Study On Strengthening And Toughening Mechanism Of ZL111 Alloy Foam

Aluminum foam possess these properties as low density, high specific strength, sound absorption, vibration attenuation, insulation and others properties. It has prospects of extensive applications in the fields of aeronautics, astronautics, noise control, and so on.Although two steps foaming technique is a promising industrialized processing for fabricating aluminum foam, its cell stucture and the strength and toughness of aluminum foams by this processing need to be further improved. But the strength and toughness mechanism of aluminum foams is still unclear, it needs to be further exploration and research. This paper has improved the strength and toughness of aluminum foams significantly through the chemical composition control by melt modification and heat treatment.The main results are as follows:(1) The stability-control mechanism of ZL111melt alloy foam were summarized through the diagram of experiment model:the good stability area of ZL111melt alloy foam were:the range of foaming temperature between605℃to615℃, the range of melt viscosity between1.25mPa.s～1.75mPa.s. it slows down the effect of gravity and capillary drainage.(2) ZL111alloy foams prepared by the experiment of modification were studied. the best modification process of strengthen-toughen of ZL111alloy foams were obtained:ZL111alloy foams can reach the best modification effect by composite modification with Y&Sr, At this point the addition amount of Sr is0.06%, Y is0.3%; the modification temperature is610—; modification time is30min. It was concluded that the micro-structure of aluminum foam is much smaller and uniform by composite modification than single modification. Meanwhile, the average size of a-Al was refined from75～120μm to20～40μm.(3) By comparing different heat treatment process of ZL111alloy foam, it is concluded that the best microstructure and strength-toughness properties of ZL111alloy foam by the process T63heat treatment. The best heat treatment process were: T63heat treatment process,the solution temperature540℃and treating time is7h+the aging temperature is170℃and aging time is6.5h.(4) It was concluded that there were some tiny second phase precipitated and dispersed in crystal boundary by melt modification and T63heat treatment. The Microstructure of ZL111alloy foam which were processed by composite modification and T63heat treatment were analyzed by SEM and XRD.The results indicated that the second phase mainly were:Al、Si、Al5FeSi、CuAl2、Mg2Si. These tiny second phase can strengthening and toughening the ZL111alloy foam.(5) The fundamental strengthening and toughening mechanism of ZL111alloy foam were summarized by the diagram:through the combination of a small amount of second phase and under the low temperature physical viscosity of melt to achieve stability-control of ZL111melt alloy foam, thus, it can realize strengthening and uniforming control the pore structure of the ZL111alloy foam. Through the melt modification to achieve the grain refinement and strengthen the matrix of alloy foam. Then by incomplete solution treating and aging treatment on the basis of grain refinement to adjust and control the microstructure of aluminum foam, the approximate ideal deformation mode of high strength and toughness of ZL111alloy foam were obtained.