基于小冲杆试验技术评估充氢锆合金材料的拉伸性能

Evaluation of Tensile Properties of Hydrogen-charged Zirconium Alloy Materials Based on Small Punch Test Technique

摘要:

锆合金由于具有良好的机械性能、耐腐蚀性能等而被用作反应堆内燃料元件的包壳材料。然而，Zr-4已不能满足核电技术在更高燃耗条件下的使用要求，因此，通过调控合金成分开发新型锆合金具有重要意义。本研究对Zr-4以及其他两种新型锆合金材料在室温、315℃条件下进行常规拉伸试验，结合计算结果分析了成分差异造成的沉淀相改变，提出了析出强化机制对于锆合金性能提升的重要意义。首次利用小冲杆试验对锆合金原样的力学性能进行测试，该工作确定了常规拉伸试验与小冲杆试验结果之间的经验公式中与锆合金材料本身相关的系数数值，验证了小冲杆试验用于锆合金拉伸性能评估的可行性。利用气相渗氢法在400℃对Zr-4以及其他两种新型锆合金进行充氢处理，并利用小冲杆试验对锆合金充氢试样的力学性能进行测试。结果显示，充氢锆合金在载荷-位移曲线的塑性失稳阶段出现“平台区”特殊现象。本论文对该现象进行探究，用金相分析表征了氢化物的形貌特征并对其含量进行了定量估算，推测氢化物与基体断裂韧性上的差异、氢化物相特殊的长链构型以及强取向性与这一现象有着重要关联。

Abstract:

Zirconium alloys are used as cladding materials for fuel components in reactors due to their excellent mechanical properties, excellent corrosion resistance and low thermal neutron absorption cross-section. However, Zr-4 can no longer reach the requirements of nuclear power technology under higher burn-up conditions. Therefore, it is of great significance to develop new zirconium alloys by regulating the alloy composition. In this study, Zr-4 and two other new zirconium alloy materials were subjected to conventional tensile tests at room temperature and 315℃. The precipitation phase changes caused by composition differences were analyzed based on the calculation results. And the importance of precipitation strengthening mechanism was proposed for the performance improvement of zirconium alloys. The mechanical properties of zirconium alloy were tested for the first time by using small punch test. The coefficient values related to the zirconium alloy material itself were determined in the empirical formula between the conventional tensile test and the small punch test. The feasibility of the small punch test for the evaluation of the tensile properties of zirconium alloys was verified. Zr-4 and two other new zirconium alloys were hydrogen-charged at 400°C by gaseous hydrogen permeation, and their mechanical properties were tested by SPT. The results show that the hydrogen-charged Zr alloys have a special phenomenon of "platform region" in the plastic instability stage of the load-displacement curve. In this paper, the morphological characteristics of hydrides were characterized by metallographic analysis and their contents was quantitatively estimated. It was speculated that the difference in the fracture toughness between hydrides and matrix, the special long chain configuration of the hydride phase and its strong orientation have an important correlation with this phenomenon.