Effect of Solution Treatment on Microstructure and Properties of Biodegradable Mg-Zn-Gd-Y-Zr Alloy

The effect of solution treatment on the microstructure of Mg-Zn-Gd-Y-Zr alloy was studied by OM, SEM and TEM, and the corrosion resistance and mechanical properties of the alloy were tested. The results show that the solution treatment can effectively improve the inhomogeneity structure of the as-cast alloy. The grain size of the alloy increases with the increase of solution treatment temperature in the range of 460-510 degrees C, and the second phase dissolves and tends to be spherical. When the solution temperature is higher than 490 degrees C, a small amount of Zn2Zr3 phase is precipitated and the precipitation phase tends to increase and coarsen with the increase of temperature. The T4-490 sample exhibits uniform microstructure, good corrosion resistance and mechanical properties. The corrosion rate of the mass loss test is 0.472 +/- 0.048 mm/a, and the tensile strength, yield strength and elongation are 196.2 +/- 3.5 MPa, 111.1 +/- 6.4 MPa and (18.9 +/- 1.3)%, respectively. The tensile properties of T4-490 sample after immersed in SBF decrease sharply within 1 similar to 7 d, and decrease more slowly within 7 similar to 14 d. With the extension of soaking time, the fracture form changes from quasi cleavage fracture to brittle fracture.