Creep Deformation of Polysynthetically Twinned (PST) Ti-48mol%Al

Effects of α2 spacing on creep deformation characteristics of hard oriented PST crystals of TiAl alloy

“…This value is greater than the typical value of 3-5 reported on polycrystalline materials [6,19,20]. Similar high values of n have been reported on the hard oriented PST crystals by the present authors [4,5,8], but stress exponent of five has been reported by Parthasarathy et al [6]. Schmid factors of the primary slip system in g phase are 0.41 and 0.27 in the A and N orientations, respectively.…”

“…Among those microstructures fully lamellar structures are the most favorable for high temperature applications owing to their best combination of fracture toughness at room temperature and creep resistance at high temperature. According to experiments on polysynthetically twinned (PST) crystals consisting of a single colony of g and a 2 lamellae [4][5][6][7][8], their creep resistance is strongly dependent on the lamellar orientation with respect to the stress axis. The hard oriented PST crystals, in which lamellar boundaries aligned perpendicular or parallel to the stress axis, show creep resistance superior to the soft orientation, in which the lamellar boundaries are inclined to stress axis.…”

Microstructure stability during creep deformation of hard-oriented polysynthetically twinned crystal of TiAl alloy

“…[4,[12][13][14] The control of lamellar orientation is another important way to improve creep resistance of lamellar materials. Studies of creep resistance by Wegmann et al, [15,16] Shiratori et al, [17] Parthasarathy et al, [18] and Kim et al [19] revealed anisotropic behavior depending on the stress axis. Hard orientations with lamellar boundaries perpendicular or parallel to the stress axis showed longer creep life and superior creep resistance compared to other orientations.…”

Creep behaviour of two-phase lamellar TiAl: Crystal plasticity modelling and analysis

“…In past few decades, experiments were conducted to identify key roles of microstructure on creep resistance of TiAl alloys. Systemic analyses were performed on bulk materials of single TiAl phases [8,9], combined (α 2 Ti 3 Al+TiAl) multi-phases with lamellar structures, known as PST-TiAl [10][11][12], and polycrystals of single and multi-phase lamellar grains [12][13][14]. It was found that the creep responses of single TiAl phases and multi-phase combinations were significantly different, which comes from different inherent boundaries.…”