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Raihanuzzaman, R.M.,Jeong, T.S.,Ghomashchi, R.,Xie, Z.,Hong, S.J. Elsevier Sequoia 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.615 No.suppl1
The aim of this study was to observe the effect of short-duration, high-energy ball milling on the mechanical properties of sintered WC-Co. Mixed powders of WC-7.5wt% nano Co were ball milled at three different time using WC vial and balls, while other parameters were kept constant. The powders were then consolidated using spark plasma sintering. Density and hardness of the sintered samples were measured as a function of milling time, used to mix the powders prior to consolidation. It was found that both density and hardness increased with milling time, with hardness reaching a maximum of 14.95GPa for the sample milled for 10min. Microstructures of the sintered samples suggested a slight decline in grain size and increase in Co distribution with increasing milling time. It was also evident that milling of WC-Co powders resulted in the sintered samples having overall irregular shaped grains.
Conventional sintering of WC with nano-sized Co binder: Characterization and mechanical behavior
Raihanuzzaman, R.Md.,Han, S.T.,Ghomashchi, R.,Kim, H.S.,Hong, S.J. MPR Pub. Services 2015 International journal of refractory metals & hard Vol.53 No.1
In this study, WC particles of 1-3μm were blended with two different sizes of Co particles and sintered conventionally at two different temperatures. Compaction of initial powders was carried out using a relatively new dynamic compaction method called Magnetic Pulsed compaction (MPC). The maximum Vickers hardness for the samples found was around 1353HV (13.27GPa), while the maximum fracture toughness was observed at 4.6MPa.m<SUP>½</SUP>. The marked changes in density, hardness, fracture toughness and crack behavior observed in the samples indicate strong correlations among particle size, sintering process and mechanical properties of cemented carbides. In addition, the nature of crack initiation and propagation, which is indicative of the trend in fracture toughness of materials, was observed and analyzed.
Effect Of Ti Powder Addition On The Fabrication Of TiO2 Nanopowders
Raihanuzzaman, R.M.,Park, H.Y.,Ghomashchi, R.,Kwon, T.H.,Son, H.-T.,Hong, S.J. PAS 2015 ARCHIVES OF METALLURGY Vol.60 No.2
<B>Abstract</B><P>Sintered samples of Ti added TiO2 nanopowders were fabricated by combined application of magnetic pulsed compaction (MPC) and sintering. The effect of Ti nano powder on density, shrinkage and hardness of the samples were investigated as part of the study. The optimum processing conditions were found to be around 0.5 GPa MPC pressure and 1450°C sintering temperature, illustrating maximum density, hardness and minimum shrinkage. High pressure compaction using MPC was found to enhance density with increasing MPC pressure up to 0.9 GPa, and significantly reduce the total shrinkage (about 16% in this case) in the sintered bulks compared to other general processes (about 18%). While sintered samples blended with micro Ti showed presence of microstructural cracks, the samples with 1-2% nano Ti had less or no cracks on them. Overall, the inclusion of nano Ti indicated improvement in mechanical properties of TiO2 nanopowders sintered preforms as opposed to micro Ti-added TiO2.</P>