Plastic deformation of directionally solidified ingots of binary and some ternary MoSi2/Mo5Si3 eutectic composites

Hirotaka Matsunoshita; Yuta Sasai; Kosuke Fujiwara; Kyosuke Kishida; Haruyuki Inui

doi:10.1080/14686996.2016.1218248

Plastic deformation of directionally solidified ingots of binary and some ternary MoSi₂/Mo₅Si₃ eutectic composites

Sci Technol Adv Mater. 2016 Sep 8;17(1):517-529. doi: 10.1080/14686996.2016.1218248. eCollection 2016.

Authors

Hirotaka Matsunoshita¹, Yuta Sasai¹, Kosuke Fujiwara¹, Kyosuke Kishida², Haruyuki Inui²

Affiliations

¹ Department of Materials Science and Engineering, Kyoto University , Kyoto , Japan.
² Department of Materials Science and Engineering, Kyoto University, Kyoto, Japan; Center for Elements Strategy Initiative for Structural Materials (ESISM), Kyoto University, Kyoto, Japan.

Abstract

The high-temperature mechanical properties of directionally solidified (DS) ingots of binary and some ternary MoSi₂/Mo₅Si₃ eutectic composites with a script lamellar structure have been investigated as a function of loading axis orientation and growth rate in a temperature range from 900 to 1500°C. These DS ingots are plastically deformed above 1000 and 1100 °C when the compression axis orientations are parallel to [1[Formula: see text]0]_MoSi2 (nearly parallel to the growth direction) and [001]_MoSi2, respectively. [1[Formula: see text]0]_MoSi2-oriented DS eutectic composites are strengthened so much by forming a script lamellar microstructure and they exhibit yield stress values several times higher than those of MoSi₂ single crystals of the corresponding orientation. The yield stress values increase with the decrease in the average thickness of MoSi₂ phase in the script lamellar structure, indicating that microstructure refinement is effective in obtaining better high-temperature strength of these DS eutectic composites. Among the four ternary alloying elements tested (V, Nb, Ta and W), Ta is found to be the most effective in obtaining higher yield strength at 1400 °C.

Keywords: 10 Engineering and Structural materials; 103 Composites; 302 Crystallization / Heat treatment / Crystal growth; 503 TEM, STEM, SEM; Transition-metal silicides; high-temperature deformation; mechanical properties; microstructure.