Tailoring peritectic solidification and lamellar orientation in TiAl alloys through controlled heating power

The influence of temperature gradient on the microstructure and high-temperature mechanical behavior of directionally solidified Ti-47Al-6Nb-0.1C-1.6Ta-0.8Hf alloys was systematically investigated. Columnar grain alignment and lamellar orientation improve with increasing power up to 45 kW, beyond which orientation dispersion and equiaxed grains emerge, driven by the stability of the solidification front and competitive β-dendrite growth. High temperature gradients enhance peritectic reaction kinetics, promoting α-variant selection, lamellar convergence, and suppression of residual β, whereas low gradients lead to dispersed lamellar structures. Elemental analysis reveals uniform hydrogen and oxygen distribution with minimal segregation, attributed to high-vacuum melting and rapid peritectic consumption of β. High-temperature tensile testing at 900 °C shows peak strength and ductility at 45 kW, correlated with effective dislocation blockage at B2/γ and γ/α2 interfaces, where high slip-energy barriers and controlled dislocation transmission mitigate local stress concentrations. These findings demonstrate that precise control of heating power and temperature gradient enables the optimization of microstructure, phase transformation, and high-temperature mechanical performance in TiAl alloys.