The Stability of γ ’-Co3(Al,W) Phase in Co-Al-W Ternary System
The thermodynamic stability ’- Co3(Al,W) phase (L12) in the Co-Al-W ternary system at 900 °C was investigated through microstructure and EPMA analysis on a heat-treated bulk alloy. To promote microstructural evolution, the bulk alloy was cold rolled before heat treatment. By heating at 900 °C, the ’ phase was formed discontinuously in contact with the -Co (A1) phase. With increasing heat treatment time, however, the fraction of ’ phase decreased while that of , CoAl (B2) and Co3W (D019) phases increased. These results are consistent with our previous work with a diffusion-couple method, indicating that the ’ phase is metastable, and the three phases of, CoAl and Co3W are thermodynamically stable at 900 °C.
Jian-Feng Nie and Allan Morton
Y. Tsukamoto et al., "The Stability of γ ’-Co3(Al,W) Phase in Co-Al-W Ternary System", Materials Science Forum, Vols. 654-656, pp. 448-451, 2010