Structural Evolution and Phase Transformation in Nanoquasicrystalline Al-Fe-Cr Alloy: DSC Analysis

Kinetic parameters for microstructural evolution and phase transformation in water atomized Al Fe Cr based alloy with nominal composition Al94Fe3Cr3 have been examined by means of developed precise method of DSC technique and confirmed by the results of XRD analysis. Two exothermic reactions including that with a maximum at 380 – 400 C has been ascribed to dislocation reorganisation and recrystallisation pro-cess within the Al matrix although the main exothermic reaction with a maximum around 540 C arose from decomposition of icosahedral quasicrystalline particles and simultaneous formation of the metastable Al6Fe phase and more stable crystalline particles compositionally corresponded to the Al13Cr2 and Al13Fe4 phases. Activation energy for the main exothermic reaction has been found to be roughly about 53.1 kJ mol-1 which is significantly smaller than that for the bulk diffusion of either iron or chromium atoms in aluminium and very close to that for the vacancy migration.