Investigation on the damage mechanism of micro-cutting surface layer of aluminum alloy 7075 with different heat treatment processes

Abstract

This paper investigates the machinability and microscopic surface damage mechanisms of aluminum alloy 7075 subjected to different heat treatment processes during micro-cutting. Focusing on T6 and T73 heat-treated aluminum alloy 7075, the study employs a combination of experiments and simulations to analyze micro-cutting surface morphology, cutting forces, microstructure evolution, residual stress, and damage characteristics. The findings reveal that micro-cutting of aluminum alloy 7075 after T6 heat treatment exhibits no apparent speed sensitivity in the primary cutting force, while T73 heat treatment demonstrates noticeable speed sensitivity. The surface microscopic damage during micro-cutting is influenced by both cutting speed and depth, resulting in distinct forms and degrees of damage under varying conditions. An analysis of the residual compressive stress field indicates that the magnitude of residual compressive stress on the micro-cutting surface determines crack initiation, and the maximum depth of residual compressive stress dictates crack propagation. Microscopic damage in T6 heat-treated aluminum alloy 7075 predominantly occurs in the second and third deformation zones, while T73 heat treatment leads to most damage in the third deformation zone. Notably, crack propagation is evident in T6 heat treatment at any cutting speed with a cutting depth of 150 μm, whereas it is inconspicuous in T73 heat treatment at cutting speeds below 540 m/min. Furthermore, at cutting speeds below 540 m/min and a cutting depth of 150 μm, T6 heat-treated micro-cutting is prone to oxidative wear. In contrast, at a cutting speed of 72 m/min and a cutting depth of 150 μm, the predominant wear form in T73 heat-treated micro-cutting is oxidation wear. This study underscores the intricate interplay between heat treatment processes, cutting conditions, and microscopic damage in aluminum alloy 7075 micro-cutting. The nuanced insights provided contribute to a deeper understanding of the machining characteristics of this alloy, paving the way for improved processing methodologies.