| Title |
Microstructures of Rapidly Solidified and Annealed Ni - base Superalloys ( On the Rapidly quenched Structures by Melt spining and the Segregationless Phenomenon ) |
| Authors |
윤의박(Eui Park Yoon); 정홍철(Hong Chul Jeong); 나형용(Hyung Yong Ra); 장재규(Jai Kyu Jang); 조순형(Soon Hyung Cho) |
| Abstract |
In this study, Ni-Al alloys and Ni-Al-Ti alloys were rapidly solidified by melt-spinning. The resulting ribbon microstructures were studied using light microscopy and transmission electron microscopy. By extrapolating experimental results obtained at low cooling rates, the cooling rates of ribbon by melt-spinning technique were approximately determined. The cooling rates of ribbon range from 9×10⁴K/s-1.2×10^6 K/s for 60-80 ㎛ thickness. Growth rates by thermal analysis vary from 0.18 ㎝/sec to 4.7 ㎝/sec in these alloys. The formation of γ` in the Ni-7.55 wt%Al, Ni-5.94 wt%Al-2.19 wt%Ti and Ni-8.30 wt %Al-2.85 wt%Ti alloys can be suppressed by melt spinning. The high hardness observed in these alloys after heat treatment is due to the subsequent development of small, ordered precipitations in the fine-grained matrix. And, grain boundary segregation could was suppressed, with increasing cooling rate. |