摘要
块体非晶合金(BMGs)因其高强度、高硬度、高弹性极限、优异的耐磨、耐腐蚀性能等优点而受到材料学家们的广泛关注。然而,室温时BMGs在剪切应力作用下,高度局域化的原子团簇结构进行剪切转变形成剪切带,同时在剪切带内部产生大量自由体积并发生应变软化现象,使得BMGs的变形高度局域化且容易发生脆性断裂。为解决BMGs的室温脆性问题,研究学者们相继提出各种非变形、弹性变形以及塑性变形的方法来实现外部能量输入,进而通过促使BMGs内部形成非均匀结构来提升BMGs的力学性能。作为一种新兴的表面强化技术,激光冲击强化(LSP)通过将光能转换成为机械能并强制材料表面发生塑性变形,在金属材料表面和近表面引入压缩残余应力并诱导形成更细的晶粒,进而显著提升金属材料的力学性能。近年来,研究学者们针对通过LSP技术改善BMGs的力学性能开展了大量研究工作。本文重点总结近10年来LSP处理在优化BMGs结构非均匀性、表面残余应力以及力学性能方面的研究成果,以便研究人员进一步制备综合性能更加优异的BMGs,进而推动其在工业领域的应用。
The bulk metallic glasses(BMGs)have been widely studied by material scientists because of their short-range ordered and long-range disordered atomic structure arrangement,which makes them free from grain boundaries,dislocations,and laminar faults.Thereafter,the BMGs have the advantages of high strength,high hardness,high elastic limit,excellent wear resistance,and corrosion resistance.They are also considered potential candidates for engineering structural materials.However,the weakness in the mechanical properties of BMGs(room temperature brittleness and strain softening)severely limits their practical application.The main reason is that the highly localized atomic clusters of BMGs undergo shear transformation to form shear bands under shear stress at room temperature.At the same time,a large amount of free volume is generated within the shear bands,and strain softening occurs,which results in the highly localized deformation and brittle fracture of BMGs.In general,thermodynamically meta stable BMGs undergo a spontaneous transition to a lower energy state driven by energy differences,which is known as structural relaxation or"rejuvenation".This transition process will lead to an orderly and homogeneous structure in BMGs,which will significantly deteriorate the mechanical properties of BMGs.The"rejuvenation"of BMGs is a process in which the atomic structure rearranges and stores energy under the premise of external energy input,which can effectively delay or even inhibit the formation of shear bands or single propagation behavior.Therefore,the"rejuvenation"of BMGs is considered the key to improving the plastic deformation capacity of BMGs.To realize the"rejuvenation"of BMGs and solve the problems of room temperature brittleness and strain softening,various non-deformation,elastic deformation,and plastic deformation methods have been proposed to achieve the external energy input,and thus improve the mechanical properties of BMGs by promoting the formation of anon-uniform structure inside BMGs.As a new surface strengthening technology,laser shock strengthening(LSP)can introduce compressive residual stress on the surface and near surface of metal materials and also induces the formation of finer grains by converting light energy into mechanical energy and forcing plastic deformation on the material surface.In addition,the pressure of the plasma shock wave generated during LSP processing can reach several GPa,so that the depth of the compressive residual stress layer(1~2 mm)of LSP strengthening technology can reach 5~10 times that of traditional shot peening.Therefore,LSP strengthening has great potential in improving the mechanical properties of metal materials.However,unlike crystalline metal materials,BMGs do not have grains,grain boundaries,dislocations,etc.,so they have a different deformation mechanism from traditional crystalline metal materials.The recent researches show that because the pulsed laser beam energy presents Gaussian distribution characteristics,which makes the shock wave formed by a single point laser beam not only promote the severe plastic deformation,form circular micro-pits and increase the surface roughness,but also introduce gradient residual compressive stress on the surface and inside of BMGs in a certain range.In addition,severe plastic deformation not only leads to non-uniform transformation of the BMG's surface microstructure but also induces the generation of shear bands,which leads to strain softening on the BMG's surface.Due to the competition between the machining optimization caused by residual compressive stress and the strain softening caused by structural transformation,the surface of BMGs may show the characteristics of hardening or softening.On the other hand,by adjusting and optimizing the overlapping rate,energy density,and diameter of the multi-point laser beam,the residual compressive stress on BMGs'surface can be significantly increased and distributed more evenly,and the surface roughness of BMGs can be effectively controlled after LSP treatment.Finally,the combined action of residual compressive stress and microstructure"rejuvenation"can effectively inhibit the formation of a single shear band on the BMGs surface during the loading deformation process,while a large number of prefabricated shear bands inside the BMG can expand multiple times to improve the compression,tensile,and bending plasticity effectively.In recent years,researchers have carried out a lot of research on improving the mechanical properties of BMGs through LSP technology.In particular,the influence mechanism of LSP processing parameters(such as laser beam pulse power,laser beam diameter,and overlapping rate)on residual stress distribution,shear band distribution,and surface integrity(including surface topography,surface microstructure,surface hardness,and surface roughness)of BMGs was discussed in detail.In this paper,the recent 10 years'research achievements on optimizing the structure heterogeneity,surface residual stress,and mechanical properties of BMGs by LSP treatment were summarized.Meanwhile,the mechanical properties of BMGs treated by LSP under different process parameters were summarized,and the future research on the mechanism of action,process optimization,and application of BMGS treated by LSP were prospected.So that researchers can further prepare BMGs with better comprehensive properties and promote their application in the industrial field.
作者
翟海民
Zhai Haimin(State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals,Lanzhou University of Technology,Lanzhou 730050,China)
出处
《稀有金属》
北大核心
2025年第11期1750-1763,共14页
Chinese Journal of Rare Metals
基金
国家自然科学基金项目(52265024)资助
关键词
块体非晶合金
激光喷丸
回春行为
残余应力
力学性能
bulk metallic glasses
laser shock peening
rejuvenation behavior
residual stress
mechanical property
