Effect of Yttrium on Iron-Rich Phases and Mechanical Properties of As-Cast Al-Fe Alloy with Low Si Concentration

In Al–Fe alloys, the mechanical performance is determined by the morphology of iron-rich phases. In this work, AA8176(Al-1Fe)- nY (n = 0, 0.3, 0.5, 0.7, and 0.9 wt.%) alloys were prepared by the cast method. To systematically analyze the influence of Y on microstructure evolution and tensile behavior, a multi-scale characterization approach was employed, combining metallography, electron microscopy, X-ray diffraction, cooling curve analysis, and tensile tests. The results revealed that the optimal refinement effect was achieved when the amount of Y content was 0.5 wt.%. The micro-structure of the alloy was significantly modified by Y addition. The coarse needle-like Al13Fe4 phases were gradually transformed into short rod-like and particle morphology. And the average length was decreased from 10.01 μm to 2.65 μm. Meanwhile, some small size Al10Fe2Y phases were formed around the Al13Fe4 phases. Additionally, the secondary dendrite arm spacing (SDAS) of A8176 alloy was reduced from 31.33 μm to 20.24 μm. Furthermore, the mechanical properties of the AA8176 alloy were improved due to the modified microstructure. The tensile strength of the alloy was increased from 84.47 MPa to 96.86 MPa, and the elongation was increased from 18.6 % to 23.1 %. It is proposed that the growth of α-Al dendrite and Al13Fe4 phases were effectively inhibited by segregation of Y atoms around α-Al dendrite and Al13Fe4 phases during solidification. And the Al10Fe2Y phases were formed by these Y atoms with Al and Fe elements. However, the formation of coarse Al10Fe2Y phases was promoted by excessive Y content, which resulting in a substantial degradation in mechanical properties.