Dresden 2006 – wissenschaftliches Programm

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MM: Metall- und Materialphysik

MM 12: Symposium Severe Plastic Deformation III

MM 12.2: Fachvortrag

Dienstag, 28. März 2006, 10:45–11:15, IFW A

Large plastic deformation of binary FeCr alloys - a new approach to understand the creep properties of tempered martensite ferritic steels — •Gunther Eggeler — Institut für Werkstoffe, Ruhr-Universität Bochum, Germany

In the present study we use equal channel angular pressing (ECAP) to strongly deform a binary Fe10Cr alloy. The ECAP parameters are adjusted such that the Fe10Cr alloy develops an ultra fine grained microstructure which appears to be very similar to the microstructure of a tempered martensite ferritic reference steel (German grade X20). We use transmission (TEM) and scanning electron microscopy with orientation imaging (SEM&OIM) to investigate grain sizes, grain shapes and grain orientations in both materials. While the two materials show very similar ultra fine grain microstructures, the grain boundaries of X20 are stabilized by carbides. We perform creep experiments on both materials and compare creep curves as well as the evolution of microstructures during creep. The results show how imported boundary carbides are in providing the good creep resistance of tempered martensite ferritic steels. The martensitic transformation (accompanied by strong internal stresses and strains) which represents an essential first step in the heat treatment of tempered martensite ferritic steels and the subsequent aging result microstructures which in the absence of a martensitic transformation can only be established by severe plastic deformation.