Improved mechanical properties in cast Al–Si alloys by combined alloying of Fe and Cu

Al–Si eutectic alloys with the following composition (wt.%), 13.0 Si, 3.0–5.0 Cu, 0.3–0.8 Fe, < 0.3 Ni, < 0.15 Ti, < 0.4 Mg and < 0.6 Mn, were prepared by metal mold casting. The microstructure and fracture of these alloys were examined using SEM and TEM. It has been shown that Fe-rich and Cu-rich phases are solidified or precipitated in the form of a Chinese script or blocky α-Fe (Al15(Fe, Mn)3Si2) and θ(Al2Cu) at the grain boundaries of α-Al dendrites. The ultimate tensile strength (UTS) and elongation of the alloy with 3.0% Cu and 0.3% Fe reach 310 MPa and 3.2%, respectively. By increasing Cu content to 5.0% and Fe to 0.8%, the UTS of Al–Si alloy is further enhanced to 336 MPa. It was observed that these Al–Si alloys fracture in a mixed mode with quasi-cleavage and ductile fracture morphology.

Graphical abstractTensile properties of CU, CF and several commercial aluminum alloys are listed in Table 3. To quantity the overall tensile properties of experimental alloys, the quality index (Q) was also evaluated. It is seen that the tensile properties of Al–Si eutectic alloys prepared in this work are superior to those of commercial aluminum alloys. All the tensile properties are obviously improved. The highest UTS and EL reach 336 MPa and 3.2 for the alloys with 5.0% Cu and 0.8% Fe, and 3.0% Cu and 0.3% Fe. Combining the chemical composition, the improve UTS and EL can be achieved by reasonable combined alloying of Fe and Cu.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights▶ Improved mechanical properties of cast Al–Si alloys are achieved by combined alloying of Fe and Cu. ▶ Dual strengthening effects are mainly induced by tiny Chinese script and blocky α-Fe and Al2Cu crystals. ▶ There are two different morphologies of α-Fe(Al15(Fe, Mn)3Si2) with lattice constant of 1.267 nm for Chinese script α-Fe and 1.313 nm for blocky α-Fe. ▶ Fracture surfaces present characteristics of mixed quasi-cleavage and ductile fracture morphology. ▶ The experimental alloys are promising materials for the application for automotive industry.