Deformation mechanisms of ultra-thin Al layers in Al/SiC nanolaminates as a function of thickness and temperature
Deformation mechanisms of ultra-thin Al layers in Al/SiC nanolaminates as a function of thickness and temperature
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DOI：
10.1080/14786435.2016.1219075
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发表时间：
2016-08
影响因子：
1.6
通讯作者：
L. Yang;C. Mayer;N. Chawla;J. Llorca;J. Molina-Aldareguia
中科院分区：
文献类型：
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作者：
L. Yang;C. Mayer;N. Chawla;J. Llorca;J. Molina-Aldareguia
在25~100℃温度范围内，采用纳米压痕技术研究了Al/SiC纳米层状物在10~100 nm厚度范围内的力学性能。基于有限元方法对纳米压痕试验进行数值模拟，由纳米层状物的硬度得到Al层状物的强度随层厚和温度的变化关系。Al层的室温屈服应力表现出较大的“越薄越强”效应，这种效应不仅与Al层厚度有关，还与显微组织有关，且随Al层厚度的变化而变化。对于较厚的Al层(>；50 nm)，Al层在室温下的屈服应力符合由位错与晶界相互作用控制的变形机制，而对于小于50 nm的层，则以约束层滑移为主。随着温度的升高，Al的屈服应力显著降低，并随着Al层厚度的减小而增大，在100℃时产生了相反的尺寸效应，这与100℃时晶界和界面扩散控制的塑性变形机制相一致，从而限制了超薄Al层的强度。
Abstract The mechanical properties of Al/SiC nanolaminates with layer thicknesses between 10 and 100 nm were studied by nanoindentation in the temperature range 25 to 100 °C. The strength of the Al layers as a function of the layer thickness and temperature was obtained from the hardness of the nanolaminates by an inverse methodology based on the numerical simulation of the nanoindentation tests by means of the finite element method. The room temperature yield stress of the Al layers showed a large ‘the thinner, the stronger’ effect, which depended not only on the layer thickness but also on the microstructure, which changed with the Al layer thickness. The yield stress of the Al layers at ambient temperature was compatible with a deformation mechanism controlled by the interaction of dislocations with grain boundaries for the thicker layers (>50 nm), while confined layer slip appeared to be dominant for layers below 50 nm. There was a dramatic reduction in the Al yield stress with temperature, which increased as the Al layer thickness decreased, and led to an inverse size effect at 100 °C. This behavior was compatible with plastic deformation mechanisms controlled by grain boundary and interface diffusion at 100 °C, which limit the strength of the ultra-thin Al layers.