Abstract
Catastrophic brittle fracture of monolithic metallic glass (MG) hinders engineering application of MGs. Although many techniques has been tried to enhance tensile ductility of metallic glasses, the enhancement is quite limited. Here, we show the effect of electrodeposited Cu coating on tensile plasticity enhancement of Pd40Cu30Ni10P20 MG wires, with different volume fractions of copper coatings (R), from 0% to 97%. With increasing R, tensile elongation is enhanced to 7.1%. The plasticity enhancement is due to confinement of the Cu coatings, which lead to multiple and secondary shear bands, according to SEM investigations. In addition, the SEM images also show that the patterns on the fracture surface of the Cu-coated MG wires vary with volume fraction of the Cu coatings. The size of shear offset decreases with increasing R. The viscous fingerings on the fracture surface of monolithic MG wire changes into dimples on the fracture surface of Cu coated MG wires with R of 90% and 97%. The electrodeposition technique used in this work provides a useful way to enhance plasticity of monolithic MGs under tensile loading at room temperature.
Highlights
Plasticity of bulk and micro-sized metallic glass (MG) is mediated by shear bands with highly localized strain[1,2]
Pd40Cu30Ni10P20 MG wires are chosen for investigation, because such wires can have much higher ratio of lateral surface area to cross section area that provide sufficient adhesive force to prevent sliding between the MG core and the metal coating, as described in the literature[21]
All these images confirm that high quality Cu coating was well adhered to the MG wire
Summary
Plasticity of bulk and micro-sized MG is mediated by shear bands with highly localized strain[1,2]. In tension, the tensile stress enhances softening and instability, a dominant shear band slips without obstacle, and bulk and micro-sized MGs fracture elastically[3]. Various approaches have been introduced to retard the dominant shear band to improve tensile ductility of bulk and micro-sized MGs, such as designing MG matrix composites[4,5], sharp-and-deep notches[6], laminating MG with ductile crystalline metals[7,8], surface mechanical treatment[9,10,11], laser surface texturing treatment[12], and MG-based chiral nanolattice[13]. Other techniques have been introduced to improve compressive plasticity of bulk MGs. What attracted our attention was metal coating technique. Fracture morphology changes from viscous fingering to dimpling
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