This study investigated the mechanical properties of cast Fe-Pt magnetic alloys and compared them with those of dental casting alloys. The alloys tested were commercially pure (CP) Ti (T alloy M, GC, Japan), Ti-6Al-7Nb (T-alloy Tough, GC, Japan), Co-Cr (Cobaltan, Shofu, Japan), custom-made Fe-39.5at%Pt-0.75%Nb magnets, and Fe-36at%Pt keepers. Dumbbell-shaped patterns were used for all metals (ISO 6871). CP Ti and the Ti alloys were cast in an Ar-arc centrifugal casting machine (Ticast Super R, Selec Japan), and a high-frequency centrifugal casting machine for base-metal casting (Eagle, Jelenko, Germany) was used for the other alloys. The castings were bench-cooled to room temperature. The Fe-Pt keepers and magnets were sealed in evacuated silica tubes and solution-treated at 1425°C/45min (ST). The Fe-Pt magnets were then aged at 650°C/5 hrs after ST. Tensile testing (n=3) was conducted at a cross-head speed of 2 mm/min and a gauge length of 20 mm. Ultimate tensile strength (UTS) and elongation (EL) were recorded. The fractured surfaces were examined using SEM. Vickers hardness (1 kg load for 30 sec) was measured on the flat end of the tensile specimen before tensile testing. Results were [mean(SD)]:]

	CP Ti	Ti-6Al-7Nb	Co-Cr	Fe-Pt magnet	Fe-Pt keeper
UTS(MPa)	497(3)	893(11)	691(17.2)	198(27)	454(41)
EL(%)	8.9(3)a,b	5.5(1.5)a,c	10.3(1.9)b,d	2.8(0.1)c	14(4)d
Hardness(VHN)	158(3)	313(4)	350(1)	403(6)	204(5)

Identical letters indicate no statistical differences (p>0.05) in the same row(Duncan's test).

The mechanical properties of the cast Fe-Pt keepers were similar to those of cast CP Ti. On the other hand, the Fe-Pt magnets exhibited minimal elongation as substantiated by the intergranular fracture in the tensile test specimens. Although the Fe-Pt magnets lack ductility, the material is acceptable for dental use. Partially supported by NIH grant DE11787.

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