TEM quantitative characterization of short-range order and its effects on the deformation micromechanims in a Ti-6Al-4V alloy

Abstract : Local order is evidenced in nodules of the duplex microstructure of a Ti-6Al-4V alloy using in situ straining experiments in a transmission electron microscope (TEM). This local order is identified to be short range order (SRO) because of the absence of superlattice diffraction spots, which are associated with alpha(2) (Ti3Al) precipitates and because of the formation of single pairs of mobile dislocations, which are a signature of SRO. The strengthening effect of this SRO is quantitatively evaluated. Qualitatively, the presence of SRO inhibits strongly the cross-slip in nodules in comparison with dislocations gliding in lamellar colonies where no SRO is present. The well-known strengthening effect of the core structure of dislocation in Ti-alloy is revisited here in the presence of SRO to determine its possible influence.