| Structural changes during mechanical alloying and post-heat treatment of Al_(65)Cu_(20)Fe_(15) alloy powder were studied by using X-ray diffractometry, transmission electron microscopy and thermal analysis. Al_(65)Cu_(20)Fe_(15) alloy sample precessed for 10 hrs showed a layered structure consisted of Al, Cu and Fe containing layers. DSC of the specimens showed two broad exothermic peaks: one is weak in the temperature range of 300∼390℃ and the other strong 390∼480℃. The first exothermic peak seems to correspond to the formation of Al₂Cu and Al_7Cu₂Fe phases and the second peak to the formation of mixture of quasicrystalline approximant and ordered Al(Fe, Cu) β phases from the previously formed Al₂Cu, Al_7Cu₂Fe and unreacted Fe phases. Al_(65)Cu_(20)Fe_(15) alloy sample processed for 120 hrs showed a homogeneous distribution of nano scaled Al(Fe, Cu) β particle in an amorphous matrix. During heat treatment of the sample, the microstructure transformed into a mixture of ordered Al(Fe, Cu) β phase and Al_13Fe₄. Direct formation of quasicrystalline phase was not observed in as-mechanically alloyed Al_(65)Cu_(20)Fe_(15) alloy powder. |
|
