The influence of impurities on damping capacities of ZK60 magnesium alloys in the as-cast,as-extruded and T4-treated states was investigated by dynamically mechanical analyzer at room temperature.Granato and Lucke dis...The influence of impurities on damping capacities of ZK60 magnesium alloys in the as-cast,as-extruded and T4-treated states was investigated by dynamically mechanical analyzer at room temperature.Granato and Lucke dislocation pinning model was employed to explain damping properties of the alloys.It is found that reducing impurity content can decrease the amount of second-phase particles,increase grain size and improve damping capacity of the as-cast alloy slightly.The as-extruded alloy with lower impurity content is found to possess obviously higher damping capacity in the relatively high strain region than that with higher impurity concentration,which appears to originate mainly from different dislocation characteristics.The variation tendency of damping property with change of impurity content after solution-treatment is also similar to that in the as-extruded and as-cast states. Meanwhile,the purification of the alloy results in an evident improvement in tensile yield strength in the as-extruded state.展开更多
The influence of impurity content on the microstructure and mechanical properties of ZK60 magnesium alloys was investigated by optical microscopy,scanning electron microscopy and tensile test.ZK60 alloys were prepared...The influence of impurity content on the microstructure and mechanical properties of ZK60 magnesium alloys was investigated by optical microscopy,scanning electron microscopy and tensile test.ZK60 alloys were prepared by changing holding time of alloy melt during semi-continuous casting in order to control the content of impurity elements.The alloy with lower purity content is found to have less second precipitates and larger grain size in the as-cast state.However,in the as-extruded state,reducing impurities brings about a decrease in grain size and an increase in yield strength from 244 MPa to 268 MPa,while the elongations in the as-extruded alloys with different contents of impurities are almost the same.After T5 treatment,impurity content is found to have more obvious effect on the yield strength of ZK60 alloy.The yield strength of ZK60-45 alloys with low impurity content is increased up to 295 MPa after T5 treatment.展开更多
The effects of Mg doping(MgAl) and native N vacancy(VN) on the electronic structures and transport properties of Al N nanowire(Al NNW) were theoretically investigated by using density functional theory. Either the MgA...The effects of Mg doping(MgAl) and native N vacancy(VN) on the electronic structures and transport properties of Al N nanowire(Al NNW) were theoretically investigated by using density functional theory. Either the MgAl defect or the VN defect prefers to be formed on the Al NNW surfaces. Both MgAl and VN defects could increase the conductivity owing to introducing a defect band inside the band gap of Al N and split the Al N band gap into two subgaps. The defect concentration has little influence on the magnitude of the subgaps. The MgAl serves as a shallow acceptor rendering the nanowire a p-type conductor. The VN introduces a deep donor state enabling the nanowire an n-type conductor. The MgAl systems exhibit higher conductivity than the VN ones owing to the narrow subgaps of MgAl systems. The conductivity is roughly proportional to the defect concentration in the MgAl and VN defect systems. When the MgAl and VN coexist, the hole state of the MgAl defect and the electron state of the VN defect will compensate each other and their coupling state appears just above the valence-band maximum leading to a little decrease of the band gap compared with the pure Al NNW, which is unfavorable for the enhancing of the conductivity.展开更多
基金Project(50725413)supported by the National Natural Science Foundation of ChinaProject(2009BB4215)supported by the Natural Science Foundation of Chongqing Science and Technology Commission,ChinaProject(2008AB4114)supported by the Major Program of Chongqing Science and Technology Commission,China
文摘The influence of impurities on damping capacities of ZK60 magnesium alloys in the as-cast,as-extruded and T4-treated states was investigated by dynamically mechanical analyzer at room temperature.Granato and Lucke dislocation pinning model was employed to explain damping properties of the alloys.It is found that reducing impurity content can decrease the amount of second-phase particles,increase grain size and improve damping capacity of the as-cast alloy slightly.The as-extruded alloy with lower impurity content is found to possess obviously higher damping capacity in the relatively high strain region than that with higher impurity concentration,which appears to originate mainly from different dislocation characteristics.The variation tendency of damping property with change of impurity content after solution-treatment is also similar to that in the as-extruded and as-cast states. Meanwhile,the purification of the alloy results in an evident improvement in tensile yield strength in the as-extruded state.
基金Project(50725413)supported by the National Natural Science Foundation of ChinaProject(2007CB613704)supported by the National Basic Research Program of ChinaProject(20090191120013)supported by the PhD Program Foundation of Ministry of Education of China
文摘The influence of impurity content on the microstructure and mechanical properties of ZK60 magnesium alloys was investigated by optical microscopy,scanning electron microscopy and tensile test.ZK60 alloys were prepared by changing holding time of alloy melt during semi-continuous casting in order to control the content of impurity elements.The alloy with lower purity content is found to have less second precipitates and larger grain size in the as-cast state.However,in the as-extruded state,reducing impurities brings about a decrease in grain size and an increase in yield strength from 244 MPa to 268 MPa,while the elongations in the as-extruded alloys with different contents of impurities are almost the same.After T5 treatment,impurity content is found to have more obvious effect on the yield strength of ZK60 alloy.The yield strength of ZK60-45 alloys with low impurity content is increased up to 295 MPa after T5 treatment.
基金supported by the National Natural Science Foundation of China(Grant Nos.51073048,51473042)the Leaders in Academe of Har-bin City of China(Grant No.2013RFXXJ024)the Science Foundation for Backup Leader of Leading Talent Echelon in Heilongjiang Province
文摘The effects of Mg doping(MgAl) and native N vacancy(VN) on the electronic structures and transport properties of Al N nanowire(Al NNW) were theoretically investigated by using density functional theory. Either the MgAl defect or the VN defect prefers to be formed on the Al NNW surfaces. Both MgAl and VN defects could increase the conductivity owing to introducing a defect band inside the band gap of Al N and split the Al N band gap into two subgaps. The defect concentration has little influence on the magnitude of the subgaps. The MgAl serves as a shallow acceptor rendering the nanowire a p-type conductor. The VN introduces a deep donor state enabling the nanowire an n-type conductor. The MgAl systems exhibit higher conductivity than the VN ones owing to the narrow subgaps of MgAl systems. The conductivity is roughly proportional to the defect concentration in the MgAl and VN defect systems. When the MgAl and VN coexist, the hole state of the MgAl defect and the electron state of the VN defect will compensate each other and their coupling state appears just above the valence-band maximum leading to a little decrease of the band gap compared with the pure Al NNW, which is unfavorable for the enhancing of the conductivity.
