Study On The Medicinal Properties Of The Mg-Zn-Zr-Mn Biological Magnesium Alloys And Bone Screw

Biocompatibility Zn、 Zr and Mn elements were chosen to prepare theMg-3.0wt%Zn-0.8wt%Zr-xwt%Mn（x=0,0.1,0.5,1.0,1.5）alloys by using vacuum meltingmethod. The influences of Mn content on the microstructure and performance ofMg-3.0wt%Zn-0.8wt%Zr alloy were studied by using optical microscope, scanning electronicmicroscope, tensile testing machine and electrochemical workstation, then the alloycomposition was optimized. The optimized alloy was further processed to tensile samples,and the evolution law of tensile mechanical properties immersed in SBF was studied. TheMg-3.0wt%Zn-0.8wt%Zr alloy was machined into cancellous bone screw. The degradationbehavior and biological properties of cancellous bone screw in vivo and in vitro wasinvestigated.The main results and conclusions were listed as follows:1. With the increasing of Mn content, the grain size of as-cast alloys didn’t change obviously,however, the grain size decreased with the increasing of Mn content after extrusion andaging treatment. Compare with the others alloy with different Mn content, the grain sizeof Mg-3.0wt%Zn-0.8wt%Zr-1.0wt%Mn was minimum up to10μm; The tensile strengthand yield strength increased first and then decreased, the maximum tensile strength was255MP when the Mn content was1.0wt%, and elongation decreased with the Mn contentincreasing. The alloy with1.0wt%Mn content exhibit the best corrosion resistance amongthese alloy. As a consequence, the optimal composition of alloy wasMg-3.0wt%Zn-0.8wt%Zr-1.0wt%Mn.2. With immersion time increasing, the tensile strength and yield strength ofMg-3.0wt%Zn-0.8wt%Zr-1.0wt%Mn alloy decreased, the mechanical performancedropped rapidly, and fracture pattern change from micro-void coalescence fracture to becleavage fracture.3. The result of degradation experiments in vitro showed that the screw thread tip and thejoint part between of screw head and screw body of cancellous bone screw degraded faster,and the majority type of corrosion was pitting corrosion; Animal experiments have shownthat the cancellous bone screw keep intact after one month, residual volume percentage ofscrew body and head of a screw keep above60%and90%, after three months, residualvolume percentage keep above35%and45%. What’s more, corrosion rate of implants incondyles was faster than in tuberosity. There were new bone tissues can be found aroundthe implants. It is shown that magnesium alloys have excellent biocompatibility...