Experimental determination and thermodynamic calculation of the phase equilibria in the Cu–Cr–Nb and Cu–Cr–Co systems

Liu, X.J.; Zheng, Jianguo; Wang, C.P.; Ishida, K.

doi:10.1016/j.jallcom.2008.11.162

Cited by 35 publications

(25 citation statements)

References 40 publications

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“…% Ni (0.25 mole fraction) which is indicated by a dotted line in Figure 9. The calculation of the isopleth for this system shows agreement with previous calculations [21] and experiment [23] for the left hand side of the isopleth (CoCrCu), as there is indeed a significant liquid state miscibility gap for the CoCrCu alloy. The calculations also show that there exists a single-phase liquid region above the miscibility gap until approximately 27.5 at.…”

Section: Discussionsupporting

confidence: 87%

In-Situ Imaging of Molten High-Entropy Alloys Using Cold Neutrons

et al. 2019

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Real-time neutron imaging was utilized to produce a movie-like series of radiographs for in-situ observation of the remixing of liquid state immiscibility that occurs in equiatomic CoCrCu with the addition of Ni. A previous neutron imaging study demonstrated that liquid state immiscibility can be observed in-situ for the equiatomic CoCrCu alloy. In this follow-up study, equiatomic buttons of CoCrCu were placed alongside small Ni buttons inside an alumina crucible in a high-temperature vacuum furnace. The mass of the Ni buttons was specifically selected such that when melted in the same crucible as the CoCrCu buttons, the overall composition would become equiatomic CoCrCuNi. Neutron imaging was simultaneously carried out to capture 10 radiographs in 20 °C steps from 1000 °C to 1500 °C and back down to 1000 °C. This, in turn, produced a movie-like series of radiographs that allow for the observation of the buttons melting, the transition from immiscible to miscible as Ni is alloyed into the CoCrCu system, and solidification. This novel imaging process showed the phase-separated liquids remixing into a single-phase liquid when Ni dissolves into the melt, which makes this technique crucial for understanding the liquid state behavior of these complex alloy systems. As metals are not transparent to X-ray imaging techniques at this scale, neutron imaging of melting and solidification allows for the observation of liquid state phase changes in real time. Thermodynamic calculations of the isopleth for CoCrCuNix were carried out to compare the observed results to the predictions resulting from the current Thermo-Calc TCHEA3 thermodynamic database. The calculations show a very good agreement with the experimental results, as the calculations indicate that the CoCrCuNix alloy solidifies from a single-phase liquid when x ≥ 0.275, which is close to the nominal concentration of the CoCrCuNi alloy (x = 0.25). The neutron imaging shows that the solidification of CoCrCuNi results from a single-phase liquid. This is evident as no changes in the neutron attenuation were observed during the solidification of the CoCrCuNi alloy.

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Section: Discussionsupporting

confidence: 87%

In-Situ Imaging of Molten High-Entropy Alloys Using Cold Neutrons

et al. 2019

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“…In the recent review by Miracle et al, approximately 85% of all HEAs thus far contained the 3d transition metals Co, Cr, Cu, Fe, Mn, Ni, Ti, V, as well as Al [7]. Out of these 3d transition metal HEAs, approximately 33% of the 345 alloys contain equiatomic CoCrCu, which has been shown to form no ternary compound, instead shows a very large liquid phase miscibility gap and upon solidification leads to Cu-lean and Cu-rich phases [11]. In order to investigate the possible liquid phase separation in more complex alloys such as the HEAs in Reference [7], in-situ studies of liquid phase separation in "medium entropy" alloy CoCrCu were carried out to verify that the technique can identify distinct phase-separated liquids, which in turn can be applied to the other CoCrCu-containing systems.…”

Section: Introductionmentioning

confidence: 99%

In-Situ Imaging of Liquid Phase Separation in Molten Alloys Using Cold Neutrons

et al. 2017

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Understanding the liquid phases and solidification behaviors of multicomponent alloy systems becomes difficult as modern engineering alloys grow more complex, especially with the discovery of high-entropy alloys (HEAs) in 2004. Information about their liquid state behavior is scarce, and potentially quite complex due to the presence of perhaps five or more elements in equimolar ratios. These alloys are showing promise as high strength materials, many composed of solid-solution phases containing equiatomic CoCrCu, which itself does not form a ternary solid solution. Instead, this compound solidifies into highly phase separated regions, and the liquid phase separation that occurs in the alloy also leads to phase separation in systems in which Co, Cr, and Cu are present. The present study demonstrates that in-situ neutron imaging of the liquid phase separation in CoCrCu can be observed. The neutron imaging of the solidification process may resolve questions about phase separation that occurs in these alloys and those that contain Cu. These results show that neutron imaging can be utilized as a characterization technique for solidification research with the potential for imaging the liquid phases of more complex alloys, such as the HEAs which have very little published data about their liquid phases. This imaging technique could potentially allow for observation of immiscible liquid phases becoming miscible at specific temperatures, which cannot be observed with ex-situ analysis of solidified structures.

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“…The alloying elements (Cr and Nb) have negligible solubility in copper at room temperature and up to 800°C [24] and they readily react to form more stable Cr 2 Nb precipitates leaving Cu matrix free from Cr and Nb. This not only enhances the thermal conductivity of copper but also deformability.…”

Section: Resultsmentioning

confidence: 99%

“…Cr equilibrium value as per phase diagram [24]. The above mechanism of evolution of Cr 2 Nb precipitates has been studied in detail by Groza [14].…”

Section: Elementmentioning

confidence: 99%