Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Metallic glass: cracking the mystery of flaws

15.06.2015

An interdisciplinary study exposes how structural flaws dictate failure strength and deformation in nanosized alloys with super-resilient properties.

A study from A*STAR reveals that designers of metallic-glass-based nanodevices must account for tiny flaws in alloy frameworks to avoid unpredictable catastrophic failure[1]. Understanding how nanoscale metallic glass fractures and fails when subjected to external stress is critical to improving its reliability in devices and composites.


Experimental measurements (left and right) and molecular dynamics simulations (middle) of metallic glass nanopillars reveal that structural flaws play important roles in determining material strength.

Copyright : Adapted by A*STAR with permission from Ref. 1. Copyright 2014 American Chemical Society.

Recently, researchers have found evidence that artificial flaws — miniscule notches carved into the alloy — do not affect the material’s overall tensile strength. But other work has shown that such notches may actually induce the formation of localized cracks.

Mehdi Jafary-Zadeh and co-workers from the A*STAR Institute of High Performance Computing, in collaboration with researchers in the United States, used a combination of physical experiments and computational simulations to study nanoscale flaw tolerance with in-depth precision.

First, the researchers fabricated nickel–phosphorous metallic glass into narrow ‘nanopillars’ bearing tiny notches and mushroom-shaped endcaps that served as tension grips (see image). Guided by high-resolution scanning electron microscopy, they systematically pulled the structures apart until they cracked — an action that consistently occurred at the notched zone, and at failure strengths 40 per cent lower than those for unflawed nanopillars.

The team then turned to massive molecular dynamics simulations to explain these physical results. “Simulating failure modes in the nanopillar metallic glasses required large-scale, three-dimensional models containing millions of atoms,” says Jafary-Zadeh. “Performing simulations at these scales is pretty daunting, but we overcame this challenge with the help of the A*STAR Computational Resource Centre.”

When the researchers modeled atomic strain during nanopillar elongation, they found that the un-notched structures failed via a plastic type of deformation known as shear banding. However, the notched structures were brittle and failed through crack propagation from the flaw point at tensile strengths significantly smaller than the un-notched samples (see video). These observations suggest that ‘flaw insensitivity’ may not be a general feature of nanoscale mechanical systems.

“The theory of flaw insensitivity postulates that the strength of materials that are intrinsically brittle or have limited plastic deformation modes approaches a theoretical limit at the nanoscale, and does not diminish due to structural flaws,” explains Jafary-Zadeh. “However, our results show that failure strength and deformation in amorphous nanosolids depend critically on the presence of flaws.”

Jafary-Zadeh notes that the excellent agreement between experimental results and the simulations is exciting and demonstrates how such computations can bridge the knowledge gap between macroscopic mechanical fracturing and the hidden corresponding mechanisms taking place at atomistic time and length scales.

The A*STAR-affiliated researchers contributing to this research are from the Institute of High Performance Computing.

Reference

1. Gu, X. W, Jafary-Zadeh, M., Chen, D. Z., Wu, Z., Zhang, Y.-W. et al. Mechanisms of failure in nanoscale metallic glass. Nano Letters 14, 5858–5864 (2014).


Associated links
http://www.research.a-star.edu.sg/research/7286
http://www.research.a-star.edu.sg/research/6667
http://www.research.a-star.edu.sg/research/6555

A*STAR Research | ResearchSEA
Further information:
http://www.researchsea.com

More articles from Interdisciplinary Research:

nachricht A new method for the 3-D printing of living tissues
16.08.2017 | University of Oxford

nachricht Bergamotene - alluring and lethal for Manduca sexta
21.04.2017 | Max-Planck-Institut für chemische Ökologie

All articles from Interdisciplinary Research >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Gold shines through properties of nano biosensors

17.08.2017 | Physics and Astronomy

Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter

17.08.2017 | Earth Sciences

Mars 2020 mission to use smart methods to seek signs of past life

17.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>