On metastable eutectic reactions in peritectic systems: Possible applications to TiAl alloys

Laraia, Vincent J.; Heuer, A. H.

doi:10.1016/0956-716x(91)90160-3

Cited by 13 publications

(7 citation statements)

References 8 publications

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“…Reflecting, the work of V.J. Laraia, A.H. Heuer [8], a conversion of a peritectic reaction to a metastable eutectic reaction was taken into account. In this case extensive lateral mixing has to take place and therefore no pile-up of solute occurs in front of the solid-liquid interface.…”

Section: Resultsmentioning

confidence: 99%

“…The a-phase undercools and shifts to a'. The peritectic reaction with the triple tangent a-y-L, respectively, converts to a eutectic reaction with a tangent touching the energy curves a'-L-y, respectively [8]. Therefore a liquid with composition Co = 53.4 at.% Al decomposes to a and y' and the flux in front of the solidification front permits cooperative growth [4].…”

Section: Resultsmentioning

confidence: 99%

“…The almost equal slopes of the ac-liquidus and y-liquidus [6], the approximately horizontal slopes of the liquidus and solidus-lines of the peritectic y-phase, the small temperature interval between the a-and y-tips (• 10 K) and moreover the small difference between CYP and CLp (; 0. 1 at.%) are important requirements within the theory of coupled growth [4,7,8].…”

Section: Introductionmentioning

confidence: 99%

“…Hillert [7], V.J. Laraia, A.H. Heuer [8] and A. Ostrowski, E.W. Langer [4] discussed cooperative growth of peritectic systems by analyzing free energy diagrams.…”

Section: Introductionmentioning

confidence: 99%

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Coupled Peritectic Growth of the α- and Γ- Phases in Binary Titanium Aluminides

1995

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Coupled growth during three phase equilibrium solidification is well known from directionally solidified eutectic systems, and was recently generated in monotectic systems. Several theories predict a stationary peritectic reaction and coupled growth of the properitectic and the peritectic phases therefore should be possible. In spite of these theories coupled growth has not been observed up to now. The TiAl system was selected for further investigation on this topic because of its technical relevance and the fact that it meets the condition mentioned for coupled growth.In a Bridgman laboratory furnace, TiAI with 53.4 at.% Al was directionally solidified with solidification rates v between 0.025 mm/min and 0.1 mm/min and a temperature gradient up to 20 K/mm. The resulting microstructures, analyzed using optical and scanning microscopy with EDX and WDX, consist of two phases parallel to the growth direction. At v = 0.05 to 0.1 mm/min, the alloy solidifies as properitectical a, which subsequently eutectoidally transforms to a substructure of a 2 -Ti 3 Al and y-TiAl, and peritectic y. The lamellar a 2 /y-substructure is oriented parallel to the growth direction.The experimental results were compared with the existing theoretical models of a stationary peritectic reaction and the possibility of metastable eutectic growth was discussed.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Hillert [7], V.J. Laraia, A.H. Heuer [8] and A. Ostrowski, E.W. Langer [4] discussed cooperative growth of peritectic systems by analyzing free energy diagrams.…”

Section: Introductionmentioning

confidence: 99%

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Coupled Peritectic Growth of the α- and Γ- Phases in Binary Titanium Aluminides

1995

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“…The main reason for the difference is considered to be the high cooling rate associated with laser cladding, which favors the nucleation of metastable phases preferentially over stable phases in the melt, and the equilibrium peritectic reaction being replaced by nonequilibrium eutectic reactions. [21,22] B. Primary Dendrite Arm Spacing Figure 12 shows the average spacing of primary dendrites along the composition gradient in the Cu and Ni layers.…”

Section: A Solidification Path Selectionmentioning

confidence: 99%

Microstructure and Phase Evolution in Laser Cladding of Ni/Cu/Al Multilayer on Magnesium Substrates

Yue

Lin

2009

Metall Mater Trans A

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A multilayer coating of Ni/Cu/Al was fabricated on magnesium substrates using laser cladding. The solidification behavior and the phase evolution of the compositionally graded coating were studied. The results of the X-ray diffraction (XRD) analysis together with the metallographic study showed that a series of phase evolutions had occurred along the gradient (Mg) fi (Mg) + Al 12 Mg 17 fi (Mg) + Q + k 2 fi k 1 fi k 1 + c 1 fi c 1 + (Cu) + k 1 fi (Cu) + k 1 fi (Cu) fi (CuNi) fi (Ni). The rapid solidification condition had suppressed the invariant reactions that existed in the ternary Mg-Al-Cu alloy system. As a result, many of the predicted Al-rich brittle intermetallic compounds, which are detrimental to the performance of the coating, were not produced. The solidification path during the laser cladding of the Al and Cu layers was determined and the various phases, as predicted by the corresponding phase diagram, agreed well with the experimental results. Finally, the primary arm spacing (PAS) and the solidification morphology of the dendrites in the Cu and Ni layers were analyzed in relation to the solidification conditions.

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