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To delve into the impacts of multiple brazing thermal cycles at varying peak temperatures on the microstructure and properties of GH4169 alloy， this study conducted a comprehensive examination of how brazing thermal cycle processes influence the precipitates， grain size， tensile properties， and stress-rupture properties of the alloy.The findings reveal that as the thermal cycle temperature rises， the quantity of δ-phase precipitation diminishes， and its morphology undergoes a transformation from needle-like to rod-like and eventually to granular. Within the temperature range of 970-1010 ℃， the grain size experiences minimal alteration. However， when the temperature surpasses 1020 ℃， significant grain growth occurs. Both tensile strength and hardness initially ascend and then descend with an increase in the thermal cycle temperature， reaching their peak values at 1010 ℃. This phenomenon is mainly attributed to the dissolution of an appropriate amount of δ phase and the complete precipitation of γ″ and γ′ strengthening phases at this temperature， while the grain size does not show significant coarsening.The room-temperature impact toughness demonstrates distinct trends across different thermal cycle ranges. In the 970-990 ℃ range， it decreases with rising temperature due to the partial transformation of the δ-phase morphology from needle-like to rod-like. In the 990-1010 ℃ range， it increases with temperature as the δ phase dissolves and the strengthening-phase-free zone vanishes. Nevertheless， a further increase in the thermal cycle temperature leads to a reduction in toughness because of grain growth.The stress-rupture life initially declines and then rises with an increase in the thermal cycle temperature， hitting its lowest point in the 990-1000 ℃ range. This is caused by the partial transformation of the δ-phase morphology from needle-like to rod-like， which promotes microvoid nucleation and reduces the alloy's creep resistance. When the temperature further rises above 1020 ℃， the extensive precipitation of γ″ strengthening phases， along with significant grain growth， substantially enhances the alloy's creep performance. However， the substantial decrease in the needle-like δ-phase content results in increased notch sensitivity.Taking into account both mechanical properties and notch sensitivity， it is recommended to employ brazing thermal cycles around 1010 ℃ to achieve a well-balanced combination of strength and stress-rupture performance. For service environments with higher notch sensitivity requirements， a thermal cycle temperature in the range of 970-980 ℃ can be selected to minimize the risks of creep failure.
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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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