Karabudak, Filiz; Şüküroğlu, Ebru Emine; Şüküroğlu, Süleyman; Yeşildal, Ruhi

Magnesium alloys have excellent properties such as high specific strength, rigidity, good damping, electromagnetic shielding, castability, and machinability. However, corrosion, creep, and fatigue resistance are generally the properties that need to be improved. In this study, a hybrid coating was formed on AZ31 magnesium alloy with different surface roughness at different frequencies. In the hybrid coating, an oxide coating was first grown on the surface by the micro-arc oxidation method, and then, the epoxy coating was grown on this oxide coating by the dipping method. The characterization of the coatings was performed by XRD, SEM, and EDS analysis. Furthermore, the relationship between fatigue life and surface roughness was also discussed in this study. The fatigue life and strength of the coated samples were determined as a result of the tests performed on the fatigue device. It was concluded that the fatigue life and strength of hybrid coatings were much better compared to uncoated and single-layer coated samples.

Aydin, Kemal; Hidiroglu, Mehtap; Kahraman, Nizamettin

Automotive industry in recent years, has gained great importance. In line with this, DP600 and DP800 dual-phase steels and the electrical resistance spot welding method were used in the study. During the experimental trials, different welding currents (6, 7, and 8 kA) were selected and all other welding parameters were kept constant. The effects of the welding parameters on microstructure, hardness, tensile-shear, and cross-tensile strength were analyzed. In the phase measurements, 27.06–29.97% martensite and 70.73–73.85% ferrite phases were found. When the hardness values in the HAZ regions were examined, it was seen that the highest hardness values were 356 ± 5 HV in the DP600 and 451 ± 5 HV in the DP800 with a current intensity of 6 kA. Consequently, it was determined that tensile-shear and cross-tensile strengths had increased in parallel with the increase in the welding current and the highest values were determined as 8 kA–15.91 kN in tensile shear and 8 kA–4.91 kN in cross-tensile strength.