Influence of icosahedral short range order on diffusion in liquids: A study on Al-Zn-Cr alloys

Kurtuldu, Güven; Jarry, Philippe; Rappaz, M.

doi:10.1016/j.actamat.2016.05.051

Cited by 40 publications

(24 citation statements)

References 50 publications

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“…22,23 Indeed, in a liquid at high temperatures, the diffusion process is governed by uncorrelated binary atomic collisions and the diffusivities of the different components of the system should be essentially equal. However, in a glass-forming Zr-based alloy, Basuki et al 22 found that diffusivities and viscosity follow an Arrhenius-type law but a factor of 2 between Zr diffusion and the diffusion of smaller components like Co or Ni exists at high temperatures and becomes as large as four at the liquidus temperature.…”

Section: Introductionmentioning

confidence: 99%

Atomic-scale structural signature of dynamic heterogeneities in metallic liquids

Pasturel

Jakse

2017

npj Comput Mater

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With sufficiently high cooling rates, liquids will cross their equilibrium melting temperatures and can be maintained in a metastable undercooled state before solidifying. Studies of undercooled liquids reveal several intriguing dynamic phenomena and because explicit connections between liquid structure and liquids dynamics are difficult to identify, it remains a major challenge to capture the underlying structural link to these phenomena. Ab initio molecular dynamics (AIMD) simulations are yet especially powerful in providing atomic-scale details otherwise not accessible in experiments. Through the AIMD-based study of Cr additions in Al-based liquids, we evidence for the first time a close relationship between the decoupling of component diffusion and the emergence of dynamic heterogeneities in the undercooling regime. In addition, we demonstrate that the origin of both phenomena is related to a structural heterogeneity caused by a strong interplay between chemical short-range order (CSRO) and local fivefold topology (ISRO) at the short-range scale in the liquid phase that develops into an icosahedral-based medium-range order (IMRO) upon undercooling. Finally, our findings reveal that this structural signature is also captured in the temperature dependence of partial pair-distribution functions which opens up the route to more elaborated experimental studies. INTRODUCTIONThe nature of local structure in a liquid and its connection with its dynamic properties play a key role in understanding transformation pathways. On cooling, a liquid usually undergoes a first-order transition to form a crystal. However, it is also possible to form a metastable undercooled state by using cooling rates fast enough to avoid crystallization. On further cooling, a liquid becomes progressively more viscous and the dynamics changes significantly, exhibiting several intriguing dynamic phenomena such as (i) the Arrhenius-to-non-Arrhenius transition of transport quantities, i.e., diffusivity (D s ), viscosity (η) and structural relaxation time (τ), [1][2][3][4][5] (ii) the occurrence of dynamic heterogeneities (DHs) 6-9 (iii) the breakdown of the Stokes−Einstein (SE) relation.6, 9-15 So far, many studies have been devoted for understanding the physics underneath although it remains a major challenge to characterize order in disorder and to establish structure-dynamics relations.For instance, the increase in the rate of viscosity with falling temperature down in the deep undercooling regime has been used by Angell 1 to classify liquids by introducing the concept of fragility. Fragility has been related to thermodynamic properties, including the excess entropy and specific heat, [16][17][18] suggesting that it should have a structural signature. Only recently, an empirical correlation between fragility and liquid structure has been proposed.

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Section: Introductionmentioning

confidence: 99%

Atomic-scale structural signature of dynamic heterogeneities in metallic liquids

Pasturel

Jakse

2017

npj Comput Mater

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“…Studies on the trinity Al-Zn-Cr alloys are very limited throughout the literature. Recently, Kurtuldu et al have investigated the effect of trace addition on the aging behavior of aluminum alloys containing Cr; moreover, the effect of Cr addition on Zn diffusions in molten of Al-Zn-Cr alloys [8,9]. It has been a subject of interest that minor and trace additives have a noticeable effect on these alloys, as far as structure and tensile properties are concerned [10].…”

Section: Introductionmentioning

confidence: 99%

“…It has been a subject of interest that minor and trace additives have a noticeable effect on these alloys, as far as structure and tensile properties are concerned [10]. In view of the outstanding corrosion and oxidation resistance, the strengthening and toughening of these alloys have been of recent concern [7][8][9][10][11]. Running experiments on the Al-Cr-Zn system at 600 • C, eleven three-phase regions had been identified [12].…”

Section: Introductionmentioning

confidence: 99%

Mechanical and Corrosion Behavior of Al-Zn-Cr Family Alloys

Nassef

El-Garaihy

El-Hadek

2017

Metals

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Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and powder metallurgy techniques. Cr additions ranged between 5 to 10 wt. %, while Zn was added in an amount between 0 and 20 wt. %. Heat treatment processes were performed during powder metallurgy process, at different temperatures, followed by water quenching. Similar alloys were extruded with an extrusion ratio of 4.6 to get proper densification. Optical microscopy was used for microstructure investigations of the alloys investigated. The element distribution microstructure study was carried out using the Energy Dispersive X-ray analysis method. Hardness and tensile properties of the investigated alloys have been examined. Wear resistance tests were carried out and the results were compared with these of the Al-based bulk alloys. Results showed that the aluminum base alloys, containing 10 wt. % Cr and heat treated at 500 • C for one hour followed by water quenching, exhibited the highest wear resistance and better mechanical properties.

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“…It is very interesting to notice that the minor and trace additives have a noticeable effect on these alloys as far as structure and tensile properties are concerned [10]. In view of the excellent corrosion and oxidation resistance, the strengthening and toughening of these alloys have been of recent interest [7][8][9][10][11]. Running experiments on the Al-Cr-Zn system at 600 °C, eleven three phase regions had been identified [12].…”

Section: Introductionmentioning

confidence: 99%

“…al. investigated the effect of trace additions on the aging behavior of aluminum alloys containing Cr and the effect of Cr addition on Zn diffusion in liquid Al-Zn-Cr alloys [8][9]. It is very interesting to notice that the minor and trace additives have a noticeable effect on these alloys as far as structure and tensile properties are concerned [10].…”

Section: Introductionmentioning

confidence: 99%

Mechanical and Corrosion Behavior of Al-Zn-Cr Family Alloys

Nassef¹,

El-Garaihy²,

El-Hadek³

2017

Preprint

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Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and heat treated powder metallurgy. Cr addition ranged between 5 to 10 wt. % while Zn was added in an amount between 0 to 20 wt. %. Heat treatment processes were performed during powder metallurgy process at different temperatures followed by water quenching. Similar alloys were extruded, with an extrusion ratio of 4.6 to get proper densification. Optical microscopy was used for microstructure investigations of the produced alloys. The element distribution microstructure study was carried out using the Energy Dispersive X-ray analysis method. Hardness and tensile properties of the investigated alloys have been examined. Wear resistance tests were carried out and the results were compared with these of the Al-based bulk alloys. Results showed that the aluminum base alloys containing 10wt. % Chromium and heat treated at 500°C for one hour followed by water quenching exhibited the highest wear resistance and better mechanical properties.

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Influence of icosahedral short range order on diffusion in liquids: A study on Al-Zn-Cr alloys

Cited by 40 publications

References 50 publications

Atomic-scale structural signature of dynamic heterogeneities in metallic liquids

Atomic-scale structural signature of dynamic heterogeneities in metallic liquids

Mechanical and Corrosion Behavior of Al-Zn-Cr Family Alloys

Mechanical and Corrosion Behavior of Al-Zn-Cr Family Alloys

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