研究了加载频率、溶液pH值、氯离子浓度和氟化物转化膜等对挤压镁合金 AM60疲劳寿命的影响, 讨论了疲劳机理及AlMn相的作用. 结果表明: 在空气中10 Hz以下, 疲劳寿命与频率有一定的关系; 而在10 Hz以上, 疲劳寿命与频率无关. AM60在中性溶 液中疲劳寿命最短, 在碱性溶液中疲劳寿命最长. 氯离子能明显地降低疲劳寿命, 含氟转化膜提高腐蚀疲劳寿命的作用不明显. 断口分析表明, 挤压镁合金AM60疲劳裂纹的形成与AlMn 相粒子有关. 在空气中, 疲劳裂纹源为AlMn相粒子; 而在溶液介质中, 腐蚀疲劳裂纹萌生于AlMn相粒子周围的点蚀坑.
The effect of loading frequencies, pH values, chlorine ions and the fluorine--containing conversion film on fatigue life of as--extruded magnesium alloy AM60 was studied using a tensile--tension fatigue machine. The fractographic morphologies were observed by SEM, and the mechanisms of fatigue and the roles of AlMn particles were mainly discussed. The results showed that the fatigue life in ambient air has some relationship to the loading frequency when the frequency is lower than 10 Hz, and little relationship with ~loading ~frequency ~when ~greater ~than ~10 Hz. The fatigue life decreased in neutral solution, and increased in base solution with pH12. The conversion film containing fluorine can hardly improve the fatigue life. The fractography showed that fatigue crack initiations were related to AlMn particles. Fatigue cracks emanated at AlMn particles in air, while in aqueous solutions, it initiated the corrosion pits bordering upon the AlMn particles.
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