Effects of Zr and Si on Microstructure and Corrosion Resistance of Al-Zn-Mg Alloy Used for Sports Equipment

Effects of Zr and Si content on the microstructure, tensile properties and corrosion resistance in 3.5% NaCl solution of Al-Zn-Mg alloys used for sports equipment were investigated by optical microscope (OM), transmission electron microscope (TEM), electrochemical test, tensile experiment and double cantilever beam (DCB) test. The results showed that the addition of Zr and Si had significant influences on the microstructure and properties. The combined addition of both Zr and Si was even more effective than the individual addition of Zr. When Zr content was 0.15%, the grain size significantly reduced but a small mount of coarse recrystallization grains were observed. The microstructure consisted of fine-scale equiaxed grains and had minimum grain size after the combined addition of 0.15% Zr and 0.08% Si. After adding 0.15% Zr and 0.08 % Si into the alloy, the average grain size decreased from 177.8 μm to 6.8 μm, the tensile strength and yield strength increased from 283.6 MPa and 249.2 MPa to 368.1 MPa and 319.2 MPa, respectively, the stress intensity factor K_ISCC increased from 3.2 to 10.9 and the electrochemical corrosion resistance of the alloy significantly improved.