Phase equilibria, microstructure, and high-temperature strength of TiC-added Mo-Si-B alloys

Shimpei Miyamoto, Kyosuke Yoshimi, Seong Ho Ha, Takahiro Kaneko, Junya Nakamura, Tetsuya Sato, Kouichi Maruyama, Rong Tu, Takashi Goto

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52 Citations (Scopus)


TiC was added to Mo-Si-B alloys using a conventional Ar arc-melting technique, and the phase equilibria, microstructure evolution, and high-temperature strength at 1673 K (1400 C) were investigated. The primary phase changed to Mo solid solution (Moss), Mo5SiB 2 (T2), or TiC depending on the composition. Following the primary phase solidification, a Moss + TiC, Moss + T 2, or Moss + T2 + TiC + Mo2C eutectic reaction took place as the secondary solidification step. In some alloys, Moss + T2 + TiC and Moss + T 2 + Mo2C eutectic reactions were present as higher-order solidification steps. After annealing at 2073 K (1800 C) for 24 hours, Mo ss, T2, TiC, and Mo2C coexisted stably with microstructural coarsening. The coarsening rate was much faster in an alloy with no TiC dispersion, suggesting that TiC has a strong pinning effect on the grain boundary and interface migration. Compression tests conducted at 1673 K (1400 C) revealed strength properties of almost all the alloys that were better than those of the Mo-Hf-C alloy (MHC). Alloy densities were 9 g/cm3 or less, which is lighter than pure Mo and MHC (≥10 g/cm3) and competitive with Ni-base superalloys. TiC-added Mo-Si-B alloys are promising candidates for ultrahigh-temperature materials beyond Ni-base superalloys.

Original languageEnglish
Pages (from-to)1112-1123
Number of pages12
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Issue number3
Publication statusPublished - 2014 Mar


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