Texture analysis of oxide dispersion strengthened (ODS) Fe alloys by X-ray and neutron diffraction

摘要

The ferritic ODS alloys studied were obtained by mechanical alloying. This strengthening method is very attractive, in particular for nuclear applications. In order to ensure the alloy a good compromise between mechanical resistance and ductility at high temperatures, it is necessary to control the microstructure and in particular the evolution during the recrystallization. First, a preliminary study, performed by X ray diffraction and optical microscopy, shows several grain growth mechanisms; in particular, the "abnormal" grain growth mechanism which conducts to a large grain size [1], [2]. After annealing (3600s at 1470 ℃), the 30% cold-worked (swaging) alloys exhibit an heterogeneous microstructure with a large grains size (～200 to 500 μm) in the heart and near the surface of the material when the intermediate zone is inhabited by small grains (～1 μm). For a higher cold-work level (60%), large size grains are only present in the periphery of the material. On account of the large grain size and strong heterogeneity of the microstructure, texture analysis using laboratory x-ray beam in not well adapted and so we have decided to use neutron beam. The neutron diffraction texture analysis has been performed at the Laboratoire Leon Brillouin on the 6T1 diffractometer on 2 different rods of the alloy (corresponding to the reduction ratios of 30% and 60%). Specific samples have been machined to characterise separately the zones with a different microstructure. After deformation, the alloys exhibit a typical α-fibre texture {hkl}<110>～ whatever the area of the sample and the reduction ratio. After recrystallization, a very inhomogeneous texture is evidenced through the thickness of the sample, in particular for the rod deformed with a reduction ratio of 30%: in the heart and in the periphery of the rod, a "single-crystal" type texture is observed; the α fibre remains for the intermediate diameter of the rod. For the rod cold rolled with a reduction ratio of 60%, the α-fibre keeps on the heart of the material and as in the precedent case, a "single-crystal" type texture is observed near the surface of the sample. EBSD measurements have been performed to explicit at explicit at a local scale this behaviour and in order to furnish some input data for the simulation of static recrystallization.