The development of nucleation controlled microstructures during laser treatment of AlSi alloys

Gremaud, M.; Allen, Douglas; Rappaz, M.; Perepezko, John H.

doi:10.1016/1359-6454(95)00393-2

Cited by 70 publications

(33 citation statements)

References 24 publications

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“…For a given velocity of the track, relating the number of Si p observed at dierent depths to the estimated V Si s , suggests that the Si p number density decreases with increasing growth front speed. This diers from the results reported by Gremaud et al [27] and contradicts classical solidi®cation theory. Generally, for faster solidi®cation rates more particles nucleate.…”

Section: Growth Rate Of Si Particlescontrasting

confidence: 52%

“…This factor is larger than unity and can be aected by the geometry of the clad tracks or by the heat conducting condition. The studies of Gremaud et al [27] assumed that during the laser remelting process of Al±26 wt% Si the primary Si particles nucleated ahead of the eutectic interface at a distance approximately equal to the average particle spacing, which means j is unity. Their assumption is not appropriate to explain our results.…”

Section: Growth Time Of Si Particlesmentioning

confidence: 99%

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Functionally graded materials produced by laser cladding

2000

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AbstractÐAlSi40 functionally graded materials (FGMs) were produced by a one-step laser cladding process on cast Al-alloy substrate as a possible solution for interfacial problems often present in laser coatings. The microstructure of the FGMs consists of a large amount of silicon primary particles surrounded by aAl dendritic halos and by Al/Si eutectic. The Si particles exhibit a continuous increase in both size and volume fraction, from 8.5 mm and 22.7% at the bottom to 52 mm and 31.4% at the top of the FGM layer, respectively. The morphology of the Si particles changes accordingly from a small polygonal shape to a coarsely branched equi-axial shape. The a-Al halos and eutectic areas show less change over the same distance. From an analysis of the temperature ®eld of the laser pool, Si particles heterogeneously nucleate on incompletely melted Si particles. The number density of Si particles is most likely being controlled by the non-homogeneous temperature ®eld of the pool that determines the decomposition of the original Si phase in the AlSi40 powder. The growth rate and time available at dierent depths of the laser pool mainly aect the ®nal size of Si particles. 7

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Section: Growth Rate Of Si Particlescontrasting

confidence: 52%

Section: Growth Time Of Si Particlesmentioning

confidence: 99%

Functionally graded materials produced by laser cladding

2000

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“…The growth of the α-Al phase results in an increased Si concentration in the residual liquid to an extent that, eventually, may shift the composition of the liquid phase into the eutectic zone. This results in the cooperative growth mechanism between Si and Al that yields the eutectic phase in the latter stages of solidification [23][24][25]. The formation of the fibrous eutectic structure can be attributed to the large energy density imposed by the laser scanning on the surface of the material along with the high heat conductivity of Al.…”

Section: Resultsmentioning

confidence: 99%

Influence of Annealing on Mechanical Properties of Al-20Si Processed by Selective Laser Melting

Prashanth

Scudino

et al. 2014

Metals

151

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Abstract:The microstructure and mechanical properties of Al-20Si produced by selective laser melting (SLM) are investigated for different heat treatment conditions. As a result of the high cooling rate during processing, the as-built SLM material displays a microstructure consisting of a supersaturated Al(Si) solid solution along with heavily refined eutectic Si and Si particles. The Si particles become coarser, and the eutectic Si gradually changes its morphology from fibrous to plate-like shape with increasing annealing temperature. The microstructural variations occurring during heat treatment significantly affect the mechanical behavior of the samples. The yield and ultimate strengths decrease from 374 and 506 MPa for the as-built SLM material to 162 and 252 MPa for the sample annealed at 673 K, whereas the ductility increases from 1.6 to 8.7%. This offers the possibility to tune microstructure and corresponding properties of the Al-20Si SLM parts to meet specific requirements.

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“…Dramatic microstructure modification can be achieved by adding elements such as Ti, P, Na, or Sr, [1][2][3][4][5][6][7] by directional solidification, [8][9][10][11][12][13] or by rapid cooling such as in surface treatment with high-energy beams. [14,15,16] Particular attention has been paid to the morphology of the primary and eutectic silicon phases. [1,4,13,17,18] Reported primary-phase morphologies include [1] hexagonal plate-shaped crystals, equiaxed octahedral crystals, equiaxed crystals containing parallel twins, starlike crystals containing two to five radiating twin planes, and spherical crystals.…”

Section: Introductionmentioning

confidence: 99%

Undercooling and solidification of Al-50 at. pct Si Alloy by electromagnetic levitation

Liu

Herlach

Vandyoussefi

et al. 2004

Metall Mater Trans A

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Electromagnetic levitation is applied to achieve containerless solidification of 10-mm-diameter droplets of Al-50 at. pct Si. A maximum undercooling of 320 K is obtained. Phase morphologies on the droplet surfaces and on the deeply etched sections of the samples solidified at different undercoolings are examined by scanning electron microscopy. The primary silicon shows well-developed faceted dendrites at a small undercooling, but a fine granular form at a large undercooling. Stratified deposits of aluminum are found within the primary silicon plates, arising from solute pileup during growth. The microstructural refinement at a large undercooling has its origins in solute restriction of crystal growth and in fragmentation of the primary silicon dendrites. The form of the Al-Si eutectic is also found to be changed into an anomalous form at a large undercooling.

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The development of nucleation controlled microstructures during laser treatment of AlSi alloys

Cited by 70 publications

References 24 publications

Functionally graded materials produced by laser cladding

Functionally graded materials produced by laser cladding

Influence of Annealing on Mechanical Properties of Al-20Si Processed by Selective Laser Melting

Undercooling and solidification of Al-50 at. pct Si Alloy by electromagnetic levitation

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