摘要
The microstructural evolution,oxidation resistance and mechanical properties of Ti-6.5Al-2Sn-4Hf-2 Nbbased alloys with different contents of tungsten(W)additions ranging from 0 to 4.0 wt.%have been investigated in this study.The addition of W changed the microstructure from Widmanstatten colony of the W-free alloy to basketweave microstructure.After thermal exposure at 650℃ for 1000 h,the retainedβphase became less continuous,and secondaryβnano-particles with high W concentration were precipitated fromαlamellas.Withinαlamellas,the W was found to mainly partitioned into the secondaryβphase and refined the ordered α_(2)-Ti_(3)Al precipitates due to increased solubility of Nb in α_(2) phase.High W addition increased activation energy for oxidation,promoting the formation of more uniform and compact compound oxides,therefore substantially enhanced the oxidation resistance of the alloy.Besides,the W addition also improved the room and high-temperature yield strength without obviously losing plasticity after long-time thermal exposure.The improved mechanical performance was mainly attributed to the introduction of moreα/βinterfaces,the precipitation of secondaryβphase and the refinedα_(2) phase with Nb segregation.
基金
supported by National Key Research and Development Program of China(No.2017YFB0306205)
the National Natural Science Foundation of China(Grant No.51671012,51831006,51971009)
the Fundamental Research Funds for the Central Universities。
