Solidification of peritectic alloys

Kerr, H. W.; Kurz, W.

doi:10.1179/095066096790151231

Cited by 100 publications

(108 citation statements)

References 39 publications

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“…For dilute Al-Ti and Al-Zr alloys, as well as other peritectic systems, to a specific cooling rate corresponds a critical solute concentration below which primary precipitation of Al 3 M (M = Ti or Zr) does not occur. [36][37][38] The compositions in Table I were expected, based on prior solidification studies ( Figure 8, discussed subsequently), to be near the threshold for avoiding primary precipitation of Al 3 M for the moderate cooling rates used here.…”

Section: A Alloy Compositions and Preparationmentioning

confidence: 99%

Nucleation and Precipitation Strengthening in Dilute Al-Ti and Al-Zr Alloys

Knipling

Dunand

Seidman

2007

Metall Mater Trans A

181

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Two conventionally solidified Al-0.2Ti alloys (with 0.18 and 0.22 at. pct Ti) exhibit no hardening after aging up to 3200 hours at 375°C or 425°C. This is due to the absence of Al 3 Ti precipitation, as confirmed by electron microscopy and electrical conductivity measurements. By contrast, an Al-0.2Zr alloy (with 0.19 at. pct Zr) displays strong age hardening at both temperatures due to precipitation of Al 3 Zr (L1 2 ) within Zr-enriched dendritic regions. This discrepancy between the two alloys is explained within the context of the equilibrium phase diagrams: (1) the disparity in solid and liquid solubilities of Ti in a-Al is much greater than that of Zr in a-Al; and (2) the relatively small liquid solubility of Ti in a-Al limits the amount of solute retained in solid solution during solidification, while the comparatively high solid solubility reduces the supersaturation effecting precipitation during post-solidification aging. The lattice parameter mismatch of Al 3 Ti (L1 2 ) with a-Al is also larger than that of Al 3 Zr (L1 2 ), further hindering nucleation of Al 3 Ti. Classical nucleation theory indicates that the minimum solute supersaturation required to overcome the elastic strain energy of Al 3 Ti nuclei cannot be obtained during conventional solidification of Al-Ti alloys (unlike for Al-Zr alloys), thus explaining the absence of Al 3 Ti precipitation and the presence of Al 3 Zr precipitation.

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Section: A Alloy Compositions and Preparationmentioning

confidence: 99%

Nucleation and Precipitation Strengthening in Dilute Al-Ti and Al-Zr Alloys

Knipling

Dunand

Seidman

2007

Metall Mater Trans A

181

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“…These alloys show a wide variety of microstructures in directional solidification at low speed [1][2][3][4][5][6][7][8][9][10][11][12][13], including regions of primary a, primary b, islands of one phase in the other and coupled growth. It is this latter microstructure that is of most interest here.…”

Section: Introductionmentioning

confidence: 99%

Modeling of peritectic coupled growth in Cu–Sn alloys

Valloton¹,

Dantzig²,

Plapp³

et al. 2013

Acta Materialia

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In directional solidification experiments on hypoperitectic Cu-Sn alloys at low velocity and high thermal gradient, both lamellar and fibrous coupled peritectic growth patterns have been observed. Two phenomena that had not been observed in previous experiments on other alloy systems are investigated here with the help of different modeling approaches. The mean volume fraction of primary phase a, g a , as determined by X-ray microtomography, decreases with solidification distance over the entire length of the coupled zone, but is always much larger than that expected from the equilibrium phase diagram. Moreover, oscillations in g a with a spatial periodicity approximately equal to the lamellar spacing are also observed. The first observation is explained semi-quantitatively by a simple 1D diffusion model, which reveals that the onset of coupled growth occurs during the initial transient of the primary phase planar front growth. A two-dimensional phase-field model is used to monitor the subsequent microstructure evolution, and shows that the lamellar structure exhibits collective 1-k oscillations. In agreement with previous studies, it was found that these oscillations lead to stable coupled growth only for a limited range of the control parameters.

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“…However, the fact that it is made of two peaks, a sharp one at 1180°C and a broader one starting at 1173°C, is puzzling. Double nucleation peaks below T per have been reported in the literature, but were finally related to the initial nucleation of the primary phase below the peritectic temperature, followed by the nucleation of the peritectic phase [18]. In the present study, the solidification peak of the primary phase is clearly visible and distinct from peak # 2, so that this mechanism can safely be discarded.…”

Section: Thermal Analysis Resultsmentioning

confidence: 56%

“…However, this change in contour could also be related to instabilities developing during solid-state transformation following direct peritectic solidification at the (Au)-(c-Fe) interface. Indeed, very few experimental evidences of peritectic reaction have been documented in literature [18,24].…”

Section: Peritectic Phase Formationmentioning

confidence: 99%

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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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Solidification of peritectic alloys

Cited by 100 publications

References 39 publications

Nucleation and Precipitation Strengthening in Dilute Al-Ti and Al-Zr Alloys

Nucleation and Precipitation Strengthening in Dilute Al-Ti and Al-Zr Alloys

Modeling of peritectic coupled growth in Cu–Sn alloys

Au–Fe alloy solidification and solid-state transformations

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