Masaki Harata1, Takao Choh2 and Makoto Kobashi2
1Graduate Student, Nagoya University, Nagoya
The effect of alloying elements on TiC particulate dispersion into liquid aluminum was investigated. TiC particles could be dispersed in liquid aluminum without excessive dissociation, because of their chemical stability. The time required for dispersion of TiC particles into molten aluminum is defined as the incorporation time. The results of measurement showed that the alloying elements were divided into three types concerning the effect on particulate incorporation time: shortening, prolonging the incorporation time and no effect.
The incorporation of TiC particles into molten aluminum proceeds accompanying TiC dissociation for wetting, resulting in the formation of an intermetallic compound of the Ti-Al system. In the case of additions of silicon, calcium and zirconium, EPMA showed that these elements promoted the reaction of TiC particulate dissociation; TiC→\underlineTi+\underlineC and shortened the incorporation time by forming an intermetallic compound with titanium. On the other hand, although alloying elements such as magnesium, lead and bithmuth were not contained in the intermetallic compound, the incorporation time was shortened by the surface active effect of these alloying elements. Copper had a little effect on the incorporation time. Since TiC dissociation is controlled by the existence of titanium in melt, the incorporation time for the Al-Ti system was prolonged consequently.
It is clear from the microstructural observation that particles segregate along grain boundaries of the matrix under slow solidification rate as air cooling in the crucible. However, under the condition of rapid solidification rate, the sound composite showing a uniform particulate distribution was obtained.
incorporation time, titanium carbide particle, composite, alloying element, intermetallic compound, melt-stirring method
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