| Aluminum foamed is a new type of engineering material.Because of its special porous structure,it has dual properties of function and structure,and is widely used in today's life.The foaming law of aluminum foam prepared by powder metallurgy under constrained conditions is studied,which provides important theoretical support for the popularization and application of aluminum foam shaped parts.This experiment adopts the powder metallurgy method of hydrogenated titanium content is respectively 0.2%,0.4%,0.6% pure aluminum aluminum rod,and USES the drawing process the drawing to the diameter of 11 mm,8.5 mm and 6.5 mm respectively in the aluminum foam precast body,will be the precast body respectively in the free state and the sealed cavity of foam to its own volume of2 times,3 times,4 times,made of foam aluminum profiled,are studied in the different stages of foaming regularity and the effect of drawing process of foam aluminum foam.The results show that the specific surface area of the precast increases and the heat absorption speed is accelerated when the precast is drawn.Under the same condition,the lower the diameter of the prefabricated body,the faster the foaming speed.As the drawing process goes on,the titanium hydride inside the prefabricated body is continuously crushed and more evenly distributed in the prefabricated body,and the number of foamed aluminum holes increases.The number of foamed aluminum holes increases as the diameter of the prefabricated body decreases,and the number of foamed aluminum holes with the diameter of 6.5mm is significantly higher than that of 8.5mm and 11 mm.In the state of free foaming,pure aluminum powder was used as the raw material,the addition amount of foaming agent TiH2 was 0.4%,and the foam was drawn into the prefabricated body with a diameter of 8.5mm,and the foam was insulated at 680 ? for 570 s to obtain a relatively uniform foam aluminum.Hydrogenated titanium content is 0.2% of the precast body foaming in the sealed cavity,at the beginning of the foam,holes and oval dip hole,crack shape with the extension of heat preservation time,hydrogenated titanium constantly release,bubble hole grew,interaction between holes and hole,oval bubble hole number is reduced,bubble hole is gradually transformed into rules of round or polygonal,bubble uniform pore distribution,and finally because of the heat preservation time is too long,molten viscosity decreased,bubble liquid and bottom of hole wall,cause bubble hole merger or break.The biggest difference between foamed aluminum foam in closed cavity and foamed aluminum foam in free state is that the foamed aluminum foam in closed cavity has a homogenization process with the extension of insulation time.When foamed in closed cavity,the prefabricated body with a content of 0.2% titanium hydride and a diameter of 11 mm foamed to a volume of 4 times.In the process of extending the insulation time,the melt viscosity kept decreasing,and the bubble hole would collapse obviously,resulting in the failure to fill the cavity.When the prefabricated body with the same diameter of 11 mm and the content of titanium hydride of 0.4% or 0.6% foams to 4times the volume,it can fill the cavity,indicating that the increase of titanium hydride content is helpful to stabilize the bubble shape,so as to fill the closed cavity. |
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