相变增韧的CuZr基非晶复合材料的设计及其力学性能

发布时间：2018-04-29 16:48

本文选题：非晶合金 + 复合材料　；参考：《太原理工大学》2017年硕士论文

【摘要】：非晶合金由于其独特的性能而受到人们极大地关注,如高强度、大的弹性极限及良好的耐腐蚀和耐磨性等。然而,在室温加载下,由于局域剪切带的快速扩展使块体非晶合金常表现出无预警的脆性断裂特征。为了提高块体非晶合金的宏观塑性,材料学者提出了制备非晶复合材料的方法,即通过内生或者外添加的方法向非晶基体中引入韧性的第二相,进而可以有效的阻止剪切带的快速扩展。近些年,研究人员成功地制备出一系列树枝晶增强的非晶复合材料,如Ti基和Zr基非晶复合材料。但是这类非晶复合材料由于在室温下缺少加工硬化机制会表现出应变软化的特征,这样极大地限制了其在工程上的应用。近几年,这个问题在B2相增强的CuZr基非晶复合材料中得到了成功的解决。B2 CuZr相在应力的诱导下可以发生马氏体相变转变为具有单斜结构的B19?相,这样极大地补偿了非晶基体在塑性变形过程中产生的应变软化,从而提高了材料的加工硬化能力。本论文以Cu Zr基非晶复合材料作为研究对象,研究了微量元素Ni对其玻璃形成能力的影响。在此基础上,系统地研究了CuZr基非晶复合材料室温下的力学行为及其独特的变形机制。但是高温下的力学性能也是考量其能否作为工程结构材料的必要条件,因此对CuZr基非晶复合材料在过冷液相区内的流变行为进行了研究与探讨。本文的主要研究内容及结论如下:(1)Ni可以有效地改变Zr48Cu48-xAl4Nix的玻璃形成能力,进而改变析出b2cuzr相的体积分数。随着ni含量从0-1%的添加,球形b2-cuzr相的体积分数增加,当ni含量添加至1%时,b2-cuzr晶体相的体积分数达到33%,随着ni含量的继续增加,该非晶复合材料的玻璃形成能力增强,b2相体积分数下降。(2)在压缩载荷下,zr48cu48-xal4nix优异的塑性变形行为归因于b2cuzr相的马氏体转变及b2cuzr相对剪切带的阻碍作用;而单轴拉伸时没有观察到明显的塑性变形,即b2cuzr相没有起到改善塑性变形能力的作用。塑性应变拉压不对称的本征原因在于非晶基体的塑性区尺寸与b2cuzr相颗粒尺寸及间距在拉伸载荷下不满足尺寸匹配关系。(3)cuzr基非晶复合材料在过冷液相区内的变形行为对温度和应变速率较为敏感,随着温度的升高和应变速率的降低,应力的峰值及开始进入塑性流变的应力明显降低。(4)cuzr基非晶复合材料在过冷液相区内的流变应力较高,这与其在过冷液相区内非晶基体的晶化行为及马氏体相变有关。铸态时存在的及基体发生晶化后形成的b2cuzr相可以在热与应力的作用转变为b19'马氏体相,其硬度值明显增加。因此针对过冷液相区内cuzr基非晶复合材料与树枝晶增强的非晶复合材料塑性流变行为的比较就相当于在室温下“软”的非晶基体和b2cuzr相与“硬”的b19'马氏体相形成的非晶复合材料与“软”的非晶基体与“硬”的树枝晶形成的非晶复合材料的塑性流变行为的比较。因此尽管cuzr基非晶复合材料中晶体的体积分数较树枝晶低,但是两种非晶复合材料在过冷液相区内表现出来的综合塑性流变应力相差较小。(5)动态冲击下,cuzr基非晶复合材料的塑性应变急剧下降,归因于B2 Cu Zr相在有限的时间内不能阻止剪切带的快速扩展。另外,通过对实验数据进行拟合得出该材料的应变速率敏感性为-0.51,主要是由于Cu Zr基非晶复合材料中非晶基体的绝热软化造成的。
[Abstract]:Amorphous alloys have attracted great attention due to their unique properties, such as high strength, large elastic limit and good corrosion resistance and wear resistance. However, under room temperature loading, the rapid expansion of the local shear band makes the bulk amorphous alloy exhibit a non early-warning brittle fracture characteristic. In order to improve the macrostructure of the bulk amorphous alloy, In view of the plasticity, the material scholars have proposed a method of preparing amorphous composites, that is, introducing ductile second phase into the amorphous matrix by endogenous or external additions, which can effectively prevent the rapid expansion of the shear band. In recent years, the researchers have successfully prepared a series of amorphous composite with dendrite enhancement, such as Ti based and Zr Basic Amorphous Composites. However, this type of Amorphous Composites, due to the lack of working hardening at room temperature, shows the characteristics of strain softening, which greatly restricts its engineering application. In recent years, this problem has been successfully induced in the B2 phase enhanced CuZr Based Amorphous Composites to induce the stress induction of the.B2 CuZr phase. The transformation of martensitic transformation into a monocline structure of B19? Phase can greatly compensate the strain softening of the amorphous matrix during the plastic deformation process, thus improving the ability of material processing and hardening. In this paper, the Cu Zr based amorphous composite was used as the research object to study the glass formation ability of the trace element Ni. On this basis, the mechanical behavior and the unique deformation mechanism of CuZr Base Amorphous Composites at room temperature are systematically studied. However, the mechanical properties at high temperature are also the necessary conditions to consider whether it can be used as a structural material. Therefore, the rheological behavior of CuZr Based Amorphous Composites in the supercooled liquid phase region is studied. The main contents and conclusions of this paper are as follows: (1) Ni can effectively change the glass formation ability of Zr48Cu48-xAl4Nix and then change the volume fraction of the precipitated b2cuzr phase. With the addition of Ni content from 0-1%, the volume fraction of the spherical b2-cuzr phase increases. When the content of Ni is added to 1%, the volume fraction of the b2-cuzr crystal phase reaches 33%, with the volume fraction of the b2-cuzr crystal phase up to 33%. With the increase of Ni content, the glass forming ability of the amorphous composite is enhanced and the volume fraction of B2 phase decreases. (2) the excellent plastic deformation behavior of zr48cu48-xal4nix is attributed to the martensitic transformation of the b2cuzr phase and the hindering effect of b2cuzr relative shear zone under the compression load, while the apparent plastic deformation is not observed during the uniaxial tensile. The b2cuzr phase does not play a role in improving the plastic deformability. The intrinsic reason for the asymmetry of the plastic strain tension is that the size of the plastic zone of the amorphous matrix and the particle size and spacing of the b2cuzr phase do not meet the size matching relationship under the tensile load. (3) the deformation behavior of the CuZr Based Amorphous Composites in the supercooled liquid phase is to the temperature and the strain change It is more sensitive, with the increase of temperature and the decrease of the strain rate, the stress peak and the stress that begin to enter the plastic flow obviously decrease. (4) the rheological stress of the CuZr based amorphous composite in the supercooled liquid phase is higher, which is related to the crystallization behavior and martensitic transformation in the amorphous matrix in the supercooled liquid phase. The b2cuzr phase formed after the crystallization of the matrix can change into b19'martensitic phase in the effect of heat and stress, and its hardness value increases obviously. Therefore, the comparison of the plastic rheological behavior of CuZr Based Amorphous Composites and dendrite reinforced Amorphous Composites in the supercooled liquid phase is equivalent to the "soft" amorphous matrix and b2cu at room temperature. The Zr phase is compared with the plastic rheological behavior of the amorphous composite formed by the "hard" b19'martensite phase and the amorphous matrix formed by the "soft" amorphous matrix and the "hard" dendrite. Therefore, although the volume fraction of the crystal in the CuZr base amorphous composite is lower than that of the dendrite, it is the two amorphous composite in the supercooled liquid phase region. In the dynamic impact, the plastic strain of CuZr based amorphous composite decreases sharply and the B2 Cu Zr phase can not prevent the rapid expansion of the shear band in a limited time. In addition, the sensitivity of the strain rate sensitivity of the material is -0.51 by fitting the experimental data. It is due to adiabatic softening of amorphous matrix in Cu Zr Based Amorphous Composites.

【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG139.8

【参考文献】