Research On Preparation,Microstructure And Mechanical Properties Of New Biomedical Zirconium Alloy

In recent years,zirconium alloy has become one of the research hotspots in the field of new biomedical implant alloys due to its characteristics of high strength,low elastic modulus,high corrosion resistance and low magnetic susceptibility.Based on the previous experience of the research group in the design and preparation of medical implanted titanium alloys,this dissertation designs and prepares a series of Zr-Ti-Nb-O zirconium alloys,and thoroughly study the influence of alloy composition,solution treatment,cold rolling process,and aging treatment on the microstructure and mechanical properties.The corrosion resistance and magnetic susceptibility of the preferred alloys are tested and compared with pure titanium and TC4.The main research contents and results are as follows:The effects of Ti,Nb and O elements on the microstructure and mechanical properties of as-cast and solution treatment zirconium alloys are studied.The results show that the Zr-（12,22,35）Ti alloy is composed of acicular martensiteα′phase in the as-cast state and solution treatment state.As the Ti content increases,the compressive yield strength and elastic modulus increase,and the compression rate decreases.In general,alloys have higher strength and elastic modulus,but poorer plasticity.For the as-cast Zr-35Ti-（0,5,10,20）Nb-（0,0.3）O alloy,as the Nb content increases,theα′phase gradually decreases and theβphase increases（Nb content≥10%,the alloy consists of pureβphase）,leading to a gradual decrease in compressive yield strength and elastic modulus,while plasticity is significantly improved.The addition of O element has a significant solid solution strengthening effect,but at the same time it also increases the elastic modulus and reduces the compression rate.The effects of solution treatment and cold rolling processes on the microstructure and mechanical properties of Zr-35Ti-（10,15,20）Nb-（0,0.3）O alloy are studied.Cold rolling transforms the equiaxedβgrains in the solid solution state into fibrousβgrains,which significantly increases the strength and reduces the elongation of the alloy,while the elastic modulus does not change much.In the same state,with the increase of Nb content,the alloy strength and elastic modulus decrease slightly,and the elongation increase significantly;with the increase of O content,the alloy strength and elastic modulus increase,and the elongation decrease.The lattice constant and residual strain increase and the subcrystal size decreases with the cold rolling,decrease the content of Nb and the addition of O element,which is a common factor that leads to alloy strengthening.The effect of aging temperature on the microstructure and mechanical properties of cold rolled Zr-35Ti-（10,15,20）Nb-（0,0.3）O alloy is studied.Aging at 400℃-550℃,with the increase of temperature,the amount ofαprecipitation increases firstly and then decreases.At450℃,the content ofαis the largest.With the same aging temperature,as the Nb content increases,the amount ofαprecipitation decreases;as the O content increases,the amount ofαprecipitation increases slightly.In general,the strength and elastic modulus of the alloy have a positive correlation with the precipitation ofα,and the addition of O element increases the strength and elastic modulus of the alloy.The research finds that Zr-35Ti-10Nb alloy aging at550℃（σ_b=1076MPa;E=65GPa;A=10.5%）and Zr-35Ti-20Nb-0.3O alloy aging at 450℃（σ_b=1285MPa;E=67GPa;A=8.9%）has lower elastic modulus and higher strength,which has good application prospects in the field of biological implant materials.The relationship between corrosion resistance and magnetic susceptibility of Zr-35Ti-（10,20）Nb,Zr-35Ti-20Nb-0.3O alloys and alloy composition is studied,and compare with pure titanium and TC4.The research finds that the I_corr and I_pass of the zirconium alloy are much smaller than that of the pure titanium and TC4;indicating that the corrosion resistance of zirconium alloy is much better than the latter,the result is consistent with the observation of the corrosion morphology.As the Nb content increases,the corrosion resistance of the zirconium alloy is significantly enhanced;as the O content increases,the corrosion resistance of the alloy decreases.The experiment also find that the magnetic susceptibility of the zirconium alloy is lower than that of pure titanium and TC4;as the Nb and O content increases,the magnetic susceptibility of the zirconium alloy increases slightly.