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测定了难变形高温合金GH4720Li在650、700、750及800℃空气环境下的疲劳裂纹扩展速率,并结合断口分析了在纯疲劳及保载90 s下,温度对合金疲劳裂纹扩展速率的影响。结果表明,随着温度升高,合金疲劳裂纹扩展速率的增长幅度变大。800℃时,合金的疲劳裂纹扩展速率急剧增大。温度升高,疲劳裂纹的扩展方式发生了明显变化,650℃时断口为沿晶和穿晶断裂混合型,700~800℃时断口以沿晶断裂为主。保载时间延长,裂纹扩展速率加快,且裂纹扩展速率的温度敏感性增加。
The fatigue crack growth rate of the alloy GH4720Li under 650, 700, 750 and 800 ℃ air environment was measured. The fatigue crack growth rate under pure fatigue and 90 s loading was analyzed by fracture analysis. The results show that the fatigue crack growth rate increases with the increase of temperature. At 800 ℃, the fatigue crack growth rate increases sharply. At the temperature of 650 ℃, the intergranular fracture and transgranular fracture are mixed, and the intergranular fracture is the main fracture at 700-800 ℃. Extended loading time, crack growth rate, and crack growth rate increased temperature sensitivity.