Materials based on the ternary Al–Mn–Ni system possess a wide variety of useful properties, leading to the possibility of utilizing these alloys for structural and functional applications. Besides these ternary alloys, the Al–Mn–Ni system plays an important role in the development of several different shape memory alloys (SMAs). Since Al, Mn and Ni are the main alloying elements in many Cu- and Fe-based SMAs, it is necessary to investigate the influence of these elements on the phase stabilities in the corresponding alloy systems. An experimental study and a thermodynamic description of the ternary Al–Mn–Ni system will enhance the understanding of these alloys and allow extrapolations into higher order systems.
Comprehensive experimental investigations were conducted by means of EPMA, DTA and XRD analyses of several heat-treated and quenched alloys in the ternary
Al–Mn–Ni system. The investigations showed a wide extension of the two-phase field β-Mn + B2 at lower temperatures, as well as the stabilization of the disordered
A2-phase at higher temperatures. Moreover, in-situ XRD and TEM studies were performed, in order to investigate the ordering phenomena of the A2- and B2-phases, as well as the eutectoid decomposition reaction of the high temperature A2-phase.
Calculations based on the assessed thermodynamic parameters of the Al–Mn–Ni system are in good agreement with the experimental data available in the literature, as well as the experiments performed in the frame of the present work. Moreover, a metastable miscibility gap between the phases A2 and B2 at lower temperatures, leading to the extension of the β-Mn + B2 two-phase field, was revealed.