Heat Treatment- and Lamp Processing-Induced Structural Transformations of an Amorphous Fe77B7Nb2.1Si13Cu0.9 Alloy and Nonmonotonic Behavior of Its Mechanical Properties

Abstract

Using a variety of characterization techniques (differential scanning calorimetry, X-ray diffraction, high-resolution transmission electron microscopy, resistivity measurements, nanoindentation, and uniaxial tension testing), we have studied structural changes produced in the amorphous phase of the Fe₇₇B₇Nb_2.1Si₁₃Cu_0.9 alloy by heating in vacuum to 750°C and lamp processing (LP) with the use of pulsed xenon lamps to a fluence F = 120 J/cm² on the sample surface. Increasing the temperature or fluence leads to three stages of structural transformations: structural relaxation of the amorphous phase below 450°C and two stages of crystallization, which show up as nonmonotonic behavior of the hardness and local plasticity of the samples. With a common character of the structural changes, the effect of LP shows up as an increase in crystallization rate (the processing time is 200 times shorter). In both cases, the fraction of plastic strain in indentation work in amorphous and crystallized samples is 25% larger than that in amorphous–crystalline composites. It has been shown that irreversible deformation of amorphous samples by uniaxial tension leads to structural relaxation and an increase in the size of the relaxation zone.