Microstructure And Deformation Mechanism Of Zn-Li Alloys

Zn-Li alloys have attracted increasing attention in recent years for their application in biomedical field.In this thesis,SEM,XRD,EBSD and TEM are used to study the phases and microstructure of Zn-Li extrusion alloys.The tensile and compressive mechanical properties of Zn-Li alloys were measured,and the relationship between the mechanical properties and the microstructure was discussed.The main results are as follows:?1?The extruded Zn alloy exhibits a tensile yield strength of 100 MPa and an elongation of 40%.When Li was added to Zn alloys,the tensile yield strength of Zn-0.1Li and Zn-0.4Li extursion alloys increased to 310 MPa and 468 MPa,respectively,but the elongation decreased to 5%and 12%,respectively.The compressive yield strengths of Zn-0.1Li and Zn-0.4Li alloys are 320MPa and 485Mpa,which are almostly indentical to the tensile yield strengths.?2?The microstructures of Zn-Li extrusion alloys are composed of??Zn?grains and multi-layer structure containning LiZn₄ and??Zn?which are generate by eutectoid reaction.With an increment of Li content,the size of Zn grains decreased,but the amout of multi-layer structure increased.The multi-layer structure can effectively improve the strength of Zn-Li alloys.?3?The lattice parameters of?-LiZn₄ and?-LiZn₄ phases are determined and confirmed using tilt-series selected area diffraction in TEM.The?-LiZn₄ phase has a hexagonal structure with a=0.256 nm,c=0.488 nm.The?-LiZn₄ phase also has a hexagonal structure with a=0.251 nm,c=0.481 nm.?4?In the extruded Zn-Li alloys,the??Zn?grains have a typical fiber texture of hexagonal structure with c axis perpendicular to the extrusion direction?ED?.In the multi-layer structure,the c axis of??Zn?grains is also perpendicular to ED,but the c axis of LiZn₄ grains is almostly parallel to ED.?5?Twins firstly appear in pure Zn grains during compression,and their amout increases with an increment of rolling reduction.With further deformation,the recrystallization grains generate and dominate the subsequent deformation process.There is no obvious recrystallization grains production in Zn-0.1Li alloy compression deformation.Stress concentration and low angle grain boundary produces in the early deformation process,after further deformation twinning apperas.Deformation stress first concentrated around LiZn₄+??Zn?composite lamellar structure grains,then began to spread.