1. Ti–6Al–4V, a typical α + β dual-phase material, is one of the dominant metal materials in aerospace, maritime and biomedical applications due to its outstanding mechanical properties, excellent ...

Textured surfaces with certain micro/nano structures have been proven to possess some advanced functions, such as reducing friction, improving wear and increasing wettability. Accurate prediction of micro/nano surface textures is of great significance for the design, fabrication and application of functional textured surfaces. In this paper, based on the kinematic analysis of cutter teeth, the discretization of ultrasonic machining process, transformation method of coordinate systems and the cubic spline data interpolation, an integrated theoretical model was established to characterize the distribution and geometric features of micro textures on the surfaces machined by different types of ultrasonic vibration-assisted milling (UVAM). Based on the theoretical model, the effect of key process parameters (vibration directions, vibration dimensions, cutting parameters and vibration parameters) on tool trajectories and microtextured surface morphology in UVAM is investigated. Besides, the effect of phase difference on the elliptical shape in 2D/3D ultrasonic elliptical vibration-assisted milling (UEVAM) was analyzed. Compared to conventional numerical models, the method of the cubic spline data interpolation is applied to the simulation of microtextured surface morphology in UVAM, which is more suitable for characterizing the morphological features of microtextured surfaces than traditional methods due to the presence of numerous micro textures. The prediction of surface roughness indicates that the magnitude of ultrasonic amplitude in z -direction should be strictly limited in 1D rotary UVAM, 2D and 3D UEVAM due to the unfavorable effect of axial ultrasonic vibration on the surface quality. This study can provide theoretical guidance for the design and fabrication of microtextured surfaces in UVAM.

Previous studies have reported significant differences in the Johnson-Cook (J-C) parameters of Ti6Al4V alloy. Thus, various serrated chip morphologies, cutting forces, and cutting temperatures are obtained when different constitutive parameters are used for numerical and simulation analyses, which decreases the reliability of the simulation model. Therefore, it is necessary to investigate and analyze simulation errors due to differences in the J-C parameters. In this study, the mechanism of the serrated chip formation of Ti6Al4V is thoroughly analyzed using the uniformly proportional J-C parameters. The serrated chip sensitivity, shear band spacing, serrated segmentation frequency, chip serration intensity, temperature field, strain energy, and cutting force is obtained. This study aims to improve the accuracy and reliability of the micro-cutting simulation models, as well as a reference for the selection of J-C constitutive parameters of simulation with Ti6Al4V manufactured with different heat treatments and additive manufacturing.

Improving the surface quality and controlling the microstructure evolution of difficult-to-cut materials are always challenges in high-speed machining (HSM). In this paper, surface topography, defects and roughness are assessed to characterize the surface features of 7050 aluminum alloy (Al 7050) under HSM conditions characterized by high temperature, strain and strain rate. Based on multi-physical field coupling, the mechanism of microstructure evolution of Al 7050 is investigated in HSM. The results indicate that the surface morphology and roughness of Al7050 during HSM are optimal at f_z = 0.025 mm/z, and the formation of surface defects (adherent chips, cavities, microcracks, material compression and tearing) in HSM is mainly affected by thermo-mechanical coupling. Significant differences are observed in the microstructure of different machined subsurfaces by electron backscatter diffraction (EBSD) technology, and high cutting speeds and high feed rates contributed to recrystallization. The crystallographic texture types on machined subsurface are mainly {110} Brass texture, {001} Cube texture, {123} S texture and {124} R texture, and the crystallographic texture type and intensity are significantly affected by multi-physical field coupling. The elastic–plastic deformation and microstructural evolution of Al7050 alloy during the HSM process are mainly influenced by the coupling effects of multiple physical fields (stress–strain field and thermo-mechanical coupling field). This study reveals the internal mechanism of multi-physical field coupling in HSM and provides valuable enlightenment for the control of microstructure evolution of difficult-to-cut materials in HSM.