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 en hanced 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) x 1 0(17) N+/cm(2) at 80 keV. The structural implications of the loss of hardne ss during annealing were studied by in situ XRD experiments with synchrotro n radiation. Additional sample characterisation was performed by SEM, ERDA and Vickers hardness tests. The hardness reduction due to annealing is caus ed by phase transformation from TiN to Ti2N in consequence of the diffusion of nitrogen as well as by rearrangements in the alpha-Ti and beta-Ti phase of the alloy. (C) 2000 Elsevier Science S.A. All rights reserved.