Exploring the Role of Mechanochemical Effects in Cutting of Aluminum Alloys With Alcohols

In metal cutting processes, a chemical ambient environment in the cutting zone can be a useful variable for process control and process performance improvement. In this work, we study how mechanochemical effects influence the chip formation process, especially focusing on a specific chemical reaction between aluminum alloys and alcohols as a model system. Using high speed in-situ imaging and particle image velocimetry, we demonstrate that the mechanochemical effect in cutting of annealed Al with use of isopropyl alcohol (IPA) is manifest in two different ways: a lubricating effect at the tool-chip interface and an embrittlement effect at the workpiece free-surface, depending on the undeformed chip thickness and cutting speed. Consequently, the highly unsteady chip flow seen in dry cutting of annealed Al, which is typically seen in cutting of ductile “gummy” metals, transitions to a laminar-type (smooth) chip-flow mode or a segmented, fracture-controlled chip flow, due to the Al-IPA reaction. In both cases, the modified chip flow modes lead to significant reduction in cutting forces and improvement of finished surface quality. The specific manifestation of the mechanochemical effect is found to be principally determined by the penetration capability of the alcohols into the tool-chip interface and the time required for the chemical reaction between aluminum and the alcohols. Also, we discuss some implications for improving the performance of practical Al cutting operations using alcohols as a fluid medium.