Mechanical responses and dynamic failure of nanostructure Cu–Al alloys under uniaxial compression

Three kinds of nanostructure (NS) Cu–Al alloys (Cu-2.57%Al, Cu-6.87%Al and Cu-11.14%Al) were produced via equal channel angular pressing at room temperature and the smallest grain size achieved was 93 nm. Mechanical properties of NS Cu–Al alloys were studied by compression tests over a wide range of strain rates (5 × 10⁻⁴–4 ×10³s⁻¹). The microstructure of NS Cu–Al alloys before-and-after mechanical testing were examined by transmission electron microscope (TEM). Deformation mechanisms of NS Cu–Al alloys with different Stacking Fault Energy (SFE) were also discussed. It is worth mentioning that the post-loading observations of NS Cu-11.14%Al (with the lowest SFE loaded at a high strain rate of 4 × 10³ s⁻¹) by Optical and Scanning Electron Microscope verified the appearance of Adiabatic Shear Band (ASB) which is found rarely in nanostructured FCC metals. TEM observation showed that the nanoscale grains in ASBs were much smaller and cleaner in contrast to the grains with high density of defects outside the bands. It should be a consequence of the recrystallization because of adiabatic temperature rise inside the band. The reasons for the formation of ASBs in NS FCC alloys were also explored and explained.