A survey of eutectoid decomposition in ten Ti-X systems

Franti, G. W.; Williams, James C.; Aaronson, H.I.

doi:10.1007/bf02661947

Cited by 61 publications

(18 citation statements)

References 9 publications

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“…Microstructures of this type have already been observed in steel by Hillert [24], who termed them as the product of "a low degree of cooperation". They are also observed in hypoeutectoid [25], eutectoid [26] and hypereutectoid Ti-X alloys [27], as well as in eutectoid ␤Cu-Al and ␤Cu-In alloys [28].…”

Section: Figurementioning

confidence: 99%

Gold nanostructures by directional solid-state decomposition

2006

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The trend in electronics industry towards miniaturisation is leading to increasing research focus on nano-electronic devices. For example, metal nanowires show potential for future application as connector lines in such devices. The controlled fabrication of these structures at scales beyond the current limits of lithographic techniques is of great interest. Self-assembly processes using gold nanoparticles are being extensively studied as one possible long-term solution. This study addresses a novel approach of obtaining gold nanostructures. It consists of applying directional solidification processing to eutectoid alloys in order to produce ordered structures, followed by phase separation by selective etching.The directional transformation of eutectoid alloys is a close derivation of the directional solidification of eutectics. In this case, two phases precipitate simultaneously from a high-temperature solid phase (Figure 1). When the growth properties of the two phases are sufficiently compatible, unidirectional decomposition can also produce aligned composite materials [1,2]. One of the most prominent examples of eutectoid reaction is the formation of pearlite by undercooling a Fe-C alloy in the ␥-state. Microstructures are best when the high-temperature phase is nearly singlecrystalline. Therefore, aligned eutectoids are often produced by accomplishing unidirectional solidification and unidirectional decomposition sequentially. Eutectic solidification and eutectoid decomposition, as examples of duplex crystal growth, are inherently more complex than single-phase crystal growth. The technique used in both cases is quite similar: a specimen is unidirectionally translated through a steep temperature gradient and traversed by a macroscopically planar transformation front. If adequate experimental conditions are arranged, the eutectoid reaction product is an aligned microstructure. The conditions to be met are: i) sufficiently steep gradient to avoid both nucleation before the actual position of the transformation front and coalescence afterwards, ii) a translation rate which permits the attainment of a transformation front with stationary moving conditions, i.e., as a first approximation, a lower translation rate than the maximum eutectoid growth rate.Although eutectic and eutectoid reactions are essentially the same in nature, there are some differences that must be pointed out. Firstly, eutectoid spacings are much finer than the eutectic spacings for the same growth rate, due to the lower values of diffusion coefficients in the solid state as compared to the liquid. Also, a decrease in eutectoid spacing, , with increasing growth rate, V, is generally slower for eutectoids than for eutectics. Data can again be fitted to a formula n V = const. However, whereas n = 2 fits to almost all data for eutectics, values of n ranging from 2 to 4 have been reported for eutectoids. The value n = 2 is consistent with volume-diffusion control, and n = 3 is predicted for grain-boundary-diffusion control.

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Section: Figurementioning

confidence: 99%

Gold nanostructures by directional solid-state decomposition

2006

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“…In fact, previous work on the solid-state eutectoid decomposition of a number of Ti-X alloys [25,26,27] showed that there were two different modes of eutectoid decomposition of b phase: the nonlamella (bainite) mode and the lamellar (pearlite) mode. Bainite phase has been defined as a nonlamellar, noncooperative, competitive product of the transformation, while pearlite has been defined as a lamellar, cooperative product of the eutectoid decomposition.…”

Section: B Decomposition Of B-timentioning

confidence: 96%

“…On the other hand, it could be due to the high Al and V content in the graded material that constrained the development of a sideplates from the proeutectoid Ti 2 Ni. Franti [25] investigated the mechanism of eutectoid decomposition in some Ti-X binary systems and found that alloys of hypoeutectoid composition decomposed predominantly into bainite, except in the case of Ti-Cu, where pearlite was the principal mode of eutectoid decomposition. As for the near-eutectoid alloys, the decomposition mode appeared to be predominantly a pearlitic transformation.…”

Section: B Decomposition Of B-timentioning

confidence: 99%

Solidification Behavior and the Evolution of Phase in Laser Rapid Forming of Graded Ti6Al4V-Rene88DT Alloy

Lin

Yue

Yang

et al. 2007

Metall Mater Trans A

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The graded material of Ti6Al4V-Rene88DT superalloy, which has shown the potential to be applied in aeroengines, was fabricated from prealloyed metal powders using the technique of laser rapid forming (LRF). A compositional gradient, from 100 pct Ti6Al4V to Ti6Al4V-38 pct Rene88DT, was achieved within a thickness of laser deposit of 54 mm. The solidification behavior and the phase evolution of the compositionally graded material were studied. The results of the X-ray diffraction (XRD) analysis together with the metallographic study showed that a series of phase evolutions, a + b fi a + b + Ti 2 Ni fi b + Ti 2 Ni, along the compositional gradient have occurred. The hardness value of the graded material was measured along the compositional gradient, and the results were explained in terms of the various phases present. The condition for columnar-to-equiaxed transition observed in the graded material was explained, based on Hunt's criterion. Finally, the morphology of b + Ti 2 Ni anomalous eutectic is discussed.

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“…For all these alloys in the quenched microstructure, neither the presence of any untransformed beta nor other second phase was reported. Subsequently, studies on isothermal treatments of Ti-6 wt pct Cu were conducted by Franti et al [1] Optical investigations showed the presence of bainite in those alloys that were isothermally aged at higher subtransus temperatures (lower undercooling). The ratio of bainite to pearlite was reported to decrease with an increase in undercooling from the transus temperature, with 95 pct bainite formed at 1048 K (775°C) and only 5 pct bainite formed at 973 K (700°C).…”

mentioning

confidence: 99%

“…Numerous studies have been conducted in the past on phase transformations in Ti-X eutectoid systems (X = Bi, Co, Cr, Cu, Fe, Mn, Ni, Pb, Pd, Pt). [1][2][3][4][5][6][7] Out of the several eutectoid-forming elements, Cu, Ni, and Si were found to form active eutectoid systems with Ti, due to their fast transformation kinetics. [2] In other words, it is difficult to inhibit eutectoid transformation in these systems even on quenching from the high-temperature single b phase field.…”

mentioning

confidence: 99%

Competing Martensitic, Bainitic, and Pearlitic Transformations in a Hypoeutectoid Ti-5Cu Alloy

Devaraj

Nag

Muddle

et al. 2011

Metall Mater Trans A

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This article discusses the competing mechanisms of martensite formation vs eutectoid decomposition via pearlitic or bainitic mechanisms during continuous cooling of a Ti-5 wt pct Cu hypoeutectoid alloy, which falls under the category of active eutectoid systems. Faster cooling rates result in a mixed microstructure of nanoscale bainite consisting of a far-from-equilibrium Ti 2 Cu phase and martensitic alpha plates, as determined from three-dimensional atom probe (3DAP) coupled with energy-filtered transmission electron microscopy (EFTEM). Slower cooling resulted in near-equilibrium eutectoid-based microstructures.

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A survey of eutectoid decomposition in ten Ti-X systems

Cited by 61 publications

References 9 publications

Gold nanostructures by directional solid-state decomposition

Gold nanostructures by directional solid-state decomposition

Solidification Behavior and the Evolution of Phase in Laser Rapid Forming of Graded Ti6Al4V-Rene88DT Alloy

Competing Martensitic, Bainitic, and Pearlitic Transformations in a Hypoeutectoid Ti-5Cu Alloy

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