A computer system for displacement sensor is developed to obtain the real-time curve of the liquid porosity of molten Al alloy foam. The relationship between the curve of Pl-t and the change of the shape of the cells (spherical, similar spherical and polygonal) in the foaming process is analyzed. The changes of cell diameter and cell wall thickness are studied. And the the controlling methods of a new Al alloy foam with spherical pores, low porosity and high strength are developed on this basis. Also, the stress-strain curve during compressive deforma- tion and energy absorption characteristics are investigated and compared with polygonal pore Al alloy foam with high porosity.
A temperature programmed decomposition (TPD) apparatus with metal tube struc- ture, in which Ar is used as the carrier gas, is established and the TPD spectrum of titanium hy- dride is acquired. Using consulting table method (CTM), spectrum superposition method (SSM) and differential spectrum technique, TPD spectrum of titanium hydride is separated and a set of thermal decomposition kinetics equations are acquired. According to these equations, the rela- tionship between decomposition quantity and time for titanium hydride at the temperature of 940 K is obtained and the result well coincides with the Al alloy melt foaming process.
Two porosity models of porous Al alloys with different pore types (ball and polygon shape) were established. The experimental results coincide well with theoretical computations. The porosity of Al alloys (Prc) consists of three parts, porosity caused by preform particles (Prp), additional porosity (Pra), and porosity caused by solidification shrinkage (Prs). Prp is the main part of Prc while Pra is the key for fabricating porous Al alloys successfully in spite of its little contribution to Prc.
The foaming process of Al alloy is similar to that of Al, but there is a solid-liquid state zone in the solidification process of cellular Al alloy which does not exist in the case of Al. In the unidirectional solidification of cellular Al alloy, the proportion of the solid phase gradually reduces from the solid front to the liquid front. This will introduce a force and result in a serious quick shrinkage. By the mathematic and physical mode, the solidification of the cellular Al alloy is studied. The data measured by experiment are close to the result calculated by the mode. This kind of shrinkage can be solved by suitable cooling method in appropriate growth stage. The compressive strength of the cellular Al alloy made by this way is 40% higher than that of cellular Al.
