https://www.tcd.ie/Physics/people/Graham.Cross/SF%20Poster%202011/Schuh-ActaMater07-Mechanical%20behaviour%20of%20amorphous%20alloys.pdf

Mechanical behavior of amorphous alloys

Shear-banding is a ubiquitous plastic-deformation mode in materials. In metallic glasses, shear bands are particularly important as they play the decisive role in controlling plasticity and failure at room temperature. While there have been several reviews on the general mechanical properties of metallic glasses, a pressing need remains for an overview focused exclusively on shear bands, which have received tremendous attention in the past several years. This article attempts to provide a comprehensive and up-to-date review on the rapid progress achieved very recently on this subject. We describe the shear bands from the inside out, and treat key materials-science issues of general interest, including the initiation of shear localization starting from shear transformations, the temperature and velocity reached in the propagating or sliding band, the structural evolution inside the shear-band material, and the parameters that strongly influence shear-banding. Several new discoveries and concepts, such as stick-slip cold shear-banding and strength/plasticity enhancement at sub-micrometer sample sizes, will also be highlighted. The understanding built-up from these accounts will be used to explain the successful control of shear bands achieved so far in the laboratory. The review also identifies a number of key remaining questions to be answered, and presents an outlook for the field.

Shear bands in metallic glasses

The fracture of bulk metallic glasses

Initiation of shear bands near a stress concentration in metallic glass

Indentation techniques have been extensively used for mechanical characterisation of materials. Development of instrumented indentation techniques at low and ultra low load levels has further improved their utility for understanding the mechanical responses of solids at micro and nano scales. The variation of hardness with the load/depth of indentation, known as indentation size effect, has led to difficulties in using hardness as a fundamental or characteristic mechanical property of materials. Detailed discussions are focused on the issue of indentation size effect in brittle and ductile solids. Various theoretical models accounting for the indentation mechanics are highlighted. The results obtained from these techniques with quasicrystals, bulk metallic glasses and nanomaterials are reviewed. The issues related to phase transformation during indentation tests are briefly discussed. The industrial use of the indentation technique has been pointed out. Some of the current issues and directions fo...

Micro- and nanoindentation techniques for mechanical characterisation of materials

Plastic flow softening in a bulk metallic glass

http://repository.ias.ac.in/6588/1/367.pdf

Deformation morphology underneath the Vickers indent in a Zr-based bulk metallic glass

The electron beam welding technique was used to join Zr41Ti14Cu12Ni10Be23 bulk metallic glass (BMG) to crystalline pure Zr. Compositional, microstructural, and mechanical property variations across the welded interface were evaluated. It is shown that a crystalline layer develops close to the welding interface. Transmission electron microscopy of this layer indicates the crystalline phase to be tetragonal with lattice parameters close to that reported for Zr2Ni. However, the composition of this phase is different as it contains other alloying additions. The interface layer close to the bulk metallic glass side contains nanocrystalline Zr2Cu phase embedded in the glassy matrix. Nanoindentation experiments indicate that the hardness of the crystalline layer, although less than the bulk metallic glass, is more than the Zr itself. Commensurately, tensile tests indicate that the failure of the welded samples occurs at the Zr side rather than at the weld joint.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400092736

R. Bhowmick

Papers

Plastic flow softening in a bulk metallic glass

Deformation morphology underneath the Vickers indent in a Zr-based bulk metallic glass

Microstructure and mechanical properties of electron beam weld joints of a Zr 41 Ti 14 Cu 12 Ni 10 Be 23 bulk metallic glass with Zr