Ageing hardening,microstructure and mechanical properties of Mg-xY-1.5LPC-0.4Zr（x=0,2,4,6）alloys（LPC represents La-based rare earth metal）were investigated.It was found that the age hardening was enhanced,the grai...Ageing hardening,microstructure and mechanical properties of Mg-xY-1.5LPC-0.4Zr（x=0,2,4,6）alloys（LPC represents La-based rare earth metal）were investigated.It was found that the age hardening was enhanced,the grains became finer and the tensile strength was improved with the increase of Y content in Mg-Y-1.5LPC-0.4Zr alloy.The results show that the formed precipitates responsible for age hardening change from fine hexagonal-shaped equilibrium Mg12RE phase to metastableβ′phase with orthorhombic-bc crystal structure when Y is added into Mg-1.5LPC-0.4Zr alloy,and the volume fraction of precipitate phases also increases.The cubic-shapedβ-Mg24Y5 precipitate phases were also observed at grain boundaries in Mg-6Y-1.5LPC-0.4Zr alloy. The distribution of prismatic shapedβ′phases and cubic shapedβ-Mg24Y5 precipitate phases in Mg matrix may account for the remarkable enhancement of tensile strength of Mg-Y-LPC-Zr alloy.The Mg-6Y-1.5LPC-0.4Zr alloy exhibits maximum tensile strength at peak-aged hardness,and the values are 250 MPa at room temperature and 210 MPa at 250°C.展开更多
为研究预应力混凝土用钢棒(steel bar for prestressed concrete, PC钢棒)-钢筋混合配筋混凝土柱的抗震性能,设计制作了5根相同尺寸、相同纵筋配筋率、不同PC钢棒替代率的PC钢棒-钢筋混合配筋混凝土柱试件,通过拟静力试验研究了PC钢棒...为研究预应力混凝土用钢棒(steel bar for prestressed concrete, PC钢棒)-钢筋混合配筋混凝土柱的抗震性能,设计制作了5根相同尺寸、相同纵筋配筋率、不同PC钢棒替代率的PC钢棒-钢筋混合配筋混凝土柱试件,通过拟静力试验研究了PC钢棒替代率对试件抗震性能的影响规律。结果表明:随着PC钢棒替代率的提高,试件的裂缝分布高度降低,裂缝数量变少,滞回曲线的饱满程度逐渐降低,耗能能力降低,残余位移角减小,自复位能力增强;当PC钢棒的替代率不大于50%时,各试件的峰值荷载接近;当PC钢棒的替代率大于50%时,试件的峰值荷载随PC钢棒替代率的增大而提高;当加载位移角相同且不大于1.0%时,配置PC钢棒的混凝土柱的残余位移角较为接近,且明显小于未配置PC钢棒的钢筋混凝土柱的残余位移角;当加载位移角相同且大于1%时,柱的残余位移角随着PC钢棒替代率的增高而降低。展开更多
The effect of thickness (1 similar to 10 mm) of the ingots on the electrochemical properties of as-cast and annealed strip cast LPCNi3.55Co0.75Mn0.4Al0.3 hydrogen storage alloys was investigated. It is found that the ...The effect of thickness (1 similar to 10 mm) of the ingots on the electrochemical properties of as-cast and annealed strip cast LPCNi3.55Co0.75Mn0.4Al0.3 hydrogen storage alloys was investigated. It is found that the 0.2 C discharge capacity of as-cast LPCNi3.55Co0.75Mn0.4Al0.3 alloy increases with the increase of the thickness of the ingots. As-east alloy with the thickness of 10 mm shows better activation property, higher 1C discharge capacity and better cyclic stability than others. It is mainly contributed to its larger unit cell volume and less internal stress. Annealed LPCNi3.55Co0.75Mn0.4Al0.3 alloy with the thickness of 3 mm shows much better comprehensive electrochemical properties than as-east one; The cyclic. stability of the alloy with the thickness of 6 mm and the activation properties of the alloys with the thickness of 3 similar to 6 mm are improved after annealing. It is mainly owing to the great release of internal stress and the decrease of the segregation of Mn in the alloys.展开更多
LPCNi 3.55 Co 0.75 Mn 0.4 Al 0.3 hydrogen storage alloy was investigated, and the effects of thickness of its strip casting ingots(as cast) on the electrochemical performances were discussed. It was ...LPCNi 3.55 Co 0.75 Mn 0.4 Al 0.3 hydrogen storage alloy was investigated, and the effects of thickness of its strip casting ingots(as cast) on the electrochemical performances were discussed. It was found that the 0.2 C discharge capacity increased with the increase of the thickness (from 1 mm to 10 mm) of the ingots, mainly due to the enlargement of the unit cell volume; Among the thickness of the ingots in our study, 10 mm sample showed a better activation property; LPCNi 3.55 Co 0.75 Mn 0.4 Al 0.3 alloy with 10mm showed higher comprehensive properties than those with other thickness under 1C rate.展开更多
Surface coatings have been extensively used to control the degradation rate of Mg alloys for bioimplant applications.However,these coatings only act as passive barriers.In corrosive media,structural damage impairs the...Surface coatings have been extensively used to control the degradation rate of Mg alloys for bioimplant applications.However,these coatings only act as passive barriers.In corrosive media,structural damage impairs their barrier properties,resulting in rapid degradation of Mg alloys.The present study incorporates phytic acid(PA)as a healing agent in polycaprolactone(PCL)microcapsules with a unique honeycomb core matrix to obtain a self-healing PA-PCLcaps coating.The contact between simulated body fluid(SBF)and PA-PCLcaps coated ZM21 exhibited Cassie-Baxter interfacial states,resulting in significant hydrophobicity with a contact angle(CA)of 116.3.The corrosion potential(Ecorr)and current density(Icorr)were found to be-0.28 V and 1.1×10^(-9)A/cm^(2),respectively,for PA-PCLcaps coating,resulting in biosafe corrosion rate of 2.5×10^(-4)mm/year.After mechanical scratching,rapid HA mineralization at scratched regions recovered the hydrogen evolution rate(HER,0.36 mL/cm^(2)/day)and pH change(pH 7.10)of scratched PA-PCLcaps coated ZM21 samples to corresponding unscratched samples within one day of immersion.The coating’s self-healing ability could be attributed to PA released from punctured microcapsules,which facilitates HA chelation.The pH-triggered(pH 10)and Mg(II)-triggered(5 mM)conditions enhanced PA release from PA-PCLcaps coating by 2.5 and 3.1 times,respectively.As a result,dense HA mineralization occurred,which protects the coating from structural defects and ensures its durability in stimulating conditions.The findings of present study provide new insight for design of multiple stimuli-feedback based self-healing coatings on biodegradable Mg alloys.展开更多
基金Project(2010A6100153)supported by Natural Science Foundation of Ningbo,China
文摘Ageing hardening,microstructure and mechanical properties of Mg-xY-1.5LPC-0.4Zr（x=0,2,4,6）alloys（LPC represents La-based rare earth metal）were investigated.It was found that the age hardening was enhanced,the grains became finer and the tensile strength was improved with the increase of Y content in Mg-Y-1.5LPC-0.4Zr alloy.The results show that the formed precipitates responsible for age hardening change from fine hexagonal-shaped equilibrium Mg12RE phase to metastableβ′phase with orthorhombic-bc crystal structure when Y is added into Mg-1.5LPC-0.4Zr alloy,and the volume fraction of precipitate phases also increases.The cubic-shapedβ-Mg24Y5 precipitate phases were also observed at grain boundaries in Mg-6Y-1.5LPC-0.4Zr alloy. The distribution of prismatic shapedβ′phases and cubic shapedβ-Mg24Y5 precipitate phases in Mg matrix may account for the remarkable enhancement of tensile strength of Mg-Y-LPC-Zr alloy.The Mg-6Y-1.5LPC-0.4Zr alloy exhibits maximum tensile strength at peak-aged hardness,and the values are 250 MPa at room temperature and 210 MPa at 250°C.
文摘为研究预应力混凝土用钢棒(steel bar for prestressed concrete, PC钢棒)-钢筋混合配筋混凝土柱的抗震性能,设计制作了5根相同尺寸、相同纵筋配筋率、不同PC钢棒替代率的PC钢棒-钢筋混合配筋混凝土柱试件,通过拟静力试验研究了PC钢棒替代率对试件抗震性能的影响规律。结果表明:随着PC钢棒替代率的提高,试件的裂缝分布高度降低,裂缝数量变少,滞回曲线的饱满程度逐渐降低,耗能能力降低,残余位移角减小,自复位能力增强;当PC钢棒的替代率不大于50%时,各试件的峰值荷载接近;当PC钢棒的替代率大于50%时,试件的峰值荷载随PC钢棒替代率的增大而提高;当加载位移角相同且不大于1.0%时,配置PC钢棒的混凝土柱的残余位移角较为接近,且明显小于未配置PC钢棒的钢筋混凝土柱的残余位移角;当加载位移角相同且大于1%时,柱的残余位移角随着PC钢棒替代率的增高而降低。
文摘The effect of thickness (1 similar to 10 mm) of the ingots on the electrochemical properties of as-cast and annealed strip cast LPCNi3.55Co0.75Mn0.4Al0.3 hydrogen storage alloys was investigated. It is found that the 0.2 C discharge capacity of as-cast LPCNi3.55Co0.75Mn0.4Al0.3 alloy increases with the increase of the thickness of the ingots. As-east alloy with the thickness of 10 mm shows better activation property, higher 1C discharge capacity and better cyclic stability than others. It is mainly contributed to its larger unit cell volume and less internal stress. Annealed LPCNi3.55Co0.75Mn0.4Al0.3 alloy with the thickness of 3 mm shows much better comprehensive electrochemical properties than as-east one; The cyclic. stability of the alloy with the thickness of 6 mm and the activation properties of the alloys with the thickness of 3 similar to 6 mm are improved after annealing. It is mainly owing to the great release of internal stress and the decrease of the segregation of Mn in the alloys.
文摘LPCNi 3.55 Co 0.75 Mn 0.4 Al 0.3 hydrogen storage alloy was investigated, and the effects of thickness of its strip casting ingots(as cast) on the electrochemical performances were discussed. It was found that the 0.2 C discharge capacity increased with the increase of the thickness (from 1 mm to 10 mm) of the ingots, mainly due to the enlargement of the unit cell volume; Among the thickness of the ingots in our study, 10 mm sample showed a better activation property; LPCNi 3.55 Co 0.75 Mn 0.4 Al 0.3 alloy with 10mm showed higher comprehensive properties than those with other thickness under 1C rate.
文摘Surface coatings have been extensively used to control the degradation rate of Mg alloys for bioimplant applications.However,these coatings only act as passive barriers.In corrosive media,structural damage impairs their barrier properties,resulting in rapid degradation of Mg alloys.The present study incorporates phytic acid(PA)as a healing agent in polycaprolactone(PCL)microcapsules with a unique honeycomb core matrix to obtain a self-healing PA-PCLcaps coating.The contact between simulated body fluid(SBF)and PA-PCLcaps coated ZM21 exhibited Cassie-Baxter interfacial states,resulting in significant hydrophobicity with a contact angle(CA)of 116.3.The corrosion potential(Ecorr)and current density(Icorr)were found to be-0.28 V and 1.1×10^(-9)A/cm^(2),respectively,for PA-PCLcaps coating,resulting in biosafe corrosion rate of 2.5×10^(-4)mm/year.After mechanical scratching,rapid HA mineralization at scratched regions recovered the hydrogen evolution rate(HER,0.36 mL/cm^(2)/day)and pH change(pH 7.10)of scratched PA-PCLcaps coated ZM21 samples to corresponding unscratched samples within one day of immersion.The coating’s self-healing ability could be attributed to PA released from punctured microcapsules,which facilitates HA chelation.The pH-triggered(pH 10)and Mg(II)-triggered(5 mM)conditions enhanced PA release from PA-PCLcaps coating by 2.5 and 3.1 times,respectively.As a result,dense HA mineralization occurred,which protects the coating from structural defects and ensures its durability in stimulating conditions.The findings of present study provide new insight for design of multiple stimuli-feedback based self-healing coatings on biodegradable Mg alloys.
