Preparation And Properties Of Ti₂AlC Ceramic Dispersion Reinforced Al Matrix Composites

Aluminum and its alloys have attracted much attention due to their advantages of low density,low cost,low thermal expansion coefficient,high thermal and electrical conductivity.Compared with ordinary Al and its alloys,Al matrix composites?AMCs?have better mechanical and friction-wear properties.Therefore,Al matrix composites have been widely used in engineering materials.The traditional hard ceramic particles are mainly as particle reinforced phases of Al-based materials.This kind of reinforcing phase has the advantage of high hardness,and high wear resistance.But it also has the disadvantages of poor processability and conductivity.The MAX phase ceramics have characteristics of metal and ceramic due to its special structure.Therefore it widely used in metal and ceramic matrix composites.The advantage of using the MAX phase as reinforcing phase of metal-based composite lies in its excellent electrical,thermal conductivity,processability and tribological properties.These excellent properties are not possessed by the traditional ceramic reinforcing phase.As typical MAX phase ceramic,Ti₂AlC not only has the basic properties of MAX phase,but also has high Young's modulus and almost the lowest theoretical density.These characteristics make Ti₂AlC ceramics have a very broad application prospect.Ti₂AlC ceramics also have the problem of poor wettability and bonding which is similar to other traditional ceramic metal matrix composites.The surface structure of reinforced phase is improved by Cu plating in order to solve this problem,which improves the binding ability with the metal matrix.Cu coated Ti₂AlC ceramic dispersion-reinforced Al matrix composites?Al-Cu/Ti₂AlC?were prepared by using pure Al as matrix and self-preparation copper-plated Ti₂AlC composite powder as reinforcing phase.The effects of different sintering temperatures on the properties of materials were studied.Ti₂AlC ceramic dispersion reinforced Al matrix composites were prepared?Al-Ti₂AlC?by the same process for comparison.Ti₂AlC ceramic powder was prepared by combustion synthesis method,and Cu was successfully plated on the surface of Ti₂AlC powder particles by electroless Cu plating.It was found that Ti₂AlC ceramics had a certain autocatalytic effect.When the plating time is 40 min and the coating load is 25%,the nano Cu particles form a complete coating on the Ti₂AlC ceramic powder particles.The phase composition analysis of these two different compositions of AMCs systems shows that.For Al-Ti₂AlC,when the sintering temperature is 470?,the products are mainly composed of Al and Ti₂AlC.After the temperature is increased to 495?,Al3 Ti phase appears in the system.When the temperature reaches 550?,a large amount of Al3 Ti phase is formed and Ti₂AlC phase is sharply decreased;For Al-Cu/Ti₂AlC,it has the same phase composition as Al-Ti₂AlC.But when the sintering temperature was 470?,the formation of solid solution structure due to Cu atoms diffused into the crystal lattice of Al matrix.As a result,the X-ray diffraction peak of Al shifted to a small angle on left.After increasing sintering temperature,the reaction between Cu atoms and Al matrix lead to the formation of Al2 Cu intermetallic compounds.After AMCs were prepared,we analyzed basic properties of the two composite material systems.When the sintering temperature was 485?,the density,hardness,and resistivity of composites had a positive correlation with the content of reinforcing phase.The density,hardness and conductivity of Al-Cu/Ti₂AlC material system are better than those of Al-Ti₂AlC system.When the mass percentage of reinforcing phase is 10%,the relative density of composite material reaches the highest value.The relative density of Al-10%Cu/Ti₂AlC and Al-10%Ti₂Al C are 98.57% and 96.39%,respectively.The electrical conductivity of two different AMCs were studied.It was found that the resistivity of Al-10%Ti₂Al C composite material decreased rapidly with increasing sintering temperature.For Al-10%Cu/Ti₂AlC composites,the change of its resistivity with temperature is not obvious and only decreases slightly at 495?.The mechanical properties of two different AMCs were studied.it was found that both AMCs have high toughness.The interface bonding effect of composite was improved due to the introduction of Cu layer.The mechanical properties of composites have been greatly improved after the introduction of Cu layer.Its main performance indexes are increased by more than 40%.