Evidence for deformation twinning of the D019-α2 phase in a high Nb containing TiAl alloy

Characteristic effects of alloying elements on β solidifying titanium aluminides: A review

“…At room temperature, TiAl intermetallic alloys comprise of three major phases of intermetallics, namely; α 2 -Ti 3 Al (D0 19 structure), γ-TiAl (L1 0 structure) and β o -TiAl (B2 structure) [ 1 , 4 , 7 , 18 , 20 , 26 , 27 , 28 , 29 ]. The γ-TiAl phase has L1 0 tetragonal structure while α 2 -Ti 3 Al phase has a D0 19 hexagonal structure [ 30 , 31 , 32 , 33 , 34 ]. Also, the γ-TiAl phase is formed at 49 to 66 at.% Al content [ 14 ] that could be stabilized up to its melting temperature (~1450 °C) [ 28 ].…”

“…The ordered γ-phase has low ductility (up to 750 °C), thereby, decreases its plastic deformation capability likewise does the ordered α 2 -phase have low ductility (up to 600 °C) [ 30 ]. This is because of the limited number of slip systems, the occurrence of planar slip [ 30 , 36 ] and lack of twinning [ 32 ] which makes these phases brittle.…”

“…The γ-TiAl phase has L1 0 tetragonal structure while α 2 -Ti 3 Al phase has a D0 19 hexagonal structure [30,31,32,33,34]. Also, the γ-TiAl phase is formed at 49 to 66 at.% Al content [14] that could be stabilized up to its melting temperature (~1450 C) [28].…”

“…Jian et al [39], reported that the α 2 -phase shows strong metallic bond with low mechanical anisotropy; while γ-phase has a covalent bond with strong universal mechanical anisotropy. It is commonly known that to maintain the ordered D0 19 structure, a large interchange shuffling is required [32,40]. The appearance of α 2 -phase deformation twinning could play a key role in high Nb-containing TNM alloys' mechanical properties enhancement.…”

Microstructure and tribological properties of laser in-situ synthesized Ti3Al composite coating on Ti-6Al-4V

“…An extra twinning in the cast Ti3Al single crystals is seen exclusively at temperatures over 1000 °C when the compression axis is along or near the c-axis [14]. In the two-phase α2 (Ti3Al) + γ (TiAl) alloys, an addition of Nb was found to enhance twinning and reduce the antiphase domain boundary (APB) energy [15]. However, the use of a large quantity Nb is not economical due to its expense.…”