| The effect Si addition on structural evolution during heat treatment was studied in mechanically alloyed Al_(65)Cu_(20)Fe_(15) and Al_(65)Cu_(20)Fe_(10)Si_5 Powders using X-ray diffractometry, transmission electron microscopy and differential scanning calrorimetry. Both alloy powders processed for 10 hr showed a layered microstructure of Al, Cu and Fe. Mechanical alloyed powders for 10 hr transformed into several different phases depending on heat treatment conditions: Both alloy powders, heat treated for 10 hr at 335℃, showed a mixed structure of Al₂Cu, Al_7Cu₂Fe and unreacted Fe; Both alloy specimens heat treated for 10 hr at 550℃ showed 1/1 cubic approximant phase as a major phase; Al_(65)Cu_(20)Fe_(15) and Al_(65)Cu_(20)Fe_(10)Si_5 alloy powders heat treated for 5 hr at 750℃ showed a mixture of Al(Fe, Cu) and Al_(13)Fe₄ and 1/1 cubic approximant phase as a major phase with some icosahedral phase and other approximant phases, respectively. Addition of Si promotes the stability of quasicrystalline and approximant phases. No icosahedral phase or approximant phases were observed in both alloy powders heat treated either at 550℃ or at 750℃ after 120 hr Mechanical alloying. |
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