Microstructure and Mechanical Properties of Al-Cu-Mn Alloy Mechanically Alloyed with 5 wt% Zr After Multi-Directional Forging

Zr-containing aluminum-based alloys and especially Al-Zr composites have high thermal resistance due to the formation of Al₃Zr dispersoids from supersaturated aluminum solid solution. The use of mechanical alloying can significantly increase the solubility of zirconium and improve the strength properties at elevated temperatures. The aim of the present work is to investigate the effect of multi-directional forging (MDF) on the microstructure and properties of Al-Cu-Mn alloy mechanically alloyed with 5 wt%Zr. Mechanical alloying was carried out by ball milling for 20 h at 300 rpm. The temperature of hot pressing and subsequent MDF operation was 400 °C. SEM, XRD and TEM were used to study the microstructure. In this work, it was shown that MDF leads to the formation of a poreless structure compared to hot pressing due to strain accumulation during hot deformation, as well as grain growth and microhardness reduction. At the same time, the highest compressive yield strength at 350 °C of 132 MPa was achieved after forging. The obtained material consisted of nanocrystalline aluminum matrix and secondary precipitates of Al₃Zr with cubic (L1₂) and tetragonal (D0₂₃) lattices as well as Al₂₀Cu₂Mn₃ phase.