Segregation mediated heterogeneous structure in a metastable ? titanium alloy with a superior combination of strength and ductility.

ABSTRACT: In ? titanium alloys, the ? stabilizers segregate easily and considerable effort has been devoted to alleviate/eliminate the segregation. In this work, instead of addressing the segregation problems, the segregation was utilized to develop a novel microstructure consisting of a nanometre-grained duplex (?+?) structure and micrometre scale ? phase with superior mechanical properties. An as-cast Ti-9Mo-6W alloy exhibited segregation of Mo and W at the tens of micrometre scale. This was subjected to cold rolling and flash annealing at 820?oC for 2 and 5?mins. The solidification segregation of Mo and W leads to a locally different microstructure after cold rolling (i.e., nanostructured ? phase in the regions rich in Mo and W and plate-like martensite and ? phase in regions relatively poor in Mo and W), which play a decisive role in the formation of the heterogeneous microstructure. Tensile tests showed that this alloy exhibited a superior combination of high yield strength (692?MPa), high tensile strength (1115?MPa), high work hardening rate and large uniform elongation (33.5%). More importantly, the new technique proposed in this work could be potentially applicable to other alloy systems with segregation problems.

SUBMITTER: Gao J 

PROVIDER: S-EPMC5951864 | biostudies-other | 2018 May

REPOSITORIES: biostudies-other