Samples were produced by rapid solidification via melt spinning. The aim was to determine the main mechanisms operating in the ordering process of these alloys when submitted to a cycle of continuous heating, as well as the influence of the chemical composition in those ordering processes. The method used to obtain these results was differential scanning calorimetry. During the processes of heating of Ni3Al alloys three exothermic reactions were observed, which could be associated in the sequence: vacancy annihilation; ordering and grain growth. In all reactions, the enthalpy involved increased with increasing Ni content in the alloy. This could be associated with microstructural factors, because the Ni3Al rapidly solidified alloys presented a characteristic bimodal distribution of ordered domains. Increasing Ni in the alloy resulted in a consequent growth of the fraction of fine ordered domains.

Calorimetric Study of Ni3Al Alloys Produced by Rapid Solidification. Barros, A.M., Tenório, J.A.S.: Intermetallics, 2005, 13[2], 137-40