Study On Powder Metallurgy Controllable Preparation Of Aluminum Foam And Foaming Mechanism Research Based On Synchrotron Radiation Technique

Aluminum foam,as a new kind of structural and functional composite material,Own to its light weight,high specific strength,specific stiffness,advantaged sound insulation and electromagnetic shielding properties,are widely used in urban construction,automobile manufacturing,electronic communication,aerospace and in other fields.Although there are many methods prepared for closed-cell aluminum foam,compared with other foaming method,powder metallurgy method its unique advantage such as nearly end forming.So foam aluminum produced by powder metallurgy method is becoming a hot spot in scientific research institutions both at home and abroad recent ten years.However,due to technical confidentiality reasons,the article about foam aluminum prepared by powder metallurgy process is rarely seen at anywhere.With the funding of The National Natural Science Foundation of China "an investigation of powder metallurgy foaming mechanism of aluminum foam based on synchrotron radiation-CT.”This paper launched a research on the powder metallurgy preparation technology and foam structure evolution.This experiment make a detailed analysis and discuss about the advantage of AlSi7Mg alloy selected components,combined with thermal analysis,XRD,SEM and other detection tools,In vacuum and argon atmospheric pressure and normal pressure air oxidation deal with hydrogenated titanium respectively,Results show that the titanium hydride color change degree only related to the oxidation degree,and its no related to the percentage changes caused by internal hydrogen release,Experiments show that the color changes of titanium hydride is proportional to pre oxidation temperature,pre oxidation time and oxygen content;by isostatic pressing new compression method include the precursor of hardness testing and detection means of foam products cross section.The results show that the isostatic compression mode is conducive to the uniform growth of the bubble hole,analyze and discuss its mechanism;Compared with thermal radiation,heating mold and melt foaming foam aluminum products respectively,through measuring profile to describe bubble distribution,introduces the effect of temperature gradient on the aluminum foam product.At the same time,through of foam aluminum by without preheating,280?degrees preheating and 480 ? degrees preheating treatment respectively,The results show that preheating temperature of 480?and thermal insulation 1h the bubble holes are uniformly best;simple comparison of air cooled and water cooled cooling system,the results show that the water cooling method to enhance the bubble hole roundness;at the same time,the new technology of foam aluminum foam was explored,to explore the use of pressure change to promote the performance of aluminum foam to improve and the application value of foamed aluminum by salt bath.Adopt the Beijing Synchrotron Radiation Facility 4W1A experiment station on the foaming process of dynamic imaging and micro CT on early foaming bubble evolution of quasi dynamic imaging,and combined with theoretical analysis to discuss the powder metallurgy foaming mechanism.At 4W1A experimental station dynamic imaging field of view three phases:the nucleation of the bubble hole,the growth of the bubble and the solidification of the bubble can be observed.It can be seen that the merger of vacuoles in the process of bubble growth and the shrinkage of the vacuole in the solidification stage,which can react to the large scale solidification of aluminum foam.The effect of oxidation on aluminum foam is discussed,and the importance of improving heating efficiency is briefly introduced.Using micro-CT conduct quasi dynamic imaging experiment of aluminum foam,Through comparative reconstruction of three-dimensional images,a simple analysis of the bubble growth process in the growth mechanism come to the conclusion that the bullae hole gobble up the small bubble hole under the action of tension.