Precipitation behavior of Widmanstätten O phase associated with interface in aged Ti2AlNb-based alloys

• Published in: Materials characterization Vol. 145; no. C; pp. 413 - 422
• Main Authors: Cai, Qi, Li, Mengchen, Zhang, Yaran, Liu, Yongchang, Ma, Zongqing, Li, Chong, Li, Huijun
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2018; Elsevier
• Subjects: Ageing; Ball milling; Hardness; Interface; Ti2AlNb alloys; Ball milling; Hardness; Ageing; Ti2AlNb alloys; Interface
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2018.09.009

Ti2AlNb-based alloys, spark plasma sintered from ball-milled octahedral Ti-22Al-25Nb powder, are aged for 0–3 h in this study. Ball milling tunes the morphology of primary orthorhombic (O) phase to be columnar, and improves the mechanical properties of the alloys. The evolution of the Widmanstätten O phase, which brought main precipitation strengthening effect, is then investigated during the ageing process. The hardness of the alloys is improved by an increasing content of O phase and the reduced width of the Widmanstätten O phase; in addition, the length of Widmanstätten O phase also brings positive effect on the hardness, which indicates that the hardness is strongly coupled with the interface of the Widmanstätten O precipitates and B2 matrix. By means of transmission electron microscopy observation, the precipitation of O initials with an amorphous state, followed by a coherent interface between (110)B2 and (002)O, which is destroyed to be semi-coherent and incoherent during the next ageing stage. [Display omitted] •Ball milling tunes the morphology of primary O phase in Ti2AlNb alloys.•The interface of Widmanstatten B2 and O affects the hardness of the alloys.•The entire precipitation process of Widmanstatten O phase is reported.