High-strength nanostructured Ti–12Mo alloy from ductile metastable beta state precursor

In this study, the metastable beta Ti–12Mo (wt.%) alloy was synthesized by the cold crucible levitation melting (CCLM) method and then quenched in water from the beta domain. The tensile test carried out on the as-quenched alloy showed an important ductility reaching 45% of elongation before fracture. From the as-quenched metastable beta state, non-isothermal electrical resistivity and dilatometry measurements were carried out to detect the phase transition in order to control the nanophase precipitation sequence. After heating, XRD analysis and TEM observations revealed a very fine nano-scale omega and alpha precipitation in the beta matrix. Tensile test results indicated a very high strengthening effect after appropriate thermo-mechanical treatments, which was observed particularly huge after a two-step annealing process where a tensile strength as high as around 1600 MPa was obtained. This highly enhanced tensile strength was attributed to the complex intragranular nanostructure observed by TEM consisting of two-scale alpha nanoprecipitates inside sub-micrometer beta grains.