Yahya Bozkurt

Microstructure and mechanical properties of friction stir welded particulate reinforced AA2124/SiC/25p–T4 composite

The purpose of the study is to present the feasibility of the joining of similar AA2124/SiC/25p–T4 composite plates by friction stir welding (FSW). Microstructure properties, microhardness, and tensile tests have been performed to evaluate the weld zone characteristics and the performance of AA2124/SiC/25p–T4 composite joints. The phase structure of a similar AA2124/SiC/25p–T4 composite weld was determined from X-ray diffraction (XRD). The temperature in the weld zone have been evaluated using thermocouples in order to demonstrate the FSWed joint of the AA2124/SiC/25p–T4 composite without melting. The obtained results revealed that FSW can be used in the joining of similar AA2124/SiC/25p–T4 composite plates. XRD measurements show that SiO2 phase was detected in the weld zones. It was determined that the peak temperatures achieved at 15 mm away from the weld center varied between 201°C and 270°C. In addition, the tensile strength of AA2124/SiC/25p–T4 butt joints was found to be approximately 20% lower than that of the base composite. The originality of this study is one of the preliminary studies on the detailed examination of the microstructural and mechanical properties of the AA2124/SiC/25p–T4 composite joint by FSW.

Friction Stir Welding of Al-B 4 C Composite Fabricated by Accumulative Roll Bonding: Evaluation of Microstructure and Mechanical Behavior

In this investigation, friction stir welding (FSW) of Al-B4C composite fabricated by 10 cycles accumulative roll bonding was conducted. In order to investigate the influences of pin geometry on microstructure and mechanical properties, four different pin geometries (cylindrical, square, triangular and hexagonal) were selected. It was found that FSW parameters had a major effect on the fragmentation and distribution of reinforcement particles in stir zone. When the tool travel speed was increased, the distribution of B4C particles was become gradually uniform in the aluminum matrix. The effect of tool rotational speed on the peak temperature was determined to be greater than the tool travel speed. The attained data of tensile properties and microhardness tests showed that the tool travel speed had bilateral effect on the tensile strength. The maximum tensile joint efficiency was obtained as 238% for FSWed of Al-2%B4C composite to annealed base Al sheet.

Improvement of Microstructure of Bovine Hydroxyapatite (BHA) by Doping with Calcium Fluoride

Composites of calcinated bovine bone derived hydroxyapatite (BHA) doped 0.5 and 1 wt% CaF2 were prepared by sintering. The production of BHA from natural sources is preferred due to money and time saving reasons. Scanning electron microscopy (SEM) and X-ray diffraction analysis together with measurements of density and compression strength were carried out in the produced samples. The experimental results indicated that compression strength of the composites increase when sintering temperature increases. The best compression strength was achieved after sintering at 1200°C for 0.5% CaF2 addition. The results are in agreement with densification measurements and microstructure analysis. With regards to the amount of CaF2, the results indicate that small additions of F, lower than 0.5%, can further improve the mechanical properties of HA.