Heat resistance of eutectic alloys of the Al – Ca – Ce system doped with La, Ni, Mn, Zr and Cr

The structure and phase composition of Al – Ca – Ce alloys doped with lanthanum, nickel, manganese, zirconium and chromium were studied using computational (Thermo-Calc) and experimental (OM, SEM, XRD) methods. The choice of experimental compositions is based on the previous studies of new promising base systems for creating multiphase heat-resistant alloys. It is shown that all alloys, except for the Al – 6 Ca – 3 Ce – 3 La alloy, have a favorable structure – either hypoeutectic or hypereutectic with primary crystals of rounded morphology and small size against the background of highly dispersed multiphase eutectics. Such a structure assumes high deformation plasticity. Mutual solubility of calcium, cerium and lanthanum in the corresponding compounds Al4Ca with the formation of Al4(Ca,Ce,La), Al11Ce3 with the formation of Al11(Ce,Ca)3 and Al11La3 with the formation of Al11(La,Ce,Ca)3 is confirmed. The alloys were rolled on a reversible rolling mill with a roll diameter of 260 mm at a rolling temperature of 450 oC and a rolling speed of 0.2 m/s. The total deformation degree of all alloys was over 80%. Hot-rolled sheets were subjected to softening annealing at a temperature of 400 oC for 1 hour with air cooling. However, in the sample of the Al – 4 Ca – 4 Ce – 4 Ni alloy, multiple cracks appeared on the last pass, so it was excluded from further testing. The alloys Al – 2 Ca – 5 Ce – 0.3 Zr – 0.2 Cr and Al – 4 Ca – 4 Ce – 4 Ni – 1 Mn – 0.3 Zr are strengthened most noticeably during rolling, the hardness of which increases by more than 20 HV. Tensile tests at a temperature of 350 оC showed that all the studied alloys significantly exceed the standard piston silumin AL25 (AK12M2MgN) in strength indicators. The best combination of properties was demonstrated by the alloys Al – 4 Ca – 4 Ce – 4 Ni – 1 Mn – 0.3 Zr and Al – 6 Ca – 1.5 Ce – 2.5 La, the ultimate strength of which at a temperature of 350 oC was 96±2 and 92±2 MPa, the yield strength was 91±2 and 89±2 MPa, and the relative elongation was 21±1 and 20±2%, respectively.The work was supported by the Russian Science Foundation grant 20-19-00746-P (23-19-45018)