The Influence Of Element Zr Over The Structure And Properties Of Medical Magnesium Alloy Mg-5.5Zn-0.8Ca

The mainly researches of this topic are the effects to Mg-5.5Zn-0.8Camicrostructure and mechanical properties under different elements of Zr (massfraction) and heat treatment processes based the determination of Zr (mass fraction)of the alloy. And through the studys of the alloies, the results of the component andrelated heat treatment process with excellent plastic forming ability and themechanical properties of the alloy can be gotten.First of all, we will make up six Mg-alloy cast ingots with different Zrelement content (mass fraction), and then the compositions and mechanicalperformances of the Mg-alloy cast ingots are analysised and tested. Finally，wediscovered that when Wzr=0(mass fraction) the alloy matrix organization grain isabout240μm, tensile strength σ_bis about134.7MPa and the elongation rate δ isabout7.1%; When Wzr%=0.7%(mass fraction) the alloy matrix organization grainsize is only about25μm or so. Because of the highly refined of the matrixorganization grain, the tensile strength σ_b and the elongation rate δ separately are174.7MPa and12.1%.The mechanical properties and the plastic forming ability ofthe composition of the alloy are better,compared to the others.Because of cooling too fast，the inclusion and oxidation during the castingcycle of the Magnesium alloy, the defects of divorced eutectic organization andcomposition segregation in the as-cast alloy are seperated dicovered in the grainboundary and matrix.The defects will hinder the further improving performance ofthe alloy greatly. Therefore, the way to eliminat the defects of the alloy with heatingtreatment is necessary.The heat treatment experiment is aimed at Mg-5.5Zn-0.8Ca-0.7Zr alloy.According to the testing result of the DSC curve, we experimentalize under differenttime of solid solution processing with the solid solution temperature of400℃. Afterthe inspection on the alloy with different solid solution time we find that: When thesolid solution time be12h the alloy will be with excellent structure and mechanicalproperties. After the solid solution treatment process, we will experimentalize underdifferent temperatures of aging processing with the aging time of20h.After theinspection on the alloy with different temperatures of aging processing we findthat:Under the temperature of165℃the Mg-5.5Zn-0.8Ca-0.7Zr alloy will have thebest structure, the tensile strength σ_b and the elongation rate δ are261.8MPa and 14.6%respectively.