Corrosion Resistance and Fatigue Fracture of Cold-worked JIS Type 2 Titanium

Abstract

Implants are currently produced using JIS type 2, type 3, type 4, titanium alloy and cold-worked JIS type 2 titanium. The mechanical properties and amount of released titanium of these materials have been reported. However, the amount of released titanium and fatigue fracture of titanium specimens in various cold-worked stages have not been clarified. Therefore, in this study, JIS type 2 titanium was cold-worked at compression ratios of 10, 20, 30, and 35%, and each test specimen's tensile strength, proof stress, elongation, hardness, fatigue fracture, amount of released titanium immersed in 1% lactic acid solution, and influence on titanium structure were evaluated. As a result, the following conclusions were drawn :

1. Mechanical properties other than elongation improved with cold-working of JIS type 2 titanium.

2. There were no significant differences in the amount of released titanium between the test specimens before cold-working of JIS type 2 titanium (AS) and those after. However, among the cold-worked test specimens, the amount of released titanium was highest in the specimen of C20.

3. The number of repeated bendings until fatigue fracture was higher with C30 than with titanium before cold-working of JIS type 2 titanium (AS), C10, and C20.

4. Regarding structural observation, a fibrous structure was more frequently observed as the compression ratio increased. There was a tendency whereby, when this fibrous structure was uniformly distributed, the amount of released titanium decreased, and the mechanical properties improved.

5. It was suggested that implants produced using C30 have stable mechanical properties, and the possibility of allergy to titanium can thus be reduced.