Fabrication Of Mg₂Si/6061Al Composite With A Quasi-continuous Network Reinforcement Distribution

Aluminum matrix composites which have the advantages of high specific strength,high wear resistance and low thermal expansion,is widely applied in aerospace,automobile manufacturing and other fields.In traditional aluminum matrix composites,reinforcement usually distribute in matrix evenly,and the strength of composite is greatly improved,but the toughness is poor due to the destruction of connection between matrix.The inhomogeneous composite can solve this problem to some extent.In all kinds of inhomogeneous composite,the microstructure of composite with a quasi-continuous network is that reinforcement distribute uniformly along the matrix particle boundary.While bearing capacity of the material is improved,the quasi-continuous network structure can maintain integrity and connection of matrix,and reduce the stress concentration at the crack tip effectively,there by improving the toughness of the composites.In this paper,Mg₂Si/6061 Al composite with quasi-continuous network reinforcement distribution was successfully fabricated by low energy ball milling and in situ reactive sintering.The 6061 Al matrix large particles powder mix with added submicron Mg,Si powder to achieve Mg,Si powder evenly distributed on the matrix surface.And Mg₂ Si with quasi-continuous network distribution is synthyesized in situ sintering process.Scanning electron microscopy?SEM?and X-Ray Diffraction?XRD?were used to characterize phase structure and microstructures of composites.And composites were heated to 530 °C for 1 h then quenched in cold water,and artificially aged at 160 °C for 12 h.Analyzing the hardness change of as sintered and heat treated composites.The ball milling parameters is 200 rpm and 2h,and 3:1 ratio of steel balls to milled material.By XRD analysis,at 660 °C,Mg₂ Si reinforcement generate in situ reaction.With the increase of sintering time,the connection of matrix increase,and the diffusion of Mg,Si increase,and the overall hardness of composite increase.After heat treatment,the composite have the largest hardness with sintering time 6 h,and the hardness is 43.77 HV.Under the conditions of 660 °C and 6 h,with the increase of Mg and Si content,the volume fraction of Mg₂ Si reinforcement increases.The relative density of quasi-continuous network composite with 0.96 wt.% Mg?0.57 wt.% Si is largest,and the hardness of this composite is 44.6 HV after heat treatment.