Research On The Preparation Of Cu/Al₂O₃Composites By Injection Molding

Alumina ceramic has been widely used for its excellent properties. However, itsuse scope has been limited for disadvantages of brittleness and poor thermal shockresistance. Its comprehensive properties can be improved by adding metal copper withexcellent wear resistance, toughness, ductility, thermal conductivity and electricalconductivity in alumina ceramic.Based on the alumina powder and copper powder as the research object, it hadbeen studied that the injection molding process to prepare Cu/Al2O3composites,including feedstock preparation, injection process, debinding and sintering process.It has been studied that the feedstock performance of the Paraffin Quito polymerbinder system. The result shows that the feedstock is suitable for injection when thepowder loading capacity is55%and the binder composition consists of75%paraffin+20%low density polyethylene+5%stearic acid.The effects of process parameters such as injection temperature, injectionpressure and injection time on the performance of green part were studied by usingorthogonal arrays design and statistical analysis method. The optimized injectionparameters are as follows: injection temperature is150℃, injection pressure is90MPa,injection time is8s; the corresponding maintaining pressure is75MPa according tothe literature; the maintaining time is10s, die temperature is40℃which wasconcluded through comparative experiment.Two-step debinding process of solvent debinding and thermal debinding forgreen parts was applied. Trichloroethylene used as its solvent, the time of solventdebinding was for6h at40℃, while the thermal debinding was carried out step bystep in a vacuum atmosphere. The debinding rate reaches to96.1%, and the surfacequality of debinded parts is perfect.The sintering process was studied by contrast test. Effects of three sinteringtemperatures such as1500℃,1550℃,1600℃with a holding time for2.5h, andinsulation time for2h,2.5h,3h respectively at1550℃on the performance of sinteredparts were studied. The results show that the suitable sintering temperature andholding time are1550℃and2.5h respectively. After sintering, the density, bendingstrength and vickers hardness of sintered parts are3.95g/cm3,542MPa and1534HVrespectively.It had been studied that the effects of four kinds of Cu contents such as0%,5%, 10%,15%on the performance of Cu/Al2O3composites when sintered under theconditions of1550℃and heat preservation for2.5h.The results showed that the density, bending strength and vickers hardness ofthe sintered parts are3.79g/cm3,520MPa and1669HV when the copper content is0%,they are3.86g/cm3,442MPa and1575HV when the copper content is5%, they are3.95g/cm3,542MPa and1534HV when the copper content is10%, and they are4.04g/cm3,465MPa and1373HV when the copper content is15%respectively.Facture mode of Cu/Al2O3composites was analyzed and found that there are threeways such as intergranular fracture, transgranular fracture and pull out of copperparticles when sintered parts break, and three kinds of fracture probabilities decreasein turn.