PDF
Full
Outline
Grain refinement can effectively enhance mechanical properties of materials at low and medium temperatures, however, it may weaken the stress rupture property above the equicohesive temperature. To study the effect of grain refinement on the stress rupture property of K447A alloy, the microstructure evolutions of alloys with three grain sizes and their corresponding stress rupture mechanisms under the conditions of 760 ℃/724 MPa, 815 ℃/600 MPa, 870 ℃/365 MPa and 980 ℃/210 MPa are investigated using scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS）. The results show that the equicohesive temperature of K447A alloy lies between 815 ℃ and 870 ℃. Grain refinement shows a temperature-dependent effect on the stress rupture life of K447A alloy. At 760 ℃/724 MPa, as the grain size decreases from 5.0 mm to 1.3 mm and then to 58 μm, the stress rupture life of K447A alloy increases from 83 h to 115 h and further to 194 h, respectively. At 815 ℃/600 MPa, the stress rupture life increases from 31 h to 84 h, as the grain size decreases, and then slightly drops to 76 h. At 870 ℃/365 MPa and 980 ℃/210 MPa, the stress rupture life shows a monotonic decreases with grain refinement. Therefore, grain refinement serves as an effective technology to improve the stress rupture property of K447A alloy below 870 ℃.The stress rupture process is dominated by intragranular deformation below 815 ℃, and grain refinement mainly extends the stress rupture life by shortening the slip band length and increasing the volume fraction of γ′ phase. Above 870 ℃, grain boundary sliding dominates the stress rupture process. The deterioration of the stress rupture property due to grain refinement can be attributed to the severe grain boundary slip at high temperatures, grain boundary oxidation and the formation of brittle AlN and a low-strength precipitation free zone（PFZ）.
PDF
106
58
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
关闭全屏
No. 86 Xueyuan South Road, Haidian District, Beijing
010-62199257
qkjq@cast.org.cn
Copyright © 2025 China Association for Science and Technology. All rights reserved. For all open access content, the relevant licensing terms apply.
Sponsored by the Office of the Leading Group for Cybersecurity and Informatization of CAST, and supported by Science and Technology Review Publishing House
