本文研究了热电站用12Cr1MoV钢在550℃的蠕变-疲劳复合性能(即循环蠕变性能).实验结果表明,在较高应力幅下,循环蠕变寿命大于纯蠕变寿命,试样断裂以穿晶型为主.在较低应力幅下,循环蠕变寿命小于纯蠕变寿命,试样发生晶间型断裂.根据对断裂试样内部位错组态和晶界状态的透射电镜观察,认为在不同应力幅下分别发生循环强化和循环弱化的原因是:在较高应力下,晶内损伤在循环蠕变的卸载过程中得以部分回复;而在较低应力下,叠加交变应力加速了晶间空洞的形成和连接.
Combined creep-fatigue behaviour (i. e. cyclic creep) of a 12Cr1MoVsteel used in power plants has been studied at 550℃. Experimental resultsindicated that, at higher stress amplitude, the rupture life of cyclic creep is longerthan that of pure creep, and the rupture is mainly transgranular. At lower stressamplitude, the rupture life of cyclic creep is shorter than that of pure creep, andthe rupture is intergranular. Based on TEM observations of dislocation structuresand grain boundaries in ruptured specimens, the reason of cyclic strengthening andcyclic weakening at different stress amplitudes is considered to be: at higher stress,the damage in the interior of grains can be partly recovered during unloading inthe case of cyclic stress; while at lower stress, superposition of cyclic stress enhances the cavity formation and linkage at grain boundaries.
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