Unusual ordered phases with long periodic stacking structures in an additively manufactured TiAl alloy

Abstract

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.

Keywords

• tial alloy
• direct laser deposition
• long-period stacking ordered phase
• mechanical property