Abstract
The formation of different phases for the reaction of Nb and Al in M/s Hitachi Ltd made wires using differential scanning calorimetry (DSC) has been investigated. The interfacial diffusion reaction has been studied in the temperature range 100–990 °C. Niobium (Nb) and aluminum (Al) react to form the phase NbAl3, subsequently NbAl3 reacts with the remaining Nb to form the A15 phase. The interfacial reactions play an important role. At higher heating rates, NbAl3 and bcc-structured NbAl are formed prior to the formation of Nb3Al, but at lower heating rates the phase observed indicates σ phase Nb2Al. DSC has been performed at different heating rates under nonisothermal conditions aimed to measure activation energy of crystallization for different phases: employing Kissinger's equation, Matusita–Sakka theory, and the Augis-Bennett method. Activation values calculated from these three different methods are found to be in good agreement with each other. The activation energy for the first phase (NbAl3) is lower than the other two phases (Nb3Al) A15 phase and Nb2Al, suggesting that NbAl3 formation occurs easily. The value of n relating to the nucleation and growth mechanisms has also been calculated using the modified Kissinger method at different temperatures.
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