Carbon content driven high temperature γ-α2 interface modifications and stability in Ti–46Al–4Nb intermetallic alloy

Comparative Study of Microstructure and Mechanical Properties of Two TiAl-Based Alloys Reinforced with Carbide Particles

“…The increase in the α 2 -α 2 interlamellar spacing can be attributed to the diffusion-controlled lateral growth of the γ lamellae at the expense of dissolution of α 2 lamellae [37,38]. In carbon-containing TiAl-based alloys, the widening of γ lamellae is hindered by the carbon atoms, which segregate to ledges and kinks at α 2 /γ lamellar interfaces and form fine secondary P-Ti 3 AlC or H-Ti 2 AlC precipitates [27,39]. Figure 7 shows Vickers hardness HV and Vickers microhardness of lamellar grains HV m of the C20 and C36 alloys after heat treatment and heat treatment combined with ageing.…”

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 ].…”

“…It possesses high specific modulus, low density, good oxidation resistance, excellent fatigue, and creep properties [ 35 ]. The γ-phase (L1 0 ) of lattice parameters a = 0.4005 nm and c = 0.4070 nm has an ordered face centred tetragonal (FCT) structure [ 14 , 34 ] and transforms to the disordered structure at about 1250 °C [ 29 ]. 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 ].…”

“…The α 2 -Ti 3 Al phase has an ordered hexagonal closed packed (HCP) structure [ 33 , 34 ] formed between 22 to 39 at.% Al content and transforms to an ordered structure from the disordered one at about 1180 °C with lattice parameters, a = 0.5782 nm and c = 0.4629 nm [ 14 , 34 ]. It is known to exhibit extremely poor toughness and tensile ductility at ambient temperatures while possessing good oxidation resistance and excellent elevated temperature specific strength [ 28 ].…”

“…It is known to exhibit extremely poor toughness and tensile ductility at ambient temperatures while possessing good oxidation resistance and excellent elevated temperature specific strength [ 28 ]. Typical TiAl-based alloy microstructures consist of alternating α 2 /γ lamellae formed within the α-phase region and present a reciprocating crystallographic relationship of (0001)-α 2 || (111)-γ and <1120>-α 2 || <110>-γ [ 34 , 37 ]. The principal modes of deformation in γ-phase are <110> slip and {111}<112> twinning while α 2 -phases is between the γ twinned phases [ 34 ].…”