Microstructure and nanomechanical behavior of individual phase in β-solidifying Ti-43Al-5Nb-3.5Cr-1Zr alloy

A near fully lamellar Ti-43Al-5Nb-3.5Cr-1Zr alloy with different lamellar orientations was investigated by electron backscattered diffraction and nanoindentation measurements to study the influence of lamellar orientation on the nanohardness of α₂/γ lamellae in a β-solidifying TiAl alloy. The results indicate that nanohardness of the α₂/γ lamellae exhibits apparent plastic anisotropy, which is simultaneously determined by the oriented angle θ₁ between the indentation direction and the lamellar plane and the deformation characteristics of the α₂ and γ phase. Furthermore, the nanohardness of the individual lamellar colony decreases with an increase in the oriented angle from hard (0°) to soft (45°) orientations. Based on the analysis of the Schmid factor, the nanohardness value of the hard oriented α₂/γ lamellae with a small Schmid factor is greater than the soft orientation with a large Schmid factor. The pile-up morphology on the γ phase is determined to be higher than that on the B2 phase at the interface through atomic force microscopy characterizations, which is attributed to the stronger plastic deformability of the γ phase. Therefore, the results can be successfully applied to understand the microscopic deformation mechanism of near fully lamellar β-solidifying TiAl alloy from a new perspective.