Journal of Materials Research | 2021
The effect of cooling conditions on Ti 6%Al 4%V microstructure observed using high-temperature in-situ scanning electron microscopy
Abstract
This study focuses on continuous imaging of microstructural changes in Ti 6% Al 4% V when cooling from the β transus of ~\u2009995\xa0°C or above. A range of microstructures were obtained by accessing different cooling rates. With cooling rates of 0.1–0.5\xa0°C/s, lamellar microstructures were observed, which initiate in a colony microstructure below temperatures of ~\u2009930\xa0°C. When the lamellar microstructure began forming at grain boundaries, cooling was interrupted to further observe the kinetics in the system. Lamellae changed in projected length\xa0from 40\xa0µm to ~\u2009160–320\xa0µm over three minutes at ~\u2009930\xa0°C, within the α\u2009+\u2009β mixed phase. On further time at temperature, the lengthening of lamellae stagnated. With further cooling\xa0at\xa00.1\xa0°C/s, lamellae grew in projected\xa0width, while the projected\xa0length remained the same. In addition, a surface topography formed at elevated temperatures (around 800\xa0°C), evolved during the α to β heating transition, and persisted upon cooling.