Electrochemical Corrosion Study in H2SO4 of NiAl with Cu Additions, Microstructure and Micro-Hardness at Room Temperature

For many years, intermetallic materials promise applications in a wide variety of technology areas. NiAl intermetallic compound is material that exhibits important characteristics such as high corrosion resistance and low density besides its ability to retain strength and stiffness at elevated temperatures. However NiAl intermetallic is too hard, brittle and exhibits very low ductility at room temperature being the reason because this material is not yet available for structural applications. In order to increase the ductility of the NiAl intermetallic compound, the addition of a third alloying element has been proved, nevertheless it is important to determine if such additions decrease or increase the hardness and the corrosion resistance of the alloy. So, the present investigation reports the corrosion performance of the NiAl intermetallic compound modified with Cu, emphasizing the EIS analysis and the relation between physical parameters and the modelling equations used in the Equivalent Electric Circuit. It was found that the addition of Cu promotes the formation of the γ’-Ni3Al phase in Cu contents greater than 15 at. %, in addition to a decrease in micro hardness and an increment in the Icorr values. In this way, the electrochemical characterization evidenced a high corrosion resistance of these intermetallic alloys.

Effects of Mineral Admixtures and Superplasticizers on Micro Hardness of Aggregate-Paste Interface in Cement Concrete

This paper presents quantitatively the results of an experimental investigation on influence of mineral admixtures and superplasticizers on Vickers micro hardness(HV) of aggregate-paste interface in cement concrete. The HV was measured by Vickers hardness testing equipment.The results indicate that addition of fly ash decreases HV of the concrete.Although it decreases with the increase of ground granulated blast furnace slag (GGBS) replacement,the HV is higher than that of concrete containing fly ash at all replacements.The flying ash and GGBS composition increases HV in later curing ages,but does not improve it in early curing ages.Aminosulfonic acid based superplasticizer and aliphatic hydroxy sulphonate condensate superplasticizer can enhance HV in early curing ages.The HV of concrete with polycarboxylic acid superplasticizer is higher in later curing ages.

Mechanical and Electrical Properties of the Ternary Ag-Sb-Zn System

This paper presents comparative review of experimental and thermodynamic assessment of ternary Ag-Sb-Zn system. Isothermal section of the Ag-Sb-Zn system at 300 ~C has been calculated by CALPHAD method using ther- modynamic parameters from literature. Microstructural analysis of a number of alloys was carried out by scanning electron microscopy and optical microscopy, whereas chemical composition of observed phases was analyzed using energy- dispersive X-ray spectroscopy. Hardness of selected alloys from four vertical sections was determined using Brinell hardness test and additionally by micro Vickers hardness test. Electrical conductivity of a number of alloys in the ternary Ag-Sb-Zn system was experimentally determined. Good overall agreement between experimental and calculated values was obtained.