Effect on microstructure and corrosion resistance of semi-solid slurry of 7A04 aluminum alloy by electromagnetic stirring

Abstract

The microstructures and corrosion resistance of electromagnetic stirring (EMS) semi-solid slurry and as-cast 7A04 aluminum alloy were compared in this work. The results show that the primary microstructure of the as-cast 7A04 aluminum alloy is mainly dendritic and columnar dendrite with obvious elements segregation. In contrast, semi-solid processing can effectively form homogeneous and round primary α-Al grains, and significantly reducing element segregation. In addition, the main phases of the two forming methods (as-cast and semi-solid) both involved α-Al, η-MgZn2, θ-Al2Cu. With the decrease of solidification temperature, the semi-solid alloy formed by electromagnetic stirring increases the precipitation of brittle phase S-Al2CuMg. The self-corrosion potential of the semi-solid alloy is greater than that of the as-cast alloy, and the polarization curve has obvious passivation characteristics. Semi-solid processing could improve corrosion resistance of 7A04 aluminum alloy obviously.

Effect of electromagnetic stirring current on microstructure and corrosion resistance of Al–Sn Alloy

“…The analysis showed that after applying EMS, the primary phase and the remaining liquid phase had uncoupled motions, which promoted crystal proliferation and refined the solidification structure, revealing the potential of EMS technology. Zhu et al [14] compared the microstructure and corrosion resistance of 7A04 aluminum alloys prepared by as-cast and EMS, and the results showed that uniform and circular primary α-Al grains could be effectively formed under the action of EMS, and element segregation was significantly reduced, thus effectively improving the corrosion resistance of 7A04 aluminum alloy.…”

Effects of Process Parameters on Microstructure and Mechanical Properties of Semi-Solid Al-7Si-0.5Mg Aluminum Alloy by Gas Induced Semi-Solid Process

“…Due to the existence of solid phase, the shrinkage produced during the solidification process is small, and it is not easy to produce hole defects [3], so that the semi-solid forming products have high compactness and can be heat treated to improve the mechanical properties again [4,5]. Initially, semi-solid processing techniques, such as mechanical stirring method [5,6] and electromagnetic stirring method [7,8], were mainly used for experimental research with few industrial applications. In recent years, researchers have designed preparation methods with simple equipment and low cost, such as gas induced semi-solid process [9,10], selfinoculation method [11], rapid slurry forming [12,13], cooling ramp method [14], serpentine channel method [15], helical groove method [16], etc., and the formation mechanism of the slurry is also being continuously improved and developed [17,18].…”