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Title: Origin of grain orientation during solidification of an aluminum alloy

Authors:
; ;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1323584
Grant/Contract Number:
NE0008280
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 115; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-03 22:22:14; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Country of Publication:
United States
Language:
English

Citation Formats

Wei, H. L., Elmer, J. W., and DebRoy, T. Origin of grain orientation during solidification of an aluminum alloy. United States: N. p., 2016. Web. doi:10.1016/j.actamat.2016.05.057.
Wei, H. L., Elmer, J. W., & DebRoy, T. Origin of grain orientation during solidification of an aluminum alloy. United States. doi:10.1016/j.actamat.2016.05.057.
Wei, H. L., Elmer, J. W., and DebRoy, T. Mon . "Origin of grain orientation during solidification of an aluminum alloy". United States. doi:10.1016/j.actamat.2016.05.057.
@article{osti_1323584,
title = {Origin of grain orientation during solidification of an aluminum alloy},
author = {Wei, H. L. and Elmer, J. W. and DebRoy, T.},
abstractNote = {},
doi = {10.1016/j.actamat.2016.05.057},
journal = {Acta Materialia},
number = C,
volume = 115,
place = {United States},
year = {Mon Aug 01 00:00:00 EDT 2016},
month = {Mon Aug 01 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.actamat.2016.05.057

Citation Metrics:
Cited by: 13works
Citation information provided by
Web of Science

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  • An experimental study has been conducted to investigate the effects of grain transport on the columnar to equiaxed transition (CET) in dendritic alloy solidification. Using the aqueous ammonium chloride solution as a transparent model alloy, experiments were performed in a vertical test cell with cooling from the top, resulting in unidirectional columnar crystals growing downwards. Ahead of the columnar front, equiaxed nuclei were observed to originate mostly by fragmentation of the columnar dendrites in the presence of a thermally driven flow in the melt beneath the columnar mushy zone. Being heavier than the liquid, these fragments fall into the bulkmore » melt where they may grow or remelt. The survival equiaxed crystals finally settle towards the floor and pile up to form an equiaxed bed. The CET occurs when the bottom equiaxed packed bed rises and eventually obstructs the columnar mushy zone growing from the upper surface. Therefore, the CET in the present configuration was predominantly controlled by the sedimentation of equiaxed crystals. A parametric study by varying initial concentration, cooling rate, and superheat was performed.« less
  • No abstract prepared.
  • The microstructural evolution during the uniaxial compression of an as-deposited bulk nanocrystalline (nc) Ni-Fe (average grain size d{approx_equal}23 nm) at ambient temperature was investigated by the high-energy x-ray diffraction (HEXRD) and the transmission-electron microscopy (TEM). HEXRD measurements indicated that the grain growth occurred in the nc Ni-Fe alloy during the uniaxial compression tests and that the grain growth shows orientation dependence, i.e., the grains preferentially grow perpendicular to the loading direction. This preferred grain growth was further confirmed by the TEM observations, indicating that the grains were elongated after the compressive plastic deformation.
  • A model is presented for the prediction of the interfacial heat-transfer coefficient during the unidirectional solidification vertically upward of an Al-7 wt pct Si alloy cast onto a water cooled copper chill. It has been experimentally determined that the casting surfaces were convex toward the chill, probably due to the deformation of the initial solidified skin of the casting. The model was, therefore, based upon a determination of the (macroscopic) nominal contact area between the respective rough surfaces and, within this region, the actual (microscopic) contact between the casting and the chill surfaces. The model produced approximate agreement with bothmore » experimentally determined values of the heat-transfer coefficient and the measured curvature of the casting surface and showed a reasonable agreement with measured temperatures in the casting and the chill also. A common experimental technique for the experimental determination of the heat-transfer coefficient involves the assumption of one-dimensional heat transfer only. An implication of the approach adopted in this model is that the heat transfer in the region of the casting-chill interface may be two-dimensional, and the subsequent error in the experimentally determined values is discussed.« less
  • Unidirectional solidification tests on an aluminum alloy were conducted with a computer-controlled instrumented rig. The alloys employed in this study were poured into isolated ingot molds (made of recrystallized alumina and covered with ceramic fiber) placed on top of a steel plate, coated either with a graphite- or ceramic-based paint in order to avoid sticking or the material. Thermal evolution during the test was captured by type-K thermocouples placed at different positions in both the ingot and the plate. The bottom surface of the plate was either cooled with water or left to cool in air. The heat-transfer coefficients acrossmore » the aluminum-steel interface were evaluated by means of a finite-difference model. It was concluded that the heat-transfer rate depends on the conditions at the interface, such as the type of coating used to protect the plate, and the solidification reactions occurring on the aluminum during its solidification.« less