Investigation Of Thermal Rotary Swaging Process Of WE43 Magnesium Alloy Bars Used For Orthopedic Implants

WE43(Mg-4Y-3Nd-Zr)alloy is a magnesium alloy which was regarded as biomedical material earlier in the world.It not only has high mechanical properties,but also has more excellent corrosion resistance.As low modulus,high strength and good toughness plastic is required for biodegradable magnesium alloy as medical surgical implants.We used advanced hot rotary swaging method to do a systematic study on the mechanical properties(including strength,hardness,ductility,etc.)as well as microstructure of the biodegradable WE43 alloy to promote it used in orthopedic implants.The hot rotary swaging and annealing process of WE43 magnesium alloy were explored.The preparation process of small-sized alloy bar was further explored and the corrosion resistance of medical WE43 magnesium alloy was preliminarily explored as well.The results showed that:At a temperature of 300 ~ 350?,hot swaging process can significantly refine the grains of WE43 magnesium alloy,crushed the second phases and greatly enhance the strength and hardness of the alloy.However,the elongation is slightly reduced.WE43 magnesium alloy can produce a significant hardening after more than 50% of the amount of deformation of hot swaging,however,even the cumulative amount of deformation reach to 75%,the alloy soften significantly and the plasticity increased after 400?×60min annealing.Further deformation processing can continue and grain size does not change significantly compared with that of before annealing.The ?12mm magnesium alloy bar can undergo accumulated deformation of 75% by proper hot rotary swaging methods,and a ?6mm magnesium alloy bar can be obtained with homogeneous microstructure and improved mechanical properties.The corrosion behavior of WE43 magnesium alloy bar of as-cast,?12mm processing state,?12mm annealing state,?6mm processing state and ?6mm annealing state was investigated,the results showed that: the corrosion current density of ?6mm annealing state is smallest,?6mm processing state followed,?12mm processing state and as-cast are nearly the same.The corrosion current density of ?12mm processing state is slightly larger compared with ?12mm annealing state.The corrosion degree of ?6mm annealing state is the lightest showing more uniform corrosion morphology,after soaking in SBF for 8 days.The results of corrosion immersion experiment also coincident with that of electrochemical analysis.Taken together,the small-sized bar of WE43 magnesium alloy with fine and uniform microstructure can be successfully obtained at a lower temperature and a large amount of plastic deformation by hot rotary swaging method.The mechanical properties significantly improved and the corrosion resistance also improved with a uniform corrosion manner,after hot rotary swaging.Thus,the bar is expected as orthopedic implant billets.