The characterization of plastic flow in three different bulk metallic glass systems

Plastic deformation behaviors of Zr52.5Al10Ni10Cu15Be12.5, Mg65Cu25Gd10 and Pd43Ni10Cu27P20 bulk metallic glasses (BMGs) are studied by using the depth-sensing nanoindentation, macroindentation and uniaxial compression. The significant difference in plastic deformation behavior cannot be correlated to the Poisson's ratio or the ratio of shear modulus to bulk modulus of the three BMGs, but can be explained by the free volume model. It is shown that the nucleation of local shear band is easy and multiple shear bands can be activated in the Zr52.5Al10Ni10Cu15Be12.5 alloy, which exhibits a distinct plastic strain during uniaxial compression and less serrated flow during nanoindentation. (c) 2006 Elsevier B.V. All rights reserved

两种Zr基块体非晶合金的变形行为

使用单轴压缩、纳米压入、界面粘结和显微观察等技术对Zr65A10Ni10-Cu15和Zr52.5Al10Ni10Cu15Be12.5合金的宏观和细观塑性变形行为进行了研究．结果表明：Be代替了部分Zr后的非晶合金的单轴压缩强度和塑性明显提高．两种合金均在低加载速率的纳米压入中表现出锯齿流变特征，在高加载速率中为连续的塑性变形，但变形行为转变的临界加载速率有明显差别．对比两种合金压痕下方塑性变形区域中剪切带形貌表明，在同样加载条件下，Zr52.5Al10Ni10Cu15Be12．5合金中形成剪切带的数量多、尺寸小、间距小，随着压入深度的增大，剪切带间距基本不变．这表明Zr65Al10Ni10Cu15合金中剪切带形成相对困难，趋向于单个剪切带的扩展，因此宏观塑性变形能力有限．而在含Be合金的塑性变形过程中剪切带容易形核，趋向于多重剪切带的同时开动，因此宏观塑性变形能力显著．两种合金塑性变形行为的差异符合自由体积模型

两种zr基块体非晶合金的变形行为

使用单轴压缩、纳米压入、界面粘结和显微观察等技术对Zr65A10Ni10-Cu15和Zr52.5Al10Ni10Cu15Be12.5合金的宏观和细观塑性变形行为进行了研究．结果表明：Be代替了部分Zr后的非晶合金的单轴压缩强度和塑性明显提高．两种合金均在低加载速率的纳米压入中表现出锯齿流变特征，在高加载速率中为连续的塑性变形，但变形行为转变的临界加载速率有明显差别．对比两种合金压痕下方塑性变形区域中剪切带形貌表明，在同样加载条件下，Zr52.5Al10Ni10Cu15Be12．5合金中形成剪切带的数量多、尺寸小、间距小，随着压入深度的增大，剪切带间距基本不变．这表明Zr65Al10Ni10Cu15合金中剪切带形成相对困难，趋向于单个剪切带的扩展，因此宏观塑性变形能力有限．而在含Be合金的塑性变形过程中剪切带容易形核，趋向于多重剪切带的同时开动，因此宏观塑性变形能力显著．两种合金塑性变形行为的差异符合自由体积模型

Ce基大块非晶合金在纳米压人过程中的变形行为

利用纳米压入技术研究了Ce基大块非晶合金的变形行为,以及加载速率对塑性变形行为的影响规律.结果表明,Ce基大块非晶合金在纳米压入过程中表现出的变形行为与其他体系大块非晶有显著差别.Ce60Al15Cu10Ni15合金在低加载速率下为连续的塑性变形,在高加载速率下表现出显著的锯齿流变特征;而Ce65Al10Cu10Ni10Nb5合金,在所研究的加载速率范围内均为连续的塑性变形．但是,这两种合金都出现了室温蠕变现象．另外,探讨了Ce基大块非晶合金的反常塑性变形行为的产生机理

PBX材料亚临界开裂实验研究

通过比较PBX材料和岩石类材料的力学性质,借助岩石断裂力学的研究方法,设计了PBX材料在三点弯曲载荷下的白光散斑实验,观察了PBX材料中裂纹扩张的规律。通过计算应力强度因子和分析裂纹尖端扩张速度,证实PBX材料中也存在亚临界开裂,为PBX材料结构件的储存开裂研究提供了新的思路和方法

Characterization of Plastic Flow in Two Zr-Based Bulk Metallic Glasses

Plastic deformation behaviors of Zr65Al10Ni10CU15 and Zr52.5Al10Ni10Cu15Be12.5 bulk metallic glasses (BMGs) are studied by using the depth-sensing nanoindentation, microindentation and uniaxial compression. The Be-containing BMG exhibits a significantly improved overall plastic strain compared with the Be-free alloy during compressive tests. Both BMGs show a loading-rate-dependent serrated flow during nanoindentation measurements, but the Be-containing alloy exhibits a much lower critical loading rate for the disappearance of the serration than the Be-free BMG. The shear band patterns developed during plastic deformation are investigated by microindentation technique, wherein much higher shear band density is found in the Be-containing alloy than in the Be-free alloy, indicating an easier nucleation of shear bands in the former BMG. The difference in the plastic deformation behavior of the two BMGs can be explained by a free volume model

Effect of structural relaxation on deformation behaviour of Zr-based metallic glass

Structural relaxation through isothermal annealing at tempertature below glass transition is conducted on Zr46.75Ti8.25Cu7.5Ni10Be27.5 (Vitreloy-4) bulk metallic glass. Defect concentration is correlated with the annealing time t according to differential scanning calorimetry thermalgrams. The effects of structural relaxation on mechanical properties and deformation behaviour are investigated by using instrumented nanoindentation. It is found that as-cast alloy exhibits pronounced serration flow during the loading process of nanoindentation, and the size and number of serrations decrease with the annealing time. The change of the deformation behaviour with structural relaxation is explained using a free volume model