CMSX-4单晶高温合金在不同温度下的低周疲劳行为

Low cycle fatigue behaviors of single-crystal superalloy CMSX-4 at different temperatures

摘要:

研究了单晶高温合金CMSX-4在中温760 ℃和高温950 ℃下的低周疲劳行为。结果表明：在760 ℃下合金具有较长的疲劳寿命和较高的疲劳强度,断裂后断面高度差大并与应力轴方向呈45°角,裂纹沿着{111}面扩展；而在950 ℃下合金具有较短的疲劳寿命和较低的疲劳强度,断面与应力轴垂直,裂纹沿着{001}面扩展。低周疲劳断口的扫描电镜结果表明, 760 ℃试样表面的微孔是主要的疲劳源,而950 ℃试样表面的氧化层是主要的疲劳源且呈现多源开裂。低周疲劳断口的透射电镜结果表明,中温760 ℃下位错具有的平面滑移和波状滑移的变形机制,是由位错的平面滑移向波状滑移转变的过程；而高温950 ℃下位错主要通过交滑移和攀移进行运动。

Abstract:

The low cycle fatigue behaviors of single-crystal superalloy CMSX-4 were investigated at 760 °C and 950 °C. At 760 ℃, specimens have longer fatigue lives and higher strength under higher strain amplitude. The fracture sections of specimens at 760 ℃ have a large height difference with an angle of 45° to the stress axis direction, and the cracks expand along the {111} plane; while the fracture sections of specimens at 950 ℃ are perpendicular to the stress axis, and the cracks expand along the {001} plane. Scanning electron microscope was employed to analyze the fatigue fracture, and it is found that the micropore near the surface of specimens at 760 ℃ is the main fatigue source, while the fatigue cracks originated from the oxide layer near the surface of specimens at 950 ℃ and it shows multiple sources of cracking. Transmission electron microscope was employed to analyze the dislocation motion modes. The deformation mechanism of low cycle fatigue at 760 ℃ includes planar slip and wavy slip, which is the process of transition from planar slip to wavy slip. Whereas, the dislocation at 950 ℃ mainly moves by cross-slip and a process of gliding and climbing.