Effects of size on the mechanical response of metallic glasses investigated through in situ TEM bending and compression experiments

TLDR: In this article, the authors performed quantitative bending and compression tests on micropillars made of two different amorphous alloys, with tip diameters ranging from 93 to 645 nm, in situ in a transmission electron microscope (TEM).

About: This article is published in Acta Materialia.The article was published on 2010-01-01 and is currently open access. It has received 260 citations till now.

Figures

Fig. 5. Engineering stress r versus displacement d curves of the Cu-based glass pillars under compression of tip diameters: (a) 645 nm, (b) 255 nm, (c) 178 nm and (d) 96 nm. The engineering stress is approximated by: 4P=½pðDþ 2u tan bÞ2 where P is the load, D the tip diameter, b the taper angle, and u the measured tip displacement. The insets are the enlarged plots showing the individual bursts with the start indicated by pink triangles and the end indicated by olive triangles. Dy denotes the stress drop and Dx the strain carried by an individual burst. Du is post-burst elastic unloading due to transient withdrawal of indenter to match the predefined displacement rate. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 12. Video snaps taken from the in situ TEM compression showing repeated interruption and re-initiation of an unconstrained shear band in a 240 nm tip-diameter pillar compressed at a programmed relatively low displacement rate of 2 nm s 1. The unconstrained shear band, which is free at both ends, supporting 100% the applied load and growing intermittently, is associated with seven noticeable load drop events marked in plot (i). Images (b–h) highlight evolution of the shear band after each banding event marked in the load–displacement evolution curve in (i), where the exact time when each event happens is also annotated.

Fig. 13. A deformation map derived from Eqs. (3) and (4) plotting stress required to drive a shear band in a unit volume X ¼ L3 as a function of L, illustrating a size dependence in deformation mode under bending and uniaxial deformation.

Fig. 6. Quantitative analysis of individual burst events as a function of pillar tip diameter: (a) frequency of bursts defined as the number of bursts per unit engineering strain; (b) amplitude and (c) velocity of shear displacement jumps (SDJs) transferred to 45 shear planes with the solid trend lines being power law fittings. The right axis reads the strain and strain rate of SDJs assuming 10 nm shear band thickness. Solid lines are power law fittings.

Fig. 7. Yield stress versus pillar diameter for both metallic glasses with trend lines indicated (the error bars indicate the uncertainties in stress due to column diameter determination).

Fig. 1. MG pillars of submicrometer diameter fabricated through an optimized annular FIB milling procedure out of a wedge-shaped front of a ribbon thinned by electrochemical etching.

Frequently asked questions

Q1. What are the contributions in "Effects of size on the mechanical response of metallic glasses investigated through in situ tem bending and compression experiments" ?

De Hosson et al. this paper used a transmission electron microscope ( TEM ) to measure bending and compression on micropillars made of two different amorphous alloys with tip diameters ranging from 93 to 645 nm.