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研究了两种有代表性的粒子强化(氧化物弥散强化和γ′沉淀强化)镍基高温合金的循环蠕变和应力断裂行为。研究表明,在760℃和一定的循环载荷下,试验频率从0.05至6cycles/h变化时,循环蠕变速率随频率提高而下降,而断裂寿命则一般随频率增加而增加(但对于沉淀强化高温合金,在所采用的最高频率下,断裂寿命反而下降,这是由于频率使平面滑移程度增加的结果)。分析了在加载和卸载期间的塑性和滞弹性应变以及在循环蠕变中的位错结构。结果表明,在循环加载时所观察到的行为及明显的材料强化,并不是循环应变硬化效应所造成的,而是滞弹性应变效应的结果。这种滞弹性应变在加载期间被累积,而在卸载期间则被恢复。在滞弹性机构的基础上,导出了一个循环蠕变或蠕变疲劳交互作用减速因素的现象学模型,这一模型与实验所观察到的行为相符合。
Cyclic creep and stress rupture behavior of two representative nickel-based superalloys with particle strengthening (oxide dispersion strengthening and γ ’precipitation hardening) were investigated. The results show that the cyclic creep rate decreases with increasing frequency at a test frequency of 0.05 to 6 cycles / h at 760 ° C and a certain cyclic loading, whereas the fracture life generally increases with increasing frequency (but for precipitation enhanced high temperature Alloy, at the highest frequencies used, the fracture life decreases instead, as a result of the increased frequency of plane slip. Plastic and anelastic strains during loading and unloading as well as dislocation structures in cyclic creep were analyzed. The results show that the behavior observed during cyclic loading and significant material strengthening are not caused by cyclic strain hardening but rather as a result of anelastic strain effects. This inelastic strain is accumulated during loading and recovered during unloading. On the basis of the anelastic mechanism, a phenomenological model of the deceleration factor of cyclic fatigue or creep fatigue interaction is derived, which is consistent with the experimentally observed behavior.