Research on high pressure solidification microstructure and the microhardness of Al-Mg-Zn alloy

The solidification microstructure and the microhardness of Al-11Mg-4.5Zn alloy under high pressure were researched by optical microscope, scanning electron microscope (SEM), X-ray diffraction(XRD) and microhardness tester. The results revealed that high pressure solidification refined the dendrite structure, and made the primary dendrite arms grow long. The alloy all consisted of alpha-Al phase and Mg-32(Al, Zn)(49) phase whether under normal pressure or high pressure solidification conditions. However, the morphology of the Mg-32(Al, Zn)(49) phases changed from fork-like of normal pressure to the graininess of high pressure, the size of them reduced, and that of the amount decreased. Furthermore, the solid solubility of Mg and Zn in alpha-Al phase increased comparing with those of normal pressure, and they were the largest at 4GPa high pressure, reaching 11.37% and 4.15%, respectively. The microhardness of Al-Mg-Zn alloy had an increment with the pressure increasing.