钛基非晶复合材料变形行为研究

发布时间：2018-03-25 19:13

本文选题：非晶复合材料　切入点：动态力学分析　出处：《西北工业大学》2016年博士论文

【摘要】：非晶复合材料内部的双相结构赋予了其优于金属玻璃的力学性能,其中Ti基非晶复合材料由于其较低的成本、高的比强度以及适中的杨氏模量等优点越来越受到人们的关注。但目前关于非晶复合材料的研究大多集中在制备工艺的改进、新合金的开发、微观组织的调控对宏观力学性能的影响等方面,而对合金在变形过程中的微结构演化、过冷液相区以及枝晶软化区内的变形行为等尚未有系统研究。因此,本文在具体实验研究的基础上,结合数值计算和理论分析,以自行设计的Ti基非晶复合材料为研究对象,对其力学性能、流变状态以及微观组织的演变规律等关键问题进行了深入研究,以期为非晶复合材料的成分设计和实际应用提供一定的理论支持与实践依据。论文的主要研究内容和结论如下:1.通过动态力学分析,系统研究了Ti50Zr20Nb12Cu5Be13非晶复合材料在不同温度下的动态力学性能,将该非晶复合材料的状态随温度变化分为三个区域:弹性态为主的区域,粘弹性为主的区域,随晶化弹性态升高的区域。该非晶复合材料的损耗系数与温度之间呈二次线性关系,通过准点缺陷模型对其动态力学行为分析,拟合曲线与实验数据点符合良好。2.通过单轴压缩和拉伸试验,系统研究了Ti50Zr20Nb12Cu5Be13非晶复合材料在室温下的变形行为,该非晶复合材料在压缩和拉伸条件下均表现出了优异的强度和塑性。此时第二相枝晶在变形过程中对基体中剪切带进行阻碍和吸收,促进更多的塑性剪切带生成,以提高复合材料整体的塑性。压缩断口表面主要包含脉络状区域和台阶状区域,拉伸断口表面布满了韧窝。3.通过单轴压缩和拉伸试验,分别研究了典型金属玻璃与Ti50Zr20Nb12Cu5Be13非晶复合材料在过冷液相区内的流变行为。通过激活体积和迁移原子团的计算,定量说明了在过冷液相区内金属玻璃具有最优的流变性能,Ti50Zr20Nb12Cu5Be13非晶复合材料的流变性能相对较差。通过计算应变速率敏感系数研究了该非晶复合材料在不同变形条件下对应变速率的敏感性。对变形后的非晶复合材料微观组织进行观察,发现枝晶形貌并未有明显变化,材料整体的流变性能主要依靠非晶基体的超塑性流变特性,第二相枝晶仅负责外加应力的传导。拉伸断口表面布满了韧窝,但与室温下的韧窝有明显区别。4.通过压缩和拉伸变形测试,系统研究了Ti50Zr20Nb12Cu5Be13非晶复合材料在枝晶软化区内的流变行为。结果表明非晶复合材料中非晶基体的晶化对材料压缩变形下的力学性能有着较大影响,而对拉伸变形下的力学性能影响不大。通过对该条件下应变速率敏感系数的计算,发现拉伸变形下材料对应变速率的敏感性要远远高于压缩变形条件下。变形后复合材料的枝晶形貌有很大改变,首先是玫瑰状枝晶被球化为球晶,其次是枝晶发生了严重的塑性变形。此时晶化的基体负责外加应力的传导,软化的枝晶则吸收外加应力用于自身的塑性变形。
[Abstract]:The mechanical properties of dual phase structure of amorphous composite materials of the superior metal glass, including Ti Based Amorphous Composites due to its low cost, high specific strength and moderate and Young's modulus of the advantages of more attention. But the current research on amorphous composite materials are mostly concentrated in the improvement the preparation process, the development of new alloys, the regulation of Microstructure Effects on the mechanical properties of the alloy, and the deformation in the process of microstructure evolution, the supercooled liquid region and dendrite softening deformation behavior within the area have not yet been systematically studied. Therefore, based on the specific experimental study on the combination of theoretical analysis and numerical simulation, the Ti based amorphous composites was designed as the research object, on the mechanical properties, the deep study of key issues of rheological state and microstructure evolution etc., In order to provide theoretical support and practical basis for the composition design of amorphous composite materials and practical application. The main research contents and conclusions are as follows: 1. by dynamic mechanical analysis, system to study the dynamic mechanical properties of Ti50Zr20Nb12Cu5Be13 amorphous composite materials under different temperature, the amorphous state of the composite material with temperature the change is divided into three regions: region based elastic state, viscoelastic dominated region, along with the crystallization area. In elastic state increased two linear relationship between loss coefficient and temperature of the amorphous composite materials, through the analysis on defect model on the dynamic mechanical behavior, the fitting curve and the experimental data in good agreement with.2. through the uniaxial compression and tensile test system on the deformation behavior of Ti50Zr20Nb12Cu5Be13 Amorphous Composites at room temperature, the Amorphous Composites under compressive and tensile conditions Showed excellent strength and plasticity. The second phase dendrite during the deformation of the matrix shear zone and hinder the absorption, promote more ductile shear zone formation, in order to improve the plasticity of composite materials. The overall compression fracture surface mainly contains the context like region and the step shaped region, the tensile fracture surface full of dimple.3. by uniaxial compression and tensile test, respectively study the typical metal glass and Ti50Zr20Nb12Cu5Be13 amorphous composite on rheological behavior of supercooled liquid region. By calculating the activation volume and migration of atoms, the quantitative results show that the rheological properties in the supercooled liquid region of metallic glass has the best. The rheological properties of Ti50Zr20Nb12Cu5Be13 amorphous composite materials is relatively poor. Through calculation should study the amorphous composite material corresponding sensitivity to strain rate under different deformation conditions on the strain rate sensitivity coefficient. To observe the deformation of the amorphous composite material microstructure, found that the dendrite morphology did not change obviously, the rheological properties of the whole material mainly depends on the superplastic rheological properties of amorphous matrix, the second dendrite is only responsible for the external stress conduction. The tensile fracture surface is covered with dimples, but with room temperature with dimples the obvious difference of.4. by compression and tensile deformation testing system of Ti50Zr20Nb12Cu5Be13 amorphous composite materials in dendrite softening zone rheological behavior. The results show that the Amorphous Composites crystallization of amorphous matrix has a great effect on the mechanical properties of materials under compression deformation, but it has little influence on the mechanical properties of tensile deformation. The conditions should be calculated under the strain rate sensitivity coefficient, found that the tensile deformation of materials under the strain rate sensitivity is much higher than the compression deformation conditions. The composite material after deformation The dendrite morphology changed greatly. First, rose shaped dendrites were spherulite spherulite, followed by dendrite. Severe plastic deformation took place. The substrate of crystallization was responsible for the conduction of external stress. The softened dendrite absorbed external stress for its plastic deformation.

【学位授予单位】：西北工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG139.8;TB33

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