Preparation And Properties Research Of Mg-Nd-Zn-Zr-Y Biological Material

Magnesium alloys have become the most promising biomaterial in 21 th century, due to its appropriate mechanical properties and better biocompatibility. Currently, the widely applied magnesium alloys, such as AZ、WE, are facing an obvious problem which is the fast corrosion rate and non-uniform corrosion. So how to reduce the corrosion rate and improve the biocorrosion properties is a significant research direction. Studies have already verified that the rare earth elements could enhance mechanical properties and biocorrosion property without effecting the biocompatibility. So the further research of micro alloying biological magnesium alloys is of great significance.In this paper, rare earth element Y was added to the based Mg-2Nd-0.5Zn-0.4Zr biological magnesium alloys via micro alloying. Effects of rare earth Y on microstructure of Mg-2Nd-0.5Zn-0.4Zr magnesium alloys were investigated by scanning electronic microscopy(SEM), energy spectrum analysis(EDS), X-ray diffraction(XRD) and transmission electron microscopy(TEM). The biocorrosion properties of the tested alloys in the simulated body fluid(SBF) were evaluated by means of hydrogen evolution, mass loss experiments and electrochemical methods. And its mechanical property was demonstrated via the tensile test and the hardness test. Influence of heat treatment on microstructure and properties of Mg-2Nd-0.5Zn-0.4Zr-1Y biological magnesium alloys were studied by solution treatment and aging.According to results of the test, the addition of Y could enhance the biocorrosion and mechanical property of the alloy simultaneously, also could release the degree of local corrosion. The morphology of the precipitated phase changed from continuous network to discontinuous disperse and grain size was refined after the addition of Y, leaving a new blocky Mg24Y5 phase, which improved the biocorrosion properties of the alloys. When the addition of Y is 1%, the corrosive speed of the alloy is the lowest, which is 1.051 mm/a, only 40.81% of Mg-2Nd-0.5Zn-0.4Zr alloy. At the moment, the tensile strength of the alloy is 165.52 MPa, and the percentage elongation reaches the maximum of 11.13%, increasing by 71.90% compared with the original alloy. Compared with as-cast alloy, the majority of the segregative phase was soluble in matrix and tended to be a homogeneous distribution after solution treated for proper temperature. Meanwhile, the corrosion potential is enhanced and the corrosion current density is lowered observably, which improved the biocorrosion properties of the alloys. What is more, the corrosion rate of alloys after solution treated first declines and then slightly increases with increasing solution temperature. When the solution temperature is 500℃, the biocorrosion properties reached a better level, the corrosion rate in SBF was 0.723mm/a, only the 68.81% compared with the as-cast alloys. There are a large number of small dispersive precipitated phase in Mg-2Nd-0.5Zn-0.4Zr-1Y biological magnesium alloy after aging treatment. When the aging time is 16 h, the corrosion rate is 0.488 mm/a, which has reached the corrosion resistant performance indicators of biological magnesium alloy. Additionally, mechanical properties for Mg-2Nd-0.5Zn-0.4Zr-1Y biological of magnesium alloys heat treatment has increased greatly, the strength of the tested alloy after solution treatment was 201.04 MPa, and the elongation was 19.40%, which is the best comprehensive performance.