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首页> 外文期刊>International Journal of Plasticity >Stress-level-dependency and bimodal precipitation behaviors during creep ageing of Al-Cu alloy: Experiments and modeling
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Stress-level-dependency and bimodal precipitation behaviors during creep ageing of Al-Cu alloy: Experiments and modeling

机译：抗Cu合金蠕变衰老过程中应力水平依赖性和双峰沉淀行为：实验和建模

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Understanding the deformation and strengthening mechanism at different stress levels is crucial for accurate prediction of creep ageing behaviors, especially for alloys subjected to a complex stress-state. A comprehensive investigation has been performed on the creep deformation and age hardening during creep ageing of an aluminum-copper alloy AA2219-T4 under various stress levels that lead to elastic or initial plastic deformation. Microstructural variables including dislocations and precipitates have been characterized in detail by X-ray diffractometer, scanning/transmission electron microscopy and differential scanning calorimetry. The creep mechanism is found to be dominated by diffusion creep under small stress level and then by dislocation climb with increasing stress. The high-stress-induced dislocations raise the creep strain considerably and cause a notable extension of the primary creep stage. The existence of preferential alignment of theta '' precipitates (stress-orienting effect) in creep-aged samples results in an evident decline in the age hardening potential. A typical bimodal distribution of precipitates comprised of theta '' homogeneously dispersed in the matrix and relatively large stable theta' heterogeneously nucleated at dislocations forms during high-stress ageing. The theta' precipitates exhibit no stress-orienting effect and lead to a considerable enhancement of hardening response. Based on detailed microscopic observations, a unified constitutive model is developed and calibrated by experimental data to predict the observed stress-level dependency of creep ageing behaviors. The dislocation evolution during both the loading stage and the creep stage as well as the bimodal precipitation of shearable and nonshearable phases are quantified and incorporated in a dislocation-based internal variable creep model. The proposed model is able to well describe the concurrent evolution of dislocations and precipitation, whose interplay gives rise to a c
机译：理解不同应力水平的变形和强化机制对于准确预测蠕变老化行为的性是至关重要，特别是对于经受复合应力状态的合金。在各种应力​​水平下，在铝 - 铜合金AA2219-T4下蠕变老化期间对蠕变变形和年龄硬化进行了全面的研究。导致弹性或初始塑性变形。通过X射线衍射仪，扫描/透射电子显微镜和差示扫描量热法详细描述了包括脱臼和沉淀物的微结构变量。发现蠕变机制在小的应力水平下的扩散蠕变来支配，然后通过增加应力的脱位升降。高应力诱导的脱位大大提高了蠕变菌株并引起初级蠕变阶段的显着延伸。在蠕变 - 老化样品中θ''''''''''''沉淀物（应激效果）的优先对准导致年龄硬化潜力的明显下降。在高应力老化期间，在脱位形成的沉淀物中包含沉淀物的典型双峰分布，其均匀分散在基质中，相对大的稳定θ'在脱位中形成。沉淀物表现出没有应激效果，并导致强化硬化反应的显着增强。基于详细的微观观察，通过实验数据开发和校准统一的本构模型，以预测观察到蠕变老化行为的应力水平依赖性。定量加载阶段和蠕变阶段的脱位演化以及可剪切和无烟性相的双峰沉淀，并结合在基于位错的内部可变蠕变模型中。拟议的模型能够很好地描述脱位和降水的并发演变，其相互作用产生了c

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