Effect of reinforced particles on the machinability of Al alloy under MQL, cryogenic, and hybrid lubrication

Aluminum-based metal matrix composites (MMCs) offer a high strength-to-weight ratio with excellent abrasion resistance, finding vast applications in aerospace industries. However, machining these materials is difficult due to the high hardness and wear resistance resulting in a shortened tool life. In this context, Al 7075 hybrid MMC was fabricated with reinforcing elements of TiO₂ and Gr (graphite) particles. Furthermore, the machinability of newly fabricated HMMC was investigated under dry, MQL with vegetable oil, cryogenic CO₂, and hybrid (MQL + CO₂) cutting environments. As per the originality of this work, no studies compared the machinability of Al 7075 HMMC under selected cutting environments. With the reinforcement in Al alloy, the higher cutting forces and deteriorated surface finish were observed with dry milling. The abrasion wear mechanism will dominate under all cutting environments with various feeds and speeds. The combination of MQL + CO₂ cutting environments was found to be more effective in terms of cutting forces, with a reduction of 39 to 28% compared to other selected cutting environments. The surface roughness was reduced by 18%, 15%, and 13% with favorable chip generation under MQL + CO₂ than that of dry, MQL, and CO₂ cooling modes. Additionally, MQL + CO₂ showed enhanced tool life with a significant reduction in tool wear.