Hot Tearing Susceptibility and Fluidity of Semi-Solid Gravity Cast Al-Cu Alloy

Abstract

Aluminum-copper alloys offer both high strength and excellent ductility suitable for a number of automotive applications to reduce vehicle weight; however, the alloys are difficult to cast because of their tendency for hot tearing. In this work, semi-solid gravity casting of an aluminum-copper alloy, B206, was conducted in constrained rod casting molds to study the feasibility of using the process to reduce or eliminate hot tearing. To demonstrate the feasibility of gravity casting of the metal slurries, a fluidity test was also conducted. Results show that the hot tearing susceptibility of the aluminum-copper B206 alloy cast in semi-solid state is lower than those cast in liquid state with high superheat temperatures. The grain size of the semi-solid cast Al-Cu samples appears to be finer than those cast in liquid state with high superheat temperatures. In addition, the metal slurries had sufficient fluidity to fill the molds even with low gravity pressures. The results suggest that semi-solid gravity casting is a feasible process to help reduce hot tearing.

Influence of alloying elements iron and silicon on mechanical properties of aluminum-copper type B206 alloys /

“…[18] It differs from the other alloys primarily in the lower titanium limit which is claimed to improves the alloy behaviour with respect to hot tearing by increasing its response to Ti-B based grain refiners for Ti-B additions in the range of 10-30 ppm boron. This claim was confirmed by Wannasin et al [16] who studied hot tearing susceptibility and fluidity of semi-solid gravity cast Al-Cu alloys at 5% fraction solid.…”

“…Each of the energy components can therefore be used to describe the ductility of the material with an advantage to the initiation energy, but total energy remains the perfect tool. Elongation (%) 16 …”

Effect of Si, Cu and Fe on mechanical properties of cast semi-solid 206 alloys

“…In the present case, the fine globular microstructure obtained from the SEED process combined to the silicon addition provides a microstructure that reduced hot tearing sensibility. Moreover, the partially solidified metal results in less solidification contraction to compensate for strains by movement of both liquid and solid [4]. Consequently, the study of mechanical properties was based on variants of Alloy-II and Alloy-III using a silicon level around 1% and a copper level below 5%.…”

“…Semi-solid processing however offers new opportunities for these difficult to cast alloys due to the distinctive globular structure of the slurry and the lower amount of contraction that the castings undergo upon solidification. A previous study reported a reduction of hot tearing with semi-solid gravity casting with a solid fraction as low as 5% [4]. In that respect, a higher solid fraction is more likely to minimize hot tearing susceptibility in this alloy system.…”

Effets du Si, Cu et Fe sur les propriétés statiques et dynamiques d'un alliage 206 (Al-Cu) en semi-solide produit par le procédé SEED /

“…Cette bonne performance des pièces semi-solides est possible grâce au fait que le métal partiellement solidifié procure des zones de contraction plus petites et rapprochées [44].…”