Investigation of mechanical properties of powder injection moulded alumina by adding MgO

In this study, MgO added alumina and pure alumina powders were molded by powder injection molding method. 65% PEG8000 (polyethyleneglycol) + 30% PP (polypropylene) + 5% SA (stearic acid) in weight was used as the binder. First, the rheological properties of four different feedstocks were examined andthe optimum powder/binder ratio was determined as 53%/47% in volume. Rheological properties of feedstocks (pure and in weight for 0,5%, 1%, 1,5% MgO added alumina) which contain 53% alumina+ 47% binder in volume, were investigated and flow behavior index, melt flow index and flow rate of thefeedstocks were determined seperately for all the feedstocks.The feedstocks prepared using this ratio, were granulated and then tensile and bending samples were molded by injection method. Solvent and thermal (presintering) debinding of these molded samples were carried out. As a result of sintering investigations, the samples sintered in 1775 °C for 8 hours had inferior mechanical properties. The temperature of 1775 °C and 6 hours of the holding time were determined as the optimum sinteringparameters. The highest strength and density values were obtained for 1% (wt.) MgO added alumina feedstocks. In tensile samples 69 MPa maximum tensile strength, 86,8% of theoretical density and 18,5% of shrinkage ratio were achieved. In bending samples 158 MPa maximum bending strength, 88,1% of theoretical density and 16,2% of shrinkage ratio were also achieved. SEM analysis showed that 1% (wt.) MgO added alumina feedstock samples have less pore and those have good sintering.