Research

The electrochemical behavior of different phases (ferrite, austenite, martensite, cementite) and effect of alloying addition in ferrous alloys was examined in acidic media. A comprehensive thermodynamic model, incorporating first-principles calculations, was constructed to predict cathodic and anodic behavior in acidic environments. Cementite emerged as the most corrosion resistant phase, followed by austenite, while ferrite displayed the least resistance. Interestingly, carbon additions improved corrosion resistance in ferrite and austenite. Alloying with Cr, Mn, and Cu was observed to hinder anodic dissolution, reducing electrochemical activity. Finally, the thermodynamic framework provides a reliable and efficient screening tool that can accelerate the development of alloys and coatings. 

Magnesium alloys have drawn considerable attention for several engineering applications, owing to their excellent properties like low density and high specific strength. The room temperature ductility and mechanical properties of Mg are usually enhanced by alloying additions. Based on the thermomechanical processing, the presence of critical concentration of alloying element typically leads to the formation of stable binary intermetallic phases with Mg thereby, distinctly altering the microscopic electrochemical properties of the alloy. However, the secondary intermetallic phases in Mg alloys are typically of sub-micron size, thus accurate electrochemical characterization is a challenging issue. Using first-principles calculations, the electrochemical behavior of various Mg intermetallics was comprehensively quantified. Based on the predicted corrosion potential, apart from Mg2Ca which behaves as an anode to the Mg matrix, the rest of the Mg-based intermetallics act as a cathode. The electrochemical polarization behavior of the intermetallics was strongly dependent on surface-mediated properties (surface energy and work function) and chemical bonding characteristics. Finally, the computational framework provides an accurate screening tool that can assist in alloy design and development of coatings.

Magnesium alloys contain several strengthening phases in the form of stable binary intermetallics which contribute immensely towards the improved mechanical properties of the alloy. To tailor the mechanical behavior of Mg alloys, it is imperative to accurately quantify the elastic properties of secondary intermetallic phases. However, mesoscale predictions of mechanical behavior of these intermetallics experimentally poses to be extremely challenging and prone to errors. Using first-principles calculations, the elastic constants of various Mg intermetallics (Mg17Al12, MgZn2, Mg3Nd, Mg2Si, Mg24Y5, Mg2Ca, Mg12Ce, Mg12La, Mg2Cu, and Mg2Sn) was calculated. All the intermetallics were found to be mechanically stable. Additionally, the ductile/brittle behavior was characterized and it was observed that Mg17Al12, MgZn2, Mg24Y5, and Mg2Cu showed ductile characteristics, while Mg3Nd, Mg2Si, Mg2Ca, Mg12Ce, Mg12La, and Mg2Sn demonstrated brittle nature. Finally, this study provides a comprehensive computational framework to accurately predict the mechanical behavior of Mg intermetallics.