Tetragonality mapping of martensite in a high-carbon steel by EBSD

The locally varying tetragonality in martensite grains of a high-carbon steel (1.2 mass percent C) was resolved by electron backscatter diffraction (EBSD) with a spatial resolution in the order of 100 nm. Compared to spatially integrating X-ray diffraction, which yielded an average tetragonality of c/a = 1.05, the EBSD measurements in the scanning electron microscope allowed to image a local variation of the lattice parameter ratio c/a in the range of 1.02 < c/a < 1.07. The local variation of tetragonality is confirmed by two different EBSD data analysis approaches based on the fitting of simulated to experimental EBSD patterns. The resulting EBSD-based tetragonality maps are pointing to a complex interaction of carbon concentration and local lattice distortions during the formation process of martensitic structures.

Automated summary

The study used electron backscatter diffraction (EBSD) to resolve the locally varying tetragonality in martensite grains of a high-carbon steel, revealing a local variation of lattice parameter ratio and confirming a complex interaction between carbon concentration and local lattice distortions during the formation process of martensitic structures.