Abstract
The aluminum-rich corner of the Al–Co–Pd ternary system was thermodynamically modeled by the CALPHAD method in the present study. The ternary system is a complex system with many ternary phases (W, V, F, U, Y2, C2). All ternary phases, except phase U, were modeled as stoichiometric compounds. The order–disorder model was used to describe the BCC–B2 and BCC-A2 phases. Solubility of the third element in binary intermetallic phases (Al5Co2, Al3Co, Al9Co2, Al13Co4, Al3Pd and Al3Pd2) was modeled. The experimental results collected from the literature were used in the optimization of the thermodynamic parameters. A good agreement between the experimental results and the calculations was achieved.
Highlights
Thermodynamic assessment for the Al2Pd5 phase is (Al)–Co–Pd ternary system has not yet been published
The Al–Pd binary phase diagram is based on an assessment created by Li et al [18]
Parameters for Al21Pd8 were modified with the aim of achieving better agreement with experimental results [21], which show that the Al3Pd phase forms by peritectic reaction liquid+Al3Pd2↔ Al3Pd at 1062 K
Summary
Thermodynamic assessment for the Al–Co–Pd ternary system has not yet been published. the system is of interest for the possible use of the Al–Pd based materials, for example, for catalysts [1] or as coatings with good oxidation resistance, low adhesion and high hardness [2,3,4] and in electronics as semiconductors [5,6]. The Al–Co binary subsystem contains liquid, Co-hcp and FCC-solid solutions, ordered AlCo-B2 (BCC-B2) phase with a wide homogeneity range and asymmetric shape, and several intermetallic phases Al5Co2, Al3Co, Al9Co2 and Al13Co4. Part of the diagram at temperatures below 1400 K was not shown in the mentioned study [17] and consistent experimental results concerning the miscibility gap in the FCC phase at low temperatures have not been found in the literature. In the Al–Co binary system [16], the BCC-B2 phase corresponding to the AlPd phase in Al–Pd system is described by the order–disorder model. As a result of incomplete experimental information on the existence of a low-temperature modification of this phase and completely missing information on the possible existence of a low-temperature phase in the Al–Co system, the BCC-B2 phase was modeled as equilibrium at low temperatures as in study [18]. There are seven other intermetallic phases (Al4Pd, Al3Pd (ε), Al21Pd8, Al3Pd2, Al3Pd5, Al2Pd5 and AlPd2), liquid and FCC solid solutions in the diagram
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