Evaluation of Foam Defects in A356 Aluminium Alloy Produced with TiH2 ‎and CaCO3 Foaming Agents Without Stabilized Ceramic Particles ‎

In this paper, foam defects of A356 closed cell aluminum foams produced in different process were evaluated. For this purpose, the different foam samples were separately produced using two foaming agents, Titanium Hydride and Calcium Carbonate, without addition of stabilized ceramic particles into the molten metal. Foaming process using 1-2 wt.% TiH2 was performed in the temperature ranges of 650 to 750 °C, for 0.5-2 minutes holding times. Another foaming process was also performed with 2.5-3.5 wt% CaCO3 at 700 °C and for 10-20 minutes holding time. Casting defects included the drainage, the coalescence and the cell size distribution were evaluated using the optical and scanning electron microscopic images and density measurements. The results showed that the homogeneous cellular foam of Al-Si-Mg alloys can be produced using TiH2 and CaCO3 foaming agents and without using the stabilized ceramic particles. The optimal foam are produced using 3 wt.% CaCO3 or using 1.5 wt.% TiH2 additions, separately. In each of two foam productions processes, the drainage and the coalescence foam defects are increased with increasing the holding time. While the drainage and the coalescence foam defects increase with increasing the foaming temperature in TiH2 foamed specimens and with decreasing of the mixing time in CaCO3 foamed specimens.