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在恒位移速率条件下研究了Ｆｅ－１５Ｃｒ－２５Ｎｉ合金的蠕变裂纹扩展行为．蠕变裂纹扩展分为慢速扩展阶段和稳态扩展阶段．稳态裂纹扩展由加载点位移速率控制，不受晶粒尺寸和温度因素的影响．在慢速扩展阶段，小晶粒具有较高的裂纹扩展抗力，计算出的裂纹扩展表观激活能低于蠕变激活能．断口分析表明：随晶粒尺寸的增大、温度的升高、加载点位移速率的降低，材料呈蠕变脆性断裂．
The creep crack growth behavior of Fe-15Cr-25Ni alloy was studied at constant displacement rate. Creep crack growth is divided into the slow expansion phase and steady-state expansion phase. Steady-state crack propagation is controlled by the loading point displacement rate, independent of grain size and temperature. In the slowly expanding phase, the small grains have higher crack propagation resistance, and the calculated apparent activation energy of crack propagation is lower than the creep activation energy. Fracture analysis shows that the creep and brittle fracture of the material occurs with the increase of grain size, the increase of temperature and the decrease of the displacement velocity of the loading point.