Oxide Dispersions in Rapidly Solidified Ti Alloys
- PDF / 1,792,656 Bytes
- 5 Pages / 417.6 x 639 pts Page_size
- 1 Downloads / 263 Views
OXIDE DISPERSIONS IN RAPIDLY SOLIDIFIED Ti ALLOYS D.G. KONITZER,* R. KIRCHHEIM,** AND H.L. FRASER* *Department of Metallurgy and the Materials Research Laboratory, University of Illinois, Urbana, IL 61801; **Max Planck Institut fUr Metallforschung, Institut f~r Werkstoffwissenschaften, Stuttgart, West Germany ABSTRACT Techniques of rapid solidification processing were used to refine a dispersion of rare earth oxides in Ti. The dispersion was produced by laser surface melting and subsequent heat treatment of a Ti-Er alloy. The second phase was identified as the rare earth oxide. The stability of the dispersion was investigated analytically and experimentally and the correlation between the analysis and experiments was shown to be very good. INTRODUCTION The use of Ti alloys at elevated temperatures is limited by several factors, one of which is the thermal stability of the microstructure. One alloy system which may increase the useful temperature of application of Ti alloys involves the addition of rare earth elements, with the intention of forming a dispersion of rare earth oxides in the alloy. The rationale for this alloying scheme is that the thermodynamic stability of the rare earth oxides will reduce the rate at which the dispersion coarsens. Several workers [1-3] have followed this approach to the problem using conventional processing techniques; however, the size of the dispersoid was found to be rather large L1-3J and so was not suitable for the purposes of dispersion strengthening. Rapid solidification processing (RSP) has been shown to be capable of refining the microstructure in other alloy systems and has been applied in preliminary work to the production of a fine scale dispersion of oxides in the Ti-rare earth system [4]. The present paper is aimed at studying the refined dispersions which may be formed using rapid solidification techniques, and their thermal stability. The method that is used involves laser surface melting of the specimens to produce a supersaturation of the rare earth element (and incidentally 0) in the Ti matrix, and subsequently to heat treat the specimen to allow the precipitation of the rare earth oxide on a refined scale. EXPERIMENTAL PROCEDURE Specimens to be laser treated were produced by non-consumable electrode arc melting under an Ar atmosphere in the form of buttons (weighingo .3 gms). These specimens were then sectioned and their surfaces melted using ? CO CWlaser operated at 3 kW with a specimen traverse speed of 10.6 cm s . 'ne laser treated specimens were then encapsulated under an Ar atmosphere in quartz tubes. Transmission electron microscope specimens of 3 mm diameter were prepared from the as surface melted stock, with and without various heat treatments, by mechanical grinding to approximately 0.1 mm, and jet electro-polishing in a solution of 70 methanol, 12 2-butoxyethanol, 10 H2 0 and 8 perchloric with a current of 90 mA at -100 C. The amount of rare earth element added to the Ti was Mat.
Res. Soc.
Symp. Proc. Vol.
28 (1984)
Published by Elsevier Science Pu
Data Loading...
