Growth of Intermetallic Phases in the Al-Mg System

Njiokep, Eugene M. Tanguep; Salamon, Marcel; Mehrer, H.

doi:10.4028/www.scientific.net/ddf.194-199.1581

Cited by 35 publications

(32 citation statements)

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“…The Al 3 Mg 2 b-phase was situated on the Al side of the interface and formed the thicker, more dominant, IMC layer. This is consistent with previous observations [9][10][11] where in similar binary Al-Mg diffusion couple experiments the b phase has been reported to have a higher growth rate, but forms after the c phase and grows by consuming c as well as growing into the Al substrate. [9,10] From higher magnification EBSD analysis of the region shown in Figure 3(c) (white rectangle) it can be seen that the interface in the Al(Si)-Mg samples also consisted of two Al-Mg IMC layers (although this is not as apparent in the SEM image) with irregular second phase particles being present in the lower sublayer ( Figure 3(d)).…”

Section: Characterization Of the Interfacial Reaction Productssupporting

confidence: 93%

“…[4][5][6][7]9,10] The rapid growth of this reaction layer is intrinsically linked to the high diffusion rates of Al and Mg solute, both in each other as a parent solid solution phase and through the Al-Mg IMC phases themselves, when present as a continuous barrier layer at the weld interface. [11,12] Of the IMC phases present in the binary Al-Mg system, b-Al 3 Mg 2 (the so called 'Samson phase') [13] is regarded as most detrimental to weld performance because: (i) it has the highest growth rate [4,[9][10][11] and (ii) has the lowest toughness, [9] and thus provides a preferential crack propagation path along the joint interface. [9,14] It would therefore be beneficial to implement measures for controlling the extent of IMC reaction in Al-Mg welds and, in particular, to inhibit the production of the b-Al 3 Mg 2 phase.…”

Section: Introductionmentioning

confidence: 99%

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The Effectiveness of Al-Si Coatings for Preventing Interfacial Reaction in Al-Mg Dissimilar Metal Welding

Wang

Al-Zubaidy

Prangnell

2017

Metall Mater Trans A

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The dissimilar welding of aluminum to magnesium is challenging because of the rapid formation of brittle intermetallic compounds (IMC) at the weld interface. An Al-Si coating interlayer was selected to address this problem, based on thermodynamic calculations which predicted that silicon would change the reaction path to avoid formation of the normally observed binary Al-Mg IMC phases (b-Al 3 Mg 2 and c-Al 12 Mg 17 ). Long-term static heat treatments confirmed that a Si-rich coating will preferentially produce the Mg 2 Si phase in competition with the less stable, b-Al 3 Mg 2 and c-Al 12 Mg 17 binary IMC phases, and this reduced the overall reaction layer thickness. However, when an Al-Si clad sheet was tested in a real welding scenario, using the Refill ä friction stir spot welding (FSSW) technique, Mg 2 Si was only produced in very small amounts owing to the much shorter reaction time. Surprisingly, the coating still led to a significant reduction in the IMC reaction layer thickness and the welds exhibited enhanced mechanical performance, with improved strength and fracture energy. This beneficial behavior has been attributed to the softer coating material both reducing the welding temperature and giving rise to the incorporation of Si particles into the reaction layer, which toughened the brittle interfacial IMC phases during crack propagation.

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Section: Characterization Of the Interfacial Reaction Productssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

The Effectiveness of Al-Si Coatings for Preventing Interfacial Reaction in Al-Mg Dissimilar Metal Welding

Wang

Al-Zubaidy

Prangnell

2017

Metall Mater Trans A

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“…[5][6][7][8] Therefore, many researchers have studied reactive diffusion in a large number of binary alloy diffusion couples and there have also been several attempts to model the evolution of the IMC layer. [1][2][3][4][5] It is widely accepted that reactive diffusion is mainly governed by volume diffusion, [1][2][3]9,10] and the thickness of an IMC phase generally follows a parabolic relationship with annealing time. [3,5,9,10] It is common in analyzing reactive interdiffusion to measure the thickness of the IMC layer as a function of time under isothermal conditions and then fit the data to a parabolic law of the form:…”

Section: Introductionmentioning

confidence: 99%

Modeling of Intermetallic Compounds Growth Between Dissimilar Metals

Wang

Prangnell

et al. 2015

Metall Mater Trans A

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A model has been developed to predict growth kinetics of the intermetallic phases (IMCs) formed in a reactive diffusion couple between two metals for the case where multiple IMC phases are observed. The model explicitly accounts for the effect of grain boundary diffusion through the IMC layer, and can thus be used to explore the effect of IMC grain size on the thickening of the reaction layer. The model has been applied to the industrially important case of aluminum to magnesium alloy diffusion couples in which several different IMC phases are possible. It is demonstrated that there is a transition from grain boundary-dominated diffusion to lattice-dominated diffusion at a critical grain size, which is different for each IMC phase. The varying contribution of grain boundary diffusion to the overall thickening kinetics with changing grain size helps explain the large scatter in thickening kinetics reported for diffusion couples produced under different conditions.

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“…If the phase diagram of the selected system contains intermetallics, it is expected that the multiphase diffusion will give rise to the formation of these intermetallic layers. 5 In practice, certain phases are sometimes missing from the diffusion zone or the composition of the phases can differ from those indicated on the phase diagram. Sometimes, extra phases also appear.…”

Section: Introductionmentioning

confidence: 99%

“…Sometimes, extra phases also appear. 5,6 Although in most cases parabolic growth kinetics are observed, other kinetics can be observed as well. 7 This paper originated from a study of multiphase diffusion in the Cu/Zn diffusion couple.…”

Section: Introductionmentioning

confidence: 99%

The growth of beta phase in the gamma-brass–copper diffusion couple

Hoxha¹,

Heger²

2017

Mater. Tehnol.

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In this work we make a quantitative investigation of the growth of the b-phase in the g-brass/copper diffusion couple. The diffusion couple was produced by electrolysis. The analysis of multiphase diffusion in the g-brass/copper system was based on using the concentration-depth profiles provided by electron micro-beam analyzer. The growth constant of the b-phase for each of the used temperatures was calculated from the time dependency of the b-phase thickness. Using the Matano method it was possible to calculate the interdiffusion coefficient of Zn in the b-phase. The activation energy for the diffusion of Zn in the b-phase was also determined. Keywords: g-brass-copper system, growth of intermetallics, multiphase diffusion, interdiffusion coefficients, activation energy V delu je prikazana kvantitativna preiskava rasti b-faze v difuzijskem paru g-medenina-baker. Difuzijski par je bil izdelan z elektrolizo. Analiza difuzije v ve~faznem difuzijskem sistemu g-medenina-baker temelji na uporabi profilov koncentracija-globina, dobljenih z elektronskim mikroanalizatorjem. Konstanta rasti b-faze pri vsaki od uporabljenih temperatur je bila izra~unana iz~asovne odvisnosti debeline b-faze. Z uporabo Matano metode je bilo mogo~e izra~unati koeficiente nasprotnosmerne difuzije Zn v b-fazi. Dolo~ena je bila tudi aktivacijska energija za difuzijo Zn v b-fazi. Klju~ne besede: system g-medenina-baker, rast intermetalnih zlitin, difuzija v ve~faznem sistemu, koeficienti nasprotnosmerne difuzije, aktivacijska energija

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Growth of Intermetallic Phases in the Al-Mg System

Cited by 35 publications

References 0 publications

The Effectiveness of Al-Si Coatings for Preventing Interfacial Reaction in Al-Mg Dissimilar Metal Welding

The Effectiveness of Al-Si Coatings for Preventing Interfacial Reaction in Al-Mg Dissimilar Metal Welding

Modeling of Intermetallic Compounds Growth Between Dissimilar Metals

The growth of beta phase in the gamma-brass–copper diffusion couple

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