On the Microstructure and Solidification Behavior of N-Bearing Ti-46Al-8Ta (at.%) Intermetallic Alloys

A brief discussion on the tensile creep deformation behaviour of wrought single-phase γ-TiAl

“…A series of reports on room temperature tensile deformation behaviour of c-TiAl alloys show that the near-c, two phase compositions having Al contents around 48 at.% possess the highest strengths and ductilities [1][2][3][11][12][13][14][15][16][17][18]. Extensive creep deformation studies have been carried out on a number of two phase near-c TiAI alloys produced by various processing routes [8,[19][20][21][22][23][24][25][26][27][28][29].…”

Solidification Behavior and Microstructural Features of the Cast and Hiped N-Bearing Ti-48al-2cr-2nb Intermetallic Alloys

“…N is a phase stabilizer element in titanium aluminides; so it is expected that the 1N and 2N alloys would also form a phase dendrites based on the effects of N addition on primary dendrites and their symmetry in the 0.5N alloy, Thermo-Calc R calculations, DTA analysis for the 2N alloy [33], and microstructural observations regarding remained b phase. Therefore, the addition of N altered the solidification behavior from the a phase to the b phase, as has also been noted in other research works [10,12]. According to [43e45], identifying dendrites as b or a phase dendrites based on the orientation of their lamellas (a 2 þg) to dendrite arms does not produce reliable findings; hence we advise against using this method.…”

“…By an increase in N content, the amount of g phase was decreased and the amount of a 2 phase was increased [10]. The lamellar spacing has also decreased by increasing N until the formation of the Ti 2 AlN precipitates, further N addition increased lamellar spacing, which is related to Al concentration in the matrix [10,12,36]. In another research work, the N addition up to 1 at.% into Ti-48.5Al-1.5Mo alloy showed a decrease in colony size, leading to an increase in crack path which in turn increases the fracture toughness.…”

“…A 4 vol.% Ti 2 AlN composite exhibited optimum mechanical properties at room temperature (with highest fracture strain and strength) and high temperature (with highest UTS and yield strength in 800 C), but the highest elevated-temperature elongation was observed in 3 vol.% Ti 2 AlN composite [17]. Saeedipour et al [12,13] studied the effects of N addition up to 2 at.% on the solidification, microstructure and high temperature (850 C) mechanical properties of Tie46Ale8Ta alloy using small punch test (SPT). Results showed that N addition changed the solidification path from primary b phase to primary a phase.…”

“…In addition, maximum load in SPT experiments was increased by N addition up to 1.05 at.% and was decreased by further N addition. Moreover, they reported that N addition resulted in dendrite refinement and reduction or elimination of remained b phase based on N content [12,13]. Recently Tan et al [38,39] investigated the effects of N addition up to 1.6 at.% on the microstructural and compression properties of Tie46Ale4Nbe1Mo alloy, once by adding BN compound [38] and another by adding TiN compound [39].…”