Gökhan Orhan

Continuous Casted Aluminum Flat Products Corrosion Characteristic According to Downstream Process

This study investigates the change in corrosion behavior with different temper parameters in alloyed sheet products (1050–3003–5005 and 8006) produced by twin roll continuous casting method. Corrosion properties of alloys were determined by electrochemical and salt tests according to ASTM B117 standard. Experimental studies have shown that corrosion characteristics of the alloy composition and annealing temperature are greatly affected.

Corrosion Behavior of B and Ti Grain-Refined Sr-Modified A356

Corrosion behavior of A356 aluminum alloy with different grain refiners was evaluated. For this purpose, the Sr-modified A356 alloy was grain refined with Al5Ti1B and Al3B, and then, the corrosion characteristics were determined. For the mechanical properties, impact and Vickers hardness tests were carried out. To determine the corrosion behavior, both the electrochemical impedance spectroscopy technique and by potentiodynamic polarization plots were carried out in a 3.5 wt.% NaCl solution at 25 °C. The corrosion resistance of A356 alloy was dramatically improved in sequence with the following modifications compared to the unmodified castings: Sr, Ti and B additions. This situation applies to both different cooling rates, namely die and sand casting. The increase in corrosion rate was more than 80% for all alterations of the microstructure. Additionally, charge transfer resistance was increased ten times in die cast samples, while this value was 2.5 for sand cast samples compared to the unmodified alloy. It is important to note that sand casting of the unmodified alloy was improved four times with regard to the die cast unmodified A356.

An Electrochemical Investigation of Mg–Ni Hydrogen Storage Alloys by Mechanical Alloying

The characteristics and mechanisms of enhanced electrochemical properties for Mg–Ni alloy produced by mechanical alloying MA were investigated by electrochemical measurements. Electrochemical hydrogen storage properties were characterized by cyclic charge–discharge experiment, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. The phase composition and microstructure of Mg–Ni alloy were detected by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD showed that the alloys exhibit dominatingly amorphous structures. And also, 20 h milling was enough to obtain amorphous/nano-crystalline alloy structure. The best initial discharge capacity (489 mA h g−1) and acceptable capacity retaining rate (48%) were obtained for the 20 h milled Mg50Ni50 alloy.

The Effect of Temperature on Electrochemical Codeposition of Mg–Ni Hydrogen Storage Alloys from Molten Salt System

A Mg–Ni hydrogen storage alloy was produced as a film by molten salts electrolysis and diffusion process. Mg and Ni was co-deposition on a nickel substrate from 20 wt% MgCl2 + 2 wt% NiCl2 and balans NaCl + KC1 mixture. The electrodeposition was conducted at 700–750 °C and constant current density of 0.5 A cm−2 for 60 min. The phase composition and microstructure of Mg–Ni alloy were detected by X-ray diffraction (XRD) and scanning electron microscope (SEM). The electrode performance in 6 M KOH solution were characterized by cyclic charge–discharge experiment. The best initial discharge capacity (375 mAhg−1) and acceptable capacity retaining rate (70%) were obtained at the 750 °C alloy.