氢含量对Zr-Sn-Nb-Fe合金静动态力学性能的影响

Effect of Hydrogen Content on Static and Dynamic Mechan-ical Behavior of Zr-Sn-Nb-Fe Alloy

摘要:

锆合金包壳材料在加工过程及反应堆内运行过程中都不可避免会发生吸氢，而其静动态力学性能的变化与氢含量有着密切的联系。采用气相渗氢的方法，获得了氢含量在23~132 μg/g范围的试样，研究了氢含量对Zr-Sn-Nb-Fe合金静动态力学性能的影响。结果表明，微量渗氢后的锆合金极限抗拉伸强度、屈服强度及延伸率的变化并不明显。渗氢前后的拉伸试样表面存在大量韧窝，是典型的韧性断口。而微量渗氢后的Zr-Sn-Nb-Fe合金冲击韧性出现大幅下降。未渗氢的冲击样品断口基本呈现韧性断裂为主，结合微量解理断裂的混合断裂机制。随着渗氢量的增加，氢化物出现。冲击加载条件下的高应变速率变形则会导致合金微观组织结构中出现二次裂纹，二次裂纹的萌生及扩展是冲击韧性降低的主要原因。

Abstract:

Zirconium alloy cladding materials inevitably undergo hydrogen absorption in the processing and operation process of the reactor, and its static and dynamic mechanical properties are closely related to the hydrogen content. Samples with hydrogen content ranging from 23 μg/g to 132 μg/g were obtained using the method of gas-phase hydrogen charging, and the influence of hydrogen content on static/dynamic mechanical properties of Zr-Sn-Nb-Fe alloy was studied. The results show that the effect of weak hydrogen charging on the ultimate tensile strength, yield strength, and elongation of zirconium alloy is not obvious. There are a large number of dimples on the fracture surface of the tensile sample before and after hydrogen charging, which is a typical ductile fracture. However, the impact toughness of Zr-Sn-Nb-Fe alloy decreases significantly after trace hydrogen charging. The impact sample without hydrogen charging shows the mixed fracture mechanism of ductile fracture and microcleavage fracture. The increase in hydrogen permeability leads to the emergence of hydride, and the deformation of high strain rate under the impact loading condition leads to secondary cracks in the microstructure. The initiation and expansion of the secondary cracks is the main reason for the reduction of the impact toughness.