Fabrication and evaluation of Nb/Nb5Si3 microlaminate foils

Alloys of Nb and Nb5Si3, and in particular Nb/Nb5Si3 microlaminates, have p otential as high-temperature materials. In this study, microlaminates of Nb and amorphous Nb-37.5 at. pet Si are magnetron sputter deposited from elem ental Nb and polycrystalline Nb5Si3 targets. The microlaminates are heat tr eated at high temperatures to produce crystalline layers of Nb and Nb5Si3 t hat are flat, distinct, and stable for at least 3 hours at 1200 degrees C. The layers consist of textured Nb grains and equiaxed submicron Nb5Si3 grai ns. Initial room-temperature tensile tests indicate that the microlaminates have strengths similar to cast and extruded alloys of Nb and Nb5Si3 The fr acture mode of the Nh layers is dependent on the Nb layer thickness, with t hin layers failing in a ductile manner and thick layers failing by cleavage . The Nb layers bridge periodic cracks in the Nb5Si3 layers, and using a sh ear lag analysis, the tensile strength of Nb5Si3 is estimated. The results indicate that microstructurally stable and mechanically robust microlaminat es of Nb and Nb5Si3 can be fabricated by sputter deposition with a high-tem perature heat treatment. The processing, microstructure, and mechanical pro perties of these microlaminates are discussed.