<111>取向DD499合金旋转弯曲高周疲劳性能的研究

研究了DD499单晶高温合金<111>取向700和900 ℃温度条件下光滑和缺口试样的高温旋转弯曲高周疲劳性能。结果表明：<111>取向DD499合金光滑试样的疲劳强度在700 ℃为355 MPa，在900 ℃时为400 MPa，其疲劳强度和缺口敏感性均随温度的升高而增大。<111>取向DD499合金两种温度光滑试样的疲劳断裂均为多源断裂，断裂机制均表现为沿最密排面{111}面的解理断裂特征；而缺口试样在700 ℃表现为沿缺口向中心扩展断裂，900 ℃表现为类似于光滑试样的断裂特征。

Rotary Bending High Cycle Fatigue Behavior of Single Crystal Superalloy DD499 in <111> Orientation

Smooth and notched specimens of single crystal superalloy DD499 in <111> orientation were subjected to rotary bending high cycle fatigue loading at temperatures of 700 and 900 oC in ambient atmosphere. The results show that both fatigue strength and notch sensitivity of smooth specimens of <111>-oriented DD499 alloy are increased at elevated temperature; the fatigue strength of smooth specimens are 355 MPa at 700 oC, and 400 MPa at 900 oC. High cycle fatigue failure of smooth specimens of DD499 alloy at different temperatures is in the form of cleavage fracture with multiple crack initiation sites, which was evidently observed along {111} glide plane. However, for the notched specimens, the cracks propagate towards the central area from notched roots at 700 oC, and cleavage rupture characteristics is just like that of the smooth specimens at 900 oC.