Abstract
The present study investigates the effect of low-level Ni additions (0.2, 0.5, and 0.9 wt.%) on the microstructure, hardness, and wear behavior of A384 aluminum alloys that are modified with 0.02 wt.% Sr as a silicon modifier. The aim is to improve the wear resistance of Al–Si–Cu casting alloys for high-load applications while maintaining a balance between hardness and ductility through controlled intermetallic phase formation. Four alloys were produced via high-pressure die casting (HPDC) to obtain fine microstructural features associated with rapid solidification. A strengthening sequence of solution treatment (540 °C, 2 h), artificial aging (180 °C, 5 h), and 50% cold rolling were applied. Microstructural evolution was characterized by SEM/EDX, hardness was measured in both as cast and processed states, and wear performance was evaluated under dry reciprocating sliding at different loads by using the Archard approach. The combined precipitation and deformation hardening treatments increased hardness by up to 20% compared with the as-cast condition. In the as-cast state, the lowest specific wear rate was observed for the alloy with 0.5 wt.% Ni, attributed to a balanced distribution of Ni–Cu and Ni–Fe intermetallics. After strengthening, the best wear resistance was achieved in the Sr-modified alloy without Ni addition, which also showed the highest hardness. These results demonstrate that while Ni improves as-cast wear resistance by promoting load-bearing intermetallic phases, the combination of Sr modification with precipitation and deformation hardening can deliver a comparable or superior performance in the strengthened state, which offers practical guidelines for optimizing A384 alloys.
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