REDUCTILIZATION OF EMBRITTLED LA-AL-NI AMORPHOUS-ALLOYS BY VISCOUS-FLOW DEFORMATION IN A SUPERCOOLED LIQUID REGION

A viscous flow deformation at high strain rates exceeding a critical value in the supercooled liquid region was found to induce the ductilization of an amorphous La55Al25Ni20 alloy which was embrittled by annealing at temperatures below T(g). The appearance of the tensile fracture surface also changed from a shell-like pattern typical for the brittle amorphous alloy to a pattern consisting of smooth regions and regions with vein-like structures typical for the ductile amorphous alloy. The embrittled samples exhibit an endothermic reaction resulting from the annihilation of the short-range ordering developed during annealing, accompanying the disappearance of an exothermic reaction. The deformed samples with good ductility do not show the endothermic reaction but exhibit only the exothermic reaction. Accordingly, the deformation-induced reductilization is presumed to result from the introduction of excess free volume and the formation of deformation-induced disordered atomic configuration.