Ordering process of Al{sub 5}Ti{sub 3}, h-Al{sub 2}Ti and r-Al{sub 2}Ti with fcc-based long-period superstructures in rapidly solidified Al-rich TiAl alloys
- Osaka Univ., Suita, Osaka (Japan). Dept. of Materials Science and Engineering
Change in microstructure and stability of superstructural phases in Al-rich TiAl alloys containing 58.0--62.5 at.% Al were investigated using melt-spun ribbons. Ordering processes of long-period ordered phases such as Al{sub 5}Ti{sub 3}, h-Al{sub 2}Ti and r-Al{sub 2}Ti in the L1{sub 0} matrix during annealing were examined. The presence of Al{sub 5}Ti{sub 3} and h-Al{sub 2}Ti phases in the L1{sub 0} matrix was confirmed in melt-spun Ti-60.0 at.% Al and Ti-62.5 at.% Al ribbons by electron diffraction patterns, while diffuse scattering corresponding to the Al{sub 5}Ti{sub 3} superstructure appeared in Ti-58.0 at.% Al ribbon. In Ti-58.0 at.% Al ribbon, the Al{sub 5}Ti{sub 3} phase developed as an island in the L1{sub 0} matrix having an obscure coherent boundary at and below 800 C, while it dissolved during annealing above 800 C. Although the r-Al{sub 2}Ti phase was finally formed as an equilibrium phase, the ordering of Al{sub 5}Ti{sub 3} and metastable h-Al{sub 2}Ti phases in Ti-60.0 at.% Al and Ti-62.5 at.% Al ribbons occurred prior to the precipitation of the r-Al{sub 2}Ti during annealing below 800 C. The priority for the ordering process is discussed on the basis of crystal symmetry and periodicity of Al layers parallel to the (002) plane. The anti-phase boundaries (APBs) based on the Al{sub 5}Ti{sub 3}-type ordering were observed along {l_brace}110{r_brace} planes in Ti-62.5 at.% Al ribbon annealed at 700 C and their energies were calculated using the interaction energy between neighboring atoms.
- OSTI ID:
- 338417
- Journal Information:
- Acta Materialia, Journal Name: Acta Materialia Journal Issue: 4 Vol. 47; ISSN 1359-6454; ISSN ACMAFD
- Country of Publication:
- United States
- Language:
- English
Similar Records
Structures of melt-spun and high-energy ball milled Al{sub 3}Ti-Mn-Nb intermetallic alloy
Investigation of a new type of Al{sub 3}Ti-based L1{sub 2} alloy with second phase precipitation