Details

Autor(en) / Beteiligte

• Qian, Xiaoming
• Wang, Zhaodong
• Li, Yong
• Wang, Yunfeng
• Peng, Yan

Titel

Formation mechanism of β”-Mg5Si6 and its PFZ in an Al-Mg-Si-Mn alloy: Experiment and first-principles calculations

Ist Teil von

• Materials characterization, 2023-03, Vol.197, p.112617, Article 112617

Ort / Verlag

Elsevier Inc

Erscheinungsjahr

2023

Link zum Volltext

Quelle

Elsevier ScienceDirect Journals Complete

Beschreibungen/Notizen

• Formation mechanism of β”-Mg5Si6 and its PFZ in an Al-Mg-Si-Mn alloy was studied by the means of experiment and first-principles calculations. Results show that at 270 °C during the 100 °C/h heating period, β”-Mg5Si6 precipitated inside the dendrites, whereas precipitation free zones (PFZs) of β”-Mg5Si6 presented near the dendrite arm regions. The formation of the β”-Mg5Si6 and its PFZ were related to the concentration of vacancy. Low-concentration zones of vacancy formed near the eutectics during the solidification due to the constitutional supercooling, no β”-Mg5Si6 precipitated in the low-concentration zones of vacancy due to the vacancy-dependence of β”-Mg5Si6, the Si vacancy-containing β”-Mg5Si6 was extremely unstable and Si vacancies prefer to stay away from distribution. •At 270 °C during the 100 °C/h heating, β”-Mg5Si6 precipitated inside the dendrites, whereas precipitation free zones (PFZs) of β”-Mg5Si6 presented near the dendrite arm regions. After homogenization at 430 °C for 6 h, α-Al(Fe, Mn)Si dispersoids formed inside the dendrites while the PFZs of α-Al(Fe, Mn)Si were located near the dendrite arm regions.•The element of Mg and Si at the regions near the dendrite arms were higher than the regions inside dendrites, which excluded the possibility that the β”-Mg5Si6 PFZ was attributed to the lack of alloying elements.•Low-concertation zones of vacancy formed near the eutectics during the solidification due to the constitutional supercooling, no β”-Mg5Si6 precipitated in the low concertation zones of vacancy owing to the vacancy acted as the nucleation sites for the precipitation of β”-Mg5Si6.•The results of first-principles calculations show that the Si vacancy-containing precipitates are extremely unstable and Si vacancies prefer to stay away from distribution, which further confirmed the vacancy-dependence of β”-Mg5Si6 precipitation and explained the formation of PFZs of β”-Mg5Si6 and α-Al(Fe, Mn)Si dispersoids.