RI 5546 Effect Of Common Impurities On Hardness Of Electrolytically Refined Titanium Metal ? Summary

The purpose of this investigation was to determine the effect of common impurities, that is, oxygen, nitrogen, carbon, and iron, on the Brinell hardness of electrolytic titanium. On a weight basis, nitrogen had the greatest hardening effect, followed by oxygen, carbon, and iron in order. The hardening effects of oxygen and carbon were almost identical up to a concentration of approximately 0.1 percent by weight. Above this concentration, the relative hardening effect of carbon decreased rapidly, possibly because of its limited solid solubility in a-titanium. Hardness vs. composition curves for both oxygen and nitrogen were essentially straight lines over the range of Brinell hardness numbers (B.h.n.) covered in the investigation. The hardness of titanium was also determined as a function of the percentage of impurity atoms. On this basis, iron in concentrations up to 0.17 atomic percent had a greater hardening effect than either oxygen or carbon. INTRODUCTION Determination of the as-cast hardness of arc-melted titanium is a method of quality control widely used in industry. Numerous studies4/ have been made of the effect of impurities on the hardness obtained by this method. However, most of them have been based on the use of either iodide titanium or commercially pure Kroll sponge (B.h.n. >90), as a starting material.