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Absolute Evaluation of Mechanical Properties of Thin Films Based on the Microplasticity Theory of Internal Friciton.

基于内摩擦微塑性理论的薄膜力学性能的绝对评价。

基本信息

批准号：
05650617
负责人：
NISHINO Yoichi
金额：
$ 1.41万
依托单位：
Nagoya Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

Internal friction in aluminum thin films 0.2 to 2.0mum thick on silicon substrates has been investigated between 180 and 360 K as a function of strain amplitude by means of a free-decay method of flexural vibraion. According to the constitutive equation, the internal friction in the film alone can be evaluated separately from the data on the film-substrate composite. The amplitude-dependent internal friction in aluminum films is found in the strain range approximately two orders of magnitude higher than that for bulk aluminum. On the basis of the microplasticity theory, the amplitude-dependent internal friction can be converted into the plastic strain as a function of effective stress on dislocation motion. The mechanical responses thus obtained for aluminum films show that the plastic strain of the order of 10^<-9> increases nonlinearly with increasing stress. These curves tend to shift to a higher stress with decreasing film thickness and also with decreasing temperature, both indicating a suppression of the microplastic deformation. At all temperatures examined, the microflow stress at a constant level of the plastic strain varies inversely with the film thickness, which qualitatively agrees with the variation in the macroscopic yield strengths. From a practical standpoint, the present analytical approach of internal friction is applicable for non-destructive evaluation of stree-strain responses in thin films bonded to a substrate, and is directly comparable with uniaxial tensile testing of free-standing films detached from a substrate.

利用弯曲振动的自由衰减法，研究了在180 ~ 360 K范围内，硅衬底上0.2 ~ 2.0mum厚铝薄膜的内摩擦随应变幅值的变化规律。根据本构方程，可以从膜-基复合材料的数据中单独计算膜内的内耗。在应变范围内，铝膜的内摩擦与幅值有关，比块状铝的内摩擦高约两个数量级。根据微塑性理论，可以将随幅值变化的内摩擦转化为有效应力对位错运动的函数。得到的铝膜力学响应表明，随着应力的增加，10^<-9>数量级的塑性应变呈非线性增加。随着薄膜厚度的减小和温度的降低，这些曲线趋向于向更高的应力方向移动，这都表明微塑性变形受到抑制。在所有测试温度下，恒定塑性应变水平下的微流变应力与薄膜厚度成反比，这在定性上与宏观屈服强度的变化一致。从实际的角度来看，目前的内摩擦分析方法适用于与衬底结合的薄膜的应力应变响应的无损评估，并且可以直接与从衬底分离的独立薄膜的单轴拉伸测试相比较。