Crack populations in metals

John Campbell; John Campbell

doi:10.3934/matersci.2016.4.1436

AIMS Materials Science

2016, Volume 3, Issue 4: 1436-1442. doi: 10.3934/matersci.2016.4.1436

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Technical note Special Issues

Crack populations in metals

John Campbell ^,

Department of Metallurgy and Materials, University of Birmingham, UK

Received: 30 August 2016 Accepted: 17 October 2016 Published: 25 October 2016

Most of our engineering metals are formed in the liquid state, but suffer mixing with air during pouring into molds. The result is the creation of doubled-over oxide films from the surface of the liquid, entrained in suspension in the metal, which, as a result of the lack of bonding between the opposed faces of the films, act as cracks. Multiple and additive populations of cracks are introduced during the processing of many metals, ensuring a high density of defects which survive in the solidified metal, and further survive plastic working by forging or rolling, etc. Many of our current engineering metals are therefore seriously impaired. This traditional impairment by these defects, called bifilms, is currently accepted as the norm. However, entrainment of the surface oxides during processing is not necessary, and its avoidance can deliver substantially defect-free metals for the first time. Improved casting technology to deliver these improvements is being successfully adopted for light alloys and steels.
- metal crack,
- bifilm,
- casting,
- defect population,
- consolidation
Citation: John Campbell. Crack populations in metals[J]. AIMS Materials Science, 2016, 3(4): 1436-1442. doi: 10.3934/matersci.2016.4.1436

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Abstract

Most of our engineering metals are formed in the liquid state, but suffer mixing with air during pouring into molds. The result is the creation of doubled-over oxide films from the surface of the liquid, entrained in suspension in the metal, which, as a result of the lack of bonding between the opposed faces of the films, act as cracks. Multiple and additive populations of cracks are introduced during the processing of many metals, ensuring a high density of defects which survive in the solidified metal, and further survive plastic working by forging or rolling, etc. Many of our current engineering metals are therefore seriously impaired. This traditional impairment by these defects, called bifilms, is currently accepted as the norm. However, entrainment of the surface oxides during processing is not necessary, and its avoidance can deliver substantially defect-free metals for the first time. Improved casting technology to deliver these improvements is being successfully adopted for light alloys and steels.

References

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