Experimental investigation and thermodynamic re-assessment of the Al–Mo–Ni system

• The liquidus and solidus temperatures of the NiAl–Mo system were measured.
• The Gibbs energy of vacancies in the bcc phase was considered in the modeling.
• The thermodynamic descriptions of the Al–Ni and Al–Mo systems were refined.
• A new thermodynamic database of the Al–Mo–Ni system was established.
• The thermodynamic description of the NiAl–Mo system was considerably improved.

NiAl-based alloys have been investigated, because they are promising alternative materials for high temperature structural applications. Recent advancements in directional solidification offer the opportunity to manufacture metal-matrix composites of NiAl strengthened by embedded fibers of refractory metals such as Mo. The mechanical properties of these composites can be considerably improved, compared to NiAl, at least in fiber direction. The Al–Mo–Ni system has been thermodynamically assessed by several authors. However, none of them can reproduce a satisfactory description along the section NiAl–Mo. In the present work, liquidus and solidus temperatures of the NiAl–Mo system were measured by a laser heating-fast pyrometry apparatus. The results agree well with literature data. The thermodynamic descriptions of the Al–Ni and Al–Mo systems from the literature were refined and a new thermodynamic dataset of the Al–Mo–Ni system was established. The ordered B2 phase and its disordered A2 (bcc) parent phase were described by a single Gibbs energy function. Very good agreement between the calculated phase diagram and the experimental data is obtained. The description of the section NiAl–Mo is considerably improved and we conclude that this section does not represent a quasi-binary phase diagram.

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