Grindability of Cast Ti-Al and Ti-Al-Cu Alloys

Objective: This study evaluated the grindability of a series of Ti-Al and Ti-Al-Cu alloys. Methods: Three binary Ti-Al (5, 6 and 7 mass%) alloys and six ternary Ti-Al (5 or 6 mass%)-Cu (1, 3 and 5 mass%) alloys were prepared in an argon-arc melting furnace, and were cast using a centrifugal casting machine (Ticast Super R, Selec) into magnesia molds (Selevest CB, Selec). Pure Ti, CP Ti and Ti-6Al-4V (Ti64) were used as controls. Two sizes of castings (n=2) were made (3.0mm x 8.0mm x 30.0mm; 3.5mm x 8.5 mm x 30.5mm) so that the second castings were the same size as the first after removal of the a-case. Grindability (n=8) was evaluated as volume loss (mm³) after abrasion using a SiC wheel (703-120, Brasseler) (100 gf) at 1250 m/min. The data were analyzed by two-way ANOVA (a=0.05). Results: The determined grindability [mean(S.D): mm³] are listed. Identical letters indicate no statistical differences (p>0.05).

Alloy	+a-case	-a-case	Alloy	+a-case	-a-case
5Al	2.74(0.80)ab	2.41(0.43)abc	5Al1Cu	3.57(0.72)bcd	3.47(0.88)cdef
5Al3Cu	5.73(1.09)e	4.42(1.13)f	5Al5Cu	4.99(0.69)ef	4.75(0.92)fg
6Al	3.27(1.08)bc	3.02(0.75)bcde	6Al1Cu	4.75(0.83)def	3.90(1.01)defg
6Al3Cu	5.09(0.97)ef	4.35(1.02)ef	6Al5Cu	5.01(0.64)ef	4.87(0.95)g
7Al	2.98(0.89)abc	2.87(0.82)bcd	Ti64	4.28(0.76)cde	3.71(1.08)cdefg
Pure Ti	1.83(0.70)a	1.74(0.60)ab	CP Ti	2.26(0.54)ab	1.24(0.42)a

The volume of the specimen with a-case removed tended to be greater than that of the specimen without the a-case. The volume of metal removed significantly increased with increases in Cu content (p<0.001). On the other hand, there was no significant difference in grindability among the three binary Ti-Al alloys (p>0.05). The volume of Ti-5Al+Cu and Ti-6Al+Cu removed was comparable to that of Ti-6Al-4V (p>0.05). Conclusions: The grindability of Ti-5Al+Cu and Ti-6Al+Cu was much better than that of CP Ti, due to their lower ductility resulting from the eutectoid component, a-Ti/Ti₂Cu, which promoted effective chip formation. Partially funded by NIH/NIDCR grant DE11787.