Effect of rotary forging on the structure and mechanical properties of two eutectic alloys of the Al–La and Al–Ca–La systems

Recently developed aluminum alloys based on the eutectic composition of the Al–Ca system exhibit excellent casting properties and, unlike silumins, show good deformability. The development of multi-component alloys, where calcium is partially replaced by lanthanum, cerium, nickel, and other eutectic-forming elements, improves their properties by producing a finer eutectic structure and enhancing their heat resistance. These alloys can all be strengthened through deformation, with severe plastic deformations being especially effective. Among these methods, rotary forging is of particular interest due to its ability to produce long billets. Lanthanum, at a specific concentration, significantly improves the alloy’s plasticity, making the Al–La system particularly well-suited for deformation processing. This study investigates the effect of rotary forging on the microstructure and mechanical properties of two eutectic alloys, Al–10La and Al–6Ca–3La (wt. %). Billets in the as-cast state were rotary forged from an initial diameter of 20 mm to a final nominal diameter of 5 mm under isothermal conditions: at room temperature for the Al–10La alloy and at 200 °C for the Al–6Ca–3La alloy. The results showed that rotary forging led to an elongated structure in both alloys, with micron-sized grains forming inside the dendrites and eutectic particles being refined. In the Al–10La alloy, the dislocation density was low, while in the Al–6Ca–3La alloy, the dislocation density was higher. The Al–10La alloy showed a slight tendency to soften during rotary forging, whereas the Al–6Ca–3La alloy exhibited a marked tendency to strengthen (its strength doubled). Both alloys retained high plasticity (elongation) after forging. After annealing at 300 °C, the strength of both alloys remained stable. The tensile strength of the Al–6Ca–3La alloy at 300 °C was higher than that of the Al–10La alloy, with values of 53 MPa and 44 MPa, respectively.

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