Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577, Japan
Abstract:
Rapidly solidified Ni–Al–Hf alloys of ternary eutectic compositions were studied by X-ray diffractometry, transmission electron microscopy and differential scanning calorimetry. Ni66Hf20Al14 amorphous alloy with relatively high Hf/Al ratio showed high tensile strength of 1600 MPa and high thermal stability against crystallization. The formation of a nanoscale metastable intermetallic compound having a body-centered cubic lattice with a lattice parameter of a=1.22 nm was observed in the alloys with higher Al than Hf content. The transformation of an amorphous+metastable cubic mixture to AlNi3 produces AlNi3 of the same composition as the AlNi3 phase formed on rapid solidification. Pm
m AlNi3 phase can dissolve up to 11 at.% Hf.