Nanosized substructure of heat-treated high-strength cast iron

Abstract

This paper presents the results of investigating the microstructure of high-strength VChTG cast iron by the methods of scanning electron and atomic-force microscopy and x-ray phase analysis. A nanosized substructure of ferrite, perlite, and graphite phases of the cast iron has been revealed. An ordered sandwich multilevel structure of ferrite in the initial VChTG in the form of steps of width 400–600 nm and height about 100 nm consisting of bands of width 30 nm and interband height 3–10 nm has been established. It has been shown that the width of cementite lamellae in perlite varies from 200 to 400 nm, and the lamellae themselves consist, in turn, of sublamellae of width 30 nm. Graphite inclusions consist of layered crystallites of diameter 5–200 nm with a thickness of individual layers of 0.7–1.4 nm. Upon heat treatment the size of bainite subgrains is 100–300 nm. It has been shown that there is s relation between the size of the shift of subgrains for heat-treated VChTG revealed by atomic-force microscopy and microdistortions of the α-phase lattice determined by x-ray analysis.