Alternating layers of Nb and amorphous Nb-Si were sputter deposited at room
temperature and then annealed at elevated temperatures to produce microlam
inates with flat, discrete layering and an equiaxed grain structure. The am
orphous Nb-Si layers crystallize at temperatures between 740 and 800 degree
s C depending upon whether the silicide was co-deposited from elemental tar
gets, or directly deposited from a single composite target. The first phase
to form on crystallization is Nb5Si3, but upon heating to 1000 degrees C f
or 3 h a second phase, metastable Nb3Si, forms. Annealing at 1200 degrees C
for 3 h though, eliminates the Nb3Si phase. The microstructural stability
of the microlaminates was examined by annealing samples at temperatures up
to 1400 degrees C. In all cases very limited grooving was observed and ther
e was no pinch-off of the layering. There was also no evidence of silicide
precipitates in the Nb grains after high temperature anneals. The mechanica
l properties of the microlaminates were examined using room temperature ten
sile tests. The ultimate tensile strength of the microlaminates is 590-640
MPa. Examination of fracture surfaces from the samples reveals that the Nb
layers blunt cracks in the silicide layers and contribute significantly to
the observed room temperature strength of these microlaminates. (C) 1999 El
sevier Science S.A. All rights reserved.