Oxidation and Oxide Dispersion Strengthening of Copper-Titanium and Other Alloys

摘要

The kinetics of internal oxidation of dilute Cu-Ti alloys have been studied as a function of specimen geometry, temperature and Ti concentration. Rate equations based on the quasi-steady state approximation have been shown to describe the internal oxidation of both cylinders and spheres. Similar studies on planar Co-Ti alloys have shown multiple internal zones. Rate equations have been formulated for this case and shown to agree with experiments. The above measurements have provided data for the oxygen permeabilities in both Cu and Co. The particle size, crystal structure, and morphology of internal Ti oxides in Cu have been carefully investigated and the elevated temperature coarsening of TiO2 particles has been studied. The coarsening kinetics were found to be diffusion controlled but the rate of coarsening of TiO2 is much slower than for other oxides (e.g. SiO2) in Cu. The TiO2 dispersion effectively increases the yield strength of Cutitania alloys by a factor of five to ten over that of pure copper. Good correlation can be made between the yield strengths and the Orowan mechanism for dispersion strengthening. Alloys with Ti concentrations of 1 wt. pct or less are ductile (15 - 30% elongation). The combined mechanical properties (strengths and ductilities) of polycrystalline Cu-TiO2 alloys are comparable to the best values yet reported for dispersion strengthened copper. The combined effects of a TiO2 dispersion and Cr precipitates on the mechanical properties of Cu indicate a method for obtaining outstanding mechanical properties in Cu alloy systems. (Author)