Structure and mechanical properties of Al – 6% Ca – 1% Fe alloy foundry goods, obtained by die casting

The experimental alloy Al6Ca1Fe is an example of substantiated principal possibility of alloy using on the basis of aluminium-calcium eutectic for foundry goods obtaining by die casting. The alloys were made in resistor furnace in graphite-chamotte cup on the basis of aluminium A85. Pure calcium and iron as master alloy Al – 10% Fe were introduced. Casting was carried out with the temperature of 730–740 оС, obtaining various foundry goods. Microstructure of cast samples was studied with optical microscope Olympus GX51 and scanning electron microscope TESCAN VEGA 3. Primary crystals of aluminium solid solution contain almost no calcium and iron. These elements are found in eutectic, containing ~7.4% Ca and 0.9% Fe. Besides, aluminium solid solution can be in equilibrium not only with the double system phases (Al4Ca and Al3Fe), but also with triple compound Al10CaFe2. According to this, the general form of the phase diagram Al – Ca – Fe in the rich-aluminium area is shown. In particular, the structure of liquidus surface is offered, two triple-phase areas (Al) + Al4Ca + Al10CaFe2 and (Al) + Al10CaFe2 + Al3Fe were found, and two non-variant reactions were set (the eutectic one L → (Al) + Al4Ca + Al10CaFe2 and the peritectic one L + Al3Fe → (Al) + Al10CaFe2). Comparison of experimental alloy Al6Ca1Fe and АК12 silumine showed that aluminium-calcium eutectic is much finer than aluminium-silicon one. The size of dendrite cells of solid aliminium solution is ~7 μm, and thickness of dendrite branches of aliminides, included in eutectic, is lesser than 0.5 μm. Casting properties of alloy Al6Ca1Fe (particularly, hot-shortness), are the same as of eutectic silumines. The samples for investigation of structure and properties were obtained from alloy Al6Ca1Fe by die casting on unit А71108 with locking device 250 t. Definition of mechanical properties on especially cast tensile samples (thickness from 1.9 to 6.5 mm) showed their characteristics by high stability. At the same time, the ultimate resistance is higher than 200 MPa.This paper was written within the subsidiary agreement No. 14.578.21.0220 (unique identifier ПНИЭР RFMEFI57816X0178) of the Ministry of Education and Science of Russian Federation within the realization of the Federal Target Program “Investigations and developments on priority ways of development of scientific-technological complex of Russia for 2014–2020”.