| Two alloys, Ti-6Al-2V and Ti-2Al-16V, simulating the alpha and beta phases of Ti-6Al-4V, respectively, were prepared with oxygen concentrations from 0.07 to 0.65 weight percent. Their microstructure, deformation behavior and strength were investigated with X-ray diffraction, optical microscopy, scanning electron microscopy, analytical electron microscopy and mechanical tests in order to determine the effects of oxygen concentration and heat treatment. Samples were heat treated in three conditions: solution-treated and water-quenched (STQ), aged at 350;Oxygen enhances Ti;In both alloys the hardness increases with the square root of oxygen concentration.;Oxygen strengthens the alpha alloy and embrittles it, independent of heat-treatment. Oxygen also strengthens the beta alloy but does not embrittle it.;The alpha alloy is essentially non-age-hardenable. The beta alloy's strength can be increased by as much as two-fold by aging due to ;The strengths and ductilities of the isolated alpha and beta alloys and the effects of oxygen and heat treatment on them have been shown to be of direct relevance for the two-phase Ti-6Al-4V alloy.;Dislocation structure and slip mode were investigated by analytical electron microscopy. In the alpha alloy most dislocations are a-type, with minority of ;Observation of the beta alloy under analytical electron microscopy reveals precipitation due to aging. Aging at 350;Evidence for oxygen-ordering in the alpha alloy with 0.65% oxygen has been found in the form of superdislocation pairs observed in STQ condition. The distance between the two member dislocations of a superdislocation pair in equilibrium condition is calculated to be 90 A, close to experimental result of 100 A. (Abstract shortened with permission of author.). |
