冷間加工したチタンの機械的性質と熱処理の関係

抄録

This study evaluated the mechanical properties of cold worked JIS type 2 titanium (compression ratio 39.7%) and their matching to the grades of the JIS mechanical properties. The study also evaluated the effect of heat treatment on mechanical properties at 450℃ for 60, 120, or 180 min. Additionally, the amount of released titanium immersed in 1% lactic acid solution was measured for pre- and post-cold working.
The tensile strength, yield strength and hardness of cold worked JIS type 2 titanium were similar to those of JIS type 4 titanium. Elongation matched the JIS type 3. After heat treatment, the tensile strength, yield strength and hardness of cold worked titanium decreased, and the mechanical properties did not match those of the JIS type 4 titanium. However, specimens that were heated at 450℃ matched the JIS type 3 titanium regarding tensile strength, yield strength and elongation.
On pre-cold working titanium, large and small crystal grains were clearly observed. On the other hand, on cold worked titanium, compressed crystal grains were observed overall as a fibrous structure.
The amount of released titanium for pre-cold working was the maximum when specimens were heated at 450℃ for 60 min. In contrast, the amount of released titanium was not affected by the heating time for cold worked titanium. Before heat treatment, the amount of released titanium of the as-received specimen (before heat treatment) was not affected by cold working. It is concluded that implant materials fabricated with cold worked JIS type 2 titanium may be useful for improving corrosion resistance and mechanical properties.