将选择性激光熔化和飞秒激光减材技术相结合已被认为是实现复杂和精细结构近净成形的有效工艺。在SLM工艺中, 由于熔池的运动和熔道的重叠, SLM成形件的表面具有一定的周期性结构, 这对后续飞秒激光减材影响很大。研究首先测量SLM 制备Ti-6Al-4V工件的表面结构, 设计飞秒激光减材试验。通过试验和二维数值模型, 研究了飞秒激光减材加工过程中表面形貌的演变, 预测表面粗糙度值。仿真结果与试验结果非常接近, 误差仅为7.63%。此外, 该模型还用于研究正负离焦位置的表面移动速度和加工深度: 负离焦位置的表面移动速度和加工深度均大于正离焦位置。该关系揭示了飞秒激光减材过程中表面粗糙度降低的机理。

The hybrid of laser additive and subtractive manufacturing technolog, which involves selective laser melting (SLM) and femtosecond laser subtractive manufacturing, has been considered as an effective process to achieve near-net-net forming of complex and fine structures. In the SLM process, due to the movement of the molten pool and the overlap of the molten channel, the surface of the SLM formed part has a certain periodic structure, which has a great influence on the subsequent femtosecond laser subtractive manufacturing. In this study, the surface structure of the SLMed Ti-6Al-4V workpiece was measured first, and the femtosecond laser subtractive manufacturing experiment was designed. Through experiments and a two-dimensional numerical model, the evolution of the surface morphology in the process of femtosecond laser subtractive manufacturing is studied, and the surface roughness value is predicted. The simulation results are very close to the experimental results, and the error is only 7.63%. In addition, the model is used to study the surface movement speed and processing depth of the positive/negative defocus position: both the surface movement speed and processing depth of the negative defocus position are greater than the positive defocus position, revealing the mechanism of surface roughness reduction during the femtosecond laser subtraction process.