Iron Alloys

This work describes the inhibition effect of different concentration of an aqueous extracted of Pe-ganum harmala seed on the corrosion of carbon steel in 1 M H2SO4 solution using potentiostatic polarization techniques at the temperature range (298-328) K. The result showed that the inhibition efficiency increased with increasing of extract inhibitor concentration and temperature. The adsorption of inhibitor on carbon steel surface was fit into Langmuir adsorption isotherm. Kinetic and thermodynamic parameters governing the corrosion and the adsorption process were calculated and discussed.

Defect-driven transport of impurities plays a key role in the microstructure evolution of alloys, and has a great impact on the mechanical properties at the macroscopic scale. This phenomenon is greatly enhanced in irradiated materials because of the large amount of radiation-induced crystal defects (vacancies and interstitials). For instance, the formation of nanosized solute clusters in neutron-irradiated reactor pressure vessel (RPV) ferritic steels has been shown to hinder dislocation motion and induce hardening and embrittlement. In Swedish RPV steels, this mechanical-property degradation is enhanced by the high content of manganese and nickel impurities. It has been suggested that the formation of Mn-Ni-rich clusters (which contain also Cu, Si, and P) might be the outcome of a dynamic process, where crystal defects act both as nucleation sites and solute carriers. Solute transport by point defects is therefore a crucial mechanism to understand the origin and the dynamics of the clustering process.

The first part of this work aims at modeling solute transport by point defects in dilute iron alloys, to identify the intrinsic diffusion mechanisms for a wide range of impurities. Transport and diffusion coefficients are obtained by combining accurate ab initio calculations of defect transition rates with an exact mean-field model. The results show that solute drag by single vacancies is a common phenomenon occurring at RPV temperature (about 300 °C) for all impurities found in the solute clusters, and that transport of phosphorus and manganese atoms is dominated by interstitial-type defects. These transport tendencies confirm that point defects can indeed carry impurities towards nucleated solute clusters. Moreover, the obtained flux-coupling tendencies can also explain the observed radiation-induced solute enrichment on grain boundaries and dislocations.

In the second part of this work, the acquired knowledge about solute-transport mechanisms is transferred to kinetic Monte Carlo (KMC) models, with the aim of simulating the RPV microstructure evolution. Firstly, the needed parameters in terms of solute-defect cluster stability and mobility are calculated by means of dedicated KMC simulations. Secondly, an innovative approach to the prediction of transition rates in complex multicomponent alloys is introduced. This approach relies on a neural network based on ab initio-computed migration barriers. Finally, the evolution of the Swedish RPV steels is simulated in a "gray-alloy" fashion, where impurities are introduced indirectly as a modification of the defect-cluster mobilities. The latter simulations are compared to the experimental characterization of the Swedish RPV surveillance samples, and confirm the possibility that solute clusters might form on small interstitial clusters.

In conclusion, this work identifies from a solid theoretical perspective the atomic-transport phenomena underlying the formation of embrittling nanofeatures in RPV steels. In addition, it prepares the ground for the development of predictive KMC tools that can simulate the microstructure evolution of a wide variety of irradiated alloys. This is of great interest not only for reactor pressure vessels, but also for many other materials in extreme environments.

"Solvent extraction of iron (III) from aqueous hydrochloric and sulphuric acid solutions was carried out using Tri butyl phosphine oxide [TBPO] in chloroform as extractant. Stripping of iron (III) from the organic phase was attempted with 2.0M NaOH. Extractions were nearly quantitative with both the acid solutions. Based on the results obtained, estimation of iron in food samples as well alloys was attempted successfully. A.V.L.N.S.H. Hariharan""Extraction of Iron (III) with Tributylphosphine Oxide from Hydrochloric & Sulphuric Acid Solutions"" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-1 | Issue-4 , June 2017, URL: http://www.ijtsrd.com/papers/ijtsrd112.pdf
Article URL: http://www.ijtsrd.com/chemistry/analytical-chemistry/112/extraction-of-iron-iii-with-tributylphosphine-oxide-from---hydrochloric-and-sulphuric-acid-solutions/avlnsh-hariharan"

In this study, nanostructured biodegradable Fe-35wt.%Mn alloy prepared by 10 h high energy
ball milling followed by conventional cold press and sintering. Structural and microstructural
properties were studied by X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy. Corrosion rate, mechanical properties,
biocompatibility and cell adhesion of this alloy were evaluated by SaOS-2 cell line and compared with the unmilled sample. Transmission electron microscopy proved the formation of the nanostructured alloy after sintering. The milled sample had the highest micro-hardness of 98 HV, while compression strength of the unmilled sample was higher. The ultimate
compressive strength and strain of the unmilled sample were 153.4 MPa and 34%,
respectively. Degradation by 60 days decreased both ultimate compressive strength and strain to 138 MPa and 31.5%, respectively. Lower corrosion rate observed for the  milled sample was 1.36 mm/yr. On the other hand, the milled sample enhanced cell adhesion and cell  viability evaluated by MTT assay.