| Biomedical austenitic stainless steel has excellent comprehensive properties,but its biocompatibility in practical application is poor.Due to its antibacterial and angiogenic functions,copper(Cu)can improve the biocompatibility of stainless steel.Previous studies have proved that Cu-bearing austenitic stainless steel can not only effectively kill bacteria and prevent the bacterial infection,but also promote the proliferation of endothelial cells and inhibit stent restenosis.However,the preparation process of austenitic stainless steel usually involves large deformation such as hot/cold rolling,it needs to be annealed before practical application to reduce the risk of fracture caused by the maldistribution of internal stress.In addition,the addition of most elements has a significant inhibitory effect on the static recrystallization behavior of stainless steel,thus affecting the strength and corrosion resistance of stainless steel.Hence,this paper studied the static recrystallization behavior of 316L and 316L-Cu stainless steel annealed at different temperatures.What’s more,the effect of Cu addition on the recrystallization mechanism of 316L stainless steel,the change of mechanical properties,and internal deformation mechanism after annealing are discussed,which provide a solid theoretical basis of obtain Cu-bearing stainless steel with excellent comprehensive properties.The research contents and main conclusions of this paper are as follows:(1)Study on the effect of Cu addition on static recrystallization behavior of cold-deformed 316L stainless steelThe hardness and microstructure evolution of cold-deformed 316L and 316L-Cu stainless steels annealed at different temperatures were analyzed.It was found that Cu addition retards the static recrystallization of 316L austenitic stainless steel.When annealed at 800°C for 30 min,the 316L stainless steel has been completely recrystallized,while the 316L-Cu stainless steel is fully recrystallized at 875°C during the same annealing time.The recrystallization activation energy during different annealing conditions was calculated according to the Arrhenius-type relation,which indicates that Cu addition increased the recrystallization activation energy of 316L stainless steel.The specific zone of 316L-Cu stainless steel annealed at different temperatures were further analyzed by the Transmission electron microscope(TEM),it shows that the fine Cu-rich precipitates preferentially distributed at the interface between the recrystallized grain and deformation region after annealing at 800 ~oC for30 min,which pinned the migration of grain boundaries and retarded the recrystallization process.With increasing annealing temperature,the solid solution of Cu in steel matrix gradually increased,leading to the lower volume fraction of Cu-rich precipitation in the matrix,and weakening the pinning effect of Cu-rich precipitation.(2)Study on the effect of Cu addition on the mechanical properties and deformation mechanism of 316L stainless steel at different annealing conditionsThe deformation mechanism and mechanical properties of Cu-bearing 316L stainless steel under different annealing temperatures were analyzed by the tensile tests of samples at room temperature.The results show that 316L-Cu stainless steel had a lower recrystallized volume fraction when the annealing temperature was lower than900°C,resulting in the higher strength and less plasticity of stainless steel.When the annealing temperature increases to 1000 ~oC,the stainless steels have been fully recrystallized,and the strength of 316L stainless steel is higher at this time,which indicates that Cu addition decreases the strength of 316L stainless steel.The further microstructure analysis shows that the stainless steel had a single austenitic structure before and after deformation.The matrix after deformation generated a large number of dislocation entanglements and a small number of deformation twins,which indicated that the deformation mechanism of 316L and 316L-Cu stainless steel is mainly dislocation slip,and the deformation twins have little effect on the mechanical properties of stainless steels.Therefore,although Cu addition reduces the content of deformation twins in 316L stainless steel,it has little effect on the deformation mechanism. |
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