Mapping complex microstructures in powder metallurgy steels

Abstract

New methods of characterising multiple phase powder metallurgy steels have been investigated. Mapping of microhardness with a lateral resolution of as little as 5 μm and with up to 10⁴ indents can produce distributions of mechanical properties which are characteristic of different steel grades. Maps of these properties can be correlated with the different phases observed in etched microstructures, and quantification of size and interconnectivity of the regions with, for example, different hardness or stiffness is then possible. Electron backscatter diffraction can also produce simultaneously highly detailed maps of the different phases in a powder metallurgy steel with chemical composition information. Percentages of the different phases present can be determined from the crystallography and morphology of the grains observed, but the technique is limited by the speed with which maps can be acquired.