Structure–Property Correlation of Al–Mg–Si Alloys Micro-alloyed with Sn

Abstract

Microstructure and mechanical properties of the cast and wrought Al-Mg-Si alloy micro-alloyed with 0.04 wt% and 0.08 wt% Sn were investigated at various processing conditions, viz. as-cast, solutionised, homogenised, hot rolled and peak-aged. Additionally, fracture surfaces of the alloys were also examined in the as-cast, peak-aged cast and peak-aged rolled conditions. It was observed that 0.04 wt% Sn favours the formation of a lamella-like eutectic Al ? Mg 2 Si, whereas 0.08 wt% Sn favours the formation of plate/rod-like Mg 2 Si. The formation of the former deteriorated the hardness and tensile strength, but improves the ductility, whereas the formation of the later was found to contribute to the hardness, tensile strength as well as ductility of the Al-Mg-Si alloy. Homogenisation treatment had reduced the hardness of all the alloys to the lowest value due to the dissolution and spheroidisation of the intermetallic phases. However, hot rolling had significantly increased the hardness, tensile strength and ductility of the alloys. Thus, the increase in hardness, tensile strength and ductility were more prominent in the peakaged rolled alloys relative to the peak-aged cast alloys. At the studied processing stages, the hardness and tensile strength of Al-Mg-Si alloy were found to decrease with the addition of 0.04 wt% Sn and increase with the addition of 0.08 wt% Sn. However, the ductility increased with Sn addition, and the increment was more prominent when micro-alloyed with 0.04 wt% Sn. Improvement in ductility in 0.04 wt% Sn alloy could be attributed to the formation of script-like Al(Fe, Mn)Si phase, whereas in 0.08 wt% Sn alloy could be attributed to the formation of ductile Mg 2 (Si, Sn) phase. Furthermore, the fractography study had revealed that the fracture in the alloys was mainly developed by the cracking of Al(Fe, Mn)Si intermetallic particles. The fractures mode in the as-cast and peak-aged cast alloys was mainly by transgranular brittle with a cleavage fracture surface, whereas in the peak-aged rolled alloys was mainly by transgranular ductile with a dimpled fracture surface.

Impact behaviour and fractography of 6061 alloy with Trace addition of Sn

“…Rectangular shaped mild steel die of dimensions 300×100×15 mm was used for casting the alloys. The casting temperature and vacuum pressure used are 750 ℃ and 800 mbar [11]. The chemical compositions of the alloys were determined by an optical emission spectrometer (Make: Metal Power & Model: Metavision-1008i 3 -V).…”

“…It was observed that peak-ageing treatment was more effective in increasing the toughness of the alloys. The marked improvement in the toughness of the alloys after peak-aging can be attributed to the improvement in the ductility [11], as indicated by the finer ductile dimple features on the fracture surface of the alloys in PAR state than AC state (cf. Fig.…”

“…[10] also reported a positive effect in the tensile strength of 6000 alloy at lower Sn content of 0.03 wt.%. The previous studies of 6000 Al alloys with trace Sn are limited to the hardness [5][6][7][8][9][10][11] and tensile behaviour [6,[9][10]. It is worth mentioning that the studies on the impact behaviour and fractography of 6000 series aluminium alloys with trace Sn are limited.…”