Interrupted in-situ EBSD study of crystallographic characteristics and deformation micro-mechanism in TiZrHfNb_x refractory high entropy alloys during uniaxial tensile deformation

Compared with the phase transformation and twinning, the single-slip, cross-slip and the interaction between slip and grain boundary in metastable refractory high entropy alloys (RHEAs) still need to be explored in sufficient detail. In this work, the deformation mechanisms of two metastable RHEAs (TiZrHfNb_0.4 (denoted as Nb0.4) and TiZrHfNb_0.6 (denoted as Nb0.6) RHEAs) during tensile deformation were thoroughly investigated by interrupted in-situ EBSD. The results revealed that the ultimate tensile strength (UTS) of the Nb0.4 sample is higher than that of the Nb0.6 sample. This implies that the UTS can be optimized by reducing the content of Nb element in TiZrHfNb RHEA. For the Nb0.4 sample, the deformation mechanism is dominated by the deformation of grain boundaries firstly and then by the cross-slip behavior. The cross-slip system is {112}〈111¯〉/{123}〈111¯〉 slip system. In addition to the cross-slip, the kinking bands also were found to be another important deformation mechanism during the tensile. For the Nb0.6 sample, the deformation mechanism is dominated by the deformation of grain boundaries and the single-slip behavior. The slip system is {112}〈111¯〉 slip system. The difference in the slip behavior mainly contribute to the difference in the UTS between the two types of samples. This work is helpful to enrich the understanding on deformation and contribute to better design strategies of high strength RHEAs.