Superplasticity of Hot Isostatically Pressed Hydroxyapatite

Dense and translucent hydroxyapatite polycrystals (Ca10(PO4)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.