Structural mechanisms of the mechanical degradation of Ti–Al–V alloys: in situ study during annealing

The aim of this work was to investigate the structural mechanisms of the enhanced hardness of the technical alloy Ti–6Al–4V due to N+-implantation and its degeneration. Ti–6Al–4V samples were implanted with fluences (1–6)×1017 N+/cm2 at 80 keV. The structural implications of the loss of hardness during annealing were studied by in situ XRD experiments with synchrotron radiation. Additional sample characterisation was performed by SEM, ERDA and Vickers hardness tests. The hardness reduction due to annealing is caused by phase transformation from TiN to Ti2N in consequence of the diffusion of nitrogen as well as by rearrangements in the α-Ti and β-Ti phase of the alloy.