材料期刊网

针对高强度低合金钢、钛合金和镁合金进行了腐蚀疲劳裂纹的扩展FCG、外加电压对于腐蚀疲劳裂纹扩展速率的影响以及断裂表面的研究。在外加电压对于腐蚀疲劳裂纹扩展速率影响的研究过程中，在一段时间内发生极化，可以根据此期间内的开路电压记录裂纹扩展速率，并测量极化情况下的裂纹增长速率。由于裂纹扩展测量技术的进步，测量的时间很少超过300s，这使观测非独立模式阴极极化对于腐蚀疲劳裂纹扩展速率的影响成为可能。当最大应力强度（Kmax）超过给定材料--溶液组合的特定临界特征值时，阴极极化会加速裂纹的扩展。当Kmax低于临界值，而所有其他条件（试件、溶液、pH值、载荷频率、应力比率、温度等）不变时，同样的阴极极化会妨碍裂纹扩展，或者对于裂纹扩展无影响。断口显微分析结果显示，阴极极化下加速裂纹的扩展是由于氢致腐蚀(HIC)。因此，根据氢致腐蚀机理以及KHIC和△ KHIC的显示，Kmax的临界值，以及应力范围（△ K）是由相应的腐蚀疲劳裂纹扩展的症状所确定的。当Kmax > KHIC（△ K > △ KHIC）时，腐蚀疲劳裂纹扩展的主要机理是HIC。对于大多数的材料--溶液组合的研究表明，当Kmax < KHIC（△ K < KHIC）时，应力协助扩散在腐蚀疲劳裂纹扩展中起决定性作用。

The corrosion fatigue crack growth (FCG)behaviour,the effect of applied potential on corrosion FCG rates,and the fracture surfaces were studied for high-strength low-alloy , titanium alloys and magnesium alloys. During investigation of the effect of applied potential on corrosion FCG rates,polarization was switched on for a time period in which it was possible to register the change in the crack growth rate corresponding to the open-circuit potential and to measure the crack growth rate under polarization.Due to the higher resolution of the crack extension measurement technique,the time rarely exceeded 300s.This approach made possible the observation of a non-single mode effect of cathodic polarization on corrosion FCG rates.Cathodic polarization accelerated crack growth when the maximum stress intensity(Kmax) exceeded a certain well-defined critical value characterisitic for a given material-solution combination.When Kmax was lower than the critical value,the same cathodic polarization,with all other conditions(speci-men,solution,pH,loading frequency,stress ratio,temperature,etc.)being equal,retarded or had no influence on crack growth.The results and fractographic observations suggested that the acceleration in crack growth under cathodic polarization was due to hydrogen-induced cracking(HIC).Therefore,critical values of Kmax ,as well as the stress intensity range (ΔK)were regarded as corresponding to the onset of corrosion FCG according to the HIC mechanism and designated as KHIC and ΔKHIC.HIC was the main mechanism of corrosion FCG at Kmax>KHIC(ΔK>ΔKHIC).For most of the material-solution combinations investigated,stress-assisted dissolution played a dominant role in the corrosion fatigue crack propagation at Kmax