Liquid-solid equilibria in the aluminium-rich corner of the Al-Cr-Ni system

The aspect of the phase diagram related to liquid-solid equilibria in the subsection AlCr-AlNi-Al was investigated. It is shown firstly that close to the aluminium corner, a ternary eutectic transformation occurs at 634 degrees C. Crystallization paths were studied from different liquid alloys with compositions close to those of the binary Al-Ni or Al-Cr systems. The different liquidus phase fields appear to be related to binary Al-Ni and Al-Cr phases but also to the formation of ternary phases. Transmission electron microscopy studies show that each of these ternary phases has several structures related by polytypism or superstructure ordering. The main feature of this phase diagram is that eutectic valley connects a quasi-binary eutectic alpha Cr/AlNi to the ternary eutectic Al3Ni/theta Al7Cr/Al; several pseudo-peritectic transformations interrupt this monovariant line on either side.