Structural Transformations and Thermal Expansion in Aluminum Alloys of the Al–Ni–Zr and Al–Ni–Hf Systems

Abstract

We study the structural transformations in Al–Ni–Zr and Al–Ni–Hf alloys in the concentration regions with high contents of Al. The eutectoid transformation of the Zr6Ni8Al15 phase into a microscopic mixture of compounds NiAl + ZrNi0.5Al1.5 and the peritectic formation of HfNi0.35Al1.65 from a mixture of HfNi2Al5 and Hf6Ni8Al15 are discovered. The temperature dependence of the structural parameters is analyzed and the thermal expansion coefficient for the HfNi0.35Al1.65 phase is found within the range 393–723°K.