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本文研究了GH133合金的循环应力应变反应和低周疲劳性能,并作了位错结构和断口观察。通过对比拉压对称(R=-1)试验和恒定最大正应变(ε_(max)=C)试验,证明平均拉应力起降低寿命的作用。位错结构观察证明,循环使共格γ′质点的相界处产生应力场,最终导致位错的萌生并运动,位错运动又进一步增殖位错。位错运动方式是变化的,由成对切割γ′质点到单位错切割γ′质点和位错绕过γ′质点。滑移带位错结构最终可以出现饱和的梯状结构,与典型的驻留带位错结构相似。晶界和双晶界附近位错密度高,具有位错胞结构,同时可以出现沿晶界裂纹和沿双晶界裂纹。 在循环交变作用下,材料的破坏过程可以分解为三个主要过程,即在循环作用下产生的材料变形行为的变化,疲劳裂纹的形成和疲劳裂纹不断扩展,直到一定的临界大小而发生最终破坏,这三个过程是不同的但又是相互联系的,宏观疲劳现象可以在此基础上作出适当的说明。对于含有共格γ′沉淀相的低层错能奥氏体合金,许多研究[1—8]指出,其循环反应往往是先循环硬化再循环软化,并具有面排列位错结构。关于循环软化现象,一些作者认为[8],共格沉淀相在位错往复切割下碎化而导致回溶,产生软化,更多的作者相信[4],位错切割共格相导致有序强化作用减弱或消失,产生软化。关于循环硬?
In this paper, cyclic stress-strain reaction and low cycle fatigue behavior of GH133 alloy were studied, and dislocation structure and fracture observation were made. By comparing the tension and compression symmetry (R = -1) test and the constant maximum normal strain (ε max (C)), it is proved that the average tensile stress plays a role in reducing the life span. The dislocation structure observation shows that the circulation causes the stress field at the phase boundary of the coherent γ ’particles, which eventually leads to the initiation and movement of dislocations, and the dislocation movement further proliferates the dislocations. Dislocation movement is the way to change, from the pair of cutting γ ’mass to the unit error cutting γ’ particles and dislocation bypass γ ’particle. The slipband dislocation structure can eventually appear as a saturated ladder structure, similar to the typical resident band dislocation structure. Dislocations near the grain boundaries and the twin boundaries have high dislocation density and dislocation cell structure. Simultaneously, cracks along the grain boundaries and along the twin boundaries can occur. Under cyclic alternation, the material failure process can be decomposed into three main processes, namely, the deformation behavior of the material produced under the cyclic action, the formation of fatigue cracks and the fatigue crack expanding continuously until a certain critical size occurs eventually Destruction, the three processes are different but interrelated, macroscopic fatigue can be based on this to make an appropriate explanation. For the low-lying faulty austenitic alloys with a coherent γ ’precipitated phase, many studies [1-8] indicate that the cyclic reactions tend to be cycled and softened first, with the dislocation structure in the plane. Regarding the cyclic softening phenomenon, some authors consider [8] that the coherent precipitates are fragmented under dislocation reciprocating cleavage, resulting in the dissolution and softening. More authors believe [4] that the dislocation cutting conformal phase leads to an orderly Strengthen the role of weakening or disappearance, resulting in softening. About loop hard?