Nickel-niobium alloys obtained by picosecond pulsed laser quenching

Abstract

Ni x Nb 100− x alloys were quenched from the melt by irradiation of a crystalline surface with a 30 ps Nd:YAG laser pulse with a fluence of about 1 J cm −2. The crystalline starting materials were multilayered films, prepared by d.c. sputtering from alternating elemental targets, with a layer repeat length of less than 30 Å to ensure homogenization during the ~ 1 ns lifetime of the melt. For average compositions 40⩽ x ⩽ 79, the as-deposited films were amorphous, probably due to a solid state reaction during deposition, and the films still showed the X-ray peak corresponding to the composition modulation. For all other compositions, the as-deposited films were microcrystalline. The laser-quenched alloys in the range 23 ⩽ x ⩽ 82 were amorphous. This range exceeds that in which amorphous alloys have been prepared by other melt quenching techniques or by sputtering. Laser quenching resulted in glass formation even below the T 0-line and at intermetallic compound compositions. In the range 0 ⩽ x ⩽ 18, homogeneous supersaturated b.c.c. solutions were formed. In the range 89 ⩽ x ⩽ 100, homogeneous supersaturated f.c.c. solutions containing many twins and stacking faults were formed.