Texture Analysis of rolled steel sheets by X-Ray and Electron Diffraction (EBSD)

Černík M., Hrabčáková L., Leško A.

U. S. Steel Košice, s.r.o., Slovak Republic

The rolled IF and TRIP steel sheets were evaluated by X-ray and electron diffraction methods. Textures were measured by X-ray diffraction using texture goniometer with Mo X-ray tube, employing (110), (200) (112) and (103) crystallography planes. EBSD camera was used for texture measurements by electron diffraction. ODF – orientation distribution functions were calculated from texture-measured data by use of shf – spherical harmonic function, WIMV and ADC methods. Both, X-ray and EBSD data obtained very good agreements on texture characterizations of non-grain oriented (NGO) steels in relation to their magnetic properties. The EBSD methods allow obtaining more structural information: IPF maps, grain shape, size, crystal orientation of selected grains and others.

The partially annealed IF steel sheet sample EBSD analysis shows directly the texture of individual grains, X - ray diffraction method gives the material complex texture. EBSD method allows categorizing grains according to proper criteria. The criteria ”Grain average disorientation” was used for grains categorizing into two groups; re-crystallized and deformed grains.

The rolled IF steel sample texture was formed by alpha and gamma fibers. The final texture was the superposition of the deformation and recrystallization texture. The deformation texture was formed by uncompleted alpha fiber with (001)<011>, (113)<011>, (223)<011> texture elements. The recrystallization texture was formed by gamma fiber with (111)<011> to (111)<112> texture components.

The EBSD method allows analyzing samples with complex phase composition. Comparing the X – ray diffraction method, which is limited by material texture, the retained austenite content in rolled steel sheets can be directly and exactly determinate by EBSD method. At the same time the texture is obtained for particular phases too, in this case the texture of ferrite and residual austenite. The EBSD method provides data about grain size and shape, boundaries characteristics for all present phases.

The rolled TRIP steel sample ferritic phase was formed by strong gamma fiber (111)<011> to (111)<112> and by small amount of (100)<011> and (110)<001> texture components. The retained austenite content was estimated for 5,2 %. The residual austenite texture was formed by Goss - (110)<001>, Brass - (110)<112> texture components and a small amount of Copper - (112)<111> component.