of extensive research, the growth of such faceted/nonfaceted (or f/nf) eutectics is still poorly understood. The term irregular refers to the disordered microstructures left frozen in the solid behind the growth front, whereas regular eutectics grow with fully nonfaceted solid-liquid interfaces. The growth dynamics of regular eutectics is determined by solute diffusion in the liquid, and local equilibrium at the solid-liquid interfaces, and at the triple-contact lines (trijunctions) between the liquid and the two solids [4]. During directional solidification (DS) at velocity V in a temperature gradient G, steady periodic two-phased patterns can then form in a quasi-planar geometry at a temperature close to the eutectic point. The diffusive coupling between the growing entities (e.g., lamellae or rods) extends over distances much larger than the interphase spacing l -hence the coupledgrowth appellation. In contrast, the unsteadiness of the growth dynamics of f/nf eutectics is attributable to a nonlinear growth kinetics of the faceted interfaces. A facet can remain macroscopically immobile irrespective to the diffusion field over a finite range of undercoolings ("blocked" facet). The mobility of a facet is tributary of active sources of

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Section: Melissupporting

confidence: 75%

Decoupled versus coupled growth dynamics of an irregular eutectic alloy

et al. 2020

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“…In this experiment, controlled microstructures were grown in dog-bone samples by Bridgman growth in a temperature gradient furnace with a 350°C hot zone and $ 25°C cold zone, similar to that used in Ref. 49. Subsequently, the rolled sample was directionally solidified (DS) by pulling the dog-bone along its length at a constant velocity of 20 lm/s through a temperature gradient of $ 3 K/mm.…”

Section: Methodsmentioning

confidence: 99%

Evaluating Creep Deformation in Controlled Microstructures of Sn-3Ag-0.5Cu Solder

Gourlay

Britton

2018

Journal of Elec Materi

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The reliability of solder joints is affected significantly by thermomechanical properties such as creep and thermal fatigue. In this work, the creep of directionally solidified (DS) Sn-3Ag-0.5Cu wt.% (SAC305) dog-bone samples (gauge dimension: 10 9 2 9 1.5 mm) with a controlled <110> or <100> fibre texture is investigated under constant load testing (stress level: $ 30 MPa) at a range of temperatures from 20°C to 200°C. Tensile testing is performed and the secondary creep strain rate and the localised strain gradient are studied by two-dimensional optical digital image correlation (2-D DIC). The dominating creep mechanisms and their temperature dependence are explored at the microstructural scale using electron backscatter diffraction (EBSD), which enables the understanding of the microstructural heterogeneity of creep mechanisms at different strain levels, temperatures and strain rates. Formation of subgrains and the development of recrystallization are observed with increasing strain levels. Differences in the deformation of b-Sn in dendrites and in the eutectic regions containing Ag 3 Sn and Cu 6 Sn 5 are studied and related to changes in local deformation mechanisms.

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“…X-ray imaging using synchrotron radiation has allowed observation of the solidification behavior in various metallic alloys such as Sn alloys, [7][8][9][10][11][12][13][14][15][16] Al alloys, 9,10,17,18) cast iron, [19][20][21][22][23] Fe-C steels, 11,[24][25][26][27][28] and stainless steels. 29) Installing a deformation device in the observation apparatus, in-situ observation of semisolid deformation by X-ray transmission imaging (referred to as 2D observation hereinafter) was achieved with a high spatial resolution with respect to grain size.…”

Section: Introductionmentioning

confidence: 99%

Time-resolved and <i>in-situ</i> Observation of Semisolid Deformation in Al–Cu Alloys with Equiaxed and Columnar Grain Structures by Using a Combination Technique of 4D-CT and 3DXRD

et al. 2021

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Time-resolved combined absorption tomography and three-dimensional X-ray diffraction was developed to study semisolid deformation of metallic alloys, which combined time-resolved tomography and threedimensional X-ray diffraction microscopy (3DXRD). The combined technique allowed observation of configuration and crystallographic orientation of solid grains, whereby translation and rotation of solid grains induced by interaction between solid grains during semisolid deformation was analyzed. During the compression tests of a semisolid Al-10mass%Cu alloy with the equiaxed grain structure, translation and rotation of solid grains rather than the plastic deformation played a dominant role in the deformation until strain reached − 0.04. In a portion of the specimen, a gap between solid grains expanded owing to the interaction between solid grains, and consequently apparent volume expansion (dilatancy) occurred. The solid grains around the expanded region possessed similar rotational axis directions, which were perpendicular to the normal direction of the expanded region. As the compression proceeded, both translation/ rotation and the plastic deformation of solid grains occurred owing to an increase in physical contact between solid grains. For a semisolid Al-10mass%Cu alloy with the columnar grain structure, solid grain comprised a single crystallographic domain. Inflection of the dendrite arms was confirmed by 3DXRD, where the compression of strain at − 0.25 caused the grain to be inflected up to 12 degrees. The strain distribution in the grain was estimated using the inflection angle. In-situ observation revealed that the behaviors of solid grains and the liquid phase in semisolid alloys during the compression tests differed according to the structure.

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Competition between stable and metastable eutectic growth in Sn-Ni alloys

Cited by 19 publications

References 42 publications

Decoupled versus coupled growth dynamics of an irregular eutectic alloy

Decoupled versus coupled growth dynamics of an irregular eutectic alloy

Evaluating Creep Deformation in Controlled Microstructures of Sn-3Ag-0.5Cu Solder

Time-resolved and <i>in-situ</i> Observation of Semisolid Deformation in Al–Cu Alloys with Equiaxed and Columnar Grain Structures by Using a Combination Technique of 4D-CT and 3DXRD

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