Papers by Author: Onuralp Yucel

Abstract: In this study, AZ31 in form of sheet, plate and extruded rod and AZ61 wire with different initial grain sizes were used to investigate the effect of initial grain size on recrystallization behavior and the formation of fine recrystallized grain (the so-called necklace) structure. Nucleation and growth of recrystallized grains along grain boundaries has been examined. In order to observe the effect of initial grain size and deformation on static recrsytallization and necklace formation, the specimens were annealed at 100-250°C for 10min--2hr. Specimens are also stretched to a total strain of 10, 20 and 40% at 300°C at an initial cross head speed of 1x10-3 s-1 for dynamic recrystallization studies. The results suggest that there exists a grain size limit, below which a necklace structure is not observed.

Abstract: In the present study, the production of magnesium metal from Turkish calcined dolomite containing 43.20 % MgO and 47.46 % CaO via Pidgeon process was studied under the pressure of 1 mbar. In the experiments, Turkish ferrosilicon containing 75 % Si and 24 % Fe was used as reducing agent. Effects of FeSi addition (90-150 % of stoichiometric requirement of silicon) and time (60-240 min.) were investigated on recovering of metallic magnesium from calcined dolomite (dolime) at the temperature of 1200 °C. Effects of fluxing additive (CaF2), calcined magnesite and different temperatures on Mg recoveries and concentrations were also studied using with 100 % of stoichiometric requirement of silicon for 180 min. It was found that magnesium recovery increases with increasing FeSi addition, temperature, time, CaF2 addition and decreases with increasing calcined magnesite additions under the pressure of 1 mbar.