Research On The Processing And Quality Analysis Of Aluminum Alloy Foam Precursor Through Semi-solid Melt Stirring Method

ABSTRACT:Metal foam is a lightweight functional material with series of performances such as hole-like structure, low-density, high-toughness, high impact resistance, high specific strength, high stiffness, efficient cooling, insulation, fire-retardant and etc. Precursor is the basic and only raw material for the two-step processing of metal foam. The aim of this paper to propose a new approach to obtain the precursor with uniform distributing blowing agents-processing precursor by semi-solid melt stirring, and the following researches were carried out about this approach:(1) The equipment of processing aluminum precursor was designed and manufactured which to obtain precursor by semi-solid melt stirring method. The equipment includes five main parts:the stirring part which to distribute blowing agents by mechanical stirring; the adding part which is adding to add blowing agents directly and efficiently, the sampling part which to obtain precursor samples, the controlling part which to adjust temperature and the data part which to collect the experiments’datas.(2) The characterization and evaluation method for quality and internal sturcture of both aluminum precursors and metal foam parts was proposed through diagital image technology. The main researches were focused on precursor sample treatment, image acquisition, image handling and data analysis. And it is to obtain the digital evaluation of precursor on both vertical and horizontal directions as well as the three-dimensional evaluation system. This3D system could quantitatively characterize the blowing agents or pores in precursors and aluminum foam by size, quantity and the three-dimensional distribution. Also this system could characterize agglomeration and degree of cluster of blowing agents, which could indicate objectively and accurately the quality of the precursor and defect locations. This3D system provided an alternative method for the quality evaluation of both precursor and metal foam parts.(3) The distribution and decomposition effects on blowing agents and the initial bubbles morphology in precursors were studied by changing processing parameters such as alloy composition, stirring temperature, stirring apparent viscosity, stirring time and quantity of blowing agents, and the technique of processing aluminum precursors with uniformly distributed blowing agents inside was carried out ultimately.(4)The decomposition behaviors of blowing agents as well as the growing behavior of intial bubbles in the semi-solid melt during stirring were studied in this paper. A growing model of bubbles in semi-solid melt was established, which exports the control model of the limit bubble size and its impacting factors in the semi-solid melt. And this model provided basises for the control of intial bubbles and blowing agents distribution in the procursor.This processing and evaluation methods presented by this paper were of reference value for reducing the cost of processing aluminum precursor, improving production efficiency and quality of the aluminum foam, even accelerating the pace of industrial applications of the metal foam. And the author believed that the engineering applications of this technology need to be strengthened in the future so as to expand the scope of its application.