AF1410钢的旋转弯曲疲劳破坏行为

 通过力学性能测试、微观组织和疲劳断口形貌的扫描电镜（SEM）分析等方法系统研究了一种双真空工艺熔炼的高纯度超高强度钢（AF1410）的高周旋转弯曲疲劳破坏特性及非金属夹杂对其疲劳性能的影响。结果表明：AF1410钢经510℃回火5h后，具有优异的综合力学性能，其旋转弯曲疲劳极限强度达到826MPa；通过疲劳断口的SEM观察，试验用AF1410钢的旋转弯曲疲劳裂纹源均起裂于试样表面的加工缺陷，如刀痕、细微缺口等，这些表面缺陷引起的应力集中是导致其疲劳开裂的主要原因；稀土元素La的加入使得高纯AF1410钢弯曲疲劳断口中出现细小圆形的含La非金属夹杂物，但该类稀土夹杂并未成为旋转弯曲疲劳断裂的裂纹源。

Behavior of Rotating-Bending Fatigue Failure of AF1410 Steel

High-cycle rotating-bending fatigue properties of high clean ultra-high strength steel AF1410 melted by VIM+VAR were investigated, and then the effect of nonmetal inclusion on fatigue properties in steel systematically was analyzed by mechanical test, analysis of microstructure and SEM of fractures. The results show that, after temper 5 hours at 510℃, AF1410 steel has excellent combined mechanical properties. Rotating-bending fatigue limit of the AF1410 steel reaches to 826MPa. By SEM of fractures, all the crack origins of fatigue stem from process flaws such as cutting marks, fine break. The main reason to lead to crack growth is stress concentration caused by surface flaw. One small and round non-metallic inclusion including La appears in the fractures of high clean steel AF1410 because of the addition of La. However, these inclusions can’t be the crack origins of fatigue.