Preparation And Mechanical Behavior Of Metal Hard Particle Reinforced Aluminum Matrix Composites

Particle reinforced aluminum matrix composites have been widely used in aerospace,national defense,transportation,electronic packaging and other fields due to their lightweight,high specific strength and excellent electrical and thermal conductivity.However,because of the poor interface wettability,ceramic-reinforced Al matrix composites have relatively low plasticity and toughness,which limits its application.Although the wettability issue can be solved using metal quasicrystal particles,amorphous alloys,and high entropy alloys,there are still some shortcomings,such as the majority of quasicrystals are poisonous,amorphous alloys have poor thermal stability,and high-entropy alloys have a limited range of compositions,etc.In order to further increase the strength and toughness of the aluminum matrix,it is crucial to investigate a new form of particle reinforcement phase,optimize the composition design and preparation process.In the present paper,the metal hard particles with high hardness,high strength,high corrosion resistance and high temperature stability were used as the reinforcing phase to address the issues.Aluminum matrix composites reinforced with metal hard particles were prepared by powder metallurgy process and the microstructure and compressive properties of the composites were researched.The main research contents and conclusions are as follows:Firstly,the M7/Al composites were prepared by powder metallurgy using M7 hard particles as the reinforcement.The effects of M7 hard particle content,particle size and sintering temperature on the microstructure and compressive mechanical behavior of the composites were investigated.The findings demonstrate that the interdiffusion reaction between M7 particles and the Al matrix is intensified as the sintering temperature rises,the diffusion layer becomes thicker,and multiphase intermetallic compounds are formed by in-situ reaction.The diffusion layer gradually vanishes as the sintering temperature rises,some M7 hard particles dissolve in the Al matrix,and the concentration of intermetallic compounds rises in proportion.With the increase of M7 content and the decrease of particle size,the yield strength of the composites increases.The best mechanical characteristics are 34.7 HV_0.1 and 175.2 MPa in 10 wt.%M7/Al composites sintered at 640°C,which are 27.6%and 146.1%greater than the comparable 10 wt.%Si C/Al composites.The strengthening mechanism is mainly attributed to the synergistic effect of in-situ multiphase intermetallic compound strengthening,solid solution strengthening and hard particles dispersion strengthening.Secondly,Fe Mo hard particle reinforced aluminum matrix composites were prepared by powder metallurgy process.The effects of hard particle content,ball milling time and sintering temperature on the microstructure and compressive mechanical behavior of the composites were investigated.The results show that with the increase of sintering temperature,the yield strength of Fe Mo/Al composites increases,but the plasticity reduces.The yield strength of the composites increases initially and subsequently declines as the amount of hard particles increases.The ball milling procedure has a considerable impact on the mechanical properties of the composites in addition to altering the particle shape,size,and phase composition of the prefabricated mixed powder.The composite has the best mechanical properties when the ball milling time is 15 hours and the sintering temperature is 660°C.The hardness and strength are respectively 100.8 HV_0.1 and 245.7 MPa.It is 3.5 times and 5.0 times that of pure aluminum matrix material,and 23.4%and 39.4%higher than unmilled composites,respectively.It has the same strengthening mechanism as M7/Al composites.Finally,the above process was used to create ceramic/metal（Ti C+Fe Mo）and metal/metal（Cu+Fe Mo）synergistic reinforced aluminum matrix composites,and the microstructure and compressive mechanical behavior of the composites were investigated.The results show that after 10h ball milling,the comprehensive properties of 3 wt.%Cu+10 wt.%Fe Mo/Al composites are the best,and the microhardness and yield strength are 1.06 times and 1.19 times of 1 wt.%Ti C+10 wt.%Fe Mo/Al composites,respectively.The hardness and yield strength increased by 8.2%and 23.5%,respectively,compared with Fe Mo/Al composites under the same conditions.Both ceramic/metal and metal/metal can achieve the purpose of synergistic strengthening,and the synergistic strengthening mechanism is slightly different.Ceramic/metal particle strengthening is primarily based on Orowan strengthening,whereas metal/metal particle strengthening is primarily based on intermetallic compounds.