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本文研究了定向凝固K3镍基高温合金的蠕变强度与细小γ′粒子的数置和尺寸的关系。实验结果证明,随着固溶温度升高,铸态粗大γ′逐步溶解并在随后冷却过程重新析出均匀细小正方形的γ′粒子。细小γ′体积分数(v_f)和尺寸(α)都随固溶温度的升高而增大,当固溶温度从1100℃升至1230℃,v_f从0.25增至0.63,α从0.10μm增至0.32μm。随着固溶温度的升高,第二阶段蠕变速率降低,持久寿命延长,大幅度提高合金的蠕变性能。适当的高温固溶加时效处理(如1210—1230℃,4h+900℃,32h)可提高定向凝固合金的中温(760℃,73.8kgf/mm~2)持久寿命10倍左右。合金的中温蠕变性能取决于细小γ′的体积分数(v_f),尺寸(α)及其间距(λ),在固定温度和应力下,第二阶段蠕变速率((?))与它们之间符合以下关系。 (?)∝λ~2/α或(?)∝α/v_f~(2/3)(1-v_f~(1/3))~2 用透射电镜观察了合金三个蠕变阶段位错亚结构的变化,据此提出蠕变的位错模型和合金的强化机制,并导出第二阶段蠕变速率与γ′体积分数、尺寸和间距之间的关系式,与实验结果完全符合。
In this paper, the relationship between the creep strength and the number and size of fine γ ’particles in the directionally solidified K3 Ni-base superalloy was studied. Experimental results show that as the solution temperature increases, as-cast coarse γ ’gradually dissolves and re-precipitates uniform fine square γ’ particles during subsequent cooling. Fine γ ’volume fraction (v_f) and size (α) both increased with the increase of solution temperature. When the solution temperature increased from 1100 ℃ to 1230 ℃, v_f increased from 0.25 to 0.63 and α increased from 0.10μm 0.32 μm. With the increase of solution temperature, the creep rate in the second stage decreases, and the life span of the alloy increases. The creep property of the alloy is greatly improved. Appropriate high temperature solution treatment and aging treatment (such as 1210-1230 ℃, 4h + 900 ℃, 32h) can improve the long-term life of the directional solidification alloy (760 ℃, 73.8kgf / mm ~ 2) by about 10 times. The mid-temperature creep properties of the alloy depend on the volume fraction (v_f), the size (α) and the spacing (λ) of the fine γ ’, and the second stage creep rates Between the following relations. (?) Αλ ~ 2 / α or αα / v_f ~ (2/3) (1-v_f ~ (1/3)) ~ 2 were observed by transmission electron microscopy Based on this, the dislocation model of creep and the strengthening mechanism of the alloy are proposed. The relationship between the second stage creep rate and γ ’volume fraction, size and spacing is derived, which is in good agreement with the experimental results.