| Metal matrix syntactic foams are a new type of structural/functional material which is a porous material formed by implanting hollow particles(hollow beads)into a metal matrix.It has the advantages of light weight,high specific strength,high specific stiffness,high energy absorption,good damping,sound absorption and heat insulation.It has been applied more and more widely in the fields of automobile,aerospace,military equipment and ships which can absorb energy buffer,anti-collision and anti-vibration and explosion-proof.At present,in order to improve the energy absorptive capacity of metal matrix syntactic foam materials,the development of metal matrix toughening and advanced synthesis technology has become a hot spot of research.In this paper,zinc-aluminum alloy is used as the matrix,and hollow glass beads are used as filling materials.The effects of casting,alloying elements,volume fraction of hollow glass beads and heat treatment on microstructure and quasi-static compression properties of zinc-matrix syntactic foam are investigated.The influence law and mechanism of compressive strength,yield strength,platform stress,densification strain,energy absorbing performance and deformation mechanism of composite foam materials are mainly discussed,and the composition and process parameters are optimized.The main research results are as follows:(1)The effects of stirring time and temperature on microstructure and quasi-static compression properties of zinc-matrix syntactic foam are investigated.With the increase of stirring temperature,the breakage rate of hollow glass beads decreased,the porosity decreased,and the compressive strength of the composites increased.With the extension of stirring time,the hollow glass microballoon dispersion gradually improve,but with increasing of the percentage of breakage and considering hollow glass microbeads disperstiveness and quasi-static compression performance.It is concluded that the best stirring time is 5 min,the best temperature is 600 ℃.(2)The effects of different Al and Mg contents on microstructure and quasi-static compression properties of zinc-matrix syntactic foam are analyzed.Analysis shows that with the increase of Al content,the a + ηphase in zinc aluminum alloy gradually transformed from granular tissue to lamellar tissue,the lamellar tissue grows thick.When the content of aluminum is 10%,a large number of Mg-Zn intermetallic compounds are formed between the matrix and the hollow glass microbeads,wettability is improved.With the increase of magnesium content,granular structure increased,wettability increased,but brittle intermetallic compounds also increased.When the content of magnesium is 1.5%,granular tissue disappeared and the white intermetallic compound formed is wrapped in the wall of the hollow glass microsphere.When the content of Al and Mg is 10%and 1.5%respectively,the compressive strength is 460 MPa,the yield strength is 410 MPa,the average platform stress is 229 MPa,the densification strain is 72.6%,the specific absorptive capacity is 31.2 KJ/kg,and the absorptive capacity is 174.2 MJ/m3.The above parameters are all higher than other zinc-matrix syntactic foam materials with Al and Mg content,and the best content of Al and Mg is 10%and 1.5%,respectively,according to the comprehensive analysis of quasi-static compression performance.(3)The effect of different volume fraction of hollow glass beads on quasi-static compression performance of zinc-based composite foam is discussed.With the increase of the volume fraction of hollow glass beads,the yield strength,compressive strength,average platform stress,energy absorptive capacity and specific energy absorptive are first increased and then decreased.The compression property of syntactic foam material is considered comprehensively,and the best compression property of composite foam material is obtained when the volume fraction is 25%.Its platform stress,densification strain,energy absorption capacity,specific energy absorption and energy absorption efficiency are respectively 177 MPa,75.9%,134.7 MJ/m3,30.2 KJ/kg and 67.5%.(4)The microstructure and quasi-static compression properties of Zn-l0Al-2Cu-1.5Mg-25vol.%HGM composites are studied.After heat treatment at 335 ℃/2 h,syntactic foam material is subjected to air cooling,furnace cooling and water quenching.It is found that the as-cast solid solution Cu precipitated in the ε phase,and the matrix is found to have pores;The compressive properties of the composites decreased after air cooling and furnace cooling,but the platform stress of the composites increased after water quenching.The water-quenched syntactic foam is subjected to aging treatment at 120℃/2 h/AC and 120℃/5 h/AC.It is found that the e phase and the a phase undergo four-phase transformation,and T’and η phase are formed.As the aging time prolongs,the matrix matrix begins to de-dissolve the a and η phases and gradually coarsens.After aging,the yield strength of the composite foam decreases,but the compressive strength and average platform stress are greatly improved.Among them,the quasi-static compression performance of the 120℃/2 h/AC composite material is the best,its compressive strength and platform stress are 388 MPa and 238 MPa,respectively,absorption capacity and specific energy absorption reached 187 MJ/m3 and 36 KJ/kg,respectively,which are 38.8%and 19.2%higher than the as-cast state,respectively.In this paper,the energy absorption capacity and specific energy absorption of the zinc-matrix syntactic foam prepared by the stirring casting method are higher than those of many metal-matrix syntactic foams reported in the literature,indicating that the prepared syntactic foam has potential application value in the field of energy absorption buffering and anti-collision damping. |
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