热处理对增材制造AlSi10Mg超精密车削特性的影响机理

由于激光选区熔化(增材制造)直接成型的AlSi10Mg合金零件表面相对粗糙，很难满足对表面精度要求高的行业需求。而具有获取纳米级表面精度能力的超精密加工为提高激光选区熔化零件的表面质量提供了有前景的后处理解决方案。采用金刚石刀具分别对直接成型、低温退火、固溶处理以及时效处理后的AlSi10Mg合金的微量切削特性进行研究，讨论微观组织演变与切削参数对AlSi10Mg合金的超精密切削特性的影响机理，揭示热处理状态对切削力、切削表面质量与切屑形貌等的影响规律。以探索快速高效地将成型零件表面质量提高到镜面水平的方法。结果表明：激光选区熔化直接成型的AlSi10Mg合金微观组织以微米级的网格结构为主，其显微维氏硬度和切削力均大于热处理后的样品；切削力同时受到合金的微观组织和力学性能的综合影响；直接成型的样品沟槽表面质量最好，低温退火样品次之，固溶处理样品最差；高温热处理后形成的大块的Si颗粒会增加切屑的脆性，并降低样品的X轴切削力；增加切削深度和切削速度均会导致切削力的增加和表面质量的恶化，且切削深度对切削力和表面质量的影响更大；直接成型样品的镜面加工质量最好，表面粗糙度(Ra)数值可降低到11.2 nm，远低于直接成型样品的～10 µm。本研究为实现激光选区熔化成立铝合金零件的表面质量提升到镜面水平提供了理论和应用参考。

Influence Mechanism of Heat Treatment on Ultra-precision Turning Characteristics of Additively Manufactured AlSi10Mg Parts

The surface quality of AlSi10Mg alloy fabricated directly by selective laser melting (SLM) technology generally shows insufficient surface quality, which cannot meet the stringent requirements of some industries for high accuracy in precision engineering. To this end, ultra-precision machining provides a promising post-processing solution for augmented surface quality on SLM parts. In this study, diamond tools were used to investigate the micro-cutting characteristics of as-built, annealed, solution-treated and ageing-treated SLM-AlSi10Mg alloy. The influence of microstructure evolution and cutting parameters on the ultra-precision machining characteristics of AlSi10Mg alloy was discussed. The effect of heat treatment on cutting force, cutting surface quality and chip morphology was revealed aiming to identify the methods to quickly and efficiently improve the surface quality of SLM parts to achieve mirror-surface finishing. The results show that the microstructure of the as-built AlSi10Mg alloy is dominated by a micron-level cellular structure, and its micro Vickers hardness and cutting force are greater than that of the heat-treated sample. The cutting force is simultaneously affected by the microstructure and mechanical properties of the alloy. The surface quality of the grooves of the as-built sample is the best, followed by annealed, ageing-treated and solution-treated samples. The large Si particles formed after high-temperature heat treatment will lead to brittleness of the chips and reduce the X-axis cutting force. Increasing the depth of cut and cutting speed will cause the increase in cutting force and poor surface quality, where the effect of the former factor is more pronounced. Through the present study, the best surface roughness has been improved to 11.2 nm by 3 orders of magnitude from ～10 µm of the as-built sample by SLM. This study provides a theoretical and application reference for the improvement of the surface quality of SLM aluminium alloy parts to the nanometric level.