Microstructure Evolution and Mechanical Properties Improvement of AlZnMgCu Alloys Induced by a Novel Double Electroshocking Treatment

Abstract

Herein, a novel solution method of AlZnMgCu alloy using double electroshocking treatment (D‐EST) is proposed. Compared with the conventional solid solution treatment (SST) at 475 °C for 30 min, this method can provide more desirable results, although it only takes 10.2 s. Single tensile test results show that the ultimate strength and elongation after D‐EST followed by T6 aging are, respectively, increased by 2.6% and 6.8% relative to that of SST. In addition, the microstructure of the alloy after D‐EST and SST is characterized by the scanning electron microscopy, transmission electron microscopy, and electron backscattering diffraction (EBSD). The experimental results reveal that D‐EST can give rise to more adequate dissolution of secondary phases especially intermetallic compounds and long rod‐shaped dispersion phase, finer grains, and fewer grain boundaries in the range of 5°–8°. The kinetic mechanism of D‐EST is interpreted from the point of view of electromigration and the nonuniform distribution of temperature on the microscale.

Effects of Electric and Magnetic Treatments on Microstructures of Solid Metals: A Review

“…Its characteristics are limited current density energy, lowfrequency and instantaneous pulse shock [141]. It has been verified that this method can significantly improve the properties of metals under the condition of very limited temperature rise and is suitable for various metals, such as steel [142], aluminum alloys [37] and titanium alloys [31,143]. Song et al [142] found that the residual stresses of cold rolled M50 steel be considerably decreased in the direction of transverse and rolling direction.…”

“…It was found that solid solution by ET could obtain finer grains, but the elongation of the alloy after ET solution is slightly lower in comparison with thermo solution resulting from the more undissolved second-phases. In addition, Wu et al [37] have proposed a double electroshock treatment strategy, which can improve the elongation of Al-Zn-Mg-Cu alloys after ET solution.…”

“…Compared the mechanical properties of Al-Zn-Mg-Cu alloys treated by different methods, Wu et al [37] discovered that the strength and elongation of the material treated by double electroshock treatment (D-EST) are better than those by heat solid solution treatment (SST). As shown in Figure 15, it could be found that the amount of the long rod-shape dispersions in the alloy after D-EST is significantly less than that after SST.…”

“…Figure 15 Bright field TEM images of the Al-Zn-Mg-Cu alloys at different states (a) SST, (b) D-EST (The red arrows point to the long rod-shape dispersion phases in (a) and SEDP of disperdions was inserted in (b))[37] …”