Modified mechanical properties of Mg-Nd-Zn-Ag-Zr alloy by solution treatment for cardiovascular stent application

Abstract

In order to reduce high yield ratio and improve plasticity of the as-extruded Mg-3.0Nd-0.2Zn-0.2Ag-0.4Zr alloy for using as cardiovascular stent, the alloy was solution treated at 300 °C, 350 °C, 400 °C, 450 °C, and 500 °C for 12 h, respectively. Microstructures were observed using an optical microscope (OM) and a scanning electron microscope (SEM) coupled with energy dispersive x-ray spectrum (EDS). Mechanical properties, including hardness, tensile strength, and elongation, were evaluated by nano-indentation method, Vicker’s microhardness tester, and tensile test machine. The results show that the grains grow and the amount of precipitates reduces with increasing solution temperature. Static recrystallization occurs for the long elongated grains solution treated at 450 °C and 500 °C. The yield ratio of the as-extruded alloy is 98% with yield strength of 320 MPa and ultimate tensile strength of 332 MPa. With increasing solution temperature, the yield strength decreases apparently from 315 MPa to 103 MPa, and the ultimate tensile strength reduced from 324 MPa to 205 MPa, which results in yield ratio reduction from 98% to 50%. The elongation of the alloy increases from 12.3% to 31.3% after solution treatment and shows improvement with increasing solution temperature, while the microhardness decreases. The modification of mechanical properties of the alloy with lower yield ratio and higher elongation is favorable for cardiovascular stent application.