Mechanical performance enhancement of Al93Cu4Mg1Zn1Cr1 alloy via torsional deformation-induced hierarchical structure

This work shows that strategic selection of the composition (i.e., Al 93 Cu 4 Mg 1 Zn 1 Cr 1 at. %) and cooling rate (∼62.5K/s) enables solid solution of the elements Mg, Zn and Cr in the Al matrix and formation of Al 2 Cu precipitates mostly along the grain boundaries of the matrix. Subsequent deliberate selection of the High-Pressure Torsion conditions (pressure of 12-14 GPa and 10 rotations) results in a hierarchical multi-scale architecture consisting of Al-based refined grains, multiscale Al 2 Cu precipitates as a result of fracturing and formation of shear bands. The formation of these shear bands is quite localized and they are promoted by the presence of Mg, Zn and Cr in solid solution. The nanohardness of the Al matrix is as-cast conditions (H = 1.97±0.14 GPa) increases to H = 2.81±0.28 GPa after 10 rotations due to increased strain and grain refinement. Multiplication of the dislocations is associated to the rise of strain, ultimately leading to work-hardening. Deliberately engineering a heterogeneous microstructure that spans multiple length scales rather than relying on a single uniform strengthening mechanism is a promising strategy to enhance the mechanical performance.