The investigator Ramón Jerez-Mesa of the MECAMAT research group, explores in his last paper the effects of severe plastic deformation on surfaces of metastable austenitic AISI 301LN Steel. This kind of alloys are also referred to as transformation induced plasticity steels (TRIP), because their austenitic phase is transformed into martensite by means of cold plastic deformation, hence increasing their hardness and reducing their ductility. This is the reason why these steels are used to manufacture security elements for vehicles to prevent excessive deformation of the chassis in case of impact, thus promoting safety of the passengers.

Specifically, this article tackles with different AISI 301LN sheets, each of them with different quantities of martensite in their original microstructure as a consequence of various deformation regimes in the lamination process to prepare the raw material. The effect of that quantity of martensite on the surface topology and microstructure after applying a ball burnishing process is explored in the paper. The observations in the article lead to conclude that the effect of the original contents of martensite is very influential in the results after ball burnishing. The more quantity of original martensite, the less conspicuous are the effects of the mentioned deformation mechanisms. Furthermore, SEM micrographs of the outer nanolayer of the treated material, exposed after FIB micromachining of the surface, evidences that a nanograin layer is created on the surface by means of ball burnishing. The limitation of the microscopical scale to understand the effects of ball burnishing on this kind of steels, joint to the latter result, proves that the issue should be addressed by reducing the exploration scale to a nano scale, before this kind of materials are applied on actual automobile applications.