A study of fatigue mesoscopic elasto-plastic properties of a nickel-base superalloy by instrumented microindentation measurements

In this study the fatigue mesoscopic elasto-plastic properties of nickel-base superalloy GH4145/SQ were investigated using the instrumented microindentation testing coupled with the analytic calculation. The indentation characteristic parameters of low-cycle fatigue specimens, such as the indentation curvature (C), the maximum penetration depth (hmax), the initial unloading slope (S), the residual depth of penetration (hr), the recovered elastic work (We) and the residual plastic work (Wp), were determined from the experimental load–penetration depth (P–h) curves, and the fatigue mesoscopic elasto-plastic properties (E, σy and n) were estimated using a well-developed analysis algorithm proposed by Dao et al. The distribution patterns of the fatigue mesoscopic mechanical properties were further verified in a statistical sense. The dependence of the fatigue mesoscopic elasto-plastic properties upon the imposed strain amplitude was discussed preliminarily in terms of microstructural examinations of fatigue failure specimens.