The perfect single crystal has ultra-high strength but is often accompanied by catastrophic failures after yielding. This study reveals that nano-lamellar TiAl single crystals alleviate the catastrophic failure due to a post-yielding dislocation retraction through atomistic simulations and theoretical analyses. This dislocation retraction leads to a retained post-yielding strength of 1.03 to 2.33 GPa (about 50% of the yielding strength). It is shown that this dislocation retraction is caused by local stress relaxation and interface-mediated image force. The local stress relaxation is due to successive dislocation nucleation in different slip systems, and the interface-mediated image force is caused by the heterogeneous interface. Based on dislocation theory, this study demonstrates that the size effect also plays a vital role in dislocation retraction. Theoretical modeling shows that the dislocation retraction occurs when the lamellar thickness is less than approximately 12 nm. Additionally, the post-yielding dislocation retraction is more pronounced at higher temperatures, making it more effective in alleviating catastrophic failures. These findings demonstrate a viable option for avoiding catastrophic failure of single crystals through nanoscale-lamellar design.

完美的单晶具有超高的强度，但屈服后通常会发生灾难性的故障。这项研究表明，通过原子模拟和理论分析，纳米片状TiAl单晶可减轻由于屈服后位错回缩而导致的灾难性破坏。这种位错回缩导致保留的1.03至2.33 GPa的屈服后强度（约为屈服强度的50％）。结果表明，这种位错回缩是由局部应力松弛和界面介导的图像力引起的。局部应力松弛是由于在不同滑动系统中连续的位错成核，而界面介导的成像力是由异质界面引起的。根据位错理论，这项研究表明，尺寸效应在脱位回缩中也起着至关重要的作用。理论模型表明，当层状厚度小于约12 nm时，发生位错回缩。另外，屈服后的位错回缩在更高的温度下更加明显，这使其在减轻灾难性故障方面更加有效。这些发现证明了通过纳米级薄片设计避免单晶灾难性故障的可行选择。