Researchers from the Spain’s Universidad Carlos III de Madrid (UC3M) have identified new techniques to better understand the behaviour of sintered steels on fracturing. Scientists from the UC3M Powder Technology Group (GTP) have carried out research using a scanning electron microscope to obtain high-resolution images showing how these steels fracture when extreme loads are applied to them.

The materials that are the subject of the research are commercial sintered steels widely used in the automobile industry. Specifically, an Fe-C steel, a steel pre-alloyed with molybdenum (Astaloy Mo grade, Höganäs AB) and the well-known Distaloy AE (Höganäs AB), which is iron alloyed by diffusion with copper, nickel and molybdenum.

The results have helped in understanding the connection between microstructure and properties, which in these materials, it is claimed, entails a technological challenge as not only the phases but also the residual porosity that composes their microstructure come into play. Professor José Manuel Torralba, in the UC3M department of Materials Science and Engineering and Deputy Director of the IMDEA Materials Institute, stressed the fundamental role of porosity in these steels. “The research has revealed, among other things, that the most angular and irregular pores are the first points of ‘nucleation,’ that is, those that initiate the breaking,” stated Prof Torralba.

"Mechanical and on-site characterisation tests performed in the scanning electron microscope have been essential in understanding the mechanisms of fracture,” which, until this research, “we have never been able to determine, but instead only intuit,” added Elena Bernardo, one of the authors of the study from the UC3M Powder Technology Group.

This study has made it possible to view changes in the microstructure of the material while it is being tested. Moreover, the methodology used is claimed to be applicable to any type of alloy and not only to test its behaviour under pressure, but also its behaviour at high temperatures.