Preparation, Characterization And Properties Of Mg-based Amorphous Composites

As the lightest structural material,magnesium and its magnesium alloys are widely used in transportation,electronic information,aerospace and other fields.However,compared with other alloys(Al,Ti,etc.),magnesium alloys exhibit low strength and poor corrosion resistance,which limits the commercial application of magnesium alloys.Magnesium-based composite materials prepared by adding reinforcing phases to magnesium alloys have the advantages of light weight,high strength,high corrosion resistance,etc.,and have great application potential in the fields of aerospace,automobile manufacturing,and electronic communications.Among them,researchers have used amorphous particles as the reinforcement phase of magnesium-based composite materials at home and abroad.Because of their superior mechanical properties,magnesium-based composites have become a research hotspot in magnesium-based composite materials.However,the interface between the amorphous reinforced particles and the magnesium matrix is still a bottleneck in the research and application of magnesium-based amorphous composites.In this paper,Fe-based amorphous particles(FBAs)with high hardness and high elastic modulus were used as the reinforcing phase,and amorphous reinforced magnesium-based composite materials were prepared by ordinary powder metallurgy and spark plasma sintering methods,and the microstructure,interface combination and mechanism were systematically studied.The interface formation principle and strengthening mechanism of magnesium-based amorphous composites were discussed,and the influence of interface bonding and interface reaction products on the strengthening mechanism and fracture behavior of the composites was further revealed through performance testing.According to the results of ordinary sintering,the FBAs reinforcement phase were contribute to increase the sintering density of the FBAs / Mg composite material,which was mainly due to the mismatch between the excess heat energy released by the crystallization process of the non-steady-state amorphous particles and the thermal expansion coefficient,resulting in a large amount of the residual stress and increases the driving force for sintering.In addition,FBAs particles can not only improve the mechanical properties of the material but also beneficial for improve the deformation stability of the material.With the increase of the FBAs content,the strength and plasticity of the magnesium-based composite material have been improved.The fracture of the samples was analyzed,which the cracks were mainly generated in the magnesium matrix and extend along the magnesium particle boundary or the interface between the FBAs and the magnesium particles.The addition of FBAs reinforcement particles was beneficial to suppress the concentration and extension of the cracks,thereby improving the plasticity of the composite.The structure of FBAs / Mg composites prepared by SPS is composed of broken crystal zone,FBAs particle,matrix,twin,white MgO film and MgO particles on the surface of FBAs.During the SPS sintering process,local high temperature would occur at the edge of the FBAs particles,resulting in the surface of the Mg particles melting or vaporizing due to the high temperature,forming an MgO phase with the oxygen between the particles,and enriching on the surface of the FBAs particles.The FBAs reinforced particles were tightly bonded to the matrix.With the increase of the FBAs reinforced particle mass fraction,the strength of the material increased,but the plasticity gradually decreased.The composite failure type was dissociation fracture,and the FBAs reinforcement fails in the matrix.After that,it was still wrapped in the matrix and there was no shedding.By analyzing the structure,fracture morphology and micro-crack propagation law of the composite material,it was found that the fracture mainly occurred in the interface layer between the matrix and Mg-FBAs,and the FBAs particles obviously hindered the diffusion of the micro-crack,which significantly improved the fracture surface energy,so that the composite material exhibits a relatively high mechanical strength.However,since the FBAs particles and Mg cannot be deformed cooperatively,the fracture only occurs at the interface layer between the matrix and the Mg-FBAs.Therefore,as the mass fraction of the FBAs particles increased,the plasticity of the composite would decrease.