The Study On Preparation And Properties Of New Medical Magnesium-calcium Alloys

Magnesium and magnesium alloys have been widely used in spacefight and automobile making for its excellent properties such as low density, high specific strength and high specific rigidity. And as a biomaterial for hard tissue repairing, magnesium and its alloys also have a bright foreground. In this study, the effect of certain elements had been were studied by the research on biology and metallurgy. Calcium was chosen as the additive element, and four alloys with different component of Ca had been founded. Then heat treatment and Zn ion surface implantation were carried out and the performance of corrosion of alloys in SBF was researched.The results show that the size of precipitate in the cast tissue was effectively deminished after heat treatment, and some dispersed phase with small size appeared inside grain. These conversions cause an improvement on the mechanical properties of the alloys. Results of compression and bending test on the alloys show that, modulus of alloys increased as Ca content grows, and decreases were found in the properties of intensity, deflection and yield point descended.Zn ion was implanted into the alloys in amounts of 0.90×10¹⁷ ions/cm² at the energy of 110 keV. The EDS and XRD analyses indicated that there is about 2.0 wt.% of Zn in the surface of the alloys and a few of MgZn had been observed. Then the surface nano-indentation test validated that the surface hardness and modulus had been improved by ion implantation.Alloys were soaked in SBF in order to test corrosion resistance. Results show that, Mg-Ca alloy with ultra high Rp than pure Magnesium can be obtained by proper alloying and heat treatment. And the corrosion resistance of the alloys were decided by the quality of surface deposition . On the other hand, alloy implanted with Zn ion had better performance in corrosion resistance test in SBF despite of a decrease in Rp.The alloy with 1.24 wt.% of Ca is the most valuable alloy for it bears suitable mechanical properties and behaves stable in SBF. After implantation and pro-aggradation,the max surface area of in vivo implant of this alloy reached 40 cm².