Mechanism-Driven Strength–Conductivity Synergy in Hypereutectic Al-Si Alloys Reinforced with Interface-Engineered Ni-Coated CNTs

TL;DR

This paper shows how adding nickel-coated carbon nanotubes to aluminum-silicon alloys improves both strength and electrical conductivity through microstructure refinement and interfacial engineering.

Contribution

A scalable strategy using interface-engineered Ni-CNTs to achieve strength-conductivity synergy in secondary Al-Si alloys.

Findings

0.1 wt.% Ni-CNTs improved tensile strength to 170.13 MPa and conductivity to 27.60% IACS.

Refined α-Al dendrites and uniform Si distribution enhanced mechanical and conductive properties.

Higher Ni-CNT contents caused agglomeration and property degradation.

Abstract

Secondary hypereutectic Al-Si alloys are attractive for sustainable manufacturing, yet their application is often limited by low strength and electrical conductivity due to impurity-induced microstructural defects. Achieving a balance between mechanical and conductive performance remains a significant challenge. In this work, nickel-coated carbon nanotubes (Ni-CNTs) were introduced into secondary Al-20Si alloys to tailor the microstructure and enhance properties through interfacial engineering. Composites containing 0 to 0.4 wt.% Ni-CNTs were fabricated by conventional casting and systematically characterized. The addition of 0.1 wt.% Ni-CNTs resulted in the best combination of properties, with a tensile strength of 170.13 MPa and electrical conductivity of 27.60% IACS. These improvements stem from refined α-Al dendrites, uniform eutectic Si distribution, and strong interfacial bonding. Strengthening was achieved through grain refinement, Orowan looping, dislocation generation from thermal mismatch, and the formation of reinforcing interfacial phases such as AlNi3C0.9 and Al4SiC4. At higher Ni-CNT contents, property degradation occurred due to agglomeration and phase coarsening. This study presents an effective and scalable strategy for achieving strength–conductivity synergy in secondary aluminum alloys via nanoscale interfacial design, offering guidance for the development of multifunctional lightweight materials.

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