Biodegradable magnesium(Mg)alloys have received much attention due to their biocompatibility and biodegradation.In this study,to uncover the effects of grain morphologies,including grain size and distribution on mecha...Biodegradable magnesium(Mg)alloys have received much attention due to their biocompatibility and biodegradation.In this study,to uncover the effects of grain morphologies,including grain size and distribution on mechanical and corrosion properties,biodegradable Mg-2.1Nd-0.2Zn-0.5Zr(wt.%)(denoted as JDBM)alloy mini-tubes for stent application with three typical microstructures were achieved success-fully by adjusting drawing parameters.Samples with the bimodal structure exhibit the highest strengthductility balance attributed to the combined effects of fine grains and coarse grains,but show the fastest corrosion rate of about 1.00±0.136 mm/year mainly due to the formation of micro galvanic couples between coarse and fined grains.Samples with fine equiaxed grains show the lowest corrosion rate of about 0.17±0.059 mm/year,as well as uniform corrosion mode and mechanical properties of yield strength(YS)256±5.7 MPa,ultimate tensile strength(UTS)266±3.8 MPa,and elongation to failure(EL)13.5%±1.8%,attributed to the high-density grain boundaries.Samples with coarse equiaxed grains exhibit medium corrosion resistance and mechanical properties of about 175±4.8 MPa,221±4.0 MPa,and 21.53%±4.1%.Considering the mechanical and in vitro corrosion properties,biodegradable JDBM alloy implants are recommended to be composed of fine equiaxed grains,which can be used as microstructural targets for fabrication and processing.展开更多
针对微型薯等大粒种子不易充种问题,设计了一种可振动供种的气吸圆盘式微型薯排种器。阐述了该排种器的工作原理,通过理论计算与数值模拟,确定了其主要结构参数。为寻求最佳工作参数组合,采用三因素四水平正交试验方法,对排种器进行排...针对微型薯等大粒种子不易充种问题,设计了一种可振动供种的气吸圆盘式微型薯排种器。阐述了该排种器的工作原理,通过理论计算与数值模拟,确定了其主要结构参数。为寻求最佳工作参数组合,采用三因素四水平正交试验方法,对排种器进行排种性能试验,结果表明:影响其排种性能的主次因素依次为作业速度、振动频率和吸种负压,较优参数组合为作业速度2.4 km/h、振动频率6.5 Hz、吸种负压6 k Pa,在此条件下排种合格指数为94.2、漏播指数为1.7、重播指数为4.1,满足微型薯的精密播种要求。研究了振动供种机构对微型薯造成的损伤情况:在不同的振动频率下,微型薯的破损率均小于1%,振动供种机构对微型薯的损伤不大。展开更多
基金funded by grants from the National Natural Science Foundation of China(Nos.52130104 and 52273318)the Science and Technology Innovation Commission of Shenzhen Municipality(No.JCYJ20220818102815033)the National Key Research and Development Program of China(Nos.2021YFC2400701 and 2020YFE020210).
文摘Biodegradable magnesium(Mg)alloys have received much attention due to their biocompatibility and biodegradation.In this study,to uncover the effects of grain morphologies,including grain size and distribution on mechanical and corrosion properties,biodegradable Mg-2.1Nd-0.2Zn-0.5Zr(wt.%)(denoted as JDBM)alloy mini-tubes for stent application with three typical microstructures were achieved success-fully by adjusting drawing parameters.Samples with the bimodal structure exhibit the highest strengthductility balance attributed to the combined effects of fine grains and coarse grains,but show the fastest corrosion rate of about 1.00±0.136 mm/year mainly due to the formation of micro galvanic couples between coarse and fined grains.Samples with fine equiaxed grains show the lowest corrosion rate of about 0.17±0.059 mm/year,as well as uniform corrosion mode and mechanical properties of yield strength(YS)256±5.7 MPa,ultimate tensile strength(UTS)266±3.8 MPa,and elongation to failure(EL)13.5%±1.8%,attributed to the high-density grain boundaries.Samples with coarse equiaxed grains exhibit medium corrosion resistance and mechanical properties of about 175±4.8 MPa,221±4.0 MPa,and 21.53%±4.1%.Considering the mechanical and in vitro corrosion properties,biodegradable JDBM alloy implants are recommended to be composed of fine equiaxed grains,which can be used as microstructural targets for fabrication and processing.
文摘针对微型薯等大粒种子不易充种问题,设计了一种可振动供种的气吸圆盘式微型薯排种器。阐述了该排种器的工作原理,通过理论计算与数值模拟,确定了其主要结构参数。为寻求最佳工作参数组合,采用三因素四水平正交试验方法,对排种器进行排种性能试验,结果表明:影响其排种性能的主次因素依次为作业速度、振动频率和吸种负压,较优参数组合为作业速度2.4 km/h、振动频率6.5 Hz、吸种负压6 k Pa,在此条件下排种合格指数为94.2、漏播指数为1.7、重播指数为4.1,满足微型薯的精密播种要求。研究了振动供种机构对微型薯造成的损伤情况:在不同的振动频率下,微型薯的破损率均小于1%,振动供种机构对微型薯的损伤不大。
