STRUCTURE-ANALYSIS OF AUSTENITIC CRMN STEEL ALLOYED BY NITROGEN

The aim of this work is a structural analysis of austenitic CrMn steel alloyed with nitrogen (P900). Experimental work concentrated on the t winning crystallography and discontinuous reaction of Cr2N nitrides. T ransmission electron microscopy and diffraction of thin foils were the most important experimental techniques used in present study. Attenti on was concentrated on the microscopy of interfaces and the surroundin g areas. Microdiffraction, selective diffraction and bright field and dark field imaging techniques were predominantly used. Using these tec hniques made it possible to obtain composed diffractograms, to establi sh which spot belonged to a particular phase and to obtain simple micr odiffraction patterns from real crystals. The width of the twins and t heir distances are related to dislocation ordering into slip bands dur ing cold working. Wide and thin slip bands change alternatively. A cer tain level of tension results in the formation of twins in the slip ba nds. The orientation relationships between Cr2N and the matrix were de termined. Various symmetries of their mutual position were also found. Discontinuous precipitation of Cr2N nitrides seems to be dependent on the previous cold deformation. (C) 1998 Elsevier Science S.A. All rig hts reserved.