Abstract
A prerequisite to utilize the full potential of structural heterogeneities for improving the room-temperature plastic deformation of bulk metallic glasses (BMGs) is to understand their interaction with the mechanism of shear band formation and propagation. This task requires the ability to artificially create heterogeneous microstructures with controlled morphology and orientation. Here, we analyze the effect of the designed heterogeneities generated by imprinting on the tensile mechanical behavior of the Zr52.5Ti5Cu18Ni14.5Al10 BMG by using experimental and computational methods. The imprinted material is elastically heterogeneous and displays anisotropic mechanical properties: strength and ductility increase with increasing the loading angle between imprints and tensile direction. This behavior occurs through shear band branching and their progressive rotation. Molecular dynamics and finite element simulations indicate that shear band branching and rotation originates at the interface between the heterogeneities, where the characteristic atomistic mechanism responsible for shear banding in a homogeneous glass is perturbed.
Highlights
Where dF/dh is the slope of the unloading curve, β is a geometrical constant of the order of unity, and A(hc) is the projected area of the indentation at the contact depth
The microstructure consisting of linear and periodic heterogeneities can be considered as a composite made of two alternating glassy phases with same composition but different elastic constants and, as such, it is expected to show anisotropic mechanical properties, as observed for conventional composites reinforced with continuous fibers
The tensile tests reveal that both strength and ductility increase when α increases from 0 to 45°
Summary
Plates with composition Zr52.5Ti5Cu18Ni14.5Al10 (at.%) and dimensions 1.7 × 35 × 40 mm[3] were prepared by centrifugal copper mould casting. The samples for tensile tests were prepared by wire erosion into dog-bone geometry with a length of about 40 mm and a width of the testing gauge of 2 mm. Both sides of the specimens were carefully polished to make them parallel to each other prior to imprinting. Specimens for tensile tests were prepared with the linear imprints forming an angle with the loading axis α = 0, 20 and 45°. In order to generate observable shear bands, in these samples imprinting was carried out at 100 kN (i.e. at higher load/contact area ratio than for the tensile specimens)
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