Microstructure, Mechanical Properties and Wear Resistance of (Ti2Al20La+Al3Ti)/Al-7Si Composites

Abstract:

(Ti₂Al₂₀La+Al₃Ti)/Al-7Si composites rich in Ti₂Al₂₀La and Al₃Ti reinforcement phases were prepared by the melt blending method. The influence of the addition amount of Al-Ti-La alloy on the microstructure, mechanical properties, and wear resistance of the composites was analyzed. Results reveal that the (Ti₂Al₂₀La+Al₃Ti)/Al-7Si composite (adding 10wt% Al-Ti-La alloy into the Al-7Si alloy) is composed of fine α-Al grains, short rod-like eutectic Si, and blocky Al₃Ti and Ti₂Al₂₀La phases. The tensile strength, elongation, and hardness of the composite are 176.9 MPa, 11.62%, and 73.2 HV, increased by 13.4%, 57.0%, and 26.2% compared with those of the Al-7Si alloy, respectively. It is suggested that the (Ti₂Al₂₀La+Al₃Ti)/Al-7Si composite exhibits relatively high plasticity. Furthermore, the wear resistance of the composites is increased by 20.1%. The performance enhancement is attributed to two key mechanisms. One is the formation of Al₃Ti transition layer at the interface between the Al₃Ti reinforcement phase and the aluminum matrix, which establishes a semi-coherent relationship with Al₃Ti phase. The other is the adsorption of element Si by element La within the Ti₂Al₂₀La reinforcement phase, leading to Si enrichment at the edges of the Ti₂Al₂₀La phase and thereby forming a semi-coherent Si layer.