SOME EVIDENCE FOR DIRECTIONAL ATOMIC PAIR ORDERING IN A COBALT-BASED METALLIC-GLASS

Time-of-flight neutron diffraction has been used to study structural a nisotropy in a wide-ribbon sample of the multicomponent metallic glass Fe4Co67Cr7Si8B14 prepared by continuous casting. A planar sample held at 45 degrees to the incident beam was examined by two stationary cou nters at 90 degrees left and 90 degrees right, so that the directional structure factors, S-l(Q), S-w(Q), S-t(Q) corresponding to the three orthogonal directions in the ribbon (length I, width w and thickness t ) were determined. It was found that the directional Structure Factor S-t(Q) had stronger oscillations than S-l(Q) and S-w(Q). Comparison of the directional S(Q) with the total structure factors for FeB and CoB glasses suggest that the result may be tentatively associated with 'a tomic directional pair ordering' of the Fe-Fe first neighbour pairs in the t direction. The diffraction data have been analysed in the conte xt of the atomic level stress model of metallic grass structures. (C) 1997 Elsevier Science S.A.