| To improve the room temperature ductility, we have tried to produce nanocrystalline Al₃Zr alloys with a metastable cubic L1₂structure. We have also studied the effects of the addition of Cu, Ni, Mn on the formation and the thermal stability of nanocrystalline structure and L1₂phase. It was found that the final powders synthesized by planetary ball milling were nanocrystalline with L1₂phase after 3h of milling in the Al-Zr binary alloy and after 3h, 6h of milling in the Ni, Cu added powders, respectively. Blended elemental Al 25 at.%Zr-12.5 at.%Mn powder were mechanically alloyed for 6h to an amorphous phase. Thermal analysis showed that L1₂-Al₃Zr is stable up to 625℃. However, the addition of Ni, Cu stabilized L1₂ phase up to 850℃, over 900℃ respectively, although it appears that a transformation to an equilibrium tetragonal phase is initiated during extended heat treatment. The amorphous phase formed with the addition of Mn is transformed to L1₂phase at 770℃, which is stable over 900℃. |
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