本文研究了δ-Ni_3Nb相的尺寸及分布对Inconel718合金在650℃,恒应变控制循环应变作用下断裂行为的影响。结果表明,由高温固溶及中间时效造成的δ相沿晶界的锯齿状分布,可以提高材料对裂纹沿晶扩展的抗力,使低周疲劳断口由标准工艺处理后的沿晶型转变为穿晶。但是,与形成锯齿晶界的工艺相伴随的,δ相在晶内沿孪晶界面及贯穿晶粒的粗大片状析出,降低材料对循环应变的适应能力,常常过早地在δ相与基体界面处形成微孔甚至界面分离,使材料疲劳寿命降低。
The effect of size and distribution of σ-Ni_3Nb phase on the fatiguefracture behaviour of Inconel 718 under constant controlled cyclic strain at 650℃has been studied. The serrated distribution or σ-plates along grain boundaries, form-ed by high temperature solid solution and intermediate aging, may improve the re-sistance to crack propagation along boundary, so as to change the low cycle fatiguefracture from intergranular, undergone standard heat treatment, into transgranular.However, the precipitation of coarse plate σ-phase along twin boundaries and throughgrains, after treated on the schedule for forming the serrated boundary, mayreduce the adoptability to cyclic strain and may often form too early the microvo-ids at interface between σ-phase and matrix and even disintegrate to shorten the fa-tigue life of steel.
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