Effect of different Zn/Mg ratios on the uniformity of 7185+TiB2/TiC aluminum alloy thick plates

Three types of 7185+TiB2/TiC aluminum matrix composites with different Zn/Mg ratios were prepared in this work through a water-cooled copper casting process. The effects of Zn/Mg ratio on the microstructure and mechanical properties of 20-mm-thick composites were studied by optical microscopy, electron back scattering diffraction, transmission electron microscopy, and tensile mechanical testing. The results showed that the addition of appropriate TiB2/TiC particles refined the as-cast microstructure of the alloy, and with a decrease in Zn/Mg ratio, the grain size distribution became more uniform, the crystalline phase content gradually increased, and the uniformity of the alloy increased. After aging, as the Zn/Mg ratio decreased, the size of the precipitated phase decreased, and the strengthening effect of the alloy improved. The tensile strengths of the surface layer, 1/4 layer, and center position of the A3 alloy were 558, 568, and 572 MPa, respectively. The strength difference among the different thickness layers was the smallest, and the elongation rate was greater than 12%, resulting in the best uniformity.