Plastic deformation behavior of Fe–Co–B–Si–Nb–Cr bulk metallic glasses under nanoindentation

•Additional Cr modulation of atomic structure of Fe-Co-B-Si-Nb BMGs.•An amount of free volume characterized by a combination of nanoindentation and AFM.•Free volume determined by height measurement of AFM after nanoindentation.

In this work, we investigate the effect of Cr addition on thermal properties and indentation behavior of Fe52Co20−xB20Si4Nb4Crx alloys with x = 0, 1, 3 and 5 at.%, respectively. Among all studied alloys, the Fe52Co17B20Si4Nb4Cr3 bulk metallic glass (BMG) exhibits the highest thermal stability with large supercooled liquid region of 40 K and the pronounced plastic deformation features which is serrated flow (pop-in event) and significant pile-up of materials around indents. This demonstrates that the appropriate addition of Cr in Fe-based BMG can induce the internal atomic structure modulation and promote the mechanical softening, which are discussed in terms of free volume concept.