Abstract: A twin, differential, high-temperature calorimeter for the measuremens of enthalpies of formation and transformation in solid alloys has been developed. This apparatus works at temperature up to 1500 K. Its sensitivity and reliability are proved by measuring the heats of transformation of α-to γ-phase in iron. The experimental results are in considerable agreement with those in the published literature.
The calorimeter was used to determine the heats of formation of eight alloy compositions, comprising of σ-and γ-phase, of Fe-Ni-V system. These data have not been measured before. The results show that the enthalpies of Fe-Ni-V solid alloys are negative and tend to decrease generally while the composition of alloy varies from Fe-V side to Ni-V side.

Key words: Solid alloy, Enthalpies of formation, Enthalpies of transformation, High-temperature Calorimeter