Formation and evolution of platelet-like Ti-rich precipitates in the V–4Cr–4Ti alloy

Journal Article · Fri Jan 15 04:00:00 EST 2016 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2015.11.012· OSTI ID:22587077

Zhu, Boling; Yang, Shanwu; Zhang, Mengqi; Ding, Jianwen; Long, Yi; Wan, Farong

The goal of the present investigation is to explain the obviously different appearances of Ti-rich precipitates in vanadium alloy and in steels. To achieve the goal, the formation and evolution of the precipitates in the as-cast and the heat treated V–4Cr–4Ti samples were investigated using optical and electron microscopies. The precipitates were found to be rare in the as-cast samples, and a high density of the precipitates occur in the samples subjected to isothermal holding at 600–1300 °C. The precipitates preferentially distribute within the grains rather than at the grain boundaries. All of the precipitates are platelet-like, with NaCl structure, in three-dimensional space. The further observation using high-resolution electron microscopy (HREM) reveals that a high density of twins occurs in the growth front of the precipitates, whereas the middle of the precipitates is twin-free. Meanwhile, enrichment of titanium atoms was observed in the middle of the precipitates. These results indicate that the precipitates form by a displacive transformation, followed by a diffusional process to enrich titanium further and eliminate the twined structure. - Highlights: • Precipitates in the V–4Cr–4Ti alloy are Ti-(CN) with NaCl structure. • The Ti-rich precipitates are platelet-like in three dimensional space. • Twins occur in both ends of the precipitates and the midst of these is twin-free. • Twinning and its elimination is explained by displacive followed by diffusion.

• OSTI ID: 22587077
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Vol. 111; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
77 NANOSCIENCE AND NANOTECHNOLOGY
CHROMIUM ALLOYS
DIFFUSION
GRAIN BOUNDARIES
HEAT TREATMENTS
PRECIPITATION
SODIUM CHLORIDES
STEELS
TITANIUM ALLOYS
TRANSMISSION ELECTRON MICROSCOPY
VANADIUM ALLOYS