The effect of ternary addition on the formation and the thermal stability of L1 2 Al 3Zr alloy with nanocrystalline structure by mechanical alloying

Abstract

We have tried to produce nanocrystalline L1 1 Al+25 at.% Zr+12.5 at.% M (M=Cu, Ni, Mn) alloys by planetary ball milling of elemental powders. Systematic studies on ternary addition on the formation and the thermal stability of metastable L1 2 phase are also given in this study. L1 2 Al 3Zr alloy was effectively prepared by mechanical alloying of elemental powders of Al and Zr for 3 h. In the case of ternary addition the L1 2 phase was formed after 6-h milling for Cu and 3-h milling for Ni. In Mn addition, the L1 2 phase was formed after 3 h and transformed into an amorphous phase after 6 h. The as-milled L1 2 Al 3Zr and L1 2 Al 5Zr 2Cu alloy powder had nanocrystalline structures with grain sizes less than 10 nm. L1 2 Al 3Zr alloy transformed into stable D0 23 phase at 625°C. L1 2 phase has been stabilized significantly by ternary addition up to over 900°C for Cu and 850°C for Ni, respectively. Amorphous Mn added to Al 3Zr alloy crystallized to L1 2 phase at 770°C and the crystallized L1 2 phase was stable up to over 900°C. The nanocrystalline structure was maintained after 20-min heat treatment at 900°C.