Study of the Interface Reactions between Titanium Hydride Powder (TiH2) and Pure Aluminum Melt

مهندسی متالورژی و مواد

Article 2, Volume 22, Issue 1 - Serial Number 3, January 2012   

Document Type: Original Articles

DOI: 10.22067/ma.v22i1.10814

Authors

ali Rasooli^* ; mehdi Divandari; hamid reza Shahverdi; mohamad ali Boutorabi

Abstract

In aluminum foams, bubbles are formed as a result of the decomposition of TiH2 powder in contact with the molten aluminum. Hence, the study of these reactions has an important effect in determining the mechanism of decomposition of TiH2 inside the molten aluminum. In this research, TiH2 powder was put in contact with the molten aluminum at various temperature ranges, i.e. a)700-750ºC, b)750-800ºC and c)800-1000ºC. After solidification of the melt, the solidified samples were taken for the SEM and EDAX examinations. The results showed that as soon as the TiH2 particles touch the melt, a thin layer of TiAl3 is formed around the particles. At the temperature range of (a), the TiAl3 layer formed was almost continuous, hence, the decomposition process was controlled by internal diffusion (diffusion of atoms within the TiAl3 layer). At the temperature range of (b); the TiAl3 layer had no sufficient continuity and its overall thickness was greater than that for the range (a). In this case, the powder particles had a semi-collapse shape. Consequently, the decomposition process was under the control of both the internal diffusion and the chemical reaction (reaction between the TiH2 powder and the melt). At the temperature range of (c), the TiAl3 layer formed around the TiH2 particles was shattered and finally dispersed within the melt. Therefore, the decomposition process in this case was controlled by the chemical reaction. The amount of remaining powder particles decreased with an increase in the melt temperature. The rate of decomposition process increased with increasing the melt temperature, due to the decrease of the thickness of TiAl3 layer formed around the particles, as well as its non-continuous character.