Microstructure and Mechanical Properties of a New Secondary AlSi10MnMg(Fe) Alloy for Ductile High Pressure Die Casting Parts for the Automotive Industry

Abstract

Primary AlSi10MnMg alloy is the most widely used alloy for manufacturing of vacuum assisted high pressure die castings (VPDC) with high ductility requirements. In this alloy, die soldering is avoided by a high Mn level (0.5 - 0.6 wt. %) while Fe is kept low (< 0.25 wt. %). Such combination guarantees that the Al-Fe-Mn-Si intermetallic compounds are of the α-iron rich polyhedral or Chinese script type, which is less harmful to the ductility. However, secondary alloys are cheaper and their production requires less energy than the one of primary alloys. The higher amount of Fe, a common impurity in secondary alloys, reduces ductility but also die soldering and thus manufacturing costs. Microadditions based on Mn are known to be very effective in transforming the harmful needle/platelet shaped β-compounds into α-iron compounds with a less harmful morphology. In this work a secondary alloy with 0.60 wt. % Fe and different Mn microadditions has been cast in test parts with different wall thicknesses using VPDC technology. The Mn content of the new alloy has been optimized. Mechanical properties of the optimised alloy have been determined in different heat treatment conditions and been compared to the corresponding AlSi10MnMg primary alloy. Mechanical properties similar to those of the primary alloy have been achieved.

Improvement of the secondary aluminium metallurgical quality by means of an adequate melt treatment.

“…After melting, a simple skimming was made in the surface of the melt before starting to take the different melt samples. For achieving the target composition in terms of Si, Fe, Mn, Mg and Sr for the secondary alloy as defined in Ref [9], less than 200 g of each alloying elements were added: Si and Mg as pure elements, AlFe45 alloy (45 wt. % Fe), AlMn20 (20 wt.…”

“…In F conditions (as-cast state) Mg2Si intermetallic phases are present in the microstructure. These Mg2Si phases are dissolved and then finely precipitated in the aluminium matrix after applying T6 or T7 heat treatment consisted of solution treatment, quenching and artificial aging treatment [9][10][11][12]. However, the microstructure of a secondary AlSi9Cu3(Fe)(Zn) alloy with high iron content (usually between 0.7 and 1.1 wt.…”

“…An innovational secondary aluminium alloys could be used to find comparable mechanical properties to corresponding primary alloy [9,23,25], with a lower economical cost, energy savings and finally generating less CO2 emission compared to primary aluminium alloy production [26]. However, the use of secondary alloys and its applications are significantly affected by the melt cleanliness [27][28].…”

“…% Fe and 0.4 wt. % Mn, which demonstrated similar high mechanical properties than primary AlSi10MnMg alloy is selected for this study [9]. Thermal analysis, density index, macroinclusions and micro-inclusions levels before and after the melt treatment in both primary and the recycled AlSi10MnMg aluminium are investigated to evaluate the effect of the melt treatment in melt cleanliness in both alloys.…”

Comparative Study of the Metallurgical Quality of Primary and Secondary AlSi10MnMg Aluminium Alloys

“…In the F conditions (the as-cast state), Mg 2 Si intermetallic phases are present in the microstructure. These Mg 2 Si phases are dissolved and then finely precipitated in the aluminium matrix after applying T6 or T7 heat treatments consisting of the solution treatment, quenching and artificial aging treatment [11][12][13][14]; however, the microstructure of the secondary AlSi9Cu3(Fe)(Zn) alloy with high iron content (usually between 0.7 and 1.1 wt.%) is mainly characterised by an unmodified eutectic silicon. The intermetallic iron phases have two different shapes: polygonal-polyhedral or Chinese script denominated by α-phases or π-phases (depending on the chemical composition and reactions).…”