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本文研究高温固溶处理对一种定向凝固高强度镍基高温合金的组织和性能的影响。实验结果表明,细小γ′尺寸(α)和体积分数(ν_f)都随固溶温度的升高而增大。随着固溶温度的升高,持久寿命延长,而第二阶段蠕变速率降低。经1210—1250℃高温固溶并900℃,16h时效处理(空冷)后,合金可成倍延长760℃,66kgf/mm~2的持久寿命(τ_f),而第二阶段蠕变速率((?))却随之降低,它们之间的关系符合(?)~(m·τ_f=c,其中m≈1,c=8.0.第二阶段蠕变速率((?))是细小γ′尺寸(α)和体积分数(ν_f)综合作用的结果,且εαα/ν_f~(2/3)。 用透射电镜观察了第二阶段蠕变过程位错亚结构的变化。在中温第二阶段蠕变下,在γ基体上存在高密度的不规则的三维位错网络,而在γ′粒子中,只发现少数位错对;在高温第二阶段蠕变下,在γ/γ′界面上形成规则的二维位错网络。按照位错攀移模型,提出一种第二阶段蠕变机理。

The effect of high temperature solution treatment on the structure and properties of a directionally solidified high strength nickel-base superalloy has been investigated. The size and amount of fine γ' particle in the ahoy increased with the increase of solution temperature. Creep rupture life τ_f was increased and secondary creep rate (?) decreased with the increase of the solution temperature. As the alloy was undergone 1210 to 1250℃ solution and 900℃, 16 h aging, a two-fold increase in creep rupture life was obtained at 760℃ under 66 kgf/mm~2 load, however, the secondary creep rate apparently decreased. The relationship between τ_f and (?) can be expressed as (?)~mτ_f =c, where m≈1, c≈8.0. It is thus regarded that the improvement of rupture life at intermediate temperature (760℃) is due primarily to a fall in secondary creep rate, and in turn to an extension in secondary stage of creep. The secondary creep rate is strongly dependent upon the size, a, and volume fraction, ν_f, of the fine γ' and (?)∞α/ν_f~(2/3).The dislocation substructure during secondary stage of creep has been examined by TEM. At a creep temperature of 760℃, there were a number of dense 3-dimensional dislocation networks in γ matrix, but only a few superlattice dislocation pairs appeared in γ'. When the temperature was increased to 980℃, the γ-γ' interface was found to be covered with 2-dimensional dislocation networks. A mechanism for secondary stage creep has been proposed according to the climbing model.