A study of phase transformation in a TiAlNb alloy and the effect of Cr addition

Effect of microstructural parameters on the mechanical behavior of TiAlNb(Cr,Mo) alloys with γ+σ microstructure at ambient temperature

“…In light of the limitations that exist with the 2-phase and additions of hard dispersoids, alternative alloys with high Nb-content are explored in this study which lie in the two phase -TiAl+-Nb2Al region [13][14][15][16][17][18][19]. The -phase is hard and has been shown to provide excellent creep resistance in TiAlNb alloys, but RT toughness and ductility are poor when this phase is connected and present in high volume fractions [13][14][15][16].…”

“…1. Upon quenching to RT, the -phase provided a metastable parent phase from which the  precipitation could be controlled by aging at various temperatures (865, 1000, 1050, and 1100ºC) [17][18][19]27]. Relevant details of the three phases of interest are presented in Table 1.…”

Thermodynamic assessment of the Cr–Ti and first assessment of the Al–Cr–Ti systems

“…Since the b phase may not extend to low enough titanium compositions [7] in the AleNbeTi system, b-stabilizers such as chromium [8e10] may be necessary. Additionally, chromium increases the probability of g-TiAl phase nucleation inside the b phase [11] and also improves plasticity and resistance to high temperature oxidation [12e14]. Therefore, an understanding of the phase equilibria in the AleCreTi system is key for improving the processing of high temperature alloys based on g-TiAl(Nb) þ s-Nb 2 Al.…”

Two-step nucleation of the γ-phase in a Ti-45Al-18Nb alloy

“…When enough Nb is added to TiAl, solidification takes place by the formation of the b-phase rather than the a-phase [8]. While extensive research has been conducted on the development of the g þ a 2 microstructure [1,7,9e11], very limited work has been performed on the evolution of g þ s microstructure upon the cooling of the b-phase [12].…”