Crystalline characteristics of alpha precipitates in Ti–15V–3Sn–3Al–3Cr alloy

The experiment was designed to analyse the orientation relationship between α precipitates and β matrix and to determine the habit plane of α phase in Ti–15–3 alloy using transmission electron microscopy. The orientation relationship was turned out to be 〈1 1 0〉α||〈1 1 1〉β and (0 0 1)α||{1 1 0}β obtained from diffraction patterns, which corresponded to Burgers orientation relationship. Based on the patterns and the crystal structure, it was determined that there were 12 possible orientation relationships between α precipitates with β matrix and α precipitates had 12 variants. Meanwhile, the transformation matrixes of 12 orientation relationships were established. Diffraction patterns of 〈0 0 1〉β, 〈1 1 0〉β and 〈3 1 1〉β zone axes were also calibrated by these matrixes, which verified the correctness of proposed orientation relationship. Diffraction spots of lamelliform α precipitates spread along the [1 1 1]β and [1 1 1¯]β directions in diffraction patterns of [1¯ 1 0]β zone axis, but they do not spread in diffraction patterns of [1 1 1]β zone axis, which indicates that the habit plane of variant 1, 2 and 3 is (1 1 1)β. Moreover, the habit planes of variant 4–6, variant 7–9 and variant 10–12 are (1¯ 1 1)β, (1 1¯ 1)β and (1 1 1¯)β respectively. To sum up, the habit plane of α precipitates is {1 1 1}β.