Study On Microstructure And Mechanical Properties Of Several Biomedical Zn Based Alloys

In recent years,as the representative of the biological alloy,cobalt alloys,titanium alloy and magnesium alloy has become an important branch and hotspot in the field of materials science because of its high strength,good toughness,excellent processing performance and ideal anti bending fatigue strength.As one of the indispensable trace elements of human body,Zinc is involved in most of the metabolic processes in the body.The corrosion resistance and mechanical property of zinc alloy is better than magnesium alloy.Besides,Zinc alloy has excellent biodegradability and biocompatibility.It is considered as a kind of new generation of bio alloy material with broad application prospect.At present,the research on zinc based bio alloys is still in the initial stage.The main study is on the development,microstructure and mechanical properties of the alloy,to identify alloy systems for use in biological applications and reveal the influence of microstructure and properties.In this paper,Zn-5Al,Zn-1.5Mg and Zn-3Al-1Mg alloy as the research object.The microstructure of the alloy were characterized by OM,XRD,SEM and EDS.The microstructure evolution of as cast,homogeneous and rolled alloy was analyzed.The phase composition of the alloy was determined by XRD,the phase distribution characteristics of the alloy were analyzed by OM,SEM and EDS.The rolling experience is made after homogenization treatment,the tensile properties of the rolled alloy were tested.Fracture mechanism of alloy after rolling was discussed by analyzing the fracture morphology.The main results are summarized as follows:The Zn-5Al alloy in as-cast condition and after homogenizing treatment are composed by?-Zn phase and ?-Al phase.The phase composition including ?-Zn phase,Mg2Zn11 phase and MgZn2 phase of as cast Zn-1.5Mg alloy,MgZn2 phase disappears after homogenization.?-Zn phase,?-Al phase,Mg2Zn11 phase and Mg2Al3 phase can be observed for as cast Zn-3Al-1 Mg alloy,the non equilibrium phase Mg2Al3 disappears in the process of homogenization.Lamellar eutectic structure of gray and white with Zn-5Al alloy as cast,after homogenization turned into rod shape and local dendritic structure.In the process of homogenization,The non equilibrium solidification of gray white large piece of petal-shaped non-equilibrium structure disappears;The lamellar morphology of the eutectic structure of as cast Zn-1.5Mg alloy was disappeared.The dendrite segregation disappears and the microstructure becomes more uniformity;As cast Zn-3Al-1Mg alloy after homogenization,eutectic morphology disappeared,dendrite was obviously refined,and the microstructure distribution was more uniform.Edge cracks can be observed for Zn matrix after 5 passes rolling with about 70%rolling reduction.The ?-Al phase is completely broken into small particles and the microstructure is uniformly distributed along the rolling direction.The lamellar eutectic structure presents a fine particle after rolling.After the rolling of Zn-1.5Mg alloy,the dendrite is completely broken,which presents irregular granular and disordered distribution in the matrix.The second phase of rolled Zn-3Al-1Mg alloy was crushed into a chain,the grains are broken and discontinuous distributed in the matrix,the microstructure was distributed along the deformation direction.The yield strength of rolled Zn-5Al alloy is 98MPa,tensile strength is 130MPa,the elongation is 149%and Zn-5Al alloy showed the superplastic.The yield strength and tensile strength of Zn-1.5Mg alloy were 191MPa,204MPa respectively,and the elongation was 2%.The yield strength and tensile strength of Zn-3Al-1Mg alloy were 172MPa,240MPa respectively,and the elongation was 21%.The tensile fracture surface of Zn-5 Al alloy is mainly composed of the equal axis and the fracture mechanism is ductile fracture.The tensile fracture surface of Zn-1.5Mg alloy is a typical quasi cleavage fracture,the fracture mechanism of the alloy is brittle fracture.The fracture mechanism of Zn-3Al-1Mg alloy is dominated by brittle fracture,which is a mixed fracture mechanism containing ductile fracture and brittle fracture.