Nucleation of shear bands in amorphous alloys

• DOI: 10.1073/pnas.1321518111
• Publication Date: 2014-03-05T01:22:49Z
• Authors: John H. Perepezko; Seth D. Imhoff; Ming-Wei Chen; Jun-Qiang Wang; Sergio Gonzalez
• Keywords: Kinetics; Models, Chemical; 0103 physical sciences; Alloys; Glass; Shear Strength; 01 natural sciences

SignificanceA shear band is a region of highly localized plastic flow that develops during loading in both crystalline and amorphous materials. Shear bands directly determine the ductility of an amorphous phase, but relatively little is known about their nucleation. We use nanoindentation to probe shear band nucleation by measuring the first pop-in event during loading which is associated with shear band formation. We analyze a large number of independent measurements on four different metallic glasses and reveal a bimodal distribution of nucleation events that operate at different stress levels. The discovery of multiple shear band nucleation sites challenges the current view of a single type of site and offers opportunities for controlling the ductility of amorphous alloys.