In this work,the microstructure of titania coating fabricated on the surface of hydrostatically extruded titanium grade 4 with the use of the micro-arc oxidation method was studied.The surface topography and microstru...In this work,the microstructure of titania coating fabricated on the surface of hydrostatically extruded titanium grade 4 with the use of the micro-arc oxidation method was studied.The surface topography and microstructure investigations performed with atomic force microscopy and scanning and transmission electron microscopy revealed that,by using an Na_(2)HPO_(4)electrolyte,a well-adherent porous coating is produced on the top surface and side walls of the extruded rod.The distribution of chemical elements was analyzed by using energy dispersive X-ray spectroscopy.The chemical elements dissolved in the electrolyte(Na,P and O)incorporated into the coating.Sodium locates preferentially in the outer part of the coating,while phosphorus and oxygen are distributed throughout the whole coating.The most relevant finding shows that a grain refinement caused by a hydrostatic extrusion provoked an increase in density of high-angle grain boundaries(HAGB),which in turn secured the formation of a continuous amorphous layer close to the substrate.The presence of this layer compensates for the effect of anisotropic substrate,producing a comparable and homogenous microstructure with a large number of micropores.展开更多
The study is concerned with the mechanical properties of Zn and three Zn–Mg double alloys with Mg concentrations:0.5%,1.0%and 1.5%in the form of rods with a diameter of 5 mm as potential materials for use in biodegra...The study is concerned with the mechanical properties of Zn and three Zn–Mg double alloys with Mg concentrations:0.5%,1.0%and 1.5%in the form of rods with a diameter of 5 mm as potential materials for use in biodegradable medical implants,such as vascular stents.The materials were cast,next conventionally hot extruded at 250°C and finally,hydrostatically extruded(HE)at ambient temperature.Occasionally HE process was carried at liquid nitrogen temperature or in combination with the ECAP process.After HE,the microstructure of the alloys was made up of fine-grainedαZn of mean grain size~1μm in a 2-phase coat of 50–200 nm nanograins of the fineαZn+Mg2Zn11 eutectic.The 3 to 4-fold reduction of grain size as a result of HE allowed an increase in yield strength from 100%to over 200%,elongation to fracture from 100%to thirty fold and hardness over 50%compared to the best literature results for similar alloys.Exceptions accounted for elongation to fracture in case of Zn-0.5 Mg alloy and hardness in case of Zn-1.5 Mg alloy,both of which fell by 20%.For the Zn-0.5 Mg and Zn–1Mg alloys,after immersion tests,no corrosive degradation of plasticity was observed.Achieving these properties was the result of generating large plastic deformations at ambient temperature due to the application of high pressure forming with the cumulative HE method.The results showed that Zn–Mg binary alloys after HE have mechanical and corrosive characteristics,qualifying them for applications in biodegradable implants,including vascular stents.展开更多
基金financially supported by the Institute of Metallurgy and Materials Science of the Polish Academy of Sciences within the statutory work Z-4/2021partly supported by the EU Project POWR.03.02.00–00-I004/16。
文摘In this work,the microstructure of titania coating fabricated on the surface of hydrostatically extruded titanium grade 4 with the use of the micro-arc oxidation method was studied.The surface topography and microstructure investigations performed with atomic force microscopy and scanning and transmission electron microscopy revealed that,by using an Na_(2)HPO_(4)electrolyte,a well-adherent porous coating is produced on the top surface and side walls of the extruded rod.The distribution of chemical elements was analyzed by using energy dispersive X-ray spectroscopy.The chemical elements dissolved in the electrolyte(Na,P and O)incorporated into the coating.Sodium locates preferentially in the outer part of the coating,while phosphorus and oxygen are distributed throughout the whole coating.The most relevant finding shows that a grain refinement caused by a hydrostatic extrusion provoked an increase in density of high-angle grain boundaries(HAGB),which in turn secured the formation of a continuous amorphous layer close to the substrate.The presence of this layer compensates for the effect of anisotropic substrate,producing a comparable and homogenous microstructure with a large number of micropores.
基金the National Science Centre(Poland),grant UMO-2016/23/B/ST8/00724.
文摘The study is concerned with the mechanical properties of Zn and three Zn–Mg double alloys with Mg concentrations:0.5%,1.0%and 1.5%in the form of rods with a diameter of 5 mm as potential materials for use in biodegradable medical implants,such as vascular stents.The materials were cast,next conventionally hot extruded at 250°C and finally,hydrostatically extruded(HE)at ambient temperature.Occasionally HE process was carried at liquid nitrogen temperature or in combination with the ECAP process.After HE,the microstructure of the alloys was made up of fine-grainedαZn of mean grain size~1μm in a 2-phase coat of 50–200 nm nanograins of the fineαZn+Mg2Zn11 eutectic.The 3 to 4-fold reduction of grain size as a result of HE allowed an increase in yield strength from 100%to over 200%,elongation to fracture from 100%to thirty fold and hardness over 50%compared to the best literature results for similar alloys.Exceptions accounted for elongation to fracture in case of Zn-0.5 Mg alloy and hardness in case of Zn-1.5 Mg alloy,both of which fell by 20%.For the Zn-0.5 Mg and Zn–1Mg alloys,after immersion tests,no corrosive degradation of plasticity was observed.Achieving these properties was the result of generating large plastic deformations at ambient temperature due to the application of high pressure forming with the cumulative HE method.The results showed that Zn–Mg binary alloys after HE have mechanical and corrosive characteristics,qualifying them for applications in biodegradable implants,including vascular stents.
