Research On Microwave Heating Synthesis Al-TiO₂, Al-TiO₂-B₂O₃ Systems Of Aluminum Matrix Composites

The microwave heating synthesis has been shown a novel,rapid and economical method of preparing many important materials.Microwave processing has been used to synthesize the A1-TiO₂ and Al-TiO₂-B₂O₃ systems of aluminum matrix composites.The reaction outcome and microstructures of composites were analysed by modern means such as optical microscope(OM),scanning electron microscopy(SEM),X-ray diffraction(XRD) and so on, used to compare the product particle size and organization distribution.The heating curve of microwave processing was recorded by the autonomous software jdk-6u12-i586-p,used to compare the initial reaction temperature and reaction time.Combining the thermodynamic calculation with DSC curve,microwave synthetic mechanism of the Al-YiO₂ and Al-TiO₂-B₂O₃ systems were analysed.Al₂O₃ and Al₃Ti were created at the temperature of about 1100K and 1300K,while TiB₂ at 1350K.The TiB₂ phase, smaller than Al₂O₃ grains,can become the nucleus and refine the grain size of the matrix;and the Al₂O₃ grains could not be nucleuses of the matrix during the solidification and normally segregated or distributed at the interface of the matrix grains.The optimal synthesis of microwave heating processes of the Al-TiO₂-B₂O₃ system as follows:With Al,TiO₂ and B₂O₃ powders as raw materials,milling 2h,120MP into a massive cold extrusion pressure.Microwave frequency of 2.45GHz,SiC for pre-heating materials, power 800w,synthesis time about 7min,organizations can be synthesized uniform, high-density sample.Activation energy was calculated by means of Kissinger equation,in order to preliminary study on the mechanism of microwave heating.In the Al-TiO₂-B₂O₃ system, Activation energy of conventional heating and microwave heating synthesis were 335.5 kJ/mol and 67.2kJ/mol.Compared Microwave heating synthesis to the traditional synthesis, the activation energy is only 1/5,the reaction activation energy is significantly reduced, accounting for non-thermal effect existence.Property study found that microwave heating synthesis of Al-TiO₂-B₂O₃ system composite materials increased density,the relative density close to 98%;microwave synthetic sample hardness was 47.5 MPa.When reinforcement volume fraction was 30%,B₂O₃/TiO₂ molar ratio from 0 to 1,the tensile strength increased by 256.71 MPa to 343.5 MPa, elongation increased from 3.37 percent to 6.54 percent,respectively improved 33.8%and 94%.Tensile fracture surface observed by SEM,when rod-like structures exsited,the fracture surface showed small dimples as well as rod-like structures fracture;no rod-like structures, the fracture was small equiaxed dimples.