Effects of the synergistic addition of AlCrNiTi and Ce on the microstructure and mechanical properties of hypoeutectic Al-7Si alloy.

A new strategy is proposed in this study to modify the microstructure of the Al-7Si alloy, which is widely employed in the aerospace and transportation sectors due to its lightweight, high specific strength, and specific modulus. The primary challenge of the Al-7Si alloy is its coarse microstructure, which undermines its mechanical properties. This research focuses on the effects of adding the AlCrNiTi master alloy and Ce to the Al-7Si alloy. The impact on both the microstructure evolution and the mechanical properties is examined, including analysis and discussion of the underlying mechanisms for refinement and strengthening. When the alloy was modified by 0.9 wt% of the AlCrNiTi master alloy and 0.1 wt% of Ce, there was a notable refinement of the α-Al phase, transforming it from a coarse dendritic structure to fine equiaxed grains. The addition of 0.9 wt% of the AlCrNiTi master alloy and 0.1 wt% of Ce can also reduce the secondary dendrite arm spacing (SDAS) to 5.9 μm. The eutectic Si phase underwent a significant transformation, changing from coarse flakes to fine granularity with rounded edges. Furthermore, CeSi 2 Ni 2 , Al 3 Ni intermetallic compounds, and nanoscale Al 45 Cr 7 particles were observed in the modified Al-7Si alloy. Tensile tests showed that the addition of the inoculant in the Al-7Si alloy enhanced the ultimate tensile strength (UTS) from 173 MPa to 211 MPa and increased the elongation (El) from 7.9% to 14.1%. • The effect of the complex addition of AlCrNiTi alloy and Ce on the microstructure and mechanical properties of Al-7Si alloy was investigated. • The α-Al and eutectic Si of the Al-7Si alloy underwent significant refinement and modification after the synergistic addition of 0.9 wt% AlCrNiTi master alloy and 0.1 wt% Ce. • The UTS and El were improved to 211 MPa and 14.1%, exhibiting an increase of 22% and 78.5% compared with the unmodified Al-7Si alloy. [ABSTRACT FROM AUTHOR]