Dilatant shear bands in solidifying metals

Compacted granular materials expand in response to shear, and can exhibit different behaviour from that of the solids, liquids and gases of which they are composed. Application of the physics of granular materials has increased the understanding of avalanches, geological faults, flow in hoppers and...

Full description

Saved in:
Bibliographic Details
Published in:Nature 2007-01, Vol.445 (7123), p.70-73
Main Authors: Dahle, A. K, Gourlay, C. M
Format: Article
Language:English
Subjects:
Alloys
Aluminum alloys
Applied sciences
Casting alloys
Cross-disciplinary physics: materials science
rheology
Deformation
Die casting
Exact sciences and technology
Foundry engineering
Foundry practice
Grain size
Granular materials
Liquids
Magnesium
Magnesium base alloys
Materials science
Metals. Metallurgy
Microstructure
Phase diagrams and microstructures developed by solidification and solid-solid phase transformations
Physics
Pressure before casting
Production techniques
Shear stress
Solidification
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Compacted granular materials expand in response to shear, and can exhibit different behaviour from that of the solids, liquids and gases of which they are composed. Application of the physics of granular materials has increased the understanding of avalanches, geological faults, flow in hoppers and silos, and soil mechanics. During the equiaxed solidification of metallic alloys, there exists a range of solid fractions where the microstructure consists of a geometrically crowded disordered assembly of crystals saturated with liquid. It is therefore natural to ask if such a microstructure deforms as a granular material and what relevance this might have to solidification processing. Here we show that partially solidified alloys can exhibit the characteristics of a cohesionless granular material, including Reynolds' dilatancy and strain localization in dilatant shear bands 7-18 mean crystals wide. We show that this behaviour is important in defect formation during high pressure die casting of Al and Mg alloys, a global industry that contributes over $7.3 billion to the USA's economy alone and is used in the manufacture of products that include mobile-phone covers and steering wheels. More broadly, these findings highlight the potential to apply the principles and modelling approaches developed in granular mechanics to the field of solidification processing, and also indicate the possible benefits that might be gained from exploring and exploiting further synergies between these fields.
ISSN:0028-0836
1476-4687
1476-4679
DOI:10.1038/nature05426