Study of thermal expansion anomalies of multilayer steel materials at high temperatures

The paper presents the results of a study of the anisotropy of the thermal coefficient of linear expansion (CTE), which was found in a multilayer metallic material based on steels, made by hot batch rolling. It is established that the material consisting of alternating layers of steel, has abnormally low CTE values in the direction perpendicular to the rental plane. To explain this phenomenon, a hypothesis was proposed about the relationship between normal and tangential stresses arising at the interlayer boundaries of such material. The confirmation of the hypothesis of the leading role of reactive stresses in the manifestation of the specified invar effect are the results of metallographic analysis. It is also shown that the conduct of cyclic high-temperature heating provokes recrystallization at the interlayer boundaries caused by the difference in the thermal expansion coefficient values of the adjacent layers and the effect of high temperature. (paper)