Study On The Fabrications And Properties Of A356 Aluminum Foam Composites Reinforced By In-situ ZrB₂ Particles

In this paper,the Al-K₂ZrF₆-KBF₄ in situ reaction system and direct melt foaming method were combined,MnO₂ was used as nucleating agent,metal Ca as tackifier,TiH₂ at400?/5h+500?/2.5h oxidation treatment was used as foaming agent,high porosity porosity controllable nanotube ZrB₂/A356 foam aluminum composite material with high porosity was prepared.The microstructure of ZrB₂/A356 foam aluminum was characterized by means of OM,X ray diffraction?XRD?,electron microscopy?SEM?and transmission electron microscopy?TEM?,and the microstructure of the foam composites was analyzed.study on strengthening mechanism of ZrB₂ particles The compressive properties of foam composites were tested by universal testing machine,and the bending properties of foam aluminum sandwich panels were tested.The effects of ZrB₂ particle mass fraction and foam aluminum porosity on compressive properties were studied.The best preparation parameters of nano ZrB₂/A356 foam aluminum composites are:melt in situ reaction 25min at 850?temperature range;end of the end of the reaction is added with 2wt.%tackifier metal Ca;after thickening,1.5 wt.%nucleating agent MnO₂ is added;finally,at650 wt.%foaming temperature,1000¹200 The oxidation process of blowing agent TiH₂:400?/5h+500?/2.5h,the amount of blowing agent is 2.2 wt.%.The cell wall edge of ZrB₂/A356 foam aluminum composite is composed of nano ZrB₂particles and eutectic Si bands.The main phases in the composites are Al,Si,ZrB₂ and CaAl₂;the ZrB₂ particles are distributed at the edge of Si phase and hole wall;ZrB₂ particles can passivate the Si phase and reduce the stress concentration;by measuring the two dendrite arm spacing of alpha dendrite,the nano particles can refine the foam aluminum complex.The grain size of the composite material and the ZrB₂ particles of the aluminum foam material can achieve the effect of fine-grained strengthening.By analyzing the influence of ZrB₂ particles on Si phase size and the distribution of ZrB₂ particles around Si phase,the dislocation strengthening mechanism of ZrB₂ particles is obtained.Nano ZrB₂ particles reinforced the compressive mechanical properties of aluminum foam composites.In the relative density range?0.15⁰.19?,the compressive strength of aluminum foam composites increased by 9.09%,24.24%and 15.16%when the foam aluminum in situ generated 1 wt.%,3 wt.%and 5 wt.%content of ZrB₂ particles.The energy absorption properties and compressive properties of nano ZrB₂/A356 aluminum foam composites show consistency.The energy absorption of 3 wt.%ZrB₂ particles of aluminum foam reaches 4.1MJ/m³,compared with that of A356 foam,the energy absorption of 3.3MJ/m³ increases by 24.24%.The flexural ultimate load of 3 wt.%ZrB₂ particle A356 foam aluminum sandwich panels is1.58 kN,which is 20.61%higher than the ultimate bending load of 1.31 kN of base foam aluminum sandwich panels,while the limit load point is shifted to 0.51mm,and the ultimate load is delayed by 30.6s,and the bending failure ability is improved.The three-dimensional model analysis results show that the grain loading strengthening mechanism,orowan strengthening stress mechanism and fine grain strengthening synergism.