长期中子辐照 Al-Mg-Si合金的压缩力学行为

利用材料试验机及分离式霍普金森压杆装置，开展长期中子辐照后的Al-Mg-Si合金（反应堆内实际服役近30年的LT21铝合金）在不同温度和应变率下压缩力学行为的实验研究，获得了实验温度、应变率对其屈服强度及流动应力的影响规律。结果表明:材料在一定的温度区间（?40～300 ℃）和应变率区间（0.001～3 000 s?1）内，分别呈现出较为明显的温度效应与正应变率效应；其中在较低的温度（?80～?40 ℃）和较高的应变率（3 000～5 000 s?1）区间力学性能受温度和应变率变化的影响较小；当温度升至300 ℃时，材料的塑性变形行为已趋于理想塑性流动。根据前述实验结果，计及材料内部的微观辐照缺陷对力学性能的影响，建立了考虑辐照损伤的Zerilli-Armstrong本构模型，模型的计算结果与前述实验结果吻合较好。结合文献中高纯铝的微观辐照缺陷的演化数据，对不同快中子辐照剂量LT21铝合金的屈服强度，以及另两个来自反应堆内不同受辐照区域试样在不同应变率和温度下的屈服强度进行了计算。上述研究表明，本文建立的考虑辐照损伤的Z-A本构方程不仅能较好地反映长期中子辐照后的Al-Mg-Si合金宏观应力和应变、应变率、温度等参数的关系，也能针对位错运动及辐照硬化机制进行较好地描述，并且能够为反应堆内相应结构元件的设计、运行和安全评估提供一定的参考。

Mechanical behavior of long-term neutron-irradiated Al-Mg-Si alloy under compression

The mechanical behavior of Al-Mg-Si alloy after long-term neutron irradiation (i.e. LT21 aluminum alloy served in the reactor for nearly 30 years) under compression loading with different temperature and strain rates is experimentally studied using material test system and split Hopkinson pressure bar. The effects of temperature and strain rate on its yield strength and flow stress are obtained. The results show that the material exhibits obvious temperature effect within a temperature rang from ?40 ℃ to 300 ℃ and positive strain rate effect in a strain rate rang from 0.001 to 3 000 s?1, respectively. At a lower temperature range (from ?80 to ?40 ℃) and higher strain rates (from 3 000 to 5 000 s?1), the mechanical properties are insensitive to changes in temperature and strain rate. When the temperature reaches 300 ℃, the plastic deformation behavior of the material tends to ideal plastic flow. Based on the above experimental results, a modified Zerilli-Armstrong constitutive model considering irradiation damage is established by taking into account the effect of microscale irradiation defects on the mechanical properties of materials. The Zerilli-Armstrong model predictions are in good agreement with the experimental results. Furthermore, the yield strength of LT21 aluminum alloy with different fast neutron irradiation doses and the yield strength of another two samples obtained from different irradiated regions within the reactor at different strain rates and temperature are calculated by reference to the evolution of microscale irradiation defects of high purity aluminum. The above research shows that the Zerilli-Armstrong constitutive equation considering radiation damage established in this paper can not only establish the relationship between macroscale stress and strain, strain rate and temperature of the Al-Mg-Si alloy after long-term neutron irradiation, but also describe the dislocation motion and the mechanism of irradiation hardening. It can provide reference for the design, operation and safety evaluation of the corresponding structural elements in the nuclear reactor.