Study On Preparation, Characterization And Properties Of Aluminum Alloy Foam By Powder Metallurgy Method

By using the method of cold isostatic pressing, hot vacuum deaeration, hot extrusion and heating foaming molding, four kinds of foamable precursors were produced. The composition ratio of four kinds of precursors was respectively AlSi11 which raw material is pre-alloyed powders; AlSi11 which was mixed by elementary Al and Si powders; AlSi7-4vol%SiC which was blended by mixed pre-alloyed AlSi11 powders, elementary Al powders and SiC powders; AlSi7Cu4 which was which is mixed by elementary Al, Si and Cu powders. All of the four precursors contained TiH2 as foaming agent. By hearting the four kinds of precursors, time series of aluminum foam samples were successfully fabricated. Through the analysis of foam aluminum pore structure for different heating time, the effect of the precursor structure on pore structure evolution and the stability of the foam aluminum pore wall were studied.The experimental results show that: the foam aluminum precursor produced by the process had good foamability, and different precursor system for aluminum foam differed in terms of porosity and pore structure. AlSi11 Precursor by using pre-alloyed powders system for aluminum foam porosity was up to 72%, the average pore diameter was from 1.18 mm to 3.38 mm, and pore size distribution was not uniform; aluminum foam for precursor system of AlSi11 elements mixed powders, maximum pore rate was 85%, the average pore size was from 1.38 mm to 1.99 mm, and pore size distribution was relatively uniform; foam aluminum for AlSi7-4vol%SiC precursor, the pore rate was up to 81.6%, with the average pore diameter of 0.87 mm to 1.23 mm, and pore size distribution was the most uniform; for aluminum foam produced by precursor of mixed element powder for AlSi7Cu4, sample porosity was up to 83.2%, with the average pore size of 1.11 mm to 1.32 mm, and pore size distribution was relatively homogeneous. Through analysis and study, we know that the difference of porosity and pore structure of aluminum foam, is mainly caused by the different precursor organization structure. The early precursor foaming pores nucleation number and stomatal extension mode are determined by the state of the combination of ceramic particles and aluminum matrix. The solid phase in the process of foaming of precursors(including oxide inclusions and unmelted matrix particles) will have a significant impact on the stability of foam aluminum pore structure.For the aluminum foam produced by various precursors, compression experiments was implemented. Through comparison, the effect of foam aluminum’s pore rate, pore structure and composition on its compression performance and energy absorption characteristics were studied. The results show that the compression performance of aluminum foam is influenced by the porosity, pore structure and composition factors. As porosity increasing, the performance of the aluminum foam compression and energy absorption characteristics become bad. Aluminum foam with small and uniform pores has more excellent compression property. In four kinds of samples, the composition of aluminum foam produced by AlSi7-4vol%SiC precursors is superior to the other samples in compression performance and energy absorption characteristics.