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用光学显微镜直接观测裂纹长度的方法研究了DZ-9,DZ-3合金在中温(760℃)下蠕变裂纹的扩展行为。当裂纹体平行于柱状晶生长方向时,裂纹扩展速率da/dt与应力强度因子K_1,净截面应力σ_N的关系符合Paris公式:da/dt=AK_(I~m)或da/dt=Bσ_(N~n)。DZ-3经热处理后比铸态具有更高的裂纹扩展抗力,更长的孕育期和断裂寿命。DZ-3此DZ-9有较高的裂纹扩展抗力,较长的孕育期和断裂寿命。当裂纹体垂直于柱状晶生长方向时,大大提高了裂纹扩展的抗力。组织结构分析表明:初生MC和共晶γ-γ′是微裂纹的策源地。裂纹尖端塑性区的位错组态与普通中温(T60℃)高应力蠕变试验条件下的非常相似。
The propagation of creep cracks in DZ-9 and DZ-3 alloys at moderate temperature (760 ℃) was investigated by observing the crack length directly with an optical microscope. The relationship between crack growth rate da / dt and stress intensity factor K_1 and net cross-section stress σ_N complies with the Paris formula when the crack body is parallel to the growth direction of columnar crystals: da / dt = AK_ (I ~ m) or da / dt = Bσ_ N ~ n). DZ-3 has higher crack propagation resistance, longer incubation period and fracture life than as-cast after heat treatment. DZ-3 This DZ-9 has higher crack propagation resistance, longer incubation period and fracture life. When the crack body is perpendicular to the columnar crystal growth direction, the crack propagation resistance is greatly enhanced. Tissue structure analysis shows that primary MC and eutectic γ-γ ’are the source of micro-cracks. The dislocation configuration at the crack tip plastic zone is very similar to that under normal high temperature (T60 ° C) high stress creep test conditions.