Surface topology evolution induced by chip formation and microstructure features during machining γ-TiAl alloy with increasing uncut chip thickness Article Swipe
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· 2025
· Open Access
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· DOI: https://doi.org/10.1016/j.jmrt.2025.07.244
· OA: W4413099123
γ-TiAl alloy is a promising material with low density, high specific strength, and excellent high-temperature performance for aero-engine components. However, its intrinsic brittleness at room temperature poses significant challenges in manufacturing. This study conducted orthogonal cutting tests of Ti–46Al–5Nb-1.8Cr-0.2Ta-0.1B alloy at varying uncut chip thickness (UCT) and speeds to investigate its evolution of surface and subsurface features. The chip morphology transforms from segmented to completely fragmented with the increase of UCT. Brittle fractures easily occur under high strain rates, following the formation of gaps and internal cracks between and within segmentations of chips. Plastic deformation dominates the machining surface under the UCT below 20 μm; thus, a more favorable surface is obtained. The result indicates that the chip formation principle is governed by the interplay between adiabatic shear and brittle fracture. Besides, the severe chip sawtooth and periodic fracture-induced cutting force fluctuation and forced vibration of the cutting tool, retained on the surface morphology. Surface topography showed periodic marks and was accurately identified by the multiple signals, which reflected lower frequency and larger amplitude with a further increase in the UCT. Moreover, surface microcracks tend to propagate along γ/α2 lamellar and grain boundaries due to the highly anisotropic lamellar structure. The size and incidence of the tear and microcrack increased as the level of UCT increased. Those findings provide the basic understanding for efficient and high-performance processing of γ-TiAl alloy.
