Deformation Behavior of Fe-Al Single Crystals Containing Fe₂AlTi Precipitates

Abstract:

Fe-20Al-5Ti (at.%) single crystals composed of the bcc Fe-Al matrix and the Fe₂AlTi precipitates with the L2₁ structure was examined. In the single crystals furnace-cooled (FC) from 1373 K to room temperature, coarse Fe₂AlTi phase about 300 nm in diameter were precipitated in the bcc matrix. A misfit strain and a dissolution temperature of the L2₁ precipitates are +0.59% and 1151 K, respectively. The single crystals exhibited high yield stress above 600 MPa up to 973 K while further increase in temperature resulted in a decrease in yield stress due to the dissolution of the precipitates. In the FC crystals, 1/2<111> dislocations in the bcc matrix bypassed the coarse L2₁ precipitates due to their large misfit strain, resulting in high strength. In contrast, the fine L2₁ precipitates about 30 nm in diameter were observed in the crystals after solutionization and annealing at 873 K. The crystals with the fine L2₁ precipitates demonstrated high yield stress above 1100 MPa at and below 773 K. Uncoupled or paired 1/2<111> dislocations cut the fine L2₁ precipitates, leaving an anti-phase boundary (APB) inside the precipitates. The APB inside the precipitates was considered to be responsible for strong precipitation hardening.

• Periodical: Materials Science Forum (Volume 941)
• Pages: 1372-1377
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.941.1372
• Online since: December 2018
• Authors: Hiroyuki Y. Yasuda*, Hiroyuki Yakage, Yunima Shinohara, Ken Cho
• Keywords: High-Temperature Structural Materials, Intermetallic Compound, Precipitation Hardening

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