Pollution-free grain refinement of cast TiAl alloys by vacuum mechanical vibration solidification

The implementation of the well-known methods for grain refinement of cast TiAl alloys, such as boron refiner, leads to compositional pollution and deterioration of specific types of performances. The development of pollution-free grain refinement methods is of crucial importance in aviation industries. Along these lines, in this work, a pollution-free grain refinement method was developed using the vacuum mechanical vibration (VMV) solidification technique. More specifically, a significant microstructure refinement of a typical Ti–48Al–2Cr–2Nb alloy was achieved, with the average grain size refined from the initial value of 141 μm–72 μm. As a result, the yield strength and compressive strength were both increased, almost without the sacrifice of the peak strain, which nearly overcome the strength-ductility trade-off with simple processing.