Title: Effect of cooling rate and alloying elements on Al-Si-Fe alloys

Abstract

The microstructural and mechanical analysis of a ternary Al-20Si-5Fe (wt%) system with Cr Mn, and Ti additions are presented and discussed. The manufactured alloys were characterized by means of XRF, XRD, SEM, TEM as well as Vickers microhardness and compression tests. For the master alloy, the microstructural analysis revealed the presence of Al phases, eutectic silicon (SiE) and primary silicon (SiP). When adding the alloy elements, the presence of Al3FeSi2 was observed for all systems. When the addition of transition elements increased in a proportion of 1, 3 and 5 wt%, respectively, the presence of the intermetallic Al95Fe4Cr, Fe4MnSi3, Al19Fe4Mn, Ti5Si3 phases was observed. For the AlSiFe-Cr system, it was found that the acicular intermetallic Al3FeSi2 (2D) obtained by conventional solidification showed a plate-shaped structure (3D). The highest microhardness value was found for the alloys with 5 wt% of Cr (220 HV) in conventional solidification. However, for suction casting the highest microhardness was 192 HV (3 wt%). Although the microhardness decreased with the rapid solidification, the compressive plasticity of the alloy increased considerably (> 300%), being the microstructural homogeneity the main contributor to the ductility behavior. The AlSiFe Ti system showed a homogeneous dispersion of the intermetallic Al3FeSi2 and Ti5Si3 phases as the amount of Ti increased. The presence of Ti5Si3 did favor the ductility, increasing by 200%, when compared to that of the master alloy. Finally, these results demonstrated that Ti enhanced the plastic deformation, whilst Mn improved the microhardness and toughness. The addition of Cr provided a good balance between plastic deformation and toughness.