<i>In situ</i>transmission electron microscopy observations of dislocation processes in δ′-strengthened aluminium-lithium alloys

Rösner, Harald; Liu, Wei; Nembach, E.

doi:10.1080/01418619908212034

Cited by 3 publications

(1 citation statement)

References 16 publications

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“…Each dislocation pair glided simultaneously until held up by obstacles along their path. Since the high stacking fault energy of Al obviates the formation of dislocation pairs with such wide spacing as observed in this test, it can be argued that the dislocation pairs are not Shockley partial dislocations, but rather pairs of perfect dislocations [47,49].…”

Section: In Situ Temmentioning

confidence: 92%

New insights into plastic instability in precipitation strengthened Al–Li alloys

Ovri

Lilleodden

2015

Acta Materialia

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A mechanistic model that describes the microscopic mechanisms underlying plastic instability in precipitation strengthened Al-Li based alloy systems is proposed in this work. The model is based on experimental observations from high resolution nanoindentation tests and transmission electron microscopy (TEM) based methods, including in situ TEM tensile straining. These experiments show that dynamic strain aging (DSA), which is widely accepted as the underlying mechanism for plastic instability, cannot sufficiently account for the occurrence of plastic instability in Al-Li based alloy systems. It is proposed that an altogether different mechanism controls plastic instability, namely a diffusion-controlled pseudo-locking mechanism that accompanies order hardening. This mechanism does not require the concurrent operation of DSA by Li, which may be a nonviable mechanism given the low binding energy of Li to dislocation cores, for plastic instability to occur.

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Section: In Situ Temmentioning

confidence: 92%

New insights into plastic instability in precipitation strengthened Al–Li alloys

Ovri

Lilleodden

2015

Acta Materialia

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Order strengthening: recent developments, with special reference to aluminium–lithium-alloys

Nembach

2000

Progress in Materials Science

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Derivation of the antiphase-boundary energy of L1 2 long-range-ordered precipitates from measurements of the minimum size of stable dislocation loops

Baither¹,

Mohles²,

Nembach³

2001

Philosophical Magazine Letters

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In an alloy that is strengthened by long-range-ordered particles, a matrix dislocation generates an antiphase boundary (APB) when it cuts through such a particle. The speci®c energy ® APB of this APB has been measured for two fcc alloys with spherical coherent L1 2 ordered particles: an Al±7.5 at.% Li-alloy and the commercial Ni-base superalloy Nimonic PE16. Peak-aged specimens have been deformed and Orowan loops searched for using transmission electron microscopy. ® APB has been derived from the radii of the smallest dislocation loops which have been left behind around particles. Such an approach had been used previously, for example, by Raynor and Silcock and by Nembach et al. Here an improved evaluation method has been applied; it is based on the results of computer simulations of the equilibrium con®gurations of dislocation loops.} 1. Introduction A dislocation in a disordered matrix cutting through a coherent L1 2 long-rangeordered precipitate generates an antiphase boundary (APB) inside this particle. This causes a stress which tends to drive the dislocation back out of the particle. Hence dislocation glide is impeded and the material is strengthened. Such a hardening mechanism is e ective for instance in Al-rich Al±Li alloys and in the commercial nickel-base superalloy Nimonic PE16 (Nembach and Neite 1985, Nembach 1996, 2000.The strengthening contribution of these L1 2 long-range ordered precipitates strongly depends on the energy density ® APB of the APB. To measure this important strengthening parameter ® APB , several approaches have been used in the past. For spherical particles, one method is to measure the minimum radius r min of Orowan loops found around the L1 2 -ordered precipitates in a specimen that has been deformed up to the external resolved stress ½ ext (Raynor andSilcock 1970, Nembach et al. 1992). To derive ® APB from r min , a model for the interaction of the Orowan loop with itself is required. Nembach et al. (1992) based their derivation of the function ® APB (r min ) on the mean self-stress ½ self;mean of a circular loop as calculated by Brown (1964):

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In situtransmission electron microscopy observations of dislocation processes in δ′-strengthened aluminium-lithium alloys

Cited by 3 publications

References 16 publications

New insights into plastic instability in precipitation strengthened Al–Li alloys

New insights into plastic instability in precipitation strengthened Al–Li alloys

Order strengthening: recent developments, with special reference to aluminium–lithium-alloys

Derivation of the antiphase-boundary energy of L1 2 long-range-ordered precipitates from measurements of the minimum size of stable dislocation loops

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