Effect of Al and Cu on Mold Filling of Titanium

Objectives: This study evaluated the mold filling of experimental Ti-Al, Ti-Cu and Ti-Al-Cu alloys. Methods: Ti-5mass%Al (Ti-5Al), Ti-5%Cu (Ti-5Cu) and Ti-5%Al-5%Cu (Ti-5Al-5Cu) alloys were prepared in an argon arc-melting furnace. Molds were prepared using a magnesia investment (Selevest CB, Selec, Japan) in two kinds of the wedge-shaped acrylic patterns with either 30° or 15° angle. Each alloy was cast in a centrifugal casting machine (Ticast Super R, Selec). The castings (n=6) were cut into three sections perpendicular to the angled edge to create 18 specimens; the sectioned surfaces were photographed (25x). Mold filling was evaluated as the missing length (µm) between the angled edge of the casting and the theoretical edge. Commercially pure titanium (CP Ti) was used as controls. The data were analyzed by ANOVA/Tukey's test (a=0.05). Results: The mold filling [(mean: µm) (SD)] of each alloy was as follows (means with identical letters are not significantly different in each angle) (p>0.05):

Angle	Ti-5Al	Ti-5Cu	Ti-5Al-5Cu	CP Ti
30º	308(53)a	247(107)a	449(91)b	135(27)c
15º	314(89)a	506(277)b	734(237)c	214(90)a

In each alloy, the data of the 30° angle tended to show lower value than that of the 15° angle. For both angles tested, Ti-5Al-5Cu showed significantly higher mold filling than any other metal (p<0.05). For the 30° angle tested, the mold filling of Ti-5Al and Ti-5Cu was significantly higher than that of CP Ti (p<0.05). For the 15° angle tested, the mold filling of Ti-5Cu was significantly higher than that of Ti-5Al and CP Ti (p<0.05). Conclusion: Alloying Al or Cu affected to fill metals in thin-section castings. Alloying Al and Cu together exhibited a synergic effect in a pasty metal flow. This study was partially supported by NIH-NIDCR grant DE 11787.