Kayitmazbatir Metin, Banu Mihaela
Mechanical Engineering Department, University of Michigan, 2350 Hayward, Ann Arbor, MI 48109, USA.
Materials (Basel). 2024 Jul 22;17(14):3622. doi: 10.3390/ma17143622.
Laser surface remelting of aluminum alloys has emerged as a promising technique to enhance mechanical properties through refined microstructures. This process involves rapid cooling rates ranging from 10 to 10 °C/s, which increase solid solubility within aluminum alloys, shifting their eutectic composition to a larger value of silicon content. Consequently, the resulting microstructure combines a strengthened aluminum matrix with silicon fibers. This study focuses on the laser scanning of Al-Si aluminum alloy to reduce the size of aluminum matrix spacings and transform fibrous silicon particles from micrometer to nanometer dimensions. Analysis revealed that the eutectic structure contained 17.55% silicon by weight, surpassing the equilibrium eutectic composition of 12.6% silicon. Microstructure dimensions within the molten zones, termed 'melt pools', were extensively examined using Scanning Electron Microscopy (SEM) at intervals of approximately 20 μm from the surface. A notable increase in hardness, exceeding 50% compared to the base plate, was observed in the melt pool regions. Thus, it is exemplified that laser surface remelting introduces a novel strengthening mechanism in the alloy. Moreover, this study develops an in situ method for predicting melt pool properties and dimensions. A predictive model is proposed, correlating energy density and spectral signals emitted during laser remelting with mechanical properties and melt pool dimensions. This method significantly reduces characterization time from days to seconds, offering a streamlined approach for future studies in additive manufacturing.
铝合金的激光表面重熔已成为一种很有前景的技术，可通过细化微观结构来提高机械性能。该过程涉及10⁵至10⁶℃/s的快速冷却速率，这会增加铝合金中的固溶度，使它们的共晶成分向更高的硅含量值转变。因此，最终的微观结构是强化的铝基体与硅纤维相结合。本研究聚焦于对Al-Si铝合金进行激光扫描，以减小铝基体间距的尺寸，并将纤维状硅颗粒从微米尺寸转变为纳米尺寸。分析表明，共晶结构中硅的重量含量为17.55%，超过了12.6%硅的平衡共晶成分。使用扫描电子显微镜（SEM）从表面起每隔约20μm对称为“熔池”的熔区内的微观结构尺寸进行了广泛研究。在熔池区域观察到硬度显著增加，相比基板硬度增加超过50%。因此，这例证了激光表面重熔在合金中引入了一种新的强化机制。此外，本研究开发了一种预测熔池性能和尺寸的原位方法。提出了一个预测模型，将激光重熔过程中发射的能量密度和光谱信号与机械性能和熔池尺寸相关联。该方法将表征时间从数天显著缩短至数秒，为增材制造的未来研究提供了一种简化方法。
