HIGH-TEMPERATURE LOW-CYCLE FATIGUE OF AN IRON-BASE OXIDE-DISPERSION STRENGTHENED ALLOY - GRAIN-STRUCTURE EFFECTS AND LIFETIME CORRELATIONS

The high-temperature low-cycle fatigue (LCF) behavior of the new oxide -dispersion strengthened (ODS) alloy PM 2000 is investigated at 1050 d egrees C using symmetrical and asymmetrical wave shapes. The grain str uctures range from ''single crystals'' (grain size of several centimet ers) to polycrystals with an average grain size of less than 30 mu m. It is found that the grain structure determines the fracture path but cannot be correlated with cyclic lifetimes. Instead, lifetime can be p redicted on the basis of the different Young's moduli of the grain str uctures and correlates with the reciprocal of Young's modulus. A norma lization is proposed that condenses all lifetime data, which span two orders of magnitude, into a narrow scatterband.