Residual stress and localized lattice rotation under fatigue loading

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:763

Article

Goswami, R.¹  Qadri, S. B.¹  Feng, C. R.¹  Pande, C. S.¹ 

[1] Naval Res Lab, Div Mat Sci & Technol, Washington, DC 20375 USA

关键词: Lattice rotation;    Fatigue;    TEM;    Dislocations;    Residual stresses;   

DOI  :  10.1016/j.msea.2019.138113

来源: Elsevier

【 摘 要 】

A significant change in residual stress around a fatigue crack has been observed in Al alloys. For Al 7075, the residual stress increases by 200% closer to the crack. However, in commercially pure Al (Al 1100), the residual stress decreases by 80% closer to the crack. The residual stresses are mostly the stored elastic energy as a result of deformation around the fatigue crack. To understand these results, we estimate the dislocation density as a function of distance from the crack using the full width at half maxima of 111 reflection for both alloys. The dislocation density increases by 25-30 % for Al 7075. However, it actually decreases by 10% for Al 1100. Such change in dislocation density cannot explain the observed change in residual stress closer to the crack. Additionally, the deformation leads to a significant lattice rotation, as observed by the x-ray diffraction and the electron backscatter diffraction measurements. We argue that dislocations are needed to produce the lattice rotation and the estimated lattice rotation is approximate to 11 degrees, and conclude that the deformation associated with the lattice rotation would be a major contributing factor to the residual stress. This provides a new insight on the role of lattice rotation on the residual stress under fatigue loading.

【 授权许可】

Free