Hot tearing of aluminum–copper B206 alloys with iron and silicon additions

Abstract

Hot tearing of B206 aluminum alloys with additions of iron and silicon was studied with constrained mould casting (CRC) to investigate the combined effect of these additions on hot tear resistance. Susceptibility to hot tearing was found to increase gradually with iron content when the conditions were favourable to the formation of the (FeCu) phase. Additions of silicon with a Fe/Si mass ratio ≤ 1 and rapid cooling rates, which together promote the (MnFe) phase at the expense of the (FeCu) phase, were found beneficial to the hot tearing resistance. Hot Tearing Sensitivity (HTS) of the alloys were evaluated with a new index defined to reflect the compliance of the cracked specimens. This index showed an excellent qualitative agreement with the Katgerman's hot tearing index (HCS), providing that one defines the temperature where inadequate feeding starts to be the temperature where 2% of the interdendritic volume is occupied by intermetallic phases. Examinations of the tear surfaces and crack profiles revealed that a premature crack opening created by insufficient healing correlates well the explanations based on the theoretical hot tearing index. The deleterious effect of iron on hot tearing was demonstrated on alloys having a coarse grain microstructure having Ti contents below or equal to 0.01wt%. Above this limit, fine grain microstructures were obtained and the influence of iron was not strong enough to have a significant impact on the castings produced.

Effect of Al 6061 Alloy Compositions on Mechanical Properties of the Automotive Steering Knuckle Made by Novel Casting Process

“…Another possible reason for the variation of thermal stress and SST-ET, depending on minor additions, is the formation of intermetallic phases with the minor additions. The intermetallics may prevent the molten metal from flowing, and thus may lead to an increase in both shearing stress (i.e., thermal stress) and SST [20].…”

Investigation of the effect of holding time and melt stirring on the grain refinement of an A206 alloy

“…[1][2][3][4][5][6] Due to their superior mechanical properties, Al-Cu alloys can be used in many areas such as aircraft construction, military field and automobile manufacturing. 4 Grain refinement of Al-Cu alloys significantly improves the microstructure and mechanical properties.…”

“…Previous works on casting and solidification of Al-Cu alloys consistently indicated that hot tearing can be eliminated with a good grain refinement. [1][2][3][4][7][8][9] Grain refinement was also found to be effective for reducing the amount of the porosity and size of the pores, and improving the feeding of cast Al-Cu alloys. 9 Titanium and boron are added in the form of Al-Ti-B master-alloy rods to cast aluminium alloys for the grain refinement.…”

Properties of EN AW-2024 Wrought Aluminum Alloy after Casting with Crystallization under Pressure

“…The most commonly examined are alloys of 2xxx, 6xxx and 7xxx series [7] because they offer high mechanical properties. The problem with the casting of these alloys is but (mostly) hot cracking (tearing) [8][9][10]. The aim of this research is to investigate the effect of basic parameters of casting with crystallization under pressure with forced flow [11] on mechanical properties of castings made of the EN AW-2024 wrought aluminum alloy (further only 2024 alloy).…”