The Role of Grain Boundaries in Low-Temperature Plasticity of Olivine Revealed by Nanoindentation
The Role of Grain Boundaries in Low-Temperature Plasticity of Olivine Revealed by Nanoindentation
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纳米压痕揭示晶界在橄榄石低温塑性中的作用
DOI：
10.1029/2023jb026763
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发表时间：
2023
期刊：
影响因子：
3.4
通讯作者：
Avadanii D
中科院分区：
文献类型：
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作者：
Avadanii D
橄榄石的流变特性影响岩石行星的大规模长期变形过程。对橄榄石在低温和高应力下变形的研究强调了晶粒尺寸效应对屈服应力的影响。实验室研究表明，具有较细颗粒的集料比具有较粗颗粒的集料更坚固。然而，导致橄榄石中这种效应的晶内缺陷和晶界之间的特定相互作用仍然没有得到解决。在这项研究中，直接观察和量化的橄榄石晶界的机械性能，我们进行纳米压痕测试，以及表征双晶体。具体来说，我们在亚晶界（13 °，[100]/（016））和高角度晶界（60 °，[100]/（011））上进行了室温球形和布氏纳米压痕测试。这些试验表明，如果大角度晶界在变形体积内，则塑性更容易开始，而亚晶界不会影响塑性的开始。此外，高角度晶界充当滑移传输的屏障，而亚晶界不以可测量的方式与位错相互作用。我们认为，富橄榄石岩石中晶界类型的分布可能在变形过程中产生局部力学行为差异方面发挥作用。
The rheological properties of olivine influence large‐scale, long‐term deformation processes on rocky planets. Studies of the deformation of olivine at low temperatures and high stresses have emphasized the importance of a grain‐size effect impacting yield stress. Laboratory studies indicate that aggregates with finer grains are stronger than those with coarser grains. However, the specific interactions between intracrystalline defects and grain boundaries leading to this effect in olivine remain unresolved. In this study, to directly observe and quantify the mechanical properties of olivine grain boundaries, we conduct nanoindentation tests on well characterized bicrystals. Specifically, we perform room‐temperature spherical and Berkovich nanoindentation tests on a subgrain boundary (13°, [100]/(016)) and a high‐angle grain boundary (60°, [100]/(011)). These tests reveal that plasticity is easier to initiate if the high‐angle grain boundary is within the deformation volume, whereas the subgrain boundary does not impact the initiation of plasticity. Additionally, the high‐angle grain boundary acts as a barrier to slip transmission, whereas the subgrain boundary does not interact with dislocations in a measurable manner. We suggest that the distribution of grain‐boundary types in olivine‐rich rocks might play a role in generating local differences in mechanical behavior during deformation.