Lattice distortion effect on incipient behavior of Ti-based multi-principal element alloys
Xiangkai Zhang, Pinhung Lin, Jacob C. Huang
Abstract
In this work, we studied the influence of lattice distortion on the initiation of plasticity in Ti-based (multi-principal element alloy) MPEAs at a loading rate of 500 μN/s. The surface dependence was observed in Ti20Al20Cr20V20Nb20 (Ti20) MPEA, where the lowest first burst load was determined in (110) oriented grain, which is the same as that in Ti60Al10Cr10V10Nb10 (Ti60). This implies this kind of crystallographic dependence is the intrinsic feature of present studied alloys and it is not covered by the lattice distortion effect. In spite of similar orientation dependence, a much higher load at first burst was identified in Ti20 compared with Ti60, which is attributed to the fact that the more severe lattice distortion causes a larger critical resolved shear stress (CRSS) to nucleate the dislocation and a greater lattice friction to overcome during dislocation multiplication and emission process. In addition, based on the activation volume value, the mechanism in Ti20 is regarded as the same as that in Ti60, inferring that altering the lattice distortion does not change the pop-in mechanism in MPEAs. Lastly, the lattice distortion influence on the homogeneous dislocation nucleation process was investigated and compared with the heterogeneous dislocation nucleation event.