不同桩核材料对四种牙科底层瓷颜色的影响.pdf

第 41 卷第 1 期中南大学学报(自然科学版) Vo l .4 1
2010 年 2 月 Journal of Central South University (Science and Technology) Feb. 2010

不同应力下 7B04 铝合金的疲劳断口

蹇海根,姜锋,文康,黄宏锋,韦莉莉,蒋龙

(中南大学材料科学与工程学院,湖南长沙,410083)

摘要:采用金相、电镜扫描显微技术对不同应力下铝合金的疲劳断口显微组织进行分析和对比研究,揭示该合
金疲劳裂纹萌生与扩展的微观特征。研究结果表明:疲劳裂纹一般在材料表面或近表面处萌生,与表面的距离随
加载应力升高而减小,在应力为 285 MPa 时裂纹于距表面约 250 µm 处萌生,而在 430 MPa 时裂纹萌生于材料表
面;在裂纹源附近观察不到疲劳辉纹,且加载应力越高,这个区域的面积就越小,而裂纹扩展区的疲劳辉纹间距
随应力的增大而增大;裂纹形成后,微裂纹沿着与应力轴呈 45˚角的最大切应力方向向纵深扩展,然后转向与拉
应力轴正交的方向扩展,最后瞬断,且随着应力的增大,断口上疲劳裂纹扩展区的面积减小,瞬断区的面积增大。
关键词:铝合金;疲劳断口;裂纹萌生;裂纹扩展;疲劳辉纹
中图分类号:; 文献标志码:A 文章编号:1672−7207(2010)01−0132−06

Fatigue fracture of 7B04 aluminum alloy under
different stresses

JIAN Hai-gen, JIANG Feng, WEN Kang, HUANG Hong-feng, WEI Li-li, JIANG Long

(School of Materials Science and Engineering, Central South University, Changsha 410083, China)

Abstract: The microstructures of fatigue fracture of Al alloys under various stresses were studied by optical microscope
and scanning electron microscope, and the microscopic features of crack initiation and propagation in this kind of alloy
were revealed. The results show that the fatigue cracks usually initiate at or near the free surfaces of the specimen. And
with the increase of the loading stress, the distance between the crack and the surface decreases. The cracks are 250 µm in
d