Serrated yielding in Al-Li alloys

Journal Article · Sat May 01 00:00:00 EDT 1993 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(93)90025-N· OSTI ID:6518016

Kumar, S; McShane, H B ^[1]

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1. Imperial Coll., London (United Kingdom)

Serrated yielding (SY) during tensile testing has been observed in Al-Li alloys, both in the binary and the commercial quaternary alloys, in single crystal as well as polycrystalline materials. Serrated yielding is commonly explained by a dynamic strain aging (DSA) model developed by McCormick and van den Beukel. All the solute elements present in Al-Li alloys, viz., Mg, Cu and Li are known to give DSA and SY. Several researchers believe the DSA to be the cause of SY and they attribute the disappearance of SY simply to the removal of solute from the matrix with aging. However, this argument has serious flaws. The present paper examines this aspect critically. The authors concluded that Al-Li alloys the disappearance of serrated yielding at a certain stage of aging is not due to removal of the solute from the matrix but due to the change in the nature of the metastable [delta][prime] precipitates - from fine coherent shearable precipitates to larger noncoherent nonshearable precipitates - which prevents the formation of the deformation bands. The serrated yielding reappears with extensive over aging due to the dissolution of these precipitates in favor of the equilibrium precipitates. The equilibrium precipitates, being widely spaced, are ineffective in preventing the formation of deformation bands.

• OSTI ID: 6518016
• Journal Information: Scripta Metallurgica et Materialia; (United States), Vol. 28:9; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
MICROSTRUCTURE
SHEAR PROPERTIES
LITHIUM ALLOYS
MAGNESIUM ALLOYS
DEFORMATION
EXPERIMENTAL DATA
PRECIPITATION
TRANSMISSION ELECTRON MICROSCOPY
ZIRCONIUM ADDITIONS
ALLOYS
CRYSTAL STRUCTURE
DATA
ELECTRON MICROSCOPY
INFORMATION
MECHANICAL PROPERTIES
MICROSCOPY
NUMERICAL DATA
SEPARATION PROCESSES
ZIRCONIUM ALLOYS
360103* - Metals & Alloys- Mechanical Properties
360102 - Metals & Alloys- Structure & Phase Studies