Study of Decomposition of Supersaturated Solid Solution upon Quenching of Al–Mg–Si Alloy Sheets at Different Cooling Regimes

Benarieb, I.; Puchkov, Yu. A.; Sbitneva, S. V.; Zaitsev, D. V.

doi:10.1134/s0031918x23601294

Cited by 1 publication

(1 citation statement)

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“…When precipitating in the grain interior, it forms plate-shaped particles. The metastable phase precipitates below ~400 • C, typically on dispersoids in alloys containing dispersoid-forming elements such as Mn and Cr [9,14,15]. Therefore, alloys with a high dispersoid density are more quench-sensitive [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Effect of Microstructure on the Precipitation of β-Mg2Si during Cooling after Homogenisation of Al-Mg-Si Alloys

Hennum,

Marthinsen,

Tundal

2024

Metals

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For Al-Mg-Si alloys, cooling after homogenisation is a crucial step because the precipitation of the equilibrium β-Mg2Si phase determines the processing capabilities in subsequent steps, as well as the subsequent precipitation age hardening potential, and thus, the final properties. It is therefore important to understand how microstructural variations affect the transformation of β-Mg2Si during cooling after homogenisation. In the present work, alloys with similar effective solute contents of Mg and Si, but with different microstructures and a different amount of primary Al-Fe-Si phases, were produced. Characterisation of the precipitation reaction was performed using interrupted quench experiments with cooling rates of 1–6 K/min, monitored by light optical microscopy (LOM), scanning electron microscopy (SEM) and conductivity measurements. Precipitation kinetics for β-Mg2Si was found to increase in microstructures with shorter secondary dendrite arm spacing (DAS). However, despite measuring both a higher density and volume fraction of the primary phases, no effect on the phase transformation from an increased iron content was found in terms of precipitation kinetics or particle count statistics. Furthermore, comparisons with iron-free high-purity-based alloys revealed that the precipitation reaction for β-Mg2Si was identical in the two different microstructures both in terms of onset temperature and overall kinetics. The present results show that nucleation of β-Mg2Si is not dependent on the larger constituent phases and indicates that overall transformation kinetics is governed by bulk diffusion rates.

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