Mg−1Mn−0.5Al−0.5Ca−0.5Zn(wt.%)alloy was fabricated by conventional extrusion at 673 K with an extrusion ratio of 25:1,followed by aging at 473 K.The microstructure was characterized by scanning electron microscopy,ele...Mg−1Mn−0.5Al−0.5Ca−0.5Zn(wt.%)alloy was fabricated by conventional extrusion at 673 K with an extrusion ratio of 25:1,followed by aging at 473 K.The microstructure was characterized by scanning electron microscopy,electron back-scattered diffraction,and transmission electron microscopy.The mechanical properties were determined by the tensile test.The peak-aged sample shows fine recrystallized grains with an average grain size of 1.7μm.Area fraction of Al−Ca particles in the alloy increases significantly after peak aging.Meanwhile,botháañandác+añdislocations were observed to remain in the alloy after hot extrusion.Thus,the peak-aged sample exhibits simultaneously high strength and good ductility with the ultimate tensile stress,tensile yield stress,and tension fracture elongation of 320 MPa,314 MPa,and 19.0%,respectively.展开更多
The microstructure and properties of the as-cast,as-homogenized and as-extruded Mg−6Zn−4Sn−1Mn(ZTM641)alloy with various Al contents(0,0.5,1,2,3 and 4 wt.%)were investigated by OM,XRD,DSC,SEM,TEM and uniaxial tensile ...The microstructure and properties of the as-cast,as-homogenized and as-extruded Mg−6Zn−4Sn−1Mn(ZTM641)alloy with various Al contents(0,0.5,1,2,3 and 4 wt.%)were investigated by OM,XRD,DSC,SEM,TEM and uniaxial tensile tests.The results show that when the Al content is not higher than 0.5%,the alloys are mainly composed of α-Mg,Mg_(2)Sn,Al_(8)Mn_(5)and Mg_(7)Zn_(3)phases.When the Al content is higher than 0.5%,the alloys mainly consist ofα-Mg,Mg_(2)Sn,MgZn,Mg_(32)(Al,Zn)_(49),Al_(2)Mg_(5)Zn_(2),Al_(11)Mn_(4)and Al_(8)Mn_(5)phases.A small amount of Al(≤1%)can increase the proportion of fine dynamic recrystallized(DRXed)grains during hot-extrusion process.The roomtemperature tensile test results show that the ZTM641−1Al alloy has the best comprehensive mechanical properties,in which the ultimate tensile strength is 332 MPa,yield strength is 221 MPa and the elongation is 15%.Elevatedtemperature tensile test results at 150 and 200℃ show that ZTM641−2Al alloy has the best comprehensive mechanical properties.展开更多
Biodegradable Mg-based implants are widely used in clinical applications because they exhibit mechanical properties comparable to those of human bone and require no revision surgery for their removal.Among Mg-based al...Biodegradable Mg-based implants are widely used in clinical applications because they exhibit mechanical properties comparable to those of human bone and require no revision surgery for their removal.Among Mg-based alloys,Mg–Zn–Ca–(Mn)alloys have been extensively investigated for medical applications because the constituent elements of these alloys,Mg,Zn,Ca,and Mn,are present in human tissues as nutrient elements.In this study,we investigated the effect of the hot extrusion temperature on the microstructure,mechanical properties,and biodegradation rate of Mg–Zn–Ca–(Mn)alloys.The results showed that the addition of Mn and a decrease in the extrusion temperature resulted in grain refinement followed by an increase in the strength and a decrease in the elongation at fracture of the alloys.The alloys showed different mechanical properties along the directions parallel and perpendicular to the extrusion direction.The corrosion test of the alloys in the Hanks’solution revealed that the addition of Mn significantly reduced the corrosion rate of the alloys.The Mg–2 wt%Zn–0.7 wt%Ca–1 wt%Mn alloy hot-extruded at 300℃ with an ultimate tensile strength of 278MPa,an yield strength of 229MPa,an elongation at fracture of 10%,and a corrosion rate of 0.3 mm/year was found to be suitable for orthopedic implants.展开更多
In this study,the microstructural evolution,mechanical properties and biocorrosion performance of a Mg–Zn–Ca–Mn alloy were investigated under different conditions of heat treatment,extrusion,one pass and two passes...In this study,the microstructural evolution,mechanical properties and biocorrosion performance of a Mg–Zn–Ca–Mn alloy were investigated under different conditions of heat treatment,extrusion,one pass and two passes of half equal channel angular pressing(HECAP)process.The results showed significant grain refinement of the homogenized alloy after two passes of HECAP process from 345μm to 2μm.Field emission scanning electron microscopy(FESEM)revealed the presence of finer Mg_(6)Zn_(3)Ca_(2)phase as well asα-Mn phase after HECAP process.The results also showed that mechanical characteristics such as yield strength,ultimate tensile strength and elongation of the HECAPed samples improved by~208%,~144%and~100%compared to the homogenized one,respectively.Crystallographic texture analysis indicated that most of the grains at the surface were reoriented parallel to the(0001)basal plane after HECAP process.Electrochemical corrosion tests and immersion results indicated that the sample with two passes of HEACP had the highest biocorrosion resistance confirming that the basal planes had the lowest corrosion rate compared to the non-basal ones.The mechanical behavior and bio-corrosion evaluation demonstrated that the HECAPed Mg–Zn–Ca–Mn alloy has great potential for biomedical applications and a mechanism was proposed to explain the interrelations between the thermomechanical processing and bio-corrosion behavior.展开更多
Biodegradable Zn-based alloys, particularly Zn-Mg alloys with the addition of alloying elements, have been intensively investigated aiming to improve both mechanical properties and corrosion behavior. Since such prope...Biodegradable Zn-based alloys, particularly Zn-Mg alloys with the addition of alloying elements, have been intensively investigated aiming to improve both mechanical properties and corrosion behavior. Since such properties are strongly dependent on the alloy microstructure, any evaluation should commence on understanding the conditions influencing its formation. In this study, the effect of the solidification cooling rate on the microstructural evolution of Zn-1 wt.%Mg-(0.5 wt.%Ca, 0.5 wt.%Mn) alloys during transient solidification was investigated. The results show that the microstructures of both alloys have three phases in common: η-Zn dendritic matrix, intermetallic compounds(IMCs) Zn11Mg2, and Zn2 Mg in the eutectic mixture. MnZn9 and two Ca-bearing phases(CaZn11 and CaZn13) are associated with Mn and Ca additions, respectively. These additions are shown to refine the dendritic matrix and the eutectic mixture as compared to the Zn-1 wt.%Mg alloy. A correlation between cooling rate, dendritic or eutectic spacings was developed, thus permitting experimental growth laws to be proposed. Additionally, hardness tests were performed to evaluate the effects of additions of Ca and Mn. Experimental correlations between Vickers microhardness and secondary dendritic spacings were proposed, showing that the microstructural refinement and characteristic Ca and Mn based IMCs induce an increase in hardness as compared to the binary alloy.展开更多
基金the financial supports from the Fundamental Research Funds for the Central Universities,China(Nos.2019CDCGCL316,2020CDJDPT001)Chongqing Research Program of Basic Research and Frontier Technology,China(No.cstc2019jcjy-msxmX0539)。
文摘Mg−1Mn−0.5Al−0.5Ca−0.5Zn(wt.%)alloy was fabricated by conventional extrusion at 673 K with an extrusion ratio of 25:1,followed by aging at 473 K.The microstructure was characterized by scanning electron microscopy,electron back-scattered diffraction,and transmission electron microscopy.The mechanical properties were determined by the tensile test.The peak-aged sample shows fine recrystallized grains with an average grain size of 1.7μm.Area fraction of Al−Ca particles in the alloy increases significantly after peak aging.Meanwhile,botháañandác+añdislocations were observed to remain in the alloy after hot extrusion.Thus,the peak-aged sample exhibits simultaneously high strength and good ductility with the ultimate tensile stress,tensile yield stress,and tension fracture elongation of 320 MPa,314 MPa,and 19.0%,respectively.
基金the financial supports from the National Natural Science Foundation of China(No.51701172)Educational Commission of Hunan Province,China(No.20B579)+2 种基金Major Program of Hunan Province,China(No.2018RS3091)China Postdoctoral Science Foundation(No.2018M632977)the Natural Science Foundation of Hunan Province,China(No.2018JJ3504).
文摘The microstructure and properties of the as-cast,as-homogenized and as-extruded Mg−6Zn−4Sn−1Mn(ZTM641)alloy with various Al contents(0,0.5,1,2,3 and 4 wt.%)were investigated by OM,XRD,DSC,SEM,TEM and uniaxial tensile tests.The results show that when the Al content is not higher than 0.5%,the alloys are mainly composed of α-Mg,Mg_(2)Sn,Al_(8)Mn_(5)and Mg_(7)Zn_(3)phases.When the Al content is higher than 0.5%,the alloys mainly consist ofα-Mg,Mg_(2)Sn,MgZn,Mg_(32)(Al,Zn)_(49),Al_(2)Mg_(5)Zn_(2),Al_(11)Mn_(4)and Al_(8)Mn_(5)phases.A small amount of Al(≤1%)can increase the proportion of fine dynamic recrystallized(DRXed)grains during hot-extrusion process.The roomtemperature tensile test results show that the ZTM641−1Al alloy has the best comprehensive mechanical properties,in which the ultimate tensile strength is 332 MPa,yield strength is 221 MPa and the elongation is 15%.Elevatedtemperature tensile test results at 150 and 200℃ show that ZTM641−2Al alloy has the best comprehensive mechanical properties.
基金The authors gratefully acknowledge the financial support from the Ministry of Science and Higher Education of the Russian Federation in the framework of Increase Competitiveness Program of NUST 《MISiS》(№ К2-2019-008)implemented by a governmental decree dated 16th of March 2013,N 211.
文摘Biodegradable Mg-based implants are widely used in clinical applications because they exhibit mechanical properties comparable to those of human bone and require no revision surgery for their removal.Among Mg-based alloys,Mg–Zn–Ca–(Mn)alloys have been extensively investigated for medical applications because the constituent elements of these alloys,Mg,Zn,Ca,and Mn,are present in human tissues as nutrient elements.In this study,we investigated the effect of the hot extrusion temperature on the microstructure,mechanical properties,and biodegradation rate of Mg–Zn–Ca–(Mn)alloys.The results showed that the addition of Mn and a decrease in the extrusion temperature resulted in grain refinement followed by an increase in the strength and a decrease in the elongation at fracture of the alloys.The alloys showed different mechanical properties along the directions parallel and perpendicular to the extrusion direction.The corrosion test of the alloys in the Hanks’solution revealed that the addition of Mn significantly reduced the corrosion rate of the alloys.The Mg–2 wt%Zn–0.7 wt%Ca–1 wt%Mn alloy hot-extruded at 300℃ with an ultimate tensile strength of 278MPa,an yield strength of 229MPa,an elongation at fracture of 10%,and a corrosion rate of 0.3 mm/year was found to be suitable for orthopedic implants.
文摘In this study,the microstructural evolution,mechanical properties and biocorrosion performance of a Mg–Zn–Ca–Mn alloy were investigated under different conditions of heat treatment,extrusion,one pass and two passes of half equal channel angular pressing(HECAP)process.The results showed significant grain refinement of the homogenized alloy after two passes of HECAP process from 345μm to 2μm.Field emission scanning electron microscopy(FESEM)revealed the presence of finer Mg_(6)Zn_(3)Ca_(2)phase as well asα-Mn phase after HECAP process.The results also showed that mechanical characteristics such as yield strength,ultimate tensile strength and elongation of the HECAPed samples improved by~208%,~144%and~100%compared to the homogenized one,respectively.Crystallographic texture analysis indicated that most of the grains at the surface were reoriented parallel to the(0001)basal plane after HECAP process.Electrochemical corrosion tests and immersion results indicated that the sample with two passes of HEACP had the highest biocorrosion resistance confirming that the basal planes had the lowest corrosion rate compared to the non-basal ones.The mechanical behavior and bio-corrosion evaluation demonstrated that the HECAPed Mg–Zn–Ca–Mn alloy has great potential for biomedical applications and a mechanism was proposed to explain the interrelations between the thermomechanical processing and bio-corrosion behavior.
基金The authors are grateful to FAPESP-São Paulo Research Foundation,Brazil(2014/50502-5 and 2017/16058-9)Capes-Coordenação de Aperfeiçoamento de Pessoal de Nível Superior,Brazil(Funding code 001)and CNPq-National Council for Scientific and Technological Development(406239/2018-5)for their financial supportThe authors would like to thank the Brazilian Nanotechnology National Laboratory–LNNano for allowing us to use its facilities.
文摘Biodegradable Zn-based alloys, particularly Zn-Mg alloys with the addition of alloying elements, have been intensively investigated aiming to improve both mechanical properties and corrosion behavior. Since such properties are strongly dependent on the alloy microstructure, any evaluation should commence on understanding the conditions influencing its formation. In this study, the effect of the solidification cooling rate on the microstructural evolution of Zn-1 wt.%Mg-(0.5 wt.%Ca, 0.5 wt.%Mn) alloys during transient solidification was investigated. The results show that the microstructures of both alloys have three phases in common: η-Zn dendritic matrix, intermetallic compounds(IMCs) Zn11Mg2, and Zn2 Mg in the eutectic mixture. MnZn9 and two Ca-bearing phases(CaZn11 and CaZn13) are associated with Mn and Ca additions, respectively. These additions are shown to refine the dendritic matrix and the eutectic mixture as compared to the Zn-1 wt.%Mg alloy. A correlation between cooling rate, dendritic or eutectic spacings was developed, thus permitting experimental growth laws to be proposed. Additionally, hardness tests were performed to evaluate the effects of additions of Ca and Mn. Experimental correlations between Vickers microhardness and secondary dendritic spacings were proposed, showing that the microstructural refinement and characteristic Ca and Mn based IMCs induce an increase in hardness as compared to the binary alloy.
