Studies of light alloys by positron annihilation techniques

Dupasquier, A.; Kögel, G.; Somoza, A.

doi:10.1016/j.actamat.2004.07.004

Cited by 139 publications

(84 citation statements)

References 71 publications

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“…2,3 The kinetics of precipitation after mechanical and thermal treatments can be studied by positron lifetime spectroscopy, while the chemical environment of defects can be determined by coincidence Doppler broadening ͑CDB͒ spectroscopy. The use of CDB spectroscopy was extended to study the association of vacancies with solute atoms in metallic solid solutions only a few years ago, 4,5 but several CDB works regarding alloys have been published since then.…”

Section: Introductionmentioning

confidence: 99%

“…The use of CDB spectroscopy was extended to study the association of vacancies with solute atoms in metallic solid solutions only a few years ago, 4,5 but several CDB works regarding alloys have been published since then. 2,[6][7][8][9][10] CDB spectroscopy suit studying solute-vacancy complexes in Al alloys especially well because, as open-volume defects, they effectively trap positrons. Moreover, typical solute atoms, such as Cu, Zn, and Ag, have occupied d atom shells giving strong signals in the CDB momentum spectra in contrast to Al.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of electron-positron momentum spectra of metallic alloys as supported by first-principles calculations

et al. 2007

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Electron-positron momentum distributions measured by the coincidence Doppler broadening method can be used in the chemical analysis of the annihilation environment, typically a vacancyimpurity complex in a solid. In the present work we study possibilities for a quantitative analysis, i.e., for distinguishing the average numbers of different atomic species around the defect. First-principles electronic structure calculations determining self-consistently electron and positron densities and ion positions are performed for vacancy-solute complexes in Al-Cu, Al-Mg-Cu, and Al-Mg-Cu-Ag alloys. The ensuing simulated coincidence Doppler broadening spectra are compared with measured ones for defect identification. A linear fitting procedure, which uses the spectra for positrons trapped at vacancies in pure constituent metals as components, has previously been employed to find the relative percentages of different atomic species around the vacancy [A. Somoza et al., Phys. Rev. B 65, 094107 (2002)]. We test the reliability of the procedure by the help of first-principles results for vacancy-solute complexes and vacancies in constituent metals.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of electron-positron momentum spectra of metallic alloys as supported by first-principles calculations

et al. 2007

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“…[5][6][7][8][9] A long-standing problem for industry is that some periods of NA often result in a negative effect on the mechanical hardness in the following AA. 4,[10][11][12] The microstructures of the precipitations have been studied intensively via transmission electron microscopy (TEM) 13,14) and atom probe tomography (APT) 3,[15][16][17] to reveal the age hardening mechanism.…”

Section: Introductionmentioning

confidence: 99%

“…From the various studies with Al-Mg-Si alloys, vacancy behavior is considered to play an important role in the aging process, stimulating diffusion of solute Mg and Si atoms and nucleation of clusters. Positron annihilation spectroscopy (PAS) [6][7][8][9] and muon spin relaxation spectroscopy (μSR) [22][23][24] have been successfully used to investigate the vacancy and clustering behavior in Al-Mg-Si alloys. These methods, however, are not widely accessible as special facilities and equipment are required to handle radioactive materials.…”

Section: Introductionmentioning

confidence: 99%

Early Stage Clustering Behavior in Al-Mg-Si Alloys Observed via Time Dependent Magnetization

et al. 2016

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Time dependent magnetization of Al-0.67 at.%Mg-0.73 at.%Si, Al-1.07 at.%Mg-0.33 at.%Si and Al-1.07 at.%Mg-0.53 at.%Si alloys are presented over a range of constant temperatures between 250 and 320 K. The magnetization vs. time curves for the samples show minima for temperatures near 290 K. The observed times at which the magnetization minima occur were found to depend on both the solute concentrations and the measurement temperatures. From these results the activation energies from the Si-rich clustering stage to the Mg-Si co-clustering stage were extracted. The deduced activation energies were found to be comparable to those from the positron annihilation measurements, depending on the solute concentrations.

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“…Positron annihilation spectroscopy is a very powerful technique to investigate vacancy-type defects in metals [4]. We have used positron annihilation spectroscopy measurements to study the role of vacancy-type defects in the modulated and non-modulated martensitic transformations of Ni-MnGa polycrystalline alloys.…”

Section: Introductionmentioning

confidence: 99%

Positron Annihilation Spectroscopy Study of NiMnGa Modulated and Non-Modulated Martensitic Phases

Mérida

Garcı́a

Apiñaniz

et al. 2009

MSF

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Abstract.We have studied by means of positron lifetime measurements the role that vacancy type defects play in the martensitic transformation in magnetic Ni-Mn-Ga shape memory alloys. The measurements presented in this work have been performed in two ternary alloys transforming to modulate and non-modulated martensitic phases. Positron experiments have been realized at room temperature after subsequent isochronal heating at different temperatures up to a maximum temperature of 600ºC. Positron results show a large variation of the average lifetime value with the isochronal annealing temperature in non-modulated samples. However, the response in the modulated samples is quite different. These results obtained in both samples are discussed in term of different type of positrons trapping defects and their evolution with the annealing temperature. They have also been compared with Differential Scanning Calorimetry experiments performed in the same samples. The work states the clear influence of the vacancy concentration on the martensitic transformations of these alloys.

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Studies of light alloys by positron annihilation techniques

Cited by 139 publications

References 71 publications

Analysis of electron-positron momentum spectra of metallic alloys as supported by first-principles calculations

Analysis of electron-positron momentum spectra of metallic alloys as supported by first-principles calculations

Early Stage Clustering Behavior in Al-Mg-Si Alloys Observed via Time Dependent Magnetization

Positron Annihilation Spectroscopy Study of NiMnGa Modulated and Non-Modulated Martensitic Phases

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