Coarsening of secondary dendrite arms in a temperature gradient

Halder, E.; Exner, Hans Eckart

doi:10.1016/0001-6160(88)90233-7

Cited by 15 publications

(6 citation statements)

References 9 publications

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“…Beyond this limit, the experimental values of the coarsening constant were somewhat lower than predicted by theory due to a change in the shape of the particles and to a modification of the diffusion paths. The time-exponent also varied from ⅓ to ¼. Halder and Exner modelled the effect of an applied temperature gradient [405].…”

Section: Dendrite Spacingsmentioning

confidence: 99%

Progress in modelling solidification microstructures in metals and alloys: dendrites and cells from 1700 to 2000

Kurz

Fisher

Trivedi

2018

International Materials Reviews

155

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This is the first account of the history of our understanding of, and ability to model, solidification microstructures. Its objective is to retrace the scientific steps made, from the earliest observations of the eighteenth century to our present-day understanding of dendrites and eutectics. Because of the abundance of information, especially that added during the present century, sub-division was essential: this being the first of three articles. They cover dendrites and cells from 1700 to 2000, and then from 2001 to 2015 and finally eutectics and peritectics from 1700 to 2015. The authors have striven always to identify the genesis of every advance made, being aware that such a compact history must leave many worthy contributions by the wayside; others will doubtless complete the history. This review shows how crossfertilisation between theory and experiment, and basic and applied research led to both the posing and answering of challenging fundamental questions, thus rewarding society with beneficial results.

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Section: Dendrite Spacingsmentioning

confidence: 99%

Progress in modelling solidification microstructures in metals and alloys: dendrites and cells from 1700 to 2000

Kurz

Fisher

Trivedi

2018

International Materials Reviews

155

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“…162 An equation is given for the migrating velocity of the geometric centre of the dendrite arm v m as 162 v m ~DG T m L X L (1{k eq ) (7) where D is the diffusion coefficient in the liquid, G T is the temperature gradient and m L is the slope of the liquidus line. TGZM is not an important mechanism for the coarsening of dendritic structures for technical casting conditions, 163 while it may be significant for a combination of a high temperature gradient and a low solidification velocity.…”

Section: Temperature Gradient Zone Meltingmentioning

confidence: 99%

Melting and remelting phenomena

Rettenmayr¹

2009

International Materials Reviews

131

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Melting processes influence the microstructure evolution in metal alloys during casting and heat treatments. Melting is often treated as 'inverse solidification', which is only appropriate in a limited number of cases. In the present article, asymmetry between solidification and melting is reviewed in detail. The current state of the thermodynamic description of melting under diffusion control is outlined. Kinetic aspects that break the symmetry between solidifi-cation and melting that are discussed are solute partitioning, solute concentration gradients and solute transport in the involved phases. The view on nucleation of liquid and pre-melting phenomena, mostly of pure materials, based on experimental and theoretical work, is given. Emphasis is laid on aspects of melting with technical relevance, i.e. melting of alloys. Particu-larities of thermally and solutally controlled melting are introduced. Mechanisms that involve both melting and solidification simultaneously are capillary driven coarsening, temperature gradient zone melting and liquid film migration. The impact of these processes on microstructural evolution is discussed. Open questions concerning modelling and simulation of melting, namely, the interaction of different melting mechanisms and the role of the solid/liquid inter-face, are identified.

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“…(2a) and (2b), with D L =6.4 Â 10 À3 mm 2 /s, m= À6.5 K/wt%, C L *=C E =13.0 wt%, k=0.13 and a temperature gradient within the liquid pool G d =2 K/mm. Besides, it is well known that the contribution of migration of secondary arms by TGZM to the coarsening of dendritic microstructure could be significant under certain conditions, in particular high temperature gradient and low velocity [15][16][17]. The reasons why TGZM may affect the microstructure coarsening are (i) an increase of the coarsening time (when the secondary arm is in contact with the liquid phase) and (ii) the different velocity of secondary arms at the hotter and colder sides of the solid-liquid zone [15].…”

Section: Migration Of Secondary Arm Provoked By Tgzmmentioning

confidence: 99%