Ductile bulk metallic glass by controlling structural heterogeneities

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.

Guiding shear bands in bulk metallic glasses using stress fields: A perspective from the activation of flow units

“…Here, we explore this strategy by generating a smoothly varying residual elastic stress field in a Cu 44 Zr 44 Al 8 Hf 2 Co 2 BMG using flash annealing. Flash annealing represents a unique tool for introducing elastic stress fields into BMGs while avoiding the formation of shear bands [9] as, in contrast, occurs for shot-peened, cold-rolled, or imprinted BMGs [13][14][15][16][17]. This permits us to use the trajectory of shear bands as a local probe in order to study the influence of stress fields on the underlying STZ activation mechanism without the interference resulting from the stress fields generated by preexisting bands [8].…”

Deformation Behavior of Bulk Metallic Glasses and High Entropy Alloys under Complex Stress Fields: A Review

“…Additionally, tensile ductility in BMGs has also been achieved by introducing complex stress states onto the surface of BMG specimens, such as imprinting method [ 109 , 110 ] and laser surface treatment [ 111 , 112 ]. The enhancement of macroscopic tensile ductility was attributed to the heterogeneities on the specimen surface, such as the mechanical properties and geometries, resulting from tailored complex stress fields [ 109 , 110 ]. The heterogeneities cause the formation of plastic zones with multiple shear bands.…”

“…However, since the specimens do not fracture during indentation tests and the studies mainly focused on the corresponding deformation mechanisms, these studies on the indentation tests of BMGs are therefore not discussed in detail here. Additionally, tensile ductility in BMGs has also been achieved by introducing complex stress states onto the surface of BMG specimens, such as imprinting method [109,110] and laser surface treatment [111,112]. The enhancement of macroscopic tensile ductility was attributed to the heterogeneities on the specimen surface, such as the mechanical properties and geometries, resulting from tailored complex stress fields [109,110].…”

Role of Glass Composition on Mechanical Properties of Shape Memory Alloy‐Metallic Glass Composites

“…e design and fabrication of modern engineering materials are resulted from the optimization of various mechanical features such as elasticity, ductility, and strength [1][2][3]. In the case of metallic glasses (MGs), the superior strength comes at the expense of homogenous plasticity, especially at the tensile mode [4][5][6].…”