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To meet the lightweigh requirements, the structure of castings is evolving towards thin-walled designs. Therefore, it is necessary to study the evolution characteristics of the microstructures and mechanical properties of thin-walled structures made of nickel-based superalloys. Firstly, a thin-walled casting with wall thicknesses of 1, 1.25 mm and 1.5 mm is designed. Gravity casting experiments are conducted under two different process conditions, and the microstructural analysis and mechanical property tests are carried out for two types of castings, respectively. The values of microstructural characteristics are determined, including secondary dendrite arm spacing（SDAS）, grain morphology and average grain size, as well as the size and volume percentage of the γ′ phase at different wall thicknesses of the castings under different cooling conditions. The corresponding hardness and tensile strength also are measured by experiments. The results show that SDAS increases by more than 29.9% as the wall thickness of the casting increases from 1 mm to 1.25 mm and 1.5 mm. The tensile strength of the casting fluctuates with the increase in wall thickness when the flask temperature is 900 ℃. However, the tensile strength of the casting increases as the wall thickness increases when the flask temperature is 25 ℃. The variation range of the castings cooling rates are determined through numerical simulation. The cooling rate range of castings with a sand mold temperature of 900 ℃ ranges from 16.0 ℃/s to 28.2 ℃/s while those produced with a sand mold temperature of 25 ℃ exhibit a cooling rate range of 26.2 ℃/s to 58.5 ℃/s.
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| 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 |
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