Effect Of Extrusion Process On Microstructure And Properties Of Zn-Mg-Mn Alloys

Zn alloys as a biodegradable biomaterial have attracted more and more attention due to their appropriate degradation rate and good biocompatibility compare to Mg based alloys and Fe based alloys.The poor mechanical properties of pure Zn,and it can not meet the actual needs.By adding Mg,Sr,Ca and other elements for alloying and thermal deformation methods to improve the pure Zn mechanical properties,mechanical properties than pure Zn also has greatly improved,but still can not meet the mechanical properties of biological materials requirements.Zn-Mg binary alloys have great potential as biodegradable biomaterials,but at present their problems are still mechanical properties can not meet the actual needs.Therefore,based on the Zn-Mg binary alloy,Mn is added and the content of Mg is properly adjusted.Combined with the previous research of our group,Zn-0.5Mg-1Mn,Zn-0.2Mg-1Mn,Zn-0.5Mg-0.5Mn three-component alloys were designed.The Zn-Mg-Mn ternary alloy was prepared by a series of processes including casting,homogenization and reverse hot extrusion.The hot extrusion process was mainly controlled by the extrusion rate(1mm/s,5mm/s,10mm/s),extrusion temperature(100?,150?,250?),the effects of extrusion rate and extrusion temperature on microstructure and mechanical properties of Zn-Mg-Mn alloys.It can provide meaningful experimental data and theoretical basis for the further development of Zn-based alloys.Indirectly hot extrusion experiment of the Zn based alloys,Mg elements are mainly in the form of Mg2Zn11 compounds,and it has a zonal distribution along the extrusion direction.While the Mn element is mainly exist in the form of MnZn13 compounds,generally the size below 0.5?m distributed in the Zn matrix grain boundary position,and a small amount of large size distribution along the extrusion direction.At the same time the type of alloy phase did not change significantly with the extrusion process and elemental content.When the extrusion temperature was 100?,the grain size of Zn-0.5Mg-1Mn alloy increased with the extrusion rate increasing,and the homogeneity of the microstructure decreased.The size,distribution and morphology of the second phase did not change significantly;The grain orientation in the organization is basically the same,and the grain boundary angle is dominated by the large angle.The texture of the texture is {0001} fiber texture,and the texture strength increases with the increase of extrusion speed.The increase of Zn-0.5Mg-0.5Mn alloy with the extrusion rate showed a similar pattern,but the change of the tissue was more obvious,and the Zn matrix grain and the second phase were significantly increased.The micro structure of Zn-0.2Mg-1Mn alloy change very small with the increase of extrusion rate.When the extrusion rate is certain,the grain size of the matrix of Zn-0.5Mg-1Mn alloy is significantly increased with the extrusion temperature increases,the second phase size also increases,and the average grain size increases.Grain orientation change is still not obvious,the grain boundary Angle is dominated by large angle.For Zn-0.5Mg-0.5Mn alloy,the grain size increases with the increase of extrusion temperature,but the change amplitude is higher than that of Zn-0.5Mg-1Mn alloy.The Zn-0.2Mg-1Mn alloy group maintains a similar pattern,but its tissues are relatively less affected by temperature.When the extrusion temperature is constant,with the extrusion rate increases,the tensile strength and yield strength of experimental alloys were changed very little,while the elongation decreased obviously.When the extrusion temperature is 100? and extrusion rate increased from 1mm/s to 10mm/s,for Zn-0.5Mg-1Mn alloy,the tensile strength basically keep in the range of 420?435 MPa,the yield strength remain in the range of 350?375 MPa,but elongation decreased from 38%to 10%.If the extrusion speed is certain,then the yield strength and tensile strength of the experimental alloys of the three components will not change as the extrusion temperature increases,but the elongation rate is obviously decreased.When the extrusion temperature is 100?,the extrusion rate increases from lmm/s to 10mm/s.The tensile strength of Zn-0.5Mg-1Mn alloy is maintained in the range of 420?435 MPa,and the yield strength is maintained at 350?375 MPa,but the elongation rate dropped from 38%to 10%.When the extrusion temperature is 100? and the extrusion rate is lmm/s,the best mechanical properties are obtained for the three alloys.Under the same process parameters,Compared with Zn-0.5Mg-1Mn and Zn-0.5Mg-0.5Mn alloys,the elongation rates are similar,the tensile strength and yield strength are respectively 36MPa and 74MPa,which shows that the strengthening effect of Mn is obvious.The difference of mechanical properties between Zn-0.5Mg-1Mn and Zn-0.2Mg-1Mn alloy is relatively small,while the effect of Mg on grain size is relatively small.