增强颗粒对切削SiCp/Al复合材料切屑形成过程的影响机理

为研究SiC颗粒对SiCp/Al复合材料切屑形成过程的影响，设计了一种新型弹簧式快速落刀装置。通过正交切削试验获得切屑和切屑根部，观察其形态及金相显微组织，分析SiC颗粒沿剪切带的排列机制、颗粒的断裂与破碎机理、裂纹的扩展及其对切屑形成的影响。结果表明：设计的快速落刀装置加速度大，能获取有效的切屑根部；基体塑性滑移对颗粒产生的力和力矩使得颗粒沿剪切带排列；颗粒的断裂与破碎主要发生在剪切区、工件与切屑分离面、第2变形区以及刀尖附近的已加工表面；微裂纹从自由表面和剪切区内部沿剪切面扩展；裂纹沿剪切面扩展使得切屑受力不平衡，切屑加速流出，同时裂纹两侧沿剪切面发生相对滑动，导致切屑呈不规则锯齿形。

Influence of Reinforced Particles on Chip Formation Process in Cutting SiCp/Al Metal Matrix Composites

A spring-loaded quick-stop device was designed to investigate the influence of SiC particles on the chip formation process of SiCp/Al composites. The chips and their roots are obtained by orthogonal cutting test, and their morphology and microstructure are observed. The arrangement mechanism of SiC particles along shear band, the fracture and breaking mechanisms of particles, the crack propagation and its influence on chip formation are analyzed. The results show that the acceleration of quick-stop device is large, which means that the chip roots obtained are effective, the force and torque generated by plastic sliding of matrix cause the particles to be arranged along the shear band, and the fractures of particles mainly occur in the shear zones, the separated surface of workpeice and chip, the second deformation zone and the machined surface near the tool nose. The microcracks initiating from the outside free surface and the interior of shear zone propagate along the shear plane. As the cracks propagate along the shear plane, the force applied on chips is unbalanced, which causes the chips to outflow fleetly, and the relative sliding of both sides of the cracks along the shear plane leads to the formation of irregular saw-tooth chips.