Deformation behaviour of amorphous Fe-Ni-W/Ni bilayer-confined bulk metallic glasses

Abstract

In this study, an amorphous Fe-Ni-W/Ni bilayer was successfully electroplated on a Zr-based bulk metallic glass (BMG), and the deformation behaviour of the bilayer-coating-confined BMG was investigated. The findings show that the macroscopic plasticity of the BMGs was enhanced from 1.3 % to 10.7 %. More importantly, bilayer-confined BMGs have a large plateau of the serrated flow with an insignificant decrement before failure. When characterizing the serrated flows of both uncoated and bilayer-confined BMGs by introducing absolute values of stress raises/drops, smaller amplitudes of stress drops as well as a larger stress-drop frequency during the plastic-deformation stage were found in the bilayer-confined BMGs. The origin of the increased stable plastic flow was discussed, and it is mainly attributed to the enhanced confinement caused by the introduction of the amorphous layer. The findings are significant for enhancing the macroscopic plasticity of the BMGs and for understanding the deformation mechanism of the serrated plastic flow in geometrically confined BMGs. Keywords: plastic flow, bulk metallic glass, amorphous Fe-Ni-W coating, geometric confinement V {tudiji je bilo uspe{no elektroplatirano amorfno, dvoplastno steklo Fe-Ni-W/Ni, na masivno kovinsko steklo (BMG) na osnovi Zr. Hkrati je bilo preiskovano obna{anje dvoplastnega BMG pri deformaciji. Ugotovitve ka`ejo, da se je makroskopska plasti~nost BMG pove~ala z 1,3 % na 10,7 %. [e bolj pomembno je, da ima dvoplasten BMG visok plato nazobljenega dela krivulje z nepomembnim zmanj{anjem pred poru{itvijo. Pri karakterizaciji nazob~anega poteka pri obeh; nepokritem in pri dvoplastnem BMG, z vpeljavo absolutne vrednosti narastka in padca napetosti, so bile dobljene manj{e amplitude padca napetosti kot tudi ve~ja pogostost padca napetosti med plasti~no deformacijo dvoplastno omejenega BMG. Razlo`en je izvor pove~anja stabilnega plasti~nega toka, ki se ga pripisuje okrepitvi, ki jo povzro~i amorfna plast. Ugotovitve so pomembne za pove~anje makroskopske plasti~nosti BMG in za razumevanje deformacijskega mehanizma nazob~anega plasti~nega toka v geometrijsko omejenem BMG. Klju~ne besede: plasti~ni tok, masivno kovinsko steklo, amorfna Fe-Ni-W plast, geometrijska omejenost