Effect of Alloying Addition on Castability and Other Properties of Titanium

摘要

The present study is an attempt to improve the castability of titanium by incorporation of a series of alloying elements into titanium. Experimental results indicated that a minor amount (1 wt percent) of alloying element could increase or decrease the castability of titanium, depending on the kind of element added. Among all alloying elements, silver, molybdenum, hafnium, tantalum, tin, lead and bismuth significantly enhanced the castability of titanium cast in copper mold. Additions of silver and bismuth increased the castability value by 32 percent and 35 percent, respectively. When graphite mold was used, the improvement in castability was less significant for most added elements, yet bismuth-doped titanium still exhibited a castability value higher than that of c.p. Ti by 24 percent. All 17 doped titanium had the same crystal structure (hop) as that of c.p. Ti, and had a fine acicular martensitic type structure. Cast c.p. Ti had a coarser, lath type morphology. Alloying additions largely increased microhardness and bending strength, yet did not significantly affect the modulus of titanium.