Direct observation of dual-step twinning nucleation in hexagonal close-packed crystals
Direct observation of dual-step twinning nucleation in hexagonal close-packed crystals
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DOI：
10.1038/s41467-020-16351-0
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发表时间：
2020-05-18
影响因子：
16.6
通讯作者：
Mao, Scott X.
中科院分区：
文献类型：
--
作者：
He, Yang;Li, Bin;Mao, Scott X.
基于镁和钛的先进轻质结构合金的设计和加工关键依赖于对孪生的控制，而这种控制迄今为止仍然难以捉摸，并且依赖于对六方密排（HCP）晶体中孪生成核机制的明确理解。在这里，通过使用原位高分辨率透射电子显微镜，我们直接展示了 HCP 铼纳米晶中的双步孪生成核机制。我们发现，主要的{1 0 -1 2}孪晶的成核是由棱柱基底界面上的断开引发的，这建立了与理想取向略有偏差的孪晶的晶格对应。随后，通过重新排列棱柱|基底界面上的断开，形成相干孪晶边界来纠正微小偏差；此后，相干孪晶边界通过孪晶位错传播。这些发现为 HCP 晶体中的孪晶成核机制提供了高分辨率的直接证据。六方密堆积晶体中的孪生方面仍然难以捉摸。在这里，作者直接对铼纳米晶体中的孪晶进行成像，并表明该过程是由棱柱|基底界面上的断开介导的，因为孪晶在被纠正之前最初偏离其理想取向。
Design and processing of advanced lightweight structural alloys based on magnesium and titanium rely critically on a control over twinning that remains elusive to date and is dependent on an explicit understanding on the twinning nucleation mechanism in hexagonal close-packed (HCP) crystals. Here, by using in-situ high resolution transmission electron microscopy, we directly show a dual-step twinning nucleation mechanism in HCP rhenium nanocrystals. We find that nucleation of the predominant {1 0 -1 2} twinning is initiated by disconnections on the Prismatic Basal interfaces which establish the lattice correspondence of the twin with a minor deviation from the ideal orientation. Subsequently, the minor deviation is corrected by the formation of coherent twin boundaries through rearrangement of the disconnections on the Prismatic|Basal interface; thereafter, the coherent twin boundaries propagate by twinning dislocations. The findings provide high-resolution direct evidence of the twinning nucleation mechanism in HCP crystals. Aspects of twinning in hexagonal-close-packed crystals remain elusive. Here, the authors directly image twinning in rhenium nanocrystals and show the process is mediated by disconnections on Prismatic|Basal interfaces as the twin initially deviates from its ideal orientation before it is corrected.