Nanostructure Characteristics of Al3Sc1−xZrx Nanoparticles and Their Effects on Mechanical Property and SCC Behavior of Al–Zn–Mg Alloys

Abstract

The Nanostructure characteristics of Al3Sc1−xZrx nanoparticles and their effects on the mechanical properties and stress corrosion cracking (SCC) behavior of Al–Zn–Mg alloys were investigated by 3D atom probe analyses, high-angle annular-dark-field scanning transmission electron microscopy methods, electron back scattered diffraction techniques, electrochemical measurements, slow strain rate tests and quantitative calculations. The results show that adding small amounts of scandium (0.10 percent by weight) and zirconium into Al–Zn–Mg extrusion bars can precipitate Al3Sc1−xZrx nanoparticles with a number density of (7.80 ± 3.83) × 1021 per cubic meter. Those particles, with a low lattice misfit with matrix (1.14 ± 0.03 percent) and stable core-shell L12-nanostructure in aged Al–Zn–Mg alloys, can increase the yield strength by 161 ± 7 MPa via strong Orowan strengthening (the theoretical calculated value is 159 MPa) and weak Hall-Petch strengthening (the theoretical calculated value is 6 MPa). Moreover, Al3Sc1−xZrx nanoparticles can change the fracture mechanism of alloys in 3.5% NaCl solution from intergranular cracks to transgranular failure, and decrease the proportion of high-angle grain boundaries from 87% to 31%, thus reducing the microchemistry differences around the grain boundaries and anodic dissolution kinetics, and improving intergranular SCC resistance and ductility. This study offers a new approach to the simultaneous improvement in mechanical property and corrosion performance of high strength alloys.

Effects of Heterogenization Treatment on the Hot-Working Temperature and Mechanical Properties of Al-Cu-Mg-Mn-(Zr) Alloys

“…In our study, after one-stage heterogenization, the hardness of Alloy A aged for 96 h was 75.4 ± 0.4 HRB, while for two-stage heterogenization, the hardness of Alloy A aged for 96 h was 73.7 ± 0.4 HRB. Deng [ 35 ] investigated the effects of Al 3 Sc 1−x Zr x nanoparticles on the mechanical properties of aged Al-5.2Zn-1.82Mg alloy and found that the Al 3 Sc 1−x Zr x particles improved the yield strength by 161 ± 7 MPa (40 ± 3 percent) and increased the ultimate tensile strength by 122 ± 4 MPa (27 ± 1 percent). Due to the addition of Zr, Alloy B exhibited a relatively higher hardness of around 76.5 ± 0.4 HRB.…”

“…In our study, after one-stage heterogenization, the hardness of Alloy A aged for 96 h was 75.4 ± 0.4 HRB, while for two-stage heterogenization, the hardness of Alloy A aged for 96 h was 73.7 ± 0.4 HRB. Deng [35] investigated the effects of Al3Sc1−xZrx nanoparticles on the mechanical properties of aged…”

Influence of scandium interlayer on the mechanical and metallurgical characteristics of friction stir welded AA1200-H14/ Sc/AA6061-T6

“…Sc is supposed to make alloying elements more ductile at high temperatures. The aluminium scandium's solid solubility changes greatly with temperature [7]. It also deforms at a high strain rate despite having a higher diffusivity.…”

Effect of Thermomechanical Treatment of Al-Zn-Mg-Cu with Minor Amount of Sc and Zr on the Mechanical Properties

“…Aluminum (Al) alloys are widely used in various industries. The addition of rare earth elements to Al alloys has been proven to have optimal effects [1][2][3][4][5][6][7]. Among Al alloy elements, scandium (Sc) is one of the most effective elements for Al reinforcement.…”