Formation and thermal stability of an oxide dispersion in a rapidly solidified Ti-Er alloy

There have been a number of reports concerning the strengthening of Ti alloys through the production of a fine dispersion of oxides. The oxides employed are usually those of Y and rare earth elements such as Er, Nd and Ce, since it is expected that these phases will exhibit reasonable stability against coarsening during exposure at elevated temperatures. It is also important that a fine, uniform dispersion of oxides be produced, otherwise improvement in properties will not be realized. When conventional processing techniques are used in the fabrication of these materials, the resulting dispersions are, in general, coarse and rather inhomogeneous. A possible solution to this problem involves the application of rapid solidification processing (RSP), since refinement and increased homogeneity of microstructure are expected in material processed in this manner. Although the results of two such studies have demonstrated the potential for RSP in the production of a refined distribution of oxides, optimum dispersions have not yet been effected. In addition, it is necessary to determine the thermal stability of dispersions obtained using RSP, in order to assess the possible useful application of these alloys. In the present research program, attempts are being made to produce a refined dispersion of Er2O3 in Ti using RSP. Rapid solidification is effected by use of laser surface melting of a pre-cast binary Ti-Er alloy; the rapidly solidified, laser modified region is cut from the surface of the alloy sub-strate and used for subsequent experiments. Microstructural characterization is performed on samples in the as-solidified and heat treated conditions. This paper describes some preliminary results of this study, and demonstrates that thermally stable dispersions of Er2O3 can be produced using RSP