Superior strength of tri-layered Al-Cu-Al nano-composites processed by high-pressure torsion.

Abstract

This investigation demonstrates that a solid-state reaction occurs by the application of high-pressure torsion (HPT) in the production of nanostructured multilayered hybrid Al-Cu systems. Three-layered stacks of Al/Cu/Al were subjected for up to 200 revolutions of HPT under an applied pressure of 6.0 GPa. Microstructural and mechanical properties analysis were carried out after HPT using X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectrometry (EDX), microhardness measurements and tensile tests. The SEM observations revealed the formation of a multi-nano-layered structure in the whole volume of the disks. Further investigations with the use of TEM demonstrated that each nano-layer consists of nano-grains having sizes of about 20 nm. Analysis by XRD and selected area electron diffraction (SAED) confirmed the formation of intermetallic CuAl2 and Cu9Al4 phases in the layered structures. The experiments also showed a significant improvement in microhardness (up to ~450 Hv) and tensile properties (over 900 MPa of UTS after 200 turns) when compared to both Al-1050 and 99.95%Cu alloys in the initial state and after HPT processing. The results demonstrate that HPT offers an outstanding opportunity for producing novel nanostructured Al-Cu multilayered composites having unique mechanical properties.