THERMOMECHANICAL ANALYSIS OF THE RELAXATION AND CRYSTALLIZATION OF FE85-XCOXB15 METALLIC GLASSES

The structural relaxation and crystallization of Fe85-xCoxB15 amorphou s ribbons was studied by thermomechanical analysis. The role of therma l history on reversibility of sample length change is evidenced. From flexure experiments performed at room temperature after pre-annealing, we observe a substantial increase of Young's modulus by 8% for relaxa tion and 50% for crystallization associated with a small density incre ase (about 0.08% and 2% respectively). The effect of cobalt content is revealed on the mean thermal expansion coefficient measured between 9 0-degrees-C and 140-degrees-C on the one hand and on the total residua l shrinkage measured at room temperature after complete crystallizatio n on the other hand. In agreement with other measurements, we observe a specific role of x (at.%) = 21 cobalt concentration on thermal stabi lity.