Crystallization of Ti33Cu67 metallic glass under high-current density electrical pulses

We have studied the phase and structure evolution of the Ti33Cu67 amorphous alloy subjected to electrical pulses of high current density. By varying the pulse parameters, different stages of crystallization could be observed in the samples. Partial polymorphic nanocrystallization resulting in the formation of 5- to 8-nm crystallites of the TiCu2 intermetallic in the residual amorphous matrix occurred when the maximum current density reached 9.7·108 A m-2 and the pulse duration was 140 μs, though the calculated temperature increase due to Joule heating was not enough to reach the crystallization temperature of the alloy. Samples subjected to higher current densities and higher values of the evolved Joule heat per unit mass fully crystallized and contained the Ti2Cu3 and TiCu3 phases. A common feature of the crystallized ribbons was their non-uniform microstructure with regions that experienced local melting and rapid solidification

Magnetic order in R2Ni17 intermetallics: a neutron-diffraction investigation

The crystal and magnetic structures of hexagonal intermetallic compounds of the type R2Ni17 with R = Y, Tb, Dy, Ho and Er have been investigated by neutron powder diffraction at 20 and 200 K. The crystal structures at 200 K, which is above the magnetic ordering temperature for these compounds, have been refined and show that they crystallize in the hexagonal Th2Ni17 structure (space group P6(3)/mmc). The magnetic structure at 20 K has a magnetic propagation vector (k) over right arrow = 0 and consists of a ferrimagnetic alignment of R and Ni moments. At 20 K, compounds with R = Tb, Dy and Ho are collinear ferrimagnets with moments aligned in the basal plane of the hexagonal unit cell, whilst the compound with R = Er is an axial collinear ferrimagnet. The low-temperature magnitudes of the R moments at 2b and 2d sites are markedly different, with an almost free ion value at the 2b site, whilst the 2d site moment is substantially reduced from its free ion value. (C) 2002 Elsevier Science B.V. All rights reserved