New Casting Alloys Based on the Al+Al 4 (Ca,La) Eutectic
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https://doi.org/10.1007/s11837-020-04340-z 2020 The Minerals, Metals & Materials Society
ALUMINUM AND MAGNESIUM: CASTING TECHNOLOGY AND SOLIDIFICATION
New Casting Alloys Based on the Al+Al4(Ca,La) Eutectic TORGOM K. AKOPYAN ,1,4 NIKOLAY V. LETYAGIN,1 TAT’YANA A. SVIRIDOVA,2 NATALIYA O. KOROTKOVA,1 and ALEXEY S. PROSVIRYAKOV3 1.—Department of Metal Forming, National University of Science and Technology MISiS, Leninsky pr. 4, Moscow, Russia 119049. 2.—Department of Physical Materials Science, National University of Science and Technology MISiS, Leninsky pr. 4, Moscow, Russia 119049. 3.—Department of Physical Metallurgy of Non-Ferrous Metals, National University of Science and Technology MISiS, Leninsky pr. 4, Moscow, Russia 119049. 4.—e-mail: [email protected]
The structure of the previously unstudied ternary Al-Ca-La system near the aluminum corner has been analyzed using experimental [scanning electron microscopy, electron microprobe analysis (EMPA), and x-ray diffraction analysis (XRD)] and computational analysis (thermodynamic calculations). Based on the experimental data, the projection of the liquidus surface and solid-state phase-field distribution of the ternary system have been suggested. It is shown that Al4(Ca,La) and Al11(La,Ca)3 compounds can be in equilibrium with aluminum. EMPA and XRD analyses have revealed significant mutual solubility between the binary Al4(Ca,La) and Al11(La,Ca)3 intermetallics which leads to significant changes in their structure and mechanical and physical properties. The analysis of hot tearing susceptibility together with linear contraction showed that new Al-(2–4)wt.%Ca-(0–2)wt.%La-1.5 wt.%Mn hypoeutectic quaternary alloys have excellent casting properties comparable to those of the most manufacturable casting branded aluminum alloys, e.g., A356 and 361.
INTRODUCTION Calcium and cerium (lanthanum) are unconventional alloying additives to aluminum alloys. Due to their extremely low equilibrium solid solubility in aluminum of < 0.005 wt.% for Ce(La)1 and 0.01 wt.% for Ca,2 any alloying leads to the appearance of several compounds. However, studies of these alloy systems in the context of new aluminum casting and wrought alloys have recently emerged. Indeed, there are indications3–16 that hypoeutectic microstructures comprising intermetallic phases Al4Ca (Tetr. I4/mmm, Pearson Symbol: tI10, ˚ ; c = 11.09 A ˚ ) and Al11La3 (Orthorhom. a = 4.36 A ˚ ; b = 13.14 Immm, Pearson Symbol: oI28, a = 4.43 A ˚ , c = 10.13 A ˚ ]12 in alpha-Al matrix (Al hereafter) A provide for a good balance between the mechanical properties and manufacturability. It has been shown for a number of systems, e.g., Al-Ca-Mg-Si,3 (Received May 31, 2020; accepted August 17, 2020)
Al-Ca-Ni,4 Al-Ca-Sc,5 Al-Ca-Fe-Si,6 and Al-Ca-ZnMg7 that, due to the combination of a narrow solidification temperature range and a favorable morphology of the fine eutectic, alloys containing from 2 wt.% to 6 wt.% Ca have high manufacturability during shape casting and metal forming. Most of the alloys listed can be classi
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