Influence of long-term isothermal aging on microstructure and creep rupture properties of Ni-base superalloy M4706

长期等温时效对镍基高温合金M4706组织和持久蠕变性能的影响（英文）

After a standard heat treatment,the microstructural evolution with time during isothermal aging at 850°C and its effect on the creep rupture properties of the Ni-base superalloy M4706 at 870°C and 370 MPa are investigated.It is found that as the aging time increases from 0 to 5000 h,the average diameter of coarseγ′increases from 241 to 484 nm,and the distribution of the carbides at grain boundaries changes from discontinuous to continuous.Moreover,experimental observations on the microstructures of all the crept specimens reveal that dislocation bypassing controls the creep deformation.Thus,it is concluded that the transitions in the microstructures result in the degeneration of the creep rupture properties of the experimental alloy with aging time.

研究了标准热处理态M4706合金在850°C等温时效过程中微观组织结构的演变及其对合金在870°C/370 MPa条件下持久蠕变性能的影响。试验发现,当时效时间从0 h增加到5000 h时,γ′相的平均尺寸从241 nm增加到484 nm,并且晶界处的碳化物由不连续分布变为连续分布。同时,采用透射电子显微镜对蠕变后的样品进行了观察和分析。试验结果表明,所有热处理态合金的蠕变变形主要是通过基体位错绕过γ′相来实现的。基于这些结果,认为随着时效时间的延长,这些微观组织结构的变化导致了试验合金的持久蠕变强度随时效时间的延长而不断的恶化。