Structure and yield strength of directionally solidified Ni3Al intermetallic premelted with MoSi2 phase

Ni3Al and MoSi2 intermetallic phases were are melted in Ni3Al/MoSi2 molar p roportion of ten. Pure binary Ni3Al and the quaternary alloy were subjected to directional solidification using the floating zone method at growth rat es of 10-50 mm h(-1). The phase composition and structure of the crystals w ere analyzed using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffractometry. The yield strength was s tudied in compression at 293-1293 K and in tension at room temperature. Com pared to the binary Ni3Al crystals, the quaternary Ni-Al-Mo-Si crystals rev ealed up to 5 times higher compressive yield strength at 400-800 K. Ni-Mo-S i Cl4 Laves phase precipitation in the Lit Ni3Al+Ll(0) NiAl matrix duplex p hase was found in quaternary crystals. This precipitation is assumed to cau se the observed mechanical behaviour. (C) 1998 Elsevier Science Ltd. All ri ghts reserved.