Herringbone Structure and Significantly Enhanced Hardness in W-Modified Ti2AlNb Alloys by Spark Plasma Sintering
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The W-modified Ti2AlNb-based alloys synthesized at 1100 °C by spark plasma sintering were solution treated at 1300 °C for 4 h and then aged at 800–1000 °C for 1 h. The phase composition, microstructure evolution, and microhardness of the aged alloys are investigated in this study. A significant enhancement of hardness, ~ 750 HV, is obtained in the alloy aged at 900 °C, while that of the one without W addition is only ~ 470 HV. The hardness is also higher than that of common β-Ti and Ti–6Al–4V alloys. As the ageing temperature increases, the B2/O structure evolves from B2 + O colonies to Widmannstätten structure, followed by a “disordering to ordering” procedure. This process also involves the variation of the angle between adjacent O phase from 90° to 60°. Specifically, a herringbone Widmannstätten B2 + O structure is constructed in the alloys aged in the α2 + B2 + O phase region, which is related to the diffusion of W and the substitution of W for Nb in the lattice of B2 or O.
KeywordsTi2AlNb-based alloy W addition Ageing Widmannstätten structure Microhardness
The authors are grateful to the National Natural Science Foundation of China (Granted Nos. 51474156, 51604193, 51804195, and U1660201), the National High Technology Research and Development Program (“863″ Program) of China (Granted No. 2015AA042504), and the China Postdoctoral Science Foundation (Grant No. 2017M621429) for financial support.
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