Study On In-situ Synthesis Of TiC（TiB₂） Eeinforced Al-Cu Matrix Composites By Microwave Heating

TiC and TiB₂ reinforced Al-Cu alloy matrix composites were prepared by microwave heating（MH）and traditional heating（TH）in Al-Cu-Ti-C and Al-Cu-Ti-B systems respectively.The composition,morphology and composition of the reaction products were analyzed by X-ray diffraction（XRD）,energy dispersive spectroscopy（EDS）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and differential thermal analysis（DSC）.The effects of volume fraction of reinforcement,milling time and heating mode on the reaction products were studied.The thermodynamics and kinetics of the two systems were discussed.The activation energies of the two systems by microwave heating and traditional heating were calculated respectively.The effects of microwave heating on chemical reaction were explored,and the reaction mechanism was revealed.In addition,the density,hardness and tensile properties of the composites were tested,and the optimum process for preparing TiC（TiB₂）reinforced Al-Cu alloy matrix composites by microwave heating was obtained.The reaction mechanism of Al-Cu-Ti-C system and Al-Cu-Ti-B system shows that in these two systems,Al first reacts with Ti to form intermediate product TiAl₃,and then TiC and B atoms replace Al in TiAl₃ to form TiC and TiB₂.The activation energies of TiC and TiB₂produced by microwave heating are 41.4 kJ/mol and 33.8 kJ/mol,respectively.The activation energies of TiC and TiB₂ produced by traditional heating are 270.0 kJ/mol and 113.8 kJ/mol.Microstructure studies show that short milling time in Al-Cu-Ti-C system will lead to large-sized TiAl₃ residue,TiC segregates in a small range when the volume fraction of reinforcement is 5%;TiC agglomerates seriously when the volume fraction of reinforcement is 15%;The distribute of TiC is evenly when the volume fraction of reinforcement is 10%,and the system reacts sufficient after 8 hours of ball milling.The microwave-heated samples have smaller particle size and relatively uniform distribution than the traditional heated samples.In Al-Cu-Ti-B system,TiB₂ is agglomerated into rings,and the size of TiB₂ rings can be reduced by increasing milling time.The microwave heating sample reacts more fully than the traditional heating sample.The compactness study of the samples shows that the composites prepared by powder metallurgy have poor compactness,and the composites with good compactness can be obtained by hot pressing.The research on composite process and properties shows that the optimum process parameters for the synthesis of TiC reinforced Al-Cu alloy matrix composites by microwave heating at 2 kW are:reinforcement volume fraction of 10%,ball milling for 8 h,and holding at 1273 K for 5 min.The hardness is 105.5 HV0.5.After hot pressing,the tensile strength of the composite is 367.0 MPa,the elongation is 8.09%,and the tensile strength is 14.6%higher than that of the traditionally heated composite under the same parameters.The optimum process parameters for the synthesis of TiB₂ reinforced Al-Cu alloy matrix composites by microwave heating of 2 kW are as follows:the volume fraction of the reinforcement is 10%,the ball mill is 16 h,and the heat is kept at 1273 K for 5 min.The hardness of the sample is102.4 HV0.5.The tensile strength of the composite after hot pressing is 329.1 MPa,the elongation is 6.26%,and the tensile strength is 30.1%higher than that of the traditionally heated composite under the same parameters.