【作者】 汤莹莹；

【导师】 王新云；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2009， 硕士

【摘要】 块体非晶合金是一种新型金属材料,独特的原子结构赋予其不同于普通晶态金属的优异性能,如高强度、高硬度、耐腐、耐磨、易于近净形加工成形等。其中Zr基(Zr_41.2Ti_13.8Cu_12.5Ni_10.0Be_22.5、Zr₅₅Al₁₀Ni₅Cu₃₀)是玻璃形成能力（GFA）很好的块体非晶合金形成体系。本文以Zr₅₅Al₁₀Ni₅Cu₃₀块体非晶为研究对象,研究其过冷液相区的力学性能及高温塑性变形机理,并基于高温压缩实验及早期经验模型,提出基于Maxwell-Pulse唯象形本构关系模型,通过有限元模拟方法（FEM）进行了验证。采用铜模吸铸方法成功制备了直径为3mm的Zr₅₅Al₁₀Ni₅Cu₃₀。并采用X射线衍射分析（XRD）和示差扫描量热（DSC）方法进行结构和热性能的表征,确定其玻璃转变温度Tg,晶化开始温度Tx和熔点温度Tm,得到过冷液相区温度范围。研究块体非晶合金Zr₅₅Al₁₀Ni₅Cu₃₀在过冷液相区的形变行为,采用Zwick/Roell力学性能试验机进行高温压缩实验,研究应变速率、温度、径高比、尺寸大小对非晶合金过冷液相区力学性能的影响。实验结果表明,过冷液相区非晶力学行为对温度和应变速率都很敏感。也研究了径高比对过冷液相区非晶力学性能的影响,高径比太大,会产生失稳,流动应力值较大,径高比较小,接触表面的影响增大,则摩擦影响较大,流动应力值也较大。尺寸大小的影响,当坯料尺寸减至1mm时,块体非晶合金的流变行为受尺寸效应的影响,流动应力值增大。探讨Zr₀₅₅Cu₃₀Al₁₀Ni₅块体非晶在过冷液相区的变形规律,以粘度和应变速率敏感系数为主要参数,研究其过冷液相区的牛顿流变与非牛顿流变的转变。采用X射线衍射分析（XRD）的方法,研究其高温塑性变形中的晶化行为,在出现应力过冲前后晶化现象有明显差异,而应力过冲的峰值与温度和应变速率都有关,则晶化行为也是依赖于温度和应变速率的过程。分别拟合了三种流动力学模型（扩展指数模型,自由体积模型,虚应力模型）的本构方程。并在这些流动力学模型的基础上,提出Maxwell-Pulse唯象型本构关系,用以描述该材料过冷液相区应力应变曲线。基于MSC.Marc有限元模拟软件,检验该本构方程。通过采用热力耦合模型模拟块体非晶合金高温压缩实验,分别分析了应力场和温度场的分布及数值大小,分析结果表明: Maxwell-Pulse方程能很好的拟合Zr基非晶过冷液相区的变形行为,不但能拟合牛顿流变区域变形行为,也可以拟合牛顿流变向非牛顿流变转变的变形行为。从温度场的分布可以推断块体非晶发生部分结晶或者生成纳米晶首先发生在模具与材料接触表面上,且沿径向分布方向,越靠近试样边缘区域温度越高。更多还原

【Abstract】 Bulk Metallic Glass is a new type of metal material, the unique atom structure contributes to its excellent performance such as high strength, high rigidity, decay resistance, wear resistence and the capability that is easy to near net shaping etc. Zr-based bulk metallic glass (Zr_41.2Ti_13.8Cu_12.5Ni_10.0Be_22.5, Zr₅₅Al₁₀Ni₅Cu₃₀) has a very good glass forming ability. The deformation theory and forming ability of Zr₅₅Al₁₀Ni₅Cu₃₀ in Suprecooled liquid region was choosen for our research work. Based on some classic constitutive equations and compressive experiment in high temperature, a Maxwell-Pulse constitutive equation was proposed, and be proved by using Finite Element Method.In this thesis, in order to acquire Zr₅₅Al₁₀Ni₅Cu₃₀ bulk metallic glass, copper mould casting method was introduced. The structure and thermal ability was measured by XRD and DSC methods. So its glass transition temperature, crystallization temperature and the supercooled liquid can be ensured.By doing different compression experiments of the strain rate, temperature, diameter- high- ratio, and the size of the amorphous alloy with Zwick/Roell mechanical testing maching, deformation behavior of Zr₅₅Al₁₀Ni₅Cu₃₀ bulk amorphous alloys in supercooled liquid was researched.The experimental results showed that mechanical behavior of BMG in the supercooled liquid were very sensitive for temperature and strain rates. The factor of diameter-high ratio was also studied: large diameter-high ratio would leads to instability; while small diameter-high ratio with the impact of contact surface increased, resulted in a greater friction and flow stess. Take size effect into consideration, when the size of the billet was reduced to 1mm, the bulk metallic alloy affected by the size effect and its flow stress increases.In order to discuss the deformation of Zr₅₅Al₁₀Ni₅Cu₃₀ in supercooled liquid, viscosity and strain rate sensitivity coefficient were chosen for the main parameters to study the Newtonian flow and non-Newtonian flow changes. X-ray diffraction （XRD） method was used to study the crystallization behavior in the high-temperature plastic deformation, and it performed significant different before and after stress overshoot phenomenon. As the stress peak was related with the temperature and strain rate, then crystallization behavior was also dependent on temperature and strain rate. Fitting the three flow constitutive equations （Arrhenius function, free volume model, fictive stress model）, and constructed a Maxwell-Pulse phenomenological constitutive relation to describe the supercooled liquid region stress-strain curves.The thermal-merchanical coupling models of MSC.Marc was used to examine the Maxwell-Pulse equation and simulate the compressive behavior of bulk metallic alloy in high-temperature experiments, respectively, analyzed the stress and temperature distribution and the value, the results of the analysis show that: Maxwell-Pulse equation can fit well with the experimental result, including Newton flow behavior and the change from Newton flow to non-Newtonian flow. The analysis of temperature distribution inferred that crystallization may occured first on the contact surface between materials and the mold. And along the radial direction, the more close to the edge, the higher temperature got.更多还原