Artifact-free bulk nanocrystalline Al-Li alloys with multiple deformation mechanisms and improved tensile properties

Abstract

An artifact-free bulk nanocrystalline (NC) aluminum (Al)-2% lithium (Li) alloy was synthesized in this study using in-situ consolidation via a combination of cryogenic and room temperature milling. The mechanical behavior of this alloy was investigated by tensile testing and microhardness measurements, and it was compared with coarse-grained (CG) Al alloys and a commercially pure NC Al synthesized using the same method. The transmission electron microscopy (TEM) analysis revealed that the grain size of the NC Al-2% Li alloy and NC pure Al are 18 nm and 29 nm, respectively. The NC Al-Li alloy showed extremely high yield and ultimate tensile strength values of 440 MPa and 556 MPa, respectively. In addition, a high tensile ductility of 14% was achieved in the NC Al-Li alloy along with a relatively high strain hardening exponent (0.11). The high-resolution TEM investigations indicate a dependency of these extraordinarily tensile properties on multiple deformation mechanisms such as dislocation slip and pile-up and deformation twinning.