Strengthening of mechanically alloyed Al-based alloy with high Zr contents

Al-Cu-Mn matrix alloy in the form of chips with zirconium in amounts of 5, 10 and 20 wt% was subjected to mechanical alloying. After milling in a ball mill for 20 h the prepared powders were annealed and hot-pressed. X-ray diffraction analysis was used to study the effect of zirconium content on the phase composition and microstructural parameters of the materials. The study showed that mechanical alloying leads to the formation of an Al-based nanocrystalline supersaturated solid solution with a zirconium content of up to 20%. With an increase in the zirconium concentration the microhardness of the powder alloys increases to 440 HV. The subsequent precipitation hardening as a result from the precipitation of metastable Al3Zr (L12) phase with a maximum content of 28 vol% causes an increase in the microhardness to 520 HV. The hot-pressed specimens exhibit very good room temperature and high temperature strength which increases with zirconium content.