Enhancing corrosion resistance and mechanical properties of AZ31 magnesium alloy by friction stir processing with the same speed ratio

• Published in: Journal of alloys and compounds Vol. 829; p. 154452
• Main Authors: Liu, Fenjun, Ji, Yan, Sun, Zhiyong, Liu, Jianbo, Bai, Yanxia, Shen, Zhikang
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15-07-2020; Elsevier BV
• Subjects: AZ31 alloy; Chemical precipitation; Corrosion currents; Corrosion performance; Corrosion potential; Corrosion rate; Corrosion resistance; Corrosion resistant alloys; Friction resistance; Friction stir processing; FSP; Grain size; Homogeneity; Magnesium alloys; Magnesium base alloys; Mechanical properties; Metal sheets; Microstructure evolution; Precipitates; Processing speed; Workstations; Mechanical properties; FSP; AZ31 alloy; Precipitates; Corrosion performance; Microstructure evolution
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.154452

Friction stir processing (FSP) using the same speed ratio was introduced as an alternative method to process AZ31 magnesium alloy sheets to enhance their corrosion performance and mechanical properties. In addition to the mechanical properties, the microstructure evolution and corrosion performance of the stirred zone (SZ) were investigated using EBSD, TEM, an electronic universal testing machine and an electrochemical workstation. In addition to being significantly finer and higher than that of the AZ31 alloy, the mean grain size and the number of β-Al12Mg17 precipitates in the SZ, respectively, gradually increased as the processing speed increased. The homogeneity and dispersion of the β-Al12Mg17 precipitates in the SZ increased due to a sufficient heat input caused by increasing the processing speed. In addition to slight changes in the mechanical properties, high-speed FSP, and especially FSP with a high rotation speed, obviously improved the corrosion performance of the AZ31 alloy due to the formation of homogenized and diffused distribution of β-Al12Mg17 precipitates. The SZ obtained at 5000 rpm and 125 mm/min exhibited excellent corrosion resistance. The corrosion potential of the SZ increased from −1.563 V to −1.230 V, and the corrosion current reduced from 1.55 × 10−4 A to 2.87 × 10−5 A compared to those of the as-received AZ31 alloy.
•Sound high-speed friction stir processed AZ31 stirred zone was produced with same speed ratio.•High rotation speed has a significant influence on microstructural evolution.•Excellent corrosion resistance of AZ31 can be obtained using high rotation speed FSP.•High rotation speed has a slight effect on tensile strength and yield strength of the stirred zone.