Brittle-plastic synergistic removal mechanism and grain wear in ultrasonic grinding of anisotropic fiber-reinforced MMCs

Continuous fiber-reinforced metal matrix composites (CFMMCs) are increasingly utilized in high-performance aerospace engines because of their exceptional strength along the fiber axis. Unlike particle-reinforced metal matrix composites (PMMCs), CFMMCs exhibit significant anisotropic properties, which complicate their machining processes. While extensive studies have focused on tool wear in PMMCs, a notable research gap exists regarding the grinding removal mechanisms and grain wear behaviors in CFMMCs, particularly in the context of ultrasonic vibration-assisted grinding (UVAG). This study addresses this gap by investigating grain wear along different fiber orientations—perpendicular fiber (PF), transverse fiber (TF), and longitudinal fiber (LF)—through single-grain grinding experiments on SiC fiber-reinforced Ti–5Al–2Sn–2Zr–4Mo–4Cr (TC17) matrix composites (SiC_f/TC17). A detailed analysis of surface morphologies within the grinding scratches was conducted, revealing significant differences in cubic boron nitride (CBN) grain wear patterns under different fiber orientations, particularly when UVAG was compared with conventional grinding (CG). The results indicate that ultrasonic vibration effectively mitigates fiber fracture and grain wear, with the most severe grain wear and adhesion occurring when grinding along the LF orientation. This research not only advances the understanding of CFMMC grinding mechanisms but also contributes to enhancing the machinability of CFMMCs, thereby facilitating their broader application in aerospace and other high-performance industries.