Investigation of reported anomalies in the electrotransport of interstitial solutes in titanium and iron
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O. N. CARLSON is Professor of Metallurgy, Iowa State University, and Senior Metallurgist,and F. A. SCHMIDTis Metallurgist,Ames Laboratory, USAEC, Ames, Iowa, 50010. R. R. LICHTENBERGis a Graduate Assistant, Department of Metallurgy, Iowa State University, Ames, Iowa, 50010. Manuscript submitted August 23, 1974. METALLURGICALTRANSACTIONSA
The above mentioned anomalies are based on the results of several investigations using different materials and experimental techniques. The titanium metal of Frantsevich and Kovenskiifor the carbon studies was especially high in oxygen (~ 1 wt pct) causing Oriani and Gonzalez2 to speculate as to the possible effect of the oxygen on the electronic structure of the solvent metal. The object of this investigation was to determine the electrotransport behavior of the three common interstitial solutes, carbon, nitrogen and oxygen in /3 titanium and nitrogen in both a and y iron by a single well established technique. The possible effect of the presence of oxygen on the effective valence as well as the other transport properties of carbon in/3titanium was also studied. MATERIALS A diffusion couple consisting of two semi-infinite sections of different solute concentrations was used in this investigation. The couple was prepared by joining a doped solute segment to a higher purity segment in such a manner that a sharp concentration step is produced at the interface. In the technique employed it is necessary that the solute content in either segment not exceed the solubility limit at the temperature of interest. Two grades of titanium metal were used in this investigation. A small quantity of iodide-refined titanium with a relatively low interstitial solute content was prepared at this laboratory. Sponge metal containing higher concentrations of all three solutes, particularly oxygen was obtained from Titanium Metal Corporation. Both metals were electron beam melted and subsequently swaged into rod form or doped with either nitrogen or carbon during arc melting. Chemical analyses of the swaged rods prepared from both grades of metal are given in Table L Nitrogen was added to the iodide-refined material by arc melting in an argon atmosphere containing a measured quantity of nitrogen gas. Both grades of titanium were doped with carbon by arc melting amorphous carbon containing a small amount of radioactive ~4C into these materials. The electron beam melted VOLUME 6A, APRIL 1975-725
Table I. Analyses of Titanium Base Metal Used in Transport Experiments, in Wt Ppm
Solute
Iodide-Refined Metal
Carbon Nitrogen Oxygen Iron Zirconium Tungsten
50 10 120 115 970 230
E.B.-Melted Sponge 120 30 830 525 20 615
Table II. Concentrations of Carbon, Nitrogen and Oxygen in Doped Segments of Titanium Rods, in Wt Ppm
Carbon-Doped Segment Solute Carbon Nitrogen Oxygen
High Oxygen 240 30 830
Low Oxygen
Nitrogen-Doped Segment
260 10 120
50 610 120
Oxygen-Doped Segment 120 30 830
Table III. Analyses of Segments of Composite Rods Used in Iron Electrotransport Experiments
Solute Carbon Hydrogen Nitro
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