Discontinuous reactions in solids

Manna, I.; Pabi, S.K.; Gust, W.

doi:10.1179/095066001101528402

Cited by 244 publications

(149 citation statements)

References 191 publications

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“…No evident orientation relationship could be found between the supersaturated matrix ahead of the discontinuous precipitation front and the depleted matrix behind it. This crystallographic orientation discontinuity at the precipitation front confirms the nature of the discontinuous precipitation [29].…”

Section: Fcc Phase Miscibility Gapsupporting

confidence: 56%

Au–Fe alloy solidification and solid-state transformations

2010

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In order to better understand the microstructure that forms during laser welding of an 18 carat gold and an austenitic stainless steel, solidification of the Au-Fe binary analog has been studied using thermal analysis and interrupted Bridgman experiments. For a hypoperitectic composition, the formation of the primary phase, its coarsening and the peculiar macrosegregation associated with the large density difference between the elements have been studied. Just after the peritectic phase forms around the primary dendrites, continuous and discontinuous precipitation has been shown to occur as a result of the immiscibility of the two face-centered cubic phases below the peritectic temperature. Finally, the solid-state transformations associated with the eutectoid have been characterized.

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Section: Fcc Phase Miscibility Gapsupporting

confidence: 56%

Au–Fe alloy solidification and solid-state transformations

2010

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“…Substituting Eqs. [2] through [5] into Eq. [6] and after considering the proportional relationship between n and t, the composition of the DP cell can then be calculated as [ Figure 14(e)]:…”

Section: B Initial Stages Of Discontinuous Precipitation [Cf Figurmentioning

confidence: 99%

“…[1] Discontinuous precipitation (DP) refers to an abrupt change in composition and orientation between parent phase and product phases. [2] It has been observed in the substrate beneath coatings [3][4][5] or on grain boundaries. [6][7][8] In all cases, there is the requirement of a super-saturated matrix, which provides the driving force for growth.…”

Section: Introductionmentioning

confidence: 99%

“…[6][7][8] In all cases, there is the requirement of a super-saturated matrix, which provides the driving force for growth. [2] In multi-component Ni-base superalloys, DP morphology constitutes a polycrystalline colony comprising of c¢ matrix with/without c-lamellae and needle-like tetragonal close-packed (TCP) phases segregated in Cr, W, and Re, which constitute the precipitate. [3][4][5][6][7][8] The advancement of the DP zone occurs by partitioning of Cr, W, and Re to the growing tips of the precipitates along the grain boundary.…”

Section: Introductionmentioning

confidence: 99%

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Discontinuous Precipitation in Ni-Base Superalloys During Solution Heat Treatment

Welton

D’Souza

Kelleher

et al. 2015

Metall Mater Trans A

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Discontinuous precipitation in single-crystal Ni-base superalloys during solution heat treatment has been studied. It is found that discontinuous precipitation occurs at temperatures approaching the solvus, where volume diffusion is dominant. Diffusion of Al ahead of the boundary leads to gamma prime precipitation and is accompanied by a loss in the driving force available for advancement of the grain boundary. The rate of gamma prime precipitation was tracked using in situ neutron diffraction during isothermal hold. Gamma prime precipitation is accompanied by super-saturation of Cr and W within the channels ahead of the interface. The driving force calculated for the initial stages of DP was [10-5 to 10-4] N/[lm 2 of the grain boundary]. The results provide an insight into discontinuous precipitation during solution heat treatment of Ni-base single-crystal alloys and are useful in optimizing the heat treatment process to avoid surface defect formation.

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“…[39][40][41] To reduce the energy of the grain boundary, the DP reaction can easily occur from the following reaction [22][23][24]42] :…”

Section: Comparison Of the Formation Mechanism With A Conventionalmentioning

confidence: 99%

Formation of an Intermediate Layer Between Grains in Nickel-Based Superalloy Turbine Blades

Kim

Withey

2017

Metall Mater Trans A

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The boundary region formed on the surface of nickel-based single-crystal turbine blades was investigated by high-resolution microscopy observation. There was a distinguishable intermediate layer with the size of about 2 to 5 lm between the matrix and surface defect grains such as stray grains, multiple grains, freckle grains, and even low-angle grain boundaries which were formed during the solidification of turbine blades. The intermediate layer was composed of many elongated c¢ as well as c phases. In addition, only one side of the intermediate layer was coherent to the matrix grain or defect grain due to good orientation match. At the coherent interface, the c¢ (as well as c) phase started to extend from the parent grain and coincidently, rhenium-rich particles were detected. Furthermore, the particles existed within both elongated gamma prime and gamma phases, and even at their boundary. Based on experimental observations, the formation mechanism of this intermediate layer was discussed.

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Discontinuous reactions in solids

Abstract: chemical diffusion R gas constantDiscontinuous reactions are solid state moving RF reaction frontboundary phase transitions characterised by a discontinuous or abrupt change in orientation and s segregation factor composition between the matrix phases in the

Cited by 244 publications

References 191 publications

Au–Fe alloy solidification and solid-state transformations

Au–Fe alloy solidification and solid-state transformations

Discontinuous Precipitation in Ni-Base Superalloys During Solution Heat Treatment

Formation of an Intermediate Layer Between Grains in Nickel-Based Superalloy Turbine Blades

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