DZ951合金的持久性能与断裂行为

Stress Rupture Performances and Fracture Behavior of DZ951 Alloy

研究了定向凝固镍基高温合金DZ951在广泛应力范围（50-970MPa）内的高温（650-1040℃）持久性能。利用SEM观察了持久断裂的断口和变形后的组织结构。结果表明，DZ951合金的持久强度明显高于DZ40M合金，与DZ17G合金相当。温度低于800℃时，γ’相形貌基本不发生变化：温度达到900℃时，γ’相形成完整的筏型结构。低温（〈760℃）下合金表现为解理断裂，中温（760-850℃）下为解理和准解理混合型断裂，碳化物成为有效的裂纹源。高温（〉850℃）下合金的持久断裂转变为微孔聚集型断裂，显微疏松成为主要的裂纹源。

The stress rupture performances of a directionally solidified Ni-base superalloy DZ951 have been investigated over a wide stress range of 50 to 970 MPa at high temperatures （650 to 1040 ℃）. The fracture surface and deformation microstructure were examined by SEM. The results show that the stress rupture strength of DZ951 alloy is much higher than that of DZ40M and almost the same as that of DZ 17G alloy. It is suggested that γ＇ particles remain cubic shape below 800℃, and when the test temperature reaches 900＂C, ~,＇ particles form fine rafted structure. At low temperature （〈760℃）, the fracture mode is cleavage-like. At intermediate temperature （760-850℃）, the fracture mode shows both cleavage feature and quasi-cleavage feature, and cracks can initiate at the carbide/matrix interface. At high temperature （〉850℃）, the fracture mode turns to be microviod coalessenee fracture and the alloy is sensitive to the shrinkage porosity.