EBSD analysis of microstructure evolution of pure iron subjected to sliding wear and related change in vickers microhardness

Abstract

Sliding wear tests were carried on pure iron to investigate evolution of microstructure below worn surface. After the wear tests, grain boundary formation and lattice rotation were analyzed with electron backscatter diffraction (EBSD) method. In the vicinity of the worn surface, submicron grains separated by high-angle grain boundaries were generated. Below the submicron grain region, dominant microstructures were two kinds of low-angle grain boundaries which were horizontal and inclined to the worn surface, respectively. At deeper area from the worn surface, continuous lattice rotation was detected. To correlate the microstructure and strength, Vickers microhardness was measured over a cross section of the wear-affected zone. In the submicron grain and the low-angle grain boundary regions, the microhardness was proportional to the reciprocal square root of boundary spacing. In the lattice rotation region, we calculated geometrically-necessary (GN) dislocation density from gradient of lattice rotation. The microhardness value in the lattice rotation region showed good correlation with the square root of the GN dislocation density. © 2013 The Japan Institute of Metals and Materials.