Effects of Cr and Cu on Castability of Titanium Alloys

Objective: This study evaluated the mold filling of experimental Ti-Cr and Ti-Cr-Cu alloys. Methods: Ti-13mass%Cr (13Cr), Ti-5%Cu (5Cu) and Ti-13%Cr-5%Cu (13Cr5Cu) 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 parallel to the triangle surfaces to create 18 specimens. By examining a polished triangle surface, 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) and Ti-6Al-4V (Ti64) were used as controls. The data were analyzed by Two-way ANOVA/Tukey's test (a=0.05). Results: The mold filling [mean(SD):µm)] of each alloy was as follows (means with identical letters are not significantly different) (p>0.05):

Angle	CP Ti	Ti64	5Cu	13Cr	13Cr5Cu
30°	104(38)a	129(67)a	183(79)a	168(62)a	146(52)a
15°	208(164)b	300(74)bc	375(205)c	349(157)c	397(117)c

For all alloys tested, the mold filling of the specimen with the 30° was smaller than those of the specimens with the 15° (p<0.05). There were no significant differences in the mold filling with 30° among all the alloys tested (p>0.05). Conclusion: The mold filling of 13Cr, 5Cu and 13Cr5Cu alloys was comparable to that of Ti64. These V-free alloys are good candidates for dental applications. This study was partially supported by NIH/NIDCR grant DE11787.