Microstructural evolution and mechanical properties of a Cr-rich β-solidifying TiAl-based alloy prepared by electromagnetic cold crucible continuous casting

In this work, the effect of pulling rates on the solidification structures and mechanical properties of a Cr-rich β-solidifying TiAl-based alloy prepared by electromagnetic cold crucible continuous casting was investigated. The solidification behaviors of non-equilibrium continuous casting Ti-45.5Al–4Cr-2.5Nb (in at.% unless otherwise specified) alloy at different pulling rates were discussed in detail. The continuous casting alloys were mainly composed of γ, B2 and α2 three phases, and their microstructures consisted of lamellar structures matrix and some strip-shaped (B2+γ) coupled structures distributed therein. Both the macroscopic grain size and lamellar area width of the continuous casting alloys decreased first and then increased with the increase of pulling rate, and reached the minimum at the pulling rate of 1.5 mm/min; the former evolved under the combined effects of pulling rate and dendritic fragments, while the latter was not only affected by the pulling rate, but also closely related to the segregation of solute elements during non-equilibrium solidification. The volume fraction of B2 phase mainly depended on the Cr content of B2 phase itself, and decreased with the increase of Cr content. Under the comprehensive effects of solidification structures, the room-temperature tensile strength of the continuous casting alloys increased first and then decreased with the increase of pulling rate, and reached the maximum at the pulling rate of 1.5 mm/min, it was mainly related to the macroscopic grain size, the lamellar area width and the B2 phase content in addition to the interlamellar spacing. •Macro-grain size and lamellar area width of the continuous casting alloys reached the minimum at pulling rate of 1.5 mm/min.•Obvious micro-segregation had significant effect on both the macro and micro structures.•The content of B2 phase mainly depended on its Cr content.•Room-temperature tensile strength of the investigated alloys was affected by combined effect of macro and micro structures.