Phase Diagram of Al-Ca-Mg-Si System and Its Application for the Design of Aluminum Alloys with High Magnesium Content

Abstract

Abstract:The phase transformations in the Al-Ca-Mg-Si system have been studied using thermodynamic calculations and experimental methods. We show that at 10% Magnesium (Mg), depending on the concentrations of calcium (Ca) and silicon (Si), the following phases crystallize first (apart from the aluminum (Al) solid solution): Al 4 Ca, Mg 2 Si, and Al 2 CaSi 2 . We have found that the major part of the calculated concentration range is covered by the region of the primary crystallization of the Al 2 CaSi 2 phase. Regardless of the Ca and Si content, the solidification of the aluminum-magnesium alloys ends with the following nonvariant eutectic reaction: L → (Al) + Al 4 Ca + Mg 2 Si + Al 3 Mg 2 . With respect to the temperature and composition of the liquid phase, this reaction is close to the eutectic reaction in the Al-Mg binary system. The addition of Ca and Si to the Al-10% Mg base alloy increases its hardness, reduces its density, and has no negative influence on its corrosion resistance. We have also established that the near-eutectic alloy containing about 3% Ca and 1% Si has the optimum structure.

High Strength Al–La, Al–Ce, and Al–Ni Eutectic Aluminum Alloys Obtained by High-Pressure Torsion

“…Since the volume fraction of the eutectic particles is close in all alloys-9-11%, the alloys differ mainly in the properties of the eutectic. The hardness of particles increases in the following order: Al 11 Ce 3 , Al 11 La 3 , and Al 3 Ni-3.5, 4.0, and 7.0-7.7 GPa, respectively [5,[36][37][38]. In this case, the particle refinement process can occur simultaneously with the structure formation during SPD.…”

Effect of La Addition on Solidification Behavior and Phase Composition of Cast Al-Mg-Si Alloy

“…Either way, there is no appropriate research on the solidification of Mg-rich Al-Mg-Si with REM. In contrast, the efforts [36] toward the quaternary Al-Ca-Mg-Si diagram show a very similar phase composition at room temperature (Al 3 Mg 2 + Al 4 Ca + Mg 2 Si) but also consider a formation of hexagonal Al 2 CaSi 2 phase. It was also reported that peritectic reaction L + Al 2 CaSi 2 →α-Al + Al 4 Ca + Mg 2 Si is suppressed.…”

“…However, in our study, the Mg 2 Si phase precipitates according to the eutectic reaction along with AlLaSi (or Al 2 LaSi 2 ) phase. The difference between two phases Mg 2 Si and Al 2 LaSi 2 in lattice parameters and lattice-type is enormous (cubic lattice, Fm3m space group, 12 atoms/cell, a = 6.35 Å for Mg 2 Si [36] and hexagonal lattice, P-3m1 space group, a = 4.23 Å for Al 2 LaSi 2 [26]). The possibility of the AlLaSi compound being a nucleus is minor based on the before mentioned observation.…”

Al–Ca, Al–Ce, and Al–La Eutectic Aluminum Alloys Processed by High‐Pressure Torsion

“…There are works on the study of eutectic alloys of Al-Ca, Al-Ca-Si, Al-Ca-Fe, Al-Ca-Mn, Al-Ca-Si-Fe, Al-Ca-Mn-Fe, and Al-Ca-Si-Fe-Zr systems in the pre-eutectic and eutectic regions, as well as alloys based on Al-Ni, Al-Ce, Al-Ce-Ni, Al-Ce-Cu, Al-La-Ni, and others. [3][4][5][6] The two-component base eutectic aluminum alloys (Al-Ca, Al-Ce, Al-La, etc.) are fundamentally different from other eutectic aluminum alloys, for example, Al-Cu or Al-Si, by their insolubility in the solid state according to the equilibrium phase diagram.…”

“…[7,10] The behavior of two-phase eutectic alloys both during casting and deformation differs significantly from the behavior of complex eutectic alloys, as well as from eutectic alloys additionally alloyed with other elements (Mn, Zr, and Sc). [5,6,14] In complex eutectic alloys, as well as in additionally alloyed eutectic alloys, chemical elements can affect mutual solubility and cause other effects. [5] Today, there is practically no systematic data on the effect of SPD on hardening, structure, and phase composition in eutectic aluminum alloys based on Al-X systems (where X is Ca, La, Ce, or Ni).…”