一种镍基单晶高温合金持久各向异性行为

研究了一种镍基单晶高温合金DD499的[001],[011]和[111]3个晶体取向在典型应力条件下的持久性能。结果表明,持久寿命的取向依赖性与温度和应力有关。760℃,790MPa时,[001]取向的持久寿命明显高于[011]和[111]取向;1040℃,165MPa时,持久寿命由大到小顺序为[111]>[001]>[011],但不同取向的各向异性减弱。利用SEM观察持久断裂后的断口和组织结构表明,760℃,790MPa时,[001]取向试样的断裂特征为解理和准解理混合型断裂,[011]取向为单系滑移引起的剪切断裂,而[111]取向为多系滑移引起的剪切断裂;1040℃,165MPa时,3种取向都为微孔聚集型断裂。

Anisotropic Stress Rupture Behavior of a Nickel-Base Single Crystal Superalloy

The stress rupture test was conducted to a nickel-base single crystal superalloy DD499 along [001], [011] and [111] orientations. The results indicate that anisotropic behaviors of singe crystal superalloy are significantly affected by temperature and stress level. At 760 oC, 790 MPa, the stress rupture property of [001] orientation is outstandingly superior to that of [011] and [111] orientations; while at 1040 oC, 165 MPa, the order of stress rupture is [111]>[001]>[011], but the anisotropic properties of different orientations are weakened. Fracture surface and deformation microstructure were examined by SEM. The results show that at 760 oC, 790 MPa, the fracture mode of [001] orientation is the combination of cleavage and quasi-cleavage; while the fracture mode of [011] orientation is pure shear due to single slip system and [111] orientation is pure shear caused by multiple slip systems. At 1040 oC, 165 MPa, the fracture mode of the three orientations all turns to be microvoid coalescence fracture.