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

As degradable stent materials,Zn and its alloys have suitable degradation rate and good biocompatibility compared to Fe-based alloys and Mg-based alloys.And most of the microtubules used for stent are processed by extrusion?drawing and extrusion?rolling?drawing.Extrusion is an important plastic processing method for tube blanks,the corresponding microstructures and mechanical properties of extruded tube blanks have great impact on the performance of microtubules sent.Zn-Mg-Mn alloys have been confirmed to have excellent comprehensive mechanical properties by our previous researches,therefore,Zn-Mg-Mn alloy pipes were prepared with different extrusion parameters in this work.The microstructures and mechanical properties of the alloy pipes were studied using scanning electron microscopy(SEM),X-ray diffraction(XRD),electron backscatter diffraction(EBSD),room temperature tensile and compression tests.The relationship between extrusion process,microstructures and mechanical properties was analyzed,which provided valuable basic data for the subsequent processing of degradable Zn-Mg-Mn alloy microtubes.The results obtained are as follows:The extrusion speed for the as-cast Zn-0.1Mg-1Mn alloy is 1 mm/s,extrusion ratio is 29,and the extrusion temperature reduced from 300? to 100?.The tensile strength and yield strength of Zn-0.1Mg-1Mn alloy pipes(?12 × 2 mm)gradually increased.The tensile strength and yield strength remained 387?405 MPa and 340-370 MPa,respectively.However,the elongation gradually increased from 6%to 15%.The average grain size of the alloy pipe gradually decreased from 2.4 ?m to 1 ?m and the size of the second phase also gradually decreased.The proportion of small-angle grain boundaries gradually increased from 12%to 17%.The texture of the alloy pipe is changed from ED?<1010>and ED?<1120>basal texture to non-basal texture with<0001>crystal orientation tilt 70° to 80° from ED.Forged Zn-0.1 Mg-1 Mn alloy as a blank,when the extrusion ratios are 29 and 64,the tensile strength,yield strength and elongation of Zn-0.1Mg-1Mn alloy pipes(outer diameter ?12×2mm and ? 10×1 mm)all decrease with the increase of the extrusion ratio.The tensile strength,yield strength and elongation of Zn-0.1Mg-1Mn alloy pipes from 367 MPa,319 MPa and 36%decrease to 343 MPa,312 MPa and 25%,respectively.With the increase of the extrusion ratio,the size of the second phase of the alloy pipe decreases,and the grain size increases from 1.2 ?m to 1.5 ?m.The proportion of small-angle grain boundaries does change little,and the texture type changes from non-basal texture to ED?<1010>basal texture.Forged Zn-0.1Mg-1Mn alloy as a blank,Zn-0.1Mg-1Mn alloy thin tubes(outer diameters of ? 6×1.5 mm and ?5×1 mm)were extruded at temperature of 150 and 200? with the extrusion ratios 33 and 56.The best performance best performance of Zn-0.1Mg-1Mn alloy thin tubes is obtained at an extrusion temperature of 150? and an extrusion ratio of 33.The UTS,YS and elongation are 385 MPa,377 MPa,and 41%,respectively.The extrusion temperature and extrusion ratio have little effect on the tensile strength and yield strength of the pipe.The tensile strength is maintained 380 MPa,and the yield strength is maintained 370 MPa.The elongation decreases significantly with increasing extrusion temperature.The extrusion temperature and extrusion ratio have little effect on the small-angle grain boundary proportion and texture type of the alloy pipe.The small-angle grain boundary ratio is about 10.6%,and the texture types are ED?<l010>fiber base texture.However,the average grain size increased with the increase of extrusion temperature and extrusion ratio.The Zn-0.08Mg-0.6Mn alloy tubes(outer diameters of ?10×1mm)were extruded at 0.2 and 0.5 mm/s.The most excellent performance of Zn-0.08Mg-0.6Mn alloy thin tubes is obtained with extrusion speed of 0.2 mm/s,its tensile strength,yield strength and elongation is 341 MPa,335 MPa and 24%,respectively.The increase of extrusion speed has little effect on the strength of the alloy pipe,but it will significantly reduce the elongation.With the increase of extrusion speed,the average grain size increased slightly,the proportion of small-angle grain boundaries matained 6.5%,and the texture changed from non-basal texture to ED?<1010>base texture.