Based On Semi-solid Forming Technology Of Aluminum Foam Pore Structure Control

Foamed Aluminum is one of the multi-functional compound materials and has widespread application prospects in automobile, construction industry for its unique structure and performance. Melt foaming is a main method to obtain closed-cell aluminum foam, however, the problems of hard to control the process and uneven pore structure limit its widespread application.To solve those problems, this paper has put forward a brand-new two-stage method - SSF (Semi-Solid Foaming) based on semi-solid technology. Meanwhile, this paper has introduced the technique of TiH2 surface coating and its material, the basic principles and process of SSF and has researched effects of parameters on foaming process or pore structure, the changes of microcosmic structure, as well as the question of optimal parameters. The following are the main research results:1. Using self-made surface coating agent (Aluminum sol, Al₂O₃ is the main component), the resolving time of TiH2 has increased over 100℃after coating process. The resolving time can be prolonged over 2 min under condition of constant temperature resolving. And the wet ability of molten aluminum has been better improved.2. Through adding mechanical agitation, the solidification modes and morphology of semi-solid can be changed: solidification structures change into sphere-like or sphere amorphous structure from dendritic structures so the melt can keep good fluidity in relatively low temperature that TiH₂ can disperse and mix Al-Si melt well in low temperature, at the same time, TiH₂ has good fluidity and won't resolve large amount that guarantee the obtaining of foaming precursor3. Using SSF method, relatively even pore structure has obtained. The porosity of foaming Al-Si alloy is 74.6% and dimension of aperture is 2.134mm-3.164mm(average diameter is 2.262 mm), the average circularity is 0.812. The research indicated the best technological conditions as follows: agitation temperature is 580℃, The mixing time is 0.5min,The mixing speed is 1200r/min, re-foaming temperature is 720℃and the foaming time is 15mi...