Nanoindentation simulation study on mechanical properties and microstructure evolution of twin γ-TiAl alloy

ABSTRACT To explore the mechanical properties and deformation mechanism of twin γ-TiAl alloy under load and impact, based on the special interface structure in polycrystals, twinning at room temperature is established in this paper simulation of nanoindentation response of twin γ-TiAl alloy. Through the load-displacement curve, the hardness and Young's modulus of the workpiece are obtained. By analysing the microstructure evolution behaviour under the action of the indenter, it is found that during the loading process, multiple dislocation rings are generated in the grain and slip to the lower part of the workpiece, resulting in the hardness decreasing with the increase of the indentation depth, which is consistent with the indentation size effect; The dislocation lock generated during the unloading process delayed the annihilation of the defect structure, but the dislocation and stacking fault structure disappeared completely and the stress concentrated at the defect residue; in the stress relaxation stage, the dislocation ring structure in the grain extends and annihilates away from the grain boundary, releasing a large amount of stress to reduce the indentation load, and then the defect structure around the indenter is stable to keep the load stable, with high stress at the defect.