Microscopic Mechanisms Of Mechanical Properties In ZrCu Amorphous Alloy

It is known that amorphous alloys have unique mechanical properties,while the lack of tensile ductility at room temperature limits the application of such glassy metals.Therefore,it is required to reveal the microscopic mechanism of amorphous alloy during deformation.Unlike crystal alloys,amorphous alloys are characterized by long-range disorder and short-range order structural features,which make the deformation mechanism difficult to understand.In this work,in order to understand the essential mechanism of the deformation in amorphous alloys,the microstructure changes of a ZrCu amorphous alloy under tension and compression are simulated by both experimental and simulation methods,such as the synchrotron radiation X-ray diffraction experiment and the molecular dynamics simulation.In this work,a new computational method for quantitatively detecting free volume(FV)is developed,based on which the fundamental structural mechanisms affecting the yield stage in tension and compression are investigated.It is revealed that the size of FV increases with the strain in both tension and compression,while FV have a lower expansion saturation value in compression than in tension,contributing to the higher yield strength in the former.In addition,the saturation value in compression/tension matches/mismatches the strain of 8% corresponding to the yield strength,can explain the reason why there are different yield behaviors between these two deformation modes.This work will shed light on understanding the unique mechanical properties in amorphous alloy from the atomic-level structural aspect.In addition,the distribution of FV in different zones during deformation is stuied.It is found that,both size and volume of FV increase with strain in particular in the center zone.The density of FVs in the center zone decrease with the strain till 8%,which is rather different from those in other zones.Furthermore,it is found that atomic microscopic stress is sensitive to the deformation in different zones and different deformation stages.The inhomogeneity of FV is probably due to the atomic-level stress in different zones.The present work provides an in-depth insight into the deformation mechanism from FV aspect and atomic microscopic stress,which can be helpful for understanding the unique mechanical behaviors in metallic glasses.