Thermodynamic Calculation and Microstructure Optimization of Mg-Gd-Y-Zn-Zr Biodegradable Magnesium Alloy

Abstract

In this paper, Thermo-Calc and CALPHAD calculation techniques are used to calculate and analyze the multivariate phase diagram, solidification path and microstructure content of biodegradable magnesium alloys with different components. The effects of elements y and Gd on the liquidus, phase distribution, strengthening phase content and microstructure of the alloy were discussed. Under the condition of non-equilibrium solidification, the primary MG24Y5 solid phase decreases and the (MG24Y5+MG3RE_D03) structure increases with the increase of Gd element. With the increase of Y element, the liquidus increased, the solid content of primary MG24Y5 increased, and the structure of (MG24Y5+MG3RE_D03) increased. With the simultaneous increase of Y and Gd elements, the liquidus increased, and the tissue content of (MG24Y5+MG3RE_D03) increased sharply. (MG24Y5+MG41RE5+HCP_A3) the content of residual tissue decreased. Zinc rich phases such as MgZn, MgZn2 and MG2ZN3, with relatively low content, are strengthening phases of solid solution and aging treatment, which play an important role in the mechanical properties of alloy materials. This paper solves the key technical problems of rapid degradation and poor uniformity of degradable magnesium alloy materials, obtains degradable magnesium alloy materials for stents with reliable quality, controllable degradation rate and excellent biocompatibility, forms relevant process standards and technical specifications, and verifies the feasibility of the application of this material technology in cardiovascular stent interventional therapy, Provide material basis and technical support for the further clinical application of the material.