Milled surface topography significantly influences the tribological performance of machined components by governing contact mechanics, friction, and wear during service. However, investigations into surface topography formation and tribological behavior are often conducted separately, limiting the establishment of a unified link between milling process parameters and functional performance. This review presents a process-topography-tribology framework and examines the formation mechanisms, modeling and simulation approaches, and tribological responses of milled surface topographies. Formation mechanisms are first reviewed, including kinematic-geometric effects, material removal and deformation, and dynamic responses of the machine-tool-workpiece system. Existing modeling and simulation methods for surface topography prediction are then summarized and classified, with their advantages and limitations discussed. Surface topography characterization methods and parameter systems relevant to tribological analysis are also addressed, encompassing height, spatial, directional, functional, and multi-scale parameters essential for correlating surface features with friction and wear. The effects of milled surface topography on friction, wear, and fretting behavior are subsequently analyzed. Tribological responses are shown to depend strongly on surface feature scale, anisotropy, and load-bearing characteristics. Current challenges and future research directions are finally identified, with emphasis on performance-oriented surface topography design, integration of surface prediction and tribological models, and application of digital manufacturing technologies. This review aims to offer a unified perspective connecting milling process design to tribological performance, thereby providing guidance for future research and engineering applications.

The microstructure variations of machined surface determine the performance of machined components. Accurately predicting the microstructure evolution of machined surface and thus enhancing surface hardness of machined components is an effective way to improve the service performance and realize the controllable machining of components. Machining is one the fundamental manufacturing techniques of TC4 components and the severe plastic deformation during machining process induces the complex evolutions of microstructure for TC4 machined surface. For the grain refinement phenomenon during TC4 cutting, this paper studied the multi-scale distribution characteristics of microstructure, evolution mechanisms of grain refinement and its effect on the material hardness under different cutting speeds (100 ~ 500 m/min). The results show that grain refinement degree at meso-scale (10^-6 ~ 10^-5 m) increases first and then decreases with the increasing of cutting speed. At cutting speed of 300 m/min, grain refinement degree of machined surface is 69.7% and the grains in the shear bands of chips are refined to 2 ~ 6 µm. Complex dislocation patterns and nano twining are the features of microstructure at micro-scale (10^-8 ~ 10^-7 m). The deformation twinning type is mainly characterized as {1011} compression twinning and it is generated at higher cutting speed (> 200 m/min). Grain refinement during machining of TC4 was predicted based on the modified Z-H grain refinement model and nano twining volume fraction prediction model. The hardening effect of grain refinement was also considered in the prediction model. The evolution of grain sizes and the work hardening was predicted. The relation between grain refinement and material hardness was established, and the hardness of TC4 machined surface was predicted with directional controlling the grain refinement degree and formation of nano twinning. And the hardening mechanism in microscale of TC4 machined surface was revealed.

Material removal in the cutting process is regarded as a friction system with multiple input and output variables. The complexity of the cutting friction system is caused by the extreme conditions existing on the tool–chip and tool–workpiece interfaces. The critical issue is significant to use knowledge of cutting friction behaviors to guide researchers and industrial manufacturing engineers in designing rational cutting processes to reduce tool wear and improve surface quality. This review focuses on the state of the art of research on friction behaviors in cutting procedures as well as future perspectives. First, the cutting friction phenomena under extreme conditions, such as high temperature, large strain/strain rates, sticking–sliding contact states, and diverse cutting conditions are analyzed. Second, the theoretical models of cutting friction behaviors and the application of simulation technology are discussed. Third, the factors that affect friction behaviors are analyzed, including material matching, cutting parameters, lubrication/cooling conditions, micro/nano surface textures, and tool coatings. Then, the consequences of the cutting friction phenomena, including tool wear patterns, tool life, chip formation, and the machined surface are analyzed. Finally, the research limitations and future work for cutting friction behaviors are discussed. This review contributes to the understanding of cutting friction behaviors and the development of high-quality cutting technology.