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2. Aim of the Study: Microstructure Density Microhardness

3. Mechanical Alloying (MA) is a high energy ball milling technique including excessive plastic deformation and cold welding of the particles [1, 2] To produce nanocrystalline powders and intermetallic powders [1, 2] The chemical composition of the powders can change during milling [3] During MA, collisions of the balls cause small particles broken off from the balls Cause contamination [4] Metal-Ceramic composite powders can be produced by MA [1] Homogeneously distributed ultra-fine ceramic powders in MMC [5] Mechanical properties of Tungsten (W) enhanced with fine dispersed carbides [5]

4. Nanostructured materials have Increased strength High hardness High diffusion rates Reduced sintering times There is not a review or paper about B4C reinforced W matrix composites obtained via high energy mechanical milling

5. Experimental Procedure

13. The amount of Co contamination was determined by XRF analyses The as-blended powders did not contain any Co phase By using the XRD analyses of 10 hour MA’d W-B4C-C powders, the grain size of the tungsten powder was calculated via tungsten peaks reflected from (110), (200) and (211) planes by means of modified Scherer equation [6]:

22. Whereas the particle size of the as-blended W-B4C-C powders was 23 µm, that of the MA’d powders decreased to 0.6 µm W peaks are present in the as-blended powders, however WC and W2B intermetallic phases were also identified in the MA’d W-B4C-C powders W grain size in the MA’d sample was determined as 14 nm Only W peaks were observed in the sintered sample prepared from as-blended powders Peaks of W2C and W2B intermetallic phases in addition to W peaks were observed in the 10 hour MA’d sintered composite The Vickers microhardness values of the sintered as-blended powder is 0.81 GPa and it rise to 16.5 GPa after MA Relative density increased from a value of 84% for the sintered composite prepared from as-blended powders to 93.3% for that prepared from the MA’d powders

23. ACKNOWLEDGEMENTS We would like to thank the Scientific and Research Council of Turkey (TÜBITAK) for providing the financial support for Project 105M06 out of which this study has emerged. A lot of thanks go to our laboratory group, for their support and friendship. Grateful thanks to : Ass. Prof. G. Göller (ITU) and H. Sezer (ITU, Biomaterials Laboratories) for the XRF and FEG-SEM/EDS observations, Ç. Çakir (ITU, Electron Microscopy Laboratories) for the SEM/EDS micrographs, Prof. Dr. M. Ürgen (ITU, Coating Laboratories) and S. Türkeli (ITU) for the XRD measurements, Prof. Dr. H. Çimenoglu (ITU, Mechanical Laboratories) for the Vickers Microhardness studies.