非晶合金表层结构异化及其与塑性关系的研究

发布时间：2018-01-19 18:38

本文关键词： 非晶合金激光熔凝晶化扭转剪切剪切带塑性本构方程　出处：《长安大学》2015年硕士论文　论文类型：学位论文

【摘要】：大块非晶合金性能优异,如高强度、高硬度、耐磨、耐蚀等。然而非晶合金的明显缺陷在于其塑性差,室温下压缩拉伸实验大部分表现为脆性断裂,非晶合金的这个缺陷直接影响其在工程结构材料中的应用发展。因此近年来,对于块体非晶合金材料力学性能的研究主要集中在怎样提高它在室温下的塑性变形能力。本文选取Zr基Cu46Zr46Al8和Zr52.5Cu17.9Ni14.6Al10Ti5两种体系的非晶合金分别采用YAG型激光仪对非晶合金表面进行重熔和线性扭转实验机定扭速两种预处理方法。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM),分析经过预处理的非晶合金微观形貌及成分分布;通过单轴压缩实验机对两种体系的非晶合金进行压缩,表征其塑性提升能力;并结合Zr52.5Cu17.9Ni14.6Al10Ti5体系的非晶合金扭转压缩实验数据推导出多维应力下非晶合金的塑性本构关系的两种表达式,对其屈服变形行为进行分析。实验结果表明:通过激光处理Cu46Zr46Al8非晶合金使其表面产生熔凝层,诱导生成表面纳米级晶体,形成表面晶体、心部非晶的夹心结构。变形过程中,晶体通过位错滑移变形,而心部剪切带在表面晶体阻碍下不再延单一方向扩展,在两种变形协同作用下,塑性得以提升。同时调整激光各项工艺参数,可以有效控制非晶合金表面熔凝层中晶体的大小、范围及数量。通过扭转剪切处理Zr52.5Cu17.9Ni14.6Al10Ti5非晶合金,改变其微观结构,诱导剪切带的生长和扩散,亦可有效提高非晶合金塑性,并且结合材料的扭转、压缩实验数据,证明了大块非晶合金塑性本构关系的两种方程式具有统一性。致使此结论得以普遍适用于非晶材料中,并且可以推广到其他新型材料的本构关系研究方法中。
[Abstract]:Bulk amorphous alloys have excellent properties, such as high strength, high hardness, wear resistance, corrosion resistance and so on. However, the obvious defects of amorphous alloys lie in their poor plasticity, and most of the compression tensile tests at room temperature show brittle fracture. This defect of amorphous alloy directly affects the development of its application in engineering structural materials. The mechanical properties of bulk amorphous alloys are mainly focused on how to improve their plastic deformation at room temperature. In this paper, Zr-based Cu46Zr46Al8 and Zr52.5Cu17.9 are selected. The surface of amorphous alloy of Ni14.6Al10Ti5 system was remelted by YAG laser and fixed torsion velocity was pretreated by linear torsion tester. X-ray diffraction was used. Instrument (. XRD). Scanning electron microscope (SEM) was used to analyze the microstructure and composition distribution of the pretreated amorphous alloy. Two kinds of amorphous alloys were compressed by uniaxial compression machine to characterize their plastic lifting ability. Based on the experimental data of torsional compression of amorphous alloy in Zr52.5Cu17.9Ni14.6Al10Ti5 system, two expressions of plastic constitutive relation of amorphous alloy under multi-dimensional stress are derived. The experimental results show that the surface of Cu46Zr46Al8 amorphous alloy can be fused by laser treatment, resulting in the formation of surface nanocrystalline crystal and the formation of surface crystal. The sandwich structure of the amorphous core. During the deformation process, the crystal is deformed by dislocation slip, while the core shear band does not extend in a single direction under the hindrance of the surface crystal, under the synergistic action of the two kinds of deformation. At the same time, the crystal size in the surface melting layer of amorphous alloy can be effectively controlled by adjusting the laser parameters. Range and quantity. The microstructure of Zr52.5Cu17.9Ni14.6Al10Ti5 amorphous alloy was changed by torsion shear treatment, and the growth and diffusion of shear band were induced. It can also effectively improve the plasticity of amorphous alloys and combine the torsion and compression data of the materials. It is proved that the two equations of the plastic constitutive relation of bulk amorphous alloys are unified, which makes this conclusion applicable to amorphous materials and can be extended to the study of constitutive relations of other new materials.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG139.8

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