位错载氢运动对材料氢脆行为的影响

EFFECT OF HYDROGEN TRANSPORTATION BY DISLOCATIONS ON HYDROGEN EMBRITTLEMENT OF MATERIALS

位错载氢运动会导致金属结构材料中氢原子的再分布和氢损伤的加剧,但目前仍缺乏相关实验数据支撑。本文首先对比了高锰钢预充氢后在四种应变速率(1×10^(-3) s^(-1),1×10^(-4) s^(-1),1×10^(-5) s^(-1)和1×10^(-6) s^(-1))下的断口特征,随后结合理论计算探究了不同应变速率下位错载氢对金属材料氢脆行为的影响。结果表明较慢应变速率(1×10^(-5) s^(-1) and 1×10^(-6) s^(-1))下拉伸的试样具有比较快应变速率(1×10^(-3) s^(-1)和1×10^(-4) s^(-1))拉伸时更高的氢脆敏感性和更大的断口脆性区面积。这是因为较慢应变速率下拉伸时,氢可以随位错运动,导致在塑性变形过程中形成更大的氢原子扩散距离和脆性区深度。此外,在更慢的应变速率(1×10^(-6) s^(-1))下,晶界处可以富集更多的氢,导致断口具有最大的脆性区面积。但是由于塑性变形过程中形成大量对氢原子具有强束缚作用的缺陷,导致实际位错载氢运动距离远低于理论位错载氢运动距离。

Hydrogen transportation by dislocation could lead to the redistribution of hydrogen atoms and aggravation of hydrogen damage in structural metals,but it lacks the support of experimental results.In this paper,the high-Mn steel fracture characteristics after hydrogen pre-charged under four strain rates(1×10^(-3) s^(-1),1×10^(-4) s^(-1),1×10^(-5) s^(-1) and 1×10^(-6) s^(-1))were firstly compared.Subsequently,theoretical calculations were combined to evaluate the effect of dislocation transported hydrogen on hydrogen embrittlement behaviors of metals under different strain rates.The results show that hydrogen embrittlement sensitivity and brittle area degree under the lower strain rates(1×10^(-5) s^(-1) and 1×10^(-6) s^(-1))were higher than those under the higher strain rate(1×10^(-3) s^(-1) and 1×10^(-4) s^(-1)).Hydrogen atoms could move farther due to the dislocation transported hydrogen under low strain rate,resulting in a longer hydrogen movement distance and a deeper brittle zone depth.In addition,more hydrogen atoms could be enriched at the grain boundary resulting in the largest area of brittle zone in the fracture at the slowest strain rate(1×10^(-6) s^(-1)).However,due to the formation of defects with strong binding energy of hydrogen atoms during the plastic deformation,the actual distance of dislocation transported hydrogen was much lower than the theoretical value.