Laser shock peening (LSP) is an ideal surface modification technique which has been extensively applied to improve the room-temperature plasticity of metallic glasses (MGs) by generating extra-deep compressive residual stress region and increasing the free volume content. Nevertheless, after LSP treatment, the surface quality and hardness of MGs are usually impaired simultaneously, which hinders their applications as structural and functional materials. In the current study, an attempt was made to achieve simultaneous flattening and hardening of LSP treated (LSPed) Zr-based MG by nanosecond laser irradiation in a flowing nitrogen atmosphere. The effects of laser power level on the macro- and micro-morphology, chemical composition, surface hardness, and surface roughness (a) of the laser-irradiated LSPed MG were comprehensively investigated. It was found that the minor surface defects of the LSPed MGs could be effectively reduced by nanosecond laser irradiation under appropriate laser irradiation parameters, and accordingly, the surface quality was improved (with a maximum reduction in surface roughness (a) by 86.3%). Furthermore, the nanoindentation test results indicated that nanosecond laser irradiation at a relatively high laser power of 15.6W resulted in an impressive improvement (173.9%) in surface hardness of the LSPed MG, which could be attributed to the introduction of hard nitrided phases mainly consisting of ZrN. This study provides an insightful understanding of the microstructure changes and surface characteristics of the LSPed MGs after nanosecond laser irradiation in a flowing nitrogen atmosphere, which paves the way for improving the applicability of MGs as structural and functional materials.

中文翻译：

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在流动氮气气氛中纳秒激光照射激光冲击喷丸锆基金属玻璃表面同时整平和硬化

激光冲击喷丸（LSP）是一种理想的表面改性技术，已广泛应用于通过产生超深压缩残余应力区域和增加自由体积含量来提高金属玻璃（MG）的室温塑性。然而，经过LSP处理后，MG的表面质量和硬度通常会同时受损，这阻碍了它们作为结构和功能材料的应用。在当前的研究中，尝试通过纳秒激光照射在流动的氮气气氛中实现LSP处理（LSPed）Zr基MG的同步压平和硬化。综合研究了激光功率水平对激光照射 LSPed MG 的宏观和微观形貌、化学成分、表面硬度和表面粗糙度 (a) 的影响。结果发现，在适当的激光照射参数下，纳秒激光照射可以有效减少LSPed MG的微小表面缺陷，从而提高表面质量（表面粗糙度（a）最大降低86.3%）。此外，纳米压痕测试结果表明，在相对较高的激光功率（15.6W）下进行纳秒激光照射，LSPed MG 的表面硬度显着提高（173.9％），这可归因于硬氮化相的引入，该相主要由氮化锆。这项研究提供了对流动氮气气氛中纳秒激光照射后LSPed MGs的微观结构变化和表面特征的深入了解，这为提高MGs作为结构和功能材料的适用性铺平了道路。