Manuel Castro-Román

New Insight into the Electrochromic Properties of Iron Oxides

We report on the structural, optical and magnetic properties of iron oxide films that were electrochemically cycled in a LiOH aqueous solution. We found that the electrochromic phenomenon is linked to the transformation of the film morphology; it goes from round-shaped particles to platy morphology. Additionally, the following phenomena were observed: a gradual blue shift of the optical-absorption edge, an increase of the saturation magnetization and the appearance of new Raman bands. The change of these properties helped us to understand the coloration mechanism for electrochromism in iron oxides.

Effect of Immersion Routes on the Quenching Distortion of a Long Steel Component Using a Finite Element Model

Distortion while quenching steel is a commonly found problem in industrial practice. This issue arises from the combined effect of thermal contraction and martensite transformation stresses. This problem may be exacerbated in components with long geometries. This work presents the results of a numerical and experimental investigation that assessed the effect of both the austenite grain size (AGS) of three sizes 8, 9 and 10 ASTM, and the immersion route on the distortion of a long component of SAE 5160 steel during oil quenching. The transformation kinetics were calculated using JMatPro and were validated by quench dilatometry. A three-dimensional finite element model was developed in Deform 3D. This model was then validated using thermocouple data. Results showed that the distortion was minimized when the long component was dipped sideways in the quenching medium instead of immersing the component from the distal ends when the AGS was 8 ASTM.

Characterization of Inclusion Populations in Mn-Si Deoxidized Steel

Four plant heats of Mn-Si deoxidized steel were conducted to follow the evolution of the inclusion population through ladle furnace (LF) treatment and subsequent vacuum treatment (VT). The liquid steel was sampled, and the chemical composition and size distribution of the inclusion populations were characterized. The Gumbel generalized extreme-value (GEV) and generalized Pareto (GP) distributions were used for the statistical analysis of the inclusion size distributions. The inclusions found at the beginning of the LF treatment were mostly fully liquid SiO2-Al2O3-MnO inclusions, which then evolved into fully liquid SiO2-Al2O3-CaO-MgO and partly liquid SiO2-CaO-MgO-(Al2O3-MgO) inclusions detected at the end of the VT. The final fully liquid inclusions had a desirable chemical composition for plastic behavior in subsequent metallurgical operations. The GP distribution was found to be undesirable for statistical analysis. The GEV distribution approach led to shape parameter values different from the zero value hypothesized from the Gumbel distribution. According to the GEV approach, some of the final inclusion size distributions had statistically significant differences, whereas the Gumbel approach predicted no statistically significant differences. The heats were organized according to indicators of inclusion cleanliness and a statistical comparison of the size distributions.