Abstract

Four different mechanical alloying(MA) processes were employed to fabricate very fine intermetallic compound Al_3Zr particles dispersed Al composite materials(MMC) with Al-4at.%Zr composition. Phase transformations including phase stability during MA and heat treatment processes were investigated. Part of Zr atoms were dissolved into Al matrix and part of them reacted with hydrogen produced by decomposition of PCA(methanol) to form hydride ZrH_2 during first MA process. These ZrH_2 hydrides disappeared when alloy powders were heat treated at 500circC. Stable Al_3Zr dispersoids with DO_23 structure were formed by heat treating the mechanically alloyed powders at 400circC. On the other hand, metastable Al_3Zrdispersoids with L1_2 structure were formed during first MA of powers with Al-25at.%Zr composition. These metastable Al_3Zr dispersoids transformed to stable Al_3Zr with DO_23 structure when heat treated above 450circC.

• Keywords: MA;Metastable Al3Zr;Stable Al3Zr;ZrH2;