Phase stability and relations of multi-phase alloys based on B2 CoAl and E21 Co2AlC

Kimura, Yuichi; Takahashi, Masaru; Miura, Seiji; Suzuki, Tomoo; Mishima, Yoshinao

doi:10.1016/0966-9795(95)00001-f

Cited by 25 publications

(41 citation statements)

References 16 publications

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“…6(b) and 6(c), the fcc disordered g phase coexists with the fcc-based ordered k phase. Considering the analogy with the (gϩgЈ) microstructures in Ni base superalloys, this twophase structure may be beneficial for the heat resisting properties of these alloys, as reported by Kimura et al 4) for the Co-Al-C system.…”

Section: Comparison Of the Calculated Phase Equilibria With The Expermentioning

confidence: 99%

“…The application of this material as a heat resistant alloy from the formation of a coherent fine microstructure consisting of an fcc solid solution and the k phase is attracting great attention. 4) Regardless of such a promising potential for this new material, little information on the thermodynamic properties of this carbide phase is known. Thus, we have attempted to calculate the formation energy of Fe 3 AlC using a first principle band energetic calculation method.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamic Analysis of the Fe-Al-C Ternary System by Incorporating ab initio Energetic Calculations into the CALPHAD Approach

2004

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A thermodynamic analysis of the Fe-C-Al ternary system has been carried out covering a wide range of temperatures and composition. Special care was taken to the expression of the free energy for the ternary Perovskite carbide phase, Fe 3 AlC (k), by considering the crystallographic similarity between the k phase and the L1 2 structure. The free energy was calculated using the (Fe,Al) 3 (Fe,Al) 1 (C,Va) 1 sublattice model, and the k and L1 2 structures were treated as a continuous solution. Because of the lack of experimental information available, the thermodynamic properties of the E2 1 structure were evaluated using the Full Potential Linearized Augmented Plane Wave (FLAPW) method.The ab initio energetic calculations show that the stable E2 1 structure of the k phase is highly preferred compared with the metastable Fe 3 Al-L1 2 structure. Contour plots of the charge density for the k phase indicate that the bonding between the Fe and C atoms forms in the Fe 3 AlC-E2 1 structure, and that this interaction between the atoms enhances the energetic stability of the k phase.According to our phase diagram calculations, the k phase is in equilibrium with the fcc Fe, B2-type intermetallic compound, as well as the graphite phase. This finding is in good agreement with previous experimental results.KEY WORDS: phase diagram; thermodynamic analysis; ab initio energetic calculations; ternary carbide. alloy from the formation of a coherent fine microstructure consisting of an fcc solid solution and the k phase is attracting great attention. 4) Regardless of such a promising potential for this new material, little information on the thermodynamic properties of this carbide phase is known. Thus, we have attempted to calculate the formation energy of Fe 3 AlC using a first principle band energetic calculation method. The objective of the present study was to introduce estimated values into a CALPHAD-type thermodynamic analysis, and to clarify the full phase equilibria of the Fe-Al-C ternary system. Computational ProceduresThe formation energy of the phase was calculated using the FLAPW method. A brief outline of the computational method and a description of the Gibbs free energy for each phase adopted in the thermodynamic analysis will be presented. Ab initio Energetic CalculationsThe FLAPW method, as embodied in the WIEN2k 5) software package, is one of the most accurate schemes for electronic calculations and allows for very precise calculations of the total energies in a solid, and was employed in our energetic calculations. The FLAPW method uses a scheme for solving many-electron problems based on the local spin density approximation (LSDA) technique. In this framework, a unit cell is divided into two regions: non-overlapping atomic spheres and an interstitial region. Inside the atomic spheres, the wave functions of the valence states are expanded using a linear combination of radial functions and spherical harmonics, while a plane wave expansion is used in the interstitial region. The LSDA technique includes an approximat...

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Section: Comparison Of the Calculated Phase Equilibria With The Expermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermodynamic Analysis of the Fe-Al-C Ternary System by Incorporating ab initio Energetic Calculations into the CALPHAD Approach

2004

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“…3, the large non-stoichiometry of the phase agreed with the previous experimental results. 16,17) The phase boundaries in Fig. 3 did not give any serious conflictions with the experimental data reported by Kimura, et al 16) A slight deviation may be due to the difference in the annealing temperature and cooling rate.…”

Section: Co-al-c Ternary Systemmentioning

confidence: 37%

“…16,17) The phase boundaries in Fig. 3 did not give any serious conflictions with the experimental data reported by Kimura, et al 16) A slight deviation may be due to the difference in the annealing temperature and cooling rate. Note that the previous study did not examine carbon contents as high as those in samples 6, 7 and 8.…”

Section: Co-al-c Ternary Systemmentioning

confidence: 37%

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The Phase Equilibria and Seebeck Coefficient of (Co,M)<SUB>3</SUB>AlC (M=Fe or Ni)

Maruoka

Suzuki

2006

Mater. Trans.

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The phase equilibria and the Seebeck coefficient were measured at the vicinity of the carbide (Co,M) 3 AlC (M ¼ Fe or Ni) in the Co-Al-C, Co-Fe-Al-C and Co-Ni-Al-C systems. The samples were well annealed at 1473 K and examined through X-ray diffraction measurements, energy dispersive X-ray analysis and carbon analysis. Co 3 AlC with a perovskite structure did not exist at its stoichiometric composition, but was located within a narrow compositional range near Co 3 AlC 0:67 . The maximum Seebeck coefficient was 23.3 mV/K at 873 K for Co 3 AlC 0:63 . The replacement of a small amount of Co by Fe resulted in the expansion of the single-phase area of (Co,Fe) 3 AlC x , and the Seebeck coefficient of the single phase reached its maximum, 32.6 mV/K, at 873 K and Co 3:506 Fe 0:025 AlC 0:77 in the quaternary Co-Fe-Al-C system. The addition of Ni did not stabilize this carbide, and the maximum Seebeck coefficient in the quaternary Co-Ni-Al-C system was 26.9 mV/K at 873 K.

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Formation of Cuboidal Co₃AlC Precipitates in Carbon‐Containing Co–Al–W‐Based Superalloys

et al. 2015

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The influence of Carbon addition on a ternary Co-Al-W alloy is investigated especially regarding phase stability and partitioning behavior of alloying elements. During casting and subsequent cooling, C-additon leads to the formation of an interdendritic carbide network and to the homogeneous precipitation of cuboidal E2 1 phase, Co 3 AlC, in the W-rich Co matrix. The solvus temperature of this phase is found to be about 1200°C, which is significantly higher than the solvus temperature of the ternary L12 phase Co 3 (Al,W). In the course of solution heat treatment, the Co 3 AlC precipitates are dissolved and the carbides change in morphology and chemical composition. Further annealing leads to the precipitation of small cuboidal precipitates of L1 2 phase, Co 3 (Al,W), and to a discontinuous precipitation of further phases.

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Phase stability and relations of multi-phase alloys based on B2 CoAl and E21 Co2AlC

Cited by 25 publications

References 16 publications

Thermodynamic Analysis of the Fe-Al-C Ternary System by Incorporating ab initio Energetic Calculations into the CALPHAD Approach

Thermodynamic Analysis of the Fe-Al-C Ternary System by Incorporating ab initio Energetic Calculations into the CALPHAD Approach

The Phase Equilibria and Seebeck Coefficient of (Co,M)<SUB>3</SUB>AlC (M=Fe or Ni)

Formation of Cuboidal Co₃AlC Precipitates in Carbon‐Containing Co–Al–W‐Based Superalloys

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Phase stability and relations of multi-phase alloys based on B2 CoAl and E21 Co2AlC

Cited by 25 publications

References 16 publications

Thermodynamic Analysis of the Fe-Al-C Ternary System by Incorporating ab initio Energetic Calculations into the CALPHAD Approach

Thermodynamic Analysis of the Fe-Al-C Ternary System by Incorporating ab initio Energetic Calculations into the CALPHAD Approach

The Phase Equilibria and Seebeck Coefficient of (Co,M)<SUB>3</SUB>AlC (M=Fe or Ni)

Formation of Cuboidal Co3AlC Precipitates in Carbon‐Containing Co–Al–W‐Based Superalloys

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Formation of Cuboidal Co₃AlC Precipitates in Carbon‐Containing Co–Al–W‐Based Superalloys