Achieving high strength-ductility of an Al–Mg–Si–Cu alloy via heterostructure coupling with pre-aging precipitation

Abstract

The heterostructured Al–Mg–Si–Cu alloy profile modified by TiB2–TiC particles was prepared by conventional extrusion and solution treatment, and the coupling effect of the heterostructure and the precipitates on the mechanical properties of the alloy profile was studied in this work. The results showed that the peak-aged alloy sample has high tensile strength (385 MPa) and yield strength (366 MPa) with low elongation (4.8%), while the pre-aged sample achieves higher tensile strength (426 MPa), yield strength (401 MPa), and also the elongation (8.0%). The better comprehensive mechanical properties of the pre-aged sample were attributed to the synergistic strengthening effect of precipitation strengthening and hetero-deformation induced (HDI) stress strengthening. The fine precipitates easy to shear in pre-aged sample are more advantageous than the precipitates in peak-aged sample for the heterostructured Al alloy, because they provided precipitation strengthening by hindering the slip of dislocations and did not prevent the accumulation of geometrically necessary dislocations (GNDs) resulting in HDI strengthening and HDI strain hardening. This work provides a new strategy for promoting the comprehensive mechanical properties of age-hardenable aluminum alloy with heterogeneous structure.

Keywords

• Aluminum alloy
• Heterogeneous structure
• Heat treatment
• Precipitation
• Mechanical properties