Effects of Zn Addition on Microstructural Evolution, Mechanical Properties, and Corrosion Resistance of Al‐6Mg Alloy Subjected to Equal Channel Angular Pressing Processing at 200 °C

Abstract

Al-Mg series alloys have been widely used as structural materials in the automobile, electronic device, and shipbuilding industries due to their high specific strength, good heat dissipation, and formability. [1] Recently, the mechanical properties of Al-Mg alloys have been improved further through a combination strategy of increasing the solute Mg content, severe plastic deformation processing, and heat treatment, which can alleviate the contradiction between high strength and ductility. [2,3] For instance, Zha et al. processed an Al-7Mg alloy through equal channel angular pressing (ECAP) combined with interpass annealing, which simultaneously resulted in high strength (UTS % 507 MPa) and excellent ductility (uniform elongation > %11%). [4] In addition, because Mg has the solubility limit of %1 at% in Al matrix at room temperature, the β (Al 3 Mg 2 ) phase precipitates along grain boundaries (GBs) of Al-Mg alloys with high Mg content. [5][6][7] However, because the β phase has a higher active potential than the Al matrix in Al-Mg alloys, it acts as an anode, severely deteriorating the corrosion resistance. [8] Moreover, based on the previous experimental results of Al-Mg alloys, [9][10][11] the high Mg content and severe plastic deformation processing aided the β-phase precipitation, which deteriorated the corrosion performance and mechanical properties.Alloying, an effective method to improve the mechanical properties and corrosion resistance of Al-Mg alloys, has received extensive attention. For example, Gao et al. [12][13][14] clarified the combined effects of Al 6 Mn phases and Al 3 Sc dispersoids on microstructure evolution, strength enhancement, and outstanding ductility of the extruded Al-Mg alloys. In addition, several studies have been conducted to investigate the effect of additional alloying additions on the nucleation and growth of β-phase particles of Al-Mg alloys. [15][16][17] The effect of each alloying addition on β-phase evolution was different. In general, there are mainly two approaches to enhance the corrosion resistance of Al-Mg alloys by adding alloying elements. One approach is to suppress the nucleation of β phase. For instance, the Al-5.8Mg-0.4Mn