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Microstructure evolution of NiAl–Cr(Mo) planar eutectic lamellar structure during high temperature treatment

  • Lei Wang (a1), Luhan Gao (a1), Jun Shen (a2), Yunpeng Zhang (a1), Tao Wang (a1), Zewei Wang (a1), Pengfei Qu (a1), Jianying Zhang (a1) and Guojun Zhang (a1)...

The microstructure evolution of the directionally solidified NiAl–Cr(Mo) planar eutectic lamellar structure was studied at 1150 °C and times of up to 400 h. The planar eutectic lamellar structure is obtained at the withdrawal rate range of 2.5–7.5 μm/s. The interlamellar spacing decreases gradually with increasing the withdrawal rate. The lamellar termination (like angular or smooth) commonly exists in the as-DS alloy. After high temperature treatment, the lamellar structure at 2.5 μm/s (interlamellar spacing, 3.7 μm) is almost stable, only a little migration of termination occurs at 400 h. When the withdrawal rate increases to 4.5 μm/s, the coarsening and migration of termination occur at 200 h. The adjacently coarsened terminations assemble when the coarsening processes to a certain degree, thus resulting in the formation of the blocky Cr(Mo) phase. Similarly, the above instable phenomenon occurs at 7.5 μm/s. The relevant instability mechanisms are discussed.

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Journal of Materials Research
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