In the present work, we have extensively examined the alternative-band microstructure of a Ti-47Al-2Cr-2Nb alloy fabricated via direct laser deposition by means of high resolution transmission electron microscopy and selected area electron diffraction. The studied samples exhibit two types of long-periodic stacking ordered phase with 6H and 18R structures, which were never reported for those obtained by traditional approaches. Moreover, the ordered phases possess stacking sequences of ABCBACA and ABCABCBCABCACABCABA, being analogous to the periodically arranged stacking faults in α₂ and γ phases, respectively. With the presence of these unusual structures, the as-deposited sample tends to have superior mechanical properties.

Impact statement

Unusual ordered phases with long periodic stacking structures, seldom reported in the TiAl alloys obtained by traditional approaches, were comprehensively characterized, and demonstrated to possess excellent mechanical properties.

在目前的工作中，我们已经广泛研究了通过高分辨率透射电子显微镜和选择区域电子衍射法通过直接激光沉积制备的Ti-47Al-2Cr-2Nb合金的能带替代组织。所研究的样品表现出两种类型的具有6H和18R结构的长​​周期堆积有序相，对于传统方法获得的样品从未报道过。另外，有序相具有堆叠ABCBACA和ABCABCBCABCACABCABA的序列，在α为类似于周期性排列的堆垛层错₂分别相和γ相。由于存在这些异常结构，因此沉积后的样品往往具有优异的机械性能。

影响陈述

通过传统方法获得的TiAl合金很少报道具有长周期堆积结构的异常有序相，并对其进行了全面表征，并证明其具有出色的机械性能。