Phase separation in TiAl(L10)-(Al, Cr)3Ti(L12) system

Keiichiro Oh-ishi, Hideki Kumamoto, Zenji Horita, Minoru Nemoto

    Research output: Contribution to journalArticlepeer-review


    Hardness and microstructural variations during aging of Ti-Al-Cr ternary L10- and L12-phase alloys have been investigated in terms of hardness measurements and transmission electron microscopy. Both the L10 and L12 phase alloys harden by aging at 973 K after solution annealing at higher temperatures. The amount of age hardening of the L12 phase alloy is larger than that of the L10 phase alloy. The phase separation between L10 and L12 phase have not been observed by aging at 973 K. But Al2Ti was formed in each matrix alloy during aging. The crystal structure of the Al2Ti phase is a Ga2Zr type in the L10 and a Ga2Hf type in the L12 phase, respectively. At the beginning of aging the fine coherent cuboidal Al2Ti-phase are formed in the L10 phase. By further aging, two variants of Al2Ti precipitates grow along the two {110} habit planes. On the other hand, in the L12 phase, the Al2Ti phase forms on the {100} planes of the L12 matrix lattice. After prolonged aging the precipitates are rearranged along a preferential direction of the matrix lattice and form a domain consisting of only one variant. It is suggested that the precipitation of Al2Ti in each matrix alloy occurs to form a morphology which efficiently relaxes the elastic strain between precipitate and matrix lattices.

    Original languageEnglish
    Pages (from-to)609-615
    Number of pages7
    JournalNippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
    Issue number8
    Publication statusPublished - 2000

    All Science Journal Classification (ASJC) codes

    • Condensed Matter Physics
    • Mechanics of Materials
    • Metals and Alloys
    • Materials Chemistry


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