应变速率对预充氢DP780钢氢脆敏感性的影响

Effect of Strain Rate on Hydrogen Embrittlement Susceptibility of DP780 Steel with Hydrogen Pre-charging

利用电化学预充氢和慢应变速率拉伸实验研究了不同应变速率(10^(-4)、10^(-5)和10^(-6) s^(-1))条件下DP780钢的氢脆敏感性。结果表明,随应变速率降低,材料的氢脆敏感性增强,但其变化幅度与初始预充氢状态有关。当预充氢电流密度较小时,充氢量少且钢中无初始氢致裂纹,随应变速率降低,更多氢原子可扩散至试样心部应力集中处,导致断口心部脆性区域宽度增加,氢脆敏感性增强。但当预充氢电流密度较大(≥30 mA/cm^(2))且充氢量大于8.5 mg/L时,钢中产生的初始氢致裂纹会影响氢原子向心部扩散与聚集,同时其本身可捕获H原子产生氢脆,使材料氢脆敏感性随应变速率增加幅度减小。

The hydrogen embrittlement susceptibility of DP780 steel under different strain rates(10^(-4), 10^(-5) and 10^(-6) s^(-1)) was studied by means of slow strain rate tensile test and electrocheminal hydrogen pre-charging. The results showed that the hydrogen embrittlement susceptibility increased with decreasing strain rate, while the decreasing increment of the hydrogen embritttlement susceptibility was related to the hydrogen pre-charging parameters. When the pre-charging current density was low, precharged hydrogen content was low and there was no hydrogen-induced cracks in the steel. More hydrogen atoms could diffuse to the center of sample with the decreasing strain rate, which led to the increasing width of brittle region in fracture surface center portion and hydrogen embrittlement susceptibility of the steel. However, when the pre-charging hydrogen current density was over 30 m A/cm^(2), pre-charged hydrogen content increased to 8.5 mg/L and the initial hydrogen-induced cracks generated in the steel could act as hydrogen traps, which could influence the inward diffusion and aggregation of hydrogen,therewith induce hydrogen embrittlement as a result of capturing hydrogen atom. Therefore, the hydrogen embrittlement sensitivity of the steel decreases with the increase of strain rate.