Abstract
Experimental aluminum alloy containing 0.8% Ca, 0.5% Zr, 0.5% Fe and 0.25% Si (wt.%), in the form of a long-length rod 12 mm in diameter was manufactured using an electromagnetic casting (EMC) technique. The extremely high cooling rate during alloy solidification (≈104 K/s) caused the formation of a favorable microstructure in the ingot characterized by a small size of the dendritic cells, fine eutectic particles of Ca-containing phases and full dissolution of Zr in Al the solid solution. Due to the microstructure obtained the ingots possess high manufacturability during cold forming (both drawing and rolling). Analysis of the electrical conductivity (EC) and microhardness of the cold rolled strip and cold drawn wire revealed that their temperature dependences are very close. The best combination of hardness and EC in the cold rolled strip was reached after annealing at 450 °C. TEM study of structure evolution revealed that the annealing mode used leads to the formation of L12 type Al3Zr phase precipitates with an average diameter of 10 nm and a high number density. Experimental wire alloy has the best combination of ultimate tensile strength (UTS), electrical conductivity (EC) (200 MPa and 54.8% IACS, respectively) and thermal stability (up to 450 °C) as compared with alloys based on the Al–Zr and Al– rare-earth metal (REM) systems. In addition, it is shown that the presence of calcium in the model alloy increases the electrical conductivity after cold forming operations (both drawing and rolling).
Highlights
For many years, electrical engineering applications have been recognized as one of the main uses of aluminum in terms of industry economics, which is constantly developing under the current widespread tendency for replacing copper conductors [1]
Experimental wire alloy has the best combination of ultimate tensile strength (UTS), electrical conductivity (EC) (200 MPa and 54.8% IACS, respectively) and thermal stability as compared with alloys based on the Al–Zr and Al– rare-earth metal (REM) systems
The extremely high cooling rate during ACZ alloy solidification caused the formation of a favorable microstructure (Figure 2a) characterized by small size of dendritic cells, fine eutectic particles of Ca-containing phases and full dissolution of Zr in Al solid solution
Summary
Electrical engineering applications have been recognized as one of the main uses of aluminum in terms of industry economics, which is constantly developing under the current widespread tendency for replacing copper conductors [1]. Based on the cooling rates, close to rapid solidification techniques [1,21], it may be argued that EMC is a very appropriate method for obtaining high-solute alloys, include those alloyed with transition elements It was recently demonstrated [22] that Al alloy containing 0.6% Zr, 0.4% Fe and 0.4% Si (wt.%) may be successfully manufactured by EMC to long-length 12 mm circular cross-section rods with a microstructure containing Zr-rich solid solution. This structure provided excellent processability in cold drawing down to 3 mm, and the wire product showed a remarkable combination of strength (ultimate tensile strength (UTS) ~230 MPa) and electrical conductivity (55.6% IACS), both remaining stable after heating up to 400 ◦C
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