This work aimed to fabricate magnesium zinc/hydroxyapatite （Mg-Zn/HA） composite via powder metallurgy method and to develop a mathematical model to predict the compressive strength of the composite using response su...This work aimed to fabricate magnesium zinc/hydroxyapatite （Mg-Zn/HA） composite via powder metallurgy method and to develop a mathematical model to predict the compressive strength of the composite using response surface methodology method. The effect of various mechanical milling parameters, milling speed （200-300 r/rain）, ball-to-powder weight ratio （5-12.5） and HA content （2.6-10 wt%） on the compressive strength of Mg-Zn/HA composite was investigated. The model shows that high compressive strength of Mg-Zn/HA composite was achieved when the powders were prepared with high milling speed and ball-to- powder weight ratio and low HA content. The mathematical model was adequate with error percentage lower than 3.4%. The microstructure of Mg-Zn/HA composite with different process parameters revealed that fine microstructure was observed at high milling speed and ball-to-powder weight ratio while agglomeration of HA was found in composite with 10 wt% HA. The agglomeration of HA led to degradation of interfacial bonding strength between matrix and reinforcement phases and hence decreased the overall compressive strength of Mg-Zn/HA composite. Biodegradation test revealed that sample with higher HA content had more weight gain and there was more formation of hydroxyapatite. Mg-Zn/HA composite with 8 wt% HA was found to be the best candidate for implant application because it had considerable compressive strength and good biodegradation properties.展开更多
Porous biodegradable Mg and its alloys are considered to have a great potential to serve as ideal bone substitutes.The recent progress in additive manufacturing(AM) has prompted its application to fabricate Mg scaffol...Porous biodegradable Mg and its alloys are considered to have a great potential to serve as ideal bone substitutes.The recent progress in additive manufacturing(AM) has prompted its application to fabricate Mg scaffolds with geometrically ordered porous structures.Extrusionbased AM,followed by debinding and sintering,has been recently demonstrated as a powerful approach to fabricating such Mg scaffolds,which can avoid some crucial problems encountered when applying powder bed fusion AM techniques.However,such pure Mg scaffolds exhibit a too high rate of in vitro biodegradation.In the present research,alloying through a pre-alloyed Mg-Zn powder was ultilized to enhance the corrosion resistance and mechanical properties of AM geometrically ordered Mg-Zn scaffolds simultaneously.The in vitro biodegradation behavior,mechanical properties,and electrochemical response of the fabricated Mg-Zn scaffolds were evaluated.Moreover,the response of preosteoblasts to these scaffolds was systematically evaluated and compared with their response to pure Mg scaffolds.The Mg-Zn scaffolds with a porosity of 50.3% and strut density of 93.1% were composed of the Mg matrix and MgZn2second phase particles.The in vitro biodegradation rate of the Mg-Zn scaffolds decreased by 81% at day 1,as compared to pure Mg scaffolds.Over 28 days of static immersion in modified simulated body fluid,the corrosion rate of the Mg-Zn scaffolds decreased from 2.3± 0.9 mm/y to 0.7±0.1 mm/y.The yield strength and Young’s modulus of the Mg-Zn scaffolds were about 3 times as high as those of pure Mg scaffolds and remained within the range of those of trabecular bone throughout the biodegradation tests.Indirect culture of MC3T3-E1 preosteoblasts in Mg-Zn extracts indicated favorable cytocompatibility.In direct cell culture,some cells could spread and form filopodia on the surface of the Mg-Zn scaffolds.Overall,this study demonstrates the great potential of the extrusion-based AM Mg-Zn scaffolds to be further developed as biodegradable bone-substituting bioma展开更多
A magnesium-zinc alloy rod was implanted into the marrow cavity of the distal femur in New Zealand rabbits. The femur with the implanted alloy was compared with the contralateral femur in which a bone tunnel without i...A magnesium-zinc alloy rod was implanted into the marrow cavity of the distal femur in New Zealand rabbits. The femur with the implanted alloy was compared with the contralateral femur in which a bone tunnel without implant was formed as a control. Degradation of the magnesium-zinc alloy was analyzed via X-ray, scanning electron microscopy, and element energy spectrum analysis. Serum magnesium, liver and kidney function tests, and myocardial enzymes were measured. Heart, liver, kidney and spleen were sectioned for pathological analysis, and the effects of the implanted material on the histology and function of important organs were analyzed. Magnesium-zinc alloy was resorbed from the bone marrow cavity of the femur; 87% of the alloy was degraded within 14 weeks after the surgery. There were no significant differences in serum magnesium, liver or kidney function tests, or myocardial enzymes be- fore the surgery and after degradation of the magnesium-zinc alloy. Histology of the heart, liver, kidney, and spleen did not change. This study demonstrated that magnesium-zinc alloy can be resorbed in bone, and that the degradation products have good biocompatibility with heart, liver, kidney, and spleen.展开更多
The fracture toughness of extruded Mg-1Zn-2Y(at.%)alloys,featuring a multimodal microstructure containing fine dynamically recrystallized(DRXed)grains with random crystallographic orientation and coarse-worked grains ...The fracture toughness of extruded Mg-1Zn-2Y(at.%)alloys,featuring a multimodal microstructure containing fine dynamically recrystallized(DRXed)grains with random crystallographic orientation and coarse-worked grains with a strong fiber texture,was investigated.The DRXed grains comprised randomly oriented equiaxedα-Mg grains.In contrast,the worked grains includedα-Mg and long-period stacking ordered(LPSO)phases that extended in the extrusion direction(ED).Both types displayed a strong texture,aligning the(10.10)direction parallel to the ED.The volume fractions of the DRXed and worked grains were controlled by adjusting the extrusion temperature.In the longitudinal-transverse(L-T)orientation,where the loading direction was aligned parallel to the ED,there was a tendency for the conditional fracture toughness,KQ,tended to increase as the volume fraction of the worked grains increased.However,the KQ values in the T-L orientation,where the loading direction was perpendicular to the ED,decreased with an increase in the volume fraction of the worked grains.This suggests strong anisotropy in the fracture toughness of the specimen with a high volume fraction of the worked grains,relative to the test direction.The worked grains,which included the LPSO phase and were elongated perpendicular to the initial crack plane,suppressed the straight crack extension,causing crack deflection,and generating secondary cracks.Thus,these worked grains significantly contributed to the fracture toughness of the extruded Mg-1Zn-2Y alloys in the L-T orientation.展开更多
基金Ministry of High Education(FRGS Grant No.6071304)for the financial support
文摘This work aimed to fabricate magnesium zinc/hydroxyapatite （Mg-Zn/HA） composite via powder metallurgy method and to develop a mathematical model to predict the compressive strength of the composite using response surface methodology method. The effect of various mechanical milling parameters, milling speed （200-300 r/rain）, ball-to-powder weight ratio （5-12.5） and HA content （2.6-10 wt%） on the compressive strength of Mg-Zn/HA composite was investigated. The model shows that high compressive strength of Mg-Zn/HA composite was achieved when the powders were prepared with high milling speed and ball-to- powder weight ratio and low HA content. The mathematical model was adequate with error percentage lower than 3.4%. The microstructure of Mg-Zn/HA composite with different process parameters revealed that fine microstructure was observed at high milling speed and ball-to-powder weight ratio while agglomeration of HA was found in composite with 10 wt% HA. The agglomeration of HA led to degradation of interfacial bonding strength between matrix and reinforcement phases and hence decreased the overall compressive strength of Mg-Zn/HA composite. Biodegradation test revealed that sample with higher HA content had more weight gain and there was more formation of hydroxyapatite. Mg-Zn/HA composite with 8 wt% HA was found to be the best candidate for implant application because it had considerable compressive strength and good biodegradation properties.
基金China Scholarship Council (CSC) for financial support。
文摘Porous biodegradable Mg and its alloys are considered to have a great potential to serve as ideal bone substitutes.The recent progress in additive manufacturing(AM) has prompted its application to fabricate Mg scaffolds with geometrically ordered porous structures.Extrusionbased AM,followed by debinding and sintering,has been recently demonstrated as a powerful approach to fabricating such Mg scaffolds,which can avoid some crucial problems encountered when applying powder bed fusion AM techniques.However,such pure Mg scaffolds exhibit a too high rate of in vitro biodegradation.In the present research,alloying through a pre-alloyed Mg-Zn powder was ultilized to enhance the corrosion resistance and mechanical properties of AM geometrically ordered Mg-Zn scaffolds simultaneously.The in vitro biodegradation behavior,mechanical properties,and electrochemical response of the fabricated Mg-Zn scaffolds were evaluated.Moreover,the response of preosteoblasts to these scaffolds was systematically evaluated and compared with their response to pure Mg scaffolds.The Mg-Zn scaffolds with a porosity of 50.3% and strut density of 93.1% were composed of the Mg matrix and MgZn2second phase particles.The in vitro biodegradation rate of the Mg-Zn scaffolds decreased by 81% at day 1,as compared to pure Mg scaffolds.Over 28 days of static immersion in modified simulated body fluid,the corrosion rate of the Mg-Zn scaffolds decreased from 2.3± 0.9 mm/y to 0.7±0.1 mm/y.The yield strength and Young’s modulus of the Mg-Zn scaffolds were about 3 times as high as those of pure Mg scaffolds and remained within the range of those of trabecular bone throughout the biodegradation tests.Indirect culture of MC3T3-E1 preosteoblasts in Mg-Zn extracts indicated favorable cytocompatibility.In direct cell culture,some cells could spread and form filopodia on the surface of the Mg-Zn scaffolds.Overall,this study demonstrates the great potential of the extrusion-based AM Mg-Zn scaffolds to be further developed as biodegradable bone-substituting bioma
基金Supported by the National Natural Science Foundation of China (Grant No. 30772182)the Medical-Industial intersect study in Shanghai Jiaotong University (Grant No. YG2007MS26)
文摘A magnesium-zinc alloy rod was implanted into the marrow cavity of the distal femur in New Zealand rabbits. The femur with the implanted alloy was compared with the contralateral femur in which a bone tunnel without implant was formed as a control. Degradation of the magnesium-zinc alloy was analyzed via X-ray, scanning electron microscopy, and element energy spectrum analysis. Serum magnesium, liver and kidney function tests, and myocardial enzymes were measured. Heart, liver, kidney and spleen were sectioned for pathological analysis, and the effects of the implanted material on the histology and function of important organs were analyzed. Magnesium-zinc alloy was resorbed from the bone marrow cavity of the femur; 87% of the alloy was degraded within 14 weeks after the surgery. There were no significant differences in serum magnesium, liver or kidney function tests, or myocardial enzymes be- fore the surgery and after degradation of the magnesium-zinc alloy. Histology of the heart, liver, kidney, and spleen did not change. This study demonstrated that magnesium-zinc alloy can be resorbed in bone, and that the degradation products have good biocompatibility with heart, liver, kidney, and spleen.
基金supported by the JST CREST for Research Area“Nanomechanics”[JPMJCR2094]the JSPS KAKENHI for Scientific Research B[JP21H01673]the AMADA Foundation[AF-2023044-C2].
文摘The fracture toughness of extruded Mg-1Zn-2Y(at.%)alloys,featuring a multimodal microstructure containing fine dynamically recrystallized(DRXed)grains with random crystallographic orientation and coarse-worked grains with a strong fiber texture,was investigated.The DRXed grains comprised randomly oriented equiaxedα-Mg grains.In contrast,the worked grains includedα-Mg and long-period stacking ordered(LPSO)phases that extended in the extrusion direction(ED).Both types displayed a strong texture,aligning the(10.10)direction parallel to the ED.The volume fractions of the DRXed and worked grains were controlled by adjusting the extrusion temperature.In the longitudinal-transverse(L-T)orientation,where the loading direction was aligned parallel to the ED,there was a tendency for the conditional fracture toughness,KQ,tended to increase as the volume fraction of the worked grains increased.However,the KQ values in the T-L orientation,where the loading direction was perpendicular to the ED,decreased with an increase in the volume fraction of the worked grains.This suggests strong anisotropy in the fracture toughness of the specimen with a high volume fraction of the worked grains,relative to the test direction.The worked grains,which included the LPSO phase and were elongated perpendicular to the initial crack plane,suppressed the straight crack extension,causing crack deflection,and generating secondary cracks.Thus,these worked grains significantly contributed to the fracture toughness of the extruded Mg-1Zn-2Y alloys in the L-T orientation.
