Cold-rolling induced amorphization in binary metallic alloys

•Guru Prasad Dinda und Gerhard Wilde
Forschungszentrum Karlsruhe, Institut für Nanotechnologie, Postfach 3640, 76021 Karlsruhe

Repeated cold-rolling with intermediate folding of the sheet sample represents a technique to obtain severe plastic deformation that avoids excessive heating at the internal interfaces as during ball-milling and that proceeds without the simultaneous action of a high pressure in the range of several GPa, as in recently developed extrusion - or torsion straining techniques. However, complete amorphization by cold-rolling has only been reported for a bulk glass forming quaternary Zr-Al-Ni-Cu alloy. In the present work almost completely amorphous samples of binary Cu60Zr40, Ni50Ti50 and ternary Ti35Zr10Cu55 alloys have been synthesized at ambient temperature from a layered array of individual elemental sheets by repeated cold rolling with intermediate folding. The microstructural development during the mechanical alloying process was investigated by X-ray diffraction and scanning and transmission electron microscopy at different deformation levels to investigate the crystal-to-amorphous transition during intense mechanical deformation. The development of the microstructure during cold-rolling that yields almost completely amorphous phases for selected nominal compositions is analyzed in terms of the major thermodynamic - and mechanical properties that govern the intermixing during the deformation process.