Effect of LAB on the Stress Rupture Properties and Fracture Characteristic of DD6 Single Crystal Superalloy

摘要:

用双籽晶法制备了带有扭转小角度晶界的DD6单晶高温合金双晶试板。在760 oC/758 MPa, 850 oC/550 MPa 和 980 oC/250 MPa条件下研究了小角度晶界对合金持久性能和断裂特征的影响，用扫描电镜分析了断口形貌和断裂机制。结果表明，晶界角度相对较小时，对合金的持久性能影响较小。在同一测试条件下，合金的持久性能随着晶界角度增大而减小。在同一测试条件下随着晶界角度增大，或者在相同晶界角度随着测试温度升高应力减小，持久断裂有逐渐出现沿晶断裂的趋势

Abstract:

The slabs of the second generation single crystal superalloy DD6 were cast using bi-seeded crystals with symmetric twist low angle grain boundaries. The influence of low angle boundary (LAB) on the stress rupture properties of the alloy was investigated at 760 oC/758 MPa, 850 oC/550 MPa and 980 oC/250 MPa. SEM was used to study the fracture surface and the failure mechanism. The results show that when the misorientation angle of LAB is relatively small it has a less effect on the stress rupture properties of the alloy. The stress rupture properties decrease with the misorientation increase on the same test conditions. The fracture characteristic of specimen shows intergranular rupture trend with the misorientation increases on the same conditions or with increasing of temperature and decreasing of stress for the same misorientation of LAB