Superplasticity of Hot Isostatically Pressed Hydroxyapatite

Dense and translucent hydroxyapatite polycrystals (Ca 10 (PO 4 ) 6 (OH) 2 with a grain size of 0.64 μMm) were obtained by hot isostatic pressing at 203 MPa and 1000°C for 2 h in argon. The material exhibited superplastic elongation (>150%) in a tension test at temperatures from 1000° to 1100°C and at strain rates from 7.2×10 −5 to 3.6 × 10 −4 s −1 . Extensive strain hardening was observed. The stress exponent of the yield stress was larger than 3.