Abstract Ti6Al4V alloy is one of the typically difficult-to-machine materials which is widely used in aerospace industry. During the machining process of Ti6Al4V alloys, serrated chips are easily formed and would influence cutting forces significantly. In this study, the variation of cutting forces of Ti-6Al-4V alloys during high-speed milling from 50–500 m/min is investigated, and the fracture mechanisms and microstructure evolution of chips are analyzed by optical microscope (OM), scan electron microscope (SEM) and transmission electron microscope (TEM). The results show that cutting forces and serrated degree of chips both increase first and then decrease with the increase of cutting speeds, especially when adiabatic shear bands appear. The microstructure evolution inside adiabatic shear bands also show a significant difference with different chip morphology at different cutting speeds, which finally cause the variation of cutting forces due to the change of fracture mechanisms between chip segmentations. As a result, the evolution of adiabatic shear bands is analyzed, and replica method by polydimethylsiloxane (PDMS) is used to reveal the relationship between cutting forces variation and fracture mechanism transformation in chip segmentation. It shows the relationship between cutting forces and microstructure evolution in adiabatic shear bands, and the transformation of fracture mechanism between type-I and type-II would occur around the gap between chip segmentations, where cutting forces are higher under type-I fracture.

中文翻译：

---

Ti-6Al-4V合金高速切削切屑断裂机理转变实验研究

摘要 Ti6Al4V合金是一种典型的难加工材料，广泛应用于航空航天工业。Ti6Al4V合金在加工过程中容易形成锯齿状切屑，对切削力影响较大。本研究研究了 Ti-6Al-4V 合金在 50-500 m/min 高速铣削过程中切削力的变化，并通过光学显微镜（OM）、扫描仪分析了切屑的断裂机制和微观结构演变。电子显微镜 (SEM) 和透射电子显微镜 (TEM)。结果表明，切削力和切屑锯齿度均随着切削速度的增加先增大后减小，尤其是出现绝热剪切带时。绝热剪切带内的微观结构演化也随着不同切屑形态在不同切削速度下呈现显着差异，最终由于切屑分段之间断裂机制的变化而导致切削力的变化。因此，分析了绝热剪切带的演变，并利用聚二甲基硅氧烷（PDMS）的复制方法揭示了切屑分割中切削力变化与断裂机制转变之间的关系。说明了绝热剪切带中切削力与微观结构演化的关系，I型和II型断裂机制的转变将发生在切屑分段间隙附近，I型断裂下切削力较高。由于切屑分段之间断裂机制的变化，最终导致切削力的变化。因此，分析了绝热剪切带的演变，并利用聚二甲基硅氧烷（PDMS）的复制方法揭示了切屑分割中切削力变化与断裂机制转变之间的关系。说明了绝热剪切带中切削力与微观结构演化的关系，I型和II型断裂机制的转变将发生在切屑分段间隙附近，I型断裂下切削力较高。由于切屑分段之间断裂机制的变化，最终导致切削力的变化。因此，分析了绝热剪切带的演变，并利用聚二甲基硅氧烷（PDMS）的复制方法揭示了切屑分割中切削力变化与断裂机制转变之间的关系。说明了绝热剪切带中切削力与微观结构演化的关系，I型和II型断裂机制的转变将发生在切屑分段间隙附近，I型断裂下切削力较高。利用聚二甲基硅氧烷（PDMS）的复制方法揭示了切屑分割中切削力变化与断裂机制转变之间的关系。说明了绝热剪切带中切削力与微观结构演化的关系，I型和II型断裂机制的转变将发生在切屑分段间隙附近，I型断裂下切削力较高。利用聚二甲基硅氧烷（PDMS）的复制方法揭示了切屑分割中切削力变化与断裂机制转变之间的关系。说明了绝热剪切带中切削力与微观结构演化的关系，I型和II型断裂机制的转变将发生在切屑分段间隙附近，I型断裂下切削力较高。