Nano-structural evolution of Ti(O, N, C) precipitates in V-4Cr-4Ti alloys studied by 3-dimensional atom probe

摘要

To investigate the effect of atmospheric impurities on the behavior of Ti(O, N, C) precipitates in V-4Cr-4Ti alloy at elevated temperatures, chemical and structural analysis were carried out using the laser-assisted 3-dimensional atom probe. After aging at 973 K for 40 h Ti(O, N, C) precipitates were observed around the depth of 1 μm from the specimen surface. The coarse precipitates with a diameter of about 50 nm consisted of mostly Ti, Cr, O and N. The O/N ratio of 142 was much larger than the value of 2 obtained from chemical composition of NIFS-HEAT1 alloy. The fine precipitates, which shows high O/N ratio of 4 seemed to be formed at the initial stage of aging. Thus, it is thought that the ingressed O affects the chemical composition and precipitation behavior of Ti(O, N, C) precipitates within the surface region.