Preparation And Compressive Properties Of In-situ Mg₂Si Particles Reinforced Magnesium Composite Foams

As a novel type of structural and functional engineering materials,the magnesium foams have a huge potential application in the field of rail transit,petrochemicals and aerospace.However,the wide application of Mg foams used as the structural materials in the industry is limited due to their relatively low strength.Mg₂Si particles are kinds of effective reinforcement because of its low density,high elastic modulus and high hardness.In situ synthesis of Mg₂Si particles in the matrix of the Mg composite foams can effectively improve the mechanical properties on the premise of the lightweight porous structure,which has a great value to the theoretical research and practical application of Mg foam materials.In this paper,the open-cell Mg composite foams reinforced by Mg₂Si were prepared by infiltration casting methods,and the effects of Si contents?1 wt.%,5wt.%and 9wt.%?on the microstructure and compressive properties of the foams were studied.The failure mechanism of the foams was discussed preliminarily as well.Y+Sb compound modifier were used to modify the Mg₂Si/Mg composite foams,and the effects of modifier contents?0.5 wt.%Y+0.2 wt.%Sb,0.5 wt.%Y+0.5 wt.%Sb and 0.5 wt.%Y+0.8 wt.%Sb?on the microstructure and compressive properties of the Mg₂Si/Mg composite foams were investigated.In addition,the Mg₂Si/Mg composite foams after compound modification were treated by solid solution process,and the effects of different solid solution time on the microstructure and compressive properties of the foams were explored.The failure mechanism was preliminarily analyzed as well.The main results of this study are as follows:1.The microstructure of Mg₂Si/Mg foams could obviously change with the increasing Si contents.The increasing Si contents would promote the formation of primary Mg₂Si compounds with dendritic shape,and the amount and size of primary Mg₂Si rised with the increasing Si additions.2.The compressive strength of Mg₂Si/Mg composite foams was elevated initially and then decreased with the increasing Si contents,and the energy absorption capacity was reduced with the increase of Si contents.The Mg₂Si/Mg composite foams with 5 wt.%Si additions showed highest compressive strength,and the Mg₂Si/Mg composite foams with 1 wt.%Si additions possessed highest energy absorption capacity.3.When the Y contents of the compound modifier was matained,the size of the Mg₂Si phase in Mg-5Si foams was decreased firstly and then increased with the increase of Sb contents.When the Sb contents was 0.5 wt.%,the size of primary Mg₂Si phase and eutectic Mg₂Si phase was lowest,showing the best modification effects.4.The Y contents remained unchanged.With the increased of Sb contents,the compressive strength and energy absorption capacity of Mg-5Si foams increased firstly and then decreased.When the contents of Y and Sb were 0.5 wt.%respectively,the co-modificated Mg-5Si composite foams showed the highest compressive strength and energy absorption capacity,and the ductility of the foams was significantly improved.5.When the content of Y and Sb was 0.5 wt.%,the eutectic Mg₂Si phase of Mg-1Si composite foams was effectively refined,and the compressive strength and energy absorption capacity of foams increased significantly.However,under the same modifier contents,Mg-5Si foams showed better modification effect and higher compressive properties than Mg-1Si foams.6.When the solid solution temperature?420??and the contents of the compound modifier?0.5 wt.%Y+0.5 wt.%Sb?remained unchanged.With the increase of solid solution time,the morphology of eutectic Mg₂Si phase in the co-modified Mg-5Si foams changed to nodular obviously,the edge of the primary Mg₂Si phase were rounded,and the compressive strength and energy absorption capacity of the foams were elevated.