The development and testing of a new method of qualitative analysis of the microstructure quality, for example of steel AISI 321 subjected to radial shear rolling

Abstract

The work is devoted to the problem of quantitative evaluation of the microstructure on the example of work with the TEM study of ultrafine-grained (UFG) austenitic steel for use in nuclear power. The material was obtained by radial-shear rolling and has different features of the structural structure of the cross section (from the periphery to the center), which makes it relevant to the correct assessment of the microstructure, taking into account all the features. This is difficult to do correctly, using only existing simple methods (average grain size, degree of grain misalignment, phase ratio) and most importantly, the results can not always be compared with each other. For a more objective and unambiguous assessment of different types of microstructure, a new qualimetric technique for quantitative quality analysis was developed. The new technique made it possible to make a more correct comparison of changes in the quality of the rod microstructure and to evaluate the effectiveness of the technology. According to the assessment, the greatest improvement is experienced by the central zone of the bar, from 0.13 to 0.43, that is, more than 3 times. At the same time, the quality growth of the peripheral region is low (only 1.29 times) and tends to slow down. This is due to the fact that with an increase in the degree of deformation there is no further refinement of the structure, but only improves its shape, becoming more uniform, as also evidenced by the values of the mean square deviation, showing the minimum spread of values. The resulting methodology for the qualimetric evaluation of quality can be used to create free open of image processing algorithms (e.g. MathLab), and for commercial products for quantitative metallographic analysis.