Elevated tensile properties of Ti-O alloy with a novel core-shell structure

Oxidized Ti powder was consolidated successfully by using spark plasma sintering into a fully dense bulk core-shell (CS) structured Ti alloy with isolated soft coarse-grained Ti cores and hard Ti-O solid solution shells. The temperature effect on the mechanical responses of CS Ti was assessed experimentally through tensile testing during 500-700 °C at a constant strain rate of 0.0005 s−1 and compared with those for its annealed counterpart and a pure Ti compact. All samples exhibit a decreased strength with the temperature. CS Ti exhibits a significantly enhanced tensile strength at all the testing temperatures compared with CP Ti. Contrary to the substantial brittleness of the annealed sample at 500 °C and 600 °C, CS Ti presents a much enhanced ductility at elevated temperatures, being 12% at 500 °C and 77% at 600 °C. At 700 °C, all the samples show comparable elongation. The superior mechanical performances of CS Ti at elevated temperatures can be attributed to its novel heterogeneous microstructure along with high O content.