Hot Workability of Alnico 5 and Sendust Alloys

Compression and sheath forging tests have been performed at high temperatures up to 1500 K for as-cast Alnico 5 and Sendust alloys which are brittle even at temperatures higher than Tm⁄2 (Tm: melting point). And the effects of various working factors and separation to dual phase on deformability, flow stress and microstructure of deformed materials have been examined. A large compressive strain more than 1.5 was obtained for Alnico 5 in the temperature range from 1350 to 1600 K and for Sendust in the range from 1050 to 1500 K at a strain rate of 0.0011 s−1. Materials deformed in the ductile range showed homogeneous fine structure. In the case of the Alnico alloy, the ductile temperature range was extended to lower side by the separation to dual phase. The deformability in the ductile range depended strongly on the strain rate, and at strain rates higher than 100 s−1 grain boundary brittle fracture appeared in all specimens. By the forging using a miled steel sheathed billet at a temperature of 1470 K and a strain rate of 1 s−1, a forging ratio more than 7 was obtained for both materials without cracks.