Polyetheretherketone (PEEK) composites reinforced with short carbon fibers (SCFs) (20 vol%) and nano‐SiO2 (1, 1.5, and 2 wt%) particles were prepared by incorporating nanoparticles into PEEK/SCF composites using the internal mixer. In the development of biomaterial, both mechanical and biological characteristics must be considered. Thus, the effects of nanoparticles on the mechanical and biological properties of the PEEK/SCF composites were studied. To evaluate the mechanical properties of this biomaterial, nanoindentation method and tensile test were used. Results showed that by increasing the weight percentage of nano‐SiO2, the elastic modulus, hardness, and tensile energies were increased. In vitro biological evaluations of the samples were done by performing cytotoxicity (3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐iphenyltetrazolium bromide assay) and cell adhesion assays. Cell–material interaction with the surface of the composite was examined by scanning electron microscopy (SEM). In all of the tests, osteoblast cells were used. Results of biological tests showed that the samples are biocompatible and they have no toxicity. Also, Adhered cells presented a normal morphology by SEM and many of the cells were observed to be undergoing cell division. POLYM. COMPOS., 34:1960–1968, 2013. © 2013 Society of Plastics Engineers

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The major objective of the present work is to design a high speed steel composition for tool casting. The effect of replacement of V and W by Nb as a modifier of the structure and properties of cast S 2-9-2 (AISI M7) high speed steel has been investigated with the aid of EDX and WDX attached to the scaning electron microscope. The influences of Nb on eutectic cell size, eutectic volume percentage and eutectic carbide shapes and types were determined. The values of hardnesses of steels under investigation after various heat treatment operations were studied so that the optimum value of substitutional niobium could be determined. The results show that increasing Nb can decrease the volume fraction of eutectic cell size, however the maximum hardness of the heat treated samples can be achieved in the presence of 1.8% of Nb. Der EinfluB vonNiob auf die GuBstruktur von Schnellarbeitsstahl. Das vorrangige Ziel dieser Arbeit besteht darin, eine geeignete chemische Zusammensetzung fOr einen Werkzeugstahl zu ermitteln. Anstelle der bei Schnellarbeitsstahl haufig verwendeten Elemente V und W wurde hier Nb als eingesetzt. Dessen Wirkung auf GefOgeveranderungen und Eigenschaften des gegossenen Schnellarbeitsstahls S 2-9-2 (AISI M7) wurde mit Hilfe von EDX und WDX am Rasterelektronenmikroskop untersucht. Bestimmt wurden der EinfluB von Niob auf die GroBe der eutektische Zelle, Volumenanteile sowie Carbidform und -typen bei der eutektischen Zusammensetzung. In Abhangigkeit von verschiedenen Warmebehandlungen wurden Hartewerte der untersuchten Stahlsorten ermittelt, bis der optimale SUbstitutionsgehalt an Niob bestimmt war. Die Ergebnisse zeigen, daB mit steigendem Niobgehalt der Volumenanteil der eutektischen Zelle abnimmt; das Hiirtemaximum der warmebehandelten Proben lieB sich bei 1.8% Nb ermitteln.

This paper investigates the influence of rotational and travel speed on the structure and mechanical properties of different regions of friction stir welded dissimilar AA5251–AA5083 joints. It was observed that increasing rotational speed from 800 to 1 250 rpm, at a fixed travel speed, increased the grain size from 6.31 μm to 10.64 μm. This stemmed from higher heat input which is generated at higher rotational speed. Furthermore, it was discovered that at 1 000 rpm, 115 mm min−1 and also 1 250 rpm, 85 mm min−1, defect-free welds were produced. The results of tensile testing revealed that the best consistent tensile strength was produced at 1 000 rpm rotational speed and 115 mm min−1 travel speed with an average value of about 200 MPa. Further, the results clearly showed that the hardness values gradually increase from the 5251 aluminum side to the 5083 aluminum side.

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