A new shape casting process,melt-conditioned high-pressure die-casting(MC-HPDC) was developed.In this process,liquid metal was conditioned under intensively forced convection provided by melt conditioning with advance...A new shape casting process,melt-conditioned high-pressure die-casting(MC-HPDC) was developed.In this process,liquid metal was conditioned under intensively forced convection provided by melt conditioning with advanced shear technology(MCAST) unit before being transferred to a conventional cold chamber high-pressure die-casting(HPDC) machine for shape casting. The effect of melt conditioning was investigated,which was carried out both above and below the liquidus of the alloy,on the microstructure and properties of a Mg-Al-Ca alloy(AZ91D+2%Ca(mass fraction) ,named as AZX912) .The results show that many coarse externally-solidified crystals(ESCs) can be observed in the centre of conventional HPDC samples,and hot tearing occurs at the inter-dendritic region because of the lack of feeding.With the melting conditioning,the MC-HPDC samples not only have considerably refined size of ESCs but also have significantly reduced cast defects,thus provide superior mechanical properties to conventional HPDC castings.The solidification behaviour of the alloy under different processing routes was also discussed.展开更多
The effects of Si content on the microstructure and yield strength of Al-(1.44-12.40)Si-0.7 Mg(wt.%)alloy sheets under the T4 condition were systematically studied via laser scanning confocal microscopy(LSCM),DSC,TEM ...The effects of Si content on the microstructure and yield strength of Al-(1.44-12.40)Si-0.7 Mg(wt.%)alloy sheets under the T4 condition were systematically studied via laser scanning confocal microscopy(LSCM),DSC,TEM and tensile tests.The results show that the recrystallization grain of the alloy sheets becomes more refined with an increase in Si content.When the Si content increases from 1.44 to 12.4 wt.%,the grain size of the alloy sheets decreases from approximately 47 to 10μm.Further,with an increase in Si content,the volume fraction of the GP zones in the matrix increases slightly.Based on the existing model,a yield strength model for alloy sheets was proposed.The predicted results are in good agreement with the actual experimental results and reveal the strengthening mechanisms of the Al-(1.44-12.40)Si-0.7 Mg alloy sheets under the T4 condition and how they are influenced by the Si content.展开更多
Mg-10Gd-3Y-0.5Zr alloy was cast in a step-like mould with five different cooling rates. The as-cast microstructures of the different steps were examined with optical microscope(OM) and scanning electron microscope(SEM...Mg-10Gd-3Y-0.5Zr alloy was cast in a step-like mould with five different cooling rates. The as-cast microstructures of the different steps were examined with optical microscope(OM) and scanning electron microscope(SEM). The room temperature mechanical properties were examined by tensile test. The results show that the microstructures are refined and the second phase particles are distributed much uniformly with the increase of cooling rate. The increase of yield strength,ultimate strength and elongation can be ascribed mainly to the strengthening effect of fine grains. The relationship between grain size and yield strength/hardness agrees with the Hall-Petch behavior.展开更多
Surface Mount Technology Manufacturing Grid (SMT-MG) is the application of the grid technology in the SMT product manufacturing.In this paper,as the new manufacturing mode of SMT product,SMT-MG was brought forward.The...Surface Mount Technology Manufacturing Grid (SMT-MG) is the application of the grid technology in the SMT product manufacturing.In this paper,as the new manufacturing mode of SMT product,SMT-MG was brought forward.Then the concept and intention of the SMT-MG were analyzed.And from the three aspects of sufficient condition,necessary condition and stability condition,the static and dynamic conditions under which the SMT-MG was formed were mainly discuss.Finally,it was proved that the formation and development of SMT-MG is feasible and necessary.展开更多
The Liaoji Proterozoic rift is an inter-intracontinenatl rift developed from Archean granite-greenstone tectonic regime and contains many important mineral deposits of U, B, magnesite, Pb-Zn, Au, Ag, Co and P. These d...The Liaoji Proterozoic rift is an inter-intracontinenatl rift developed from Archean granite-greenstone tectonic regime and contains many important mineral deposits of U, B, magnesite, Pb-Zn, Au, Ag, Co and P. These deposits were formed as the result of late mobilization, transportation and concentfation of the previously enriched ore-forming mate- rials in several ore-bearing formations formed during the rift stage. So the metallogeny of these deposits in the rift shows both inheritance and new generation of the ore-forming materials. In future ore-searching practice, attentions should be paid on the studies of the ore-bearing formations in the rift, on the multiple stages of metallogeny and and on multiple derivations of the ore-forming materials.展开更多
The degradation of Mg alloys relates to the service performance of Mg alloy biodegradable implants.In order to investigate the degradation behavior of Mg alloys as vascular stent materials in the near service environm...The degradation of Mg alloys relates to the service performance of Mg alloy biodegradable implants.In order to investigate the degradation behavior of Mg alloys as vascular stent materials in the near service environment,the hot-extruded fine-grained Mg-Zn-Y-Nd alloy microtubes,which are employed to manufacture vascular stents,were tested under radial compressive stress in the dynamic Hanks'Balanced Salt Solution(HBSS).The results revealed that the high flow rate accelerates the degradation of Mg alloy microtubes and its degradation is sensitive to radial compressive stress.These results contribute to understanding the service performance of Mg alloys as vascular stent materials.展开更多
采用降温往复镦粗-挤压的方法对Mg-12.5Gd-4Y-2Zn-0.5Zr(wt%)合金进行了大塑性变形.总变形道次为5道次,累积应变为6.75,温度由480℃逐道次降低到390℃.利用光学显微镜、扫描电子显微镜和X射线衍射仪研究了合金在不同变形道次下微观组织...采用降温往复镦粗-挤压的方法对Mg-12.5Gd-4Y-2Zn-0.5Zr(wt%)合金进行了大塑性变形.总变形道次为5道次,累积应变为6.75,温度由480℃逐道次降低到390℃.利用光学显微镜、扫描电子显微镜和X射线衍射仪研究了合金在不同变形道次下微观组织的演变规律.结果表明:该方法可以有效细化Mg-12.5Gd-4Y-2Zn-0.5Zr合金晶粒,随变形道次的增加,晶粒细化效果逐渐减弱.5道次变形后得完全再结晶的细小晶粒组织,平均晶粒尺寸由初始态的64.2μm减小到4.4μm.此外,随着变形道次的增加,原始晶粒内的片层状长周期堆垛有序结构(Long Period Stacking Ordered Structure,LPSO结构)逐渐溶解消失,同时,在动态再结晶晶粒界处析出大量细小颗粒状β-Mg5(Gd,Y,Zn)相.另外,原始组织中沿晶界不连续网状分布的块状LPSO相发生剧烈扭折变形,逐渐破碎成小块并均匀地沿挤压方向排列.展开更多
This study investigated the effects of multi-walled carbon nanotubes(MWCNTs) and polycaprolactone(PCL) on the quasi-in vivo corrosion behavior of AZ31B Mg alloy treated by plasma electrolytic oxidation(PEO). Thin(~2 ...This study investigated the effects of multi-walled carbon nanotubes(MWCNTs) and polycaprolactone(PCL) on the quasi-in vivo corrosion behavior of AZ31B Mg alloy treated by plasma electrolytic oxidation(PEO). Thin(~2 μm, PCTPCL4) and thick(~60 μm, PCTPCL6) PCL layers were applied only onto the MWCNTs-PEO coating(PCT) as it showed better corrosion performance. Findings reveal that incorporation of MWCNTs induced several structural and functional modifications in the PEO coating, such as increased roughness, a thicker inner barrier layer, and reduced hydrophilicity.Quasi-in vivo corrosion testing was carried out under controlled temperature, p H, and fluid flow in simulated body fluid(SBF) by electrochemical impedance spectroscopy(EIS) and hydrogen evolution experiments. EIS results revealed that, after 48 h immersion, a diffusion process controlled hydration of the ceramic coatings. Comparison of the collected hydrogen after 15 days of immersion in the quasi-in vivo environment revealed that the PEO and PCT ceramic coatings decreased hydrogen generation by up to 74% and 91%, respectively, compared to non-coated alloy.PCTPCL6 coating exhibited the lowest amount of collected hydrogen(0.2 m L/cm^(2)). The thick PCL layer delayed the onset of substrate corrosion for at least 120 h, reducing the corrosion rate by 85% compared with the PCT.展开更多
基金Project(2007CB613704) supported by the National Basic Research Program of China
文摘A new shape casting process,melt-conditioned high-pressure die-casting(MC-HPDC) was developed.In this process,liquid metal was conditioned under intensively forced convection provided by melt conditioning with advanced shear technology(MCAST) unit before being transferred to a conventional cold chamber high-pressure die-casting(HPDC) machine for shape casting. The effect of melt conditioning was investigated,which was carried out both above and below the liquidus of the alloy,on the microstructure and properties of a Mg-Al-Ca alloy(AZ91D+2%Ca(mass fraction) ,named as AZX912) .The results show that many coarse externally-solidified crystals(ESCs) can be observed in the centre of conventional HPDC samples,and hot tearing occurs at the inter-dendritic region because of the lack of feeding.With the melting conditioning,the MC-HPDC samples not only have considerably refined size of ESCs but also have significantly reduced cast defects,thus provide superior mechanical properties to conventional HPDC castings.The solidification behaviour of the alloy under different processing routes was also discussed.
基金Project(2016YFB0300801)supported by the National Key Research and Development Program of ChinaProject(51871043)supported by the National Natural Science Foundation of ChinaProject(N180212010)supported by the Fundamental Research Funds for the Central Universities of China。
文摘The effects of Si content on the microstructure and yield strength of Al-(1.44-12.40)Si-0.7 Mg(wt.%)alloy sheets under the T4 condition were systematically studied via laser scanning confocal microscopy(LSCM),DSC,TEM and tensile tests.The results show that the recrystallization grain of the alloy sheets becomes more refined with an increase in Si content.When the Si content increases from 1.44 to 12.4 wt.%,the grain size of the alloy sheets decreases from approximately 47 to 10μm.Further,with an increase in Si content,the volume fraction of the GP zones in the matrix increases slightly.Based on the existing model,a yield strength model for alloy sheets was proposed.The predicted results are in good agreement with the actual experimental results and reveal the strengthening mechanisms of the Al-(1.44-12.40)Si-0.7 Mg alloy sheets under the T4 condition and how they are influenced by the Si content.
基金Project(5133001B) supported by the National Basic Research Program (973 Program) of China
文摘Mg-10Gd-3Y-0.5Zr alloy was cast in a step-like mould with five different cooling rates. The as-cast microstructures of the different steps were examined with optical microscope(OM) and scanning electron microscope(SEM). The room temperature mechanical properties were examined by tensile test. The results show that the microstructures are refined and the second phase particles are distributed much uniformly with the increase of cooling rate. The increase of yield strength,ultimate strength and elongation can be ascribed mainly to the strengthening effect of fine grains. The relationship between grain size and yield strength/hardness agrees with the Hall-Petch behavior.
文摘Surface Mount Technology Manufacturing Grid (SMT-MG) is the application of the grid technology in the SMT product manufacturing.In this paper,as the new manufacturing mode of SMT product,SMT-MG was brought forward.Then the concept and intention of the SMT-MG were analyzed.And from the three aspects of sufficient condition,necessary condition and stability condition,the static and dynamic conditions under which the SMT-MG was formed were mainly discuss.Finally,it was proved that the formation and development of SMT-MG is feasible and necessary.
文摘The Liaoji Proterozoic rift is an inter-intracontinenatl rift developed from Archean granite-greenstone tectonic regime and contains many important mineral deposits of U, B, magnesite, Pb-Zn, Au, Ag, Co and P. These deposits were formed as the result of late mobilization, transportation and concentfation of the previously enriched ore-forming mate- rials in several ore-bearing formations formed during the rift stage. So the metallogeny of these deposits in the rift shows both inheritance and new generation of the ore-forming materials. In future ore-searching practice, attentions should be paid on the studies of the ore-bearing formations in the rift, on the multiple stages of metallogeny and and on multiple derivations of the ore-forming materials.
基金the financial support of the National Key Research and Development Program of China(2018YFC1106703)the Key Projects of the Joint Fund of the National Natural Science Foundation of China(U1804251)。
文摘The degradation of Mg alloys relates to the service performance of Mg alloy biodegradable implants.In order to investigate the degradation behavior of Mg alloys as vascular stent materials in the near service environment,the hot-extruded fine-grained Mg-Zn-Y-Nd alloy microtubes,which are employed to manufacture vascular stents,were tested under radial compressive stress in the dynamic Hanks'Balanced Salt Solution(HBSS).The results revealed that the high flow rate accelerates the degradation of Mg alloy microtubes and its degradation is sensitive to radial compressive stress.These results contribute to understanding the service performance of Mg alloys as vascular stent materials.
文摘采用降温往复镦粗-挤压的方法对Mg-12.5Gd-4Y-2Zn-0.5Zr(wt%)合金进行了大塑性变形.总变形道次为5道次,累积应变为6.75,温度由480℃逐道次降低到390℃.利用光学显微镜、扫描电子显微镜和X射线衍射仪研究了合金在不同变形道次下微观组织的演变规律.结果表明:该方法可以有效细化Mg-12.5Gd-4Y-2Zn-0.5Zr合金晶粒,随变形道次的增加,晶粒细化效果逐渐减弱.5道次变形后得完全再结晶的细小晶粒组织,平均晶粒尺寸由初始态的64.2μm减小到4.4μm.此外,随着变形道次的增加,原始晶粒内的片层状长周期堆垛有序结构(Long Period Stacking Ordered Structure,LPSO结构)逐渐溶解消失,同时,在动态再结晶晶粒界处析出大量细小颗粒状β-Mg5(Gd,Y,Zn)相.另外,原始组织中沿晶界不连续网状分布的块状LPSO相发生剧烈扭折变形,逐渐破碎成小块并均匀地沿挤压方向排列.
基金the financial support of the Iran National Science Foundation INSF (Grant No. 97014179)supported by RTI2018-096391-B-C33 (MCIU/AEI/FEDER, UE) and S2018/NMT4411 (Regional government of Madrid and EU Structural and Social Funds)+1 种基金the support of RYC-2017-21843financial support from the Spanish National Science Foundation (CSIC) and the Ministerio de Ciencia, Innovacióny Universidades (MINECO) grant number RTI2018-096328-B-I00。
文摘This study investigated the effects of multi-walled carbon nanotubes(MWCNTs) and polycaprolactone(PCL) on the quasi-in vivo corrosion behavior of AZ31B Mg alloy treated by plasma electrolytic oxidation(PEO). Thin(~2 μm, PCTPCL4) and thick(~60 μm, PCTPCL6) PCL layers were applied only onto the MWCNTs-PEO coating(PCT) as it showed better corrosion performance. Findings reveal that incorporation of MWCNTs induced several structural and functional modifications in the PEO coating, such as increased roughness, a thicker inner barrier layer, and reduced hydrophilicity.Quasi-in vivo corrosion testing was carried out under controlled temperature, p H, and fluid flow in simulated body fluid(SBF) by electrochemical impedance spectroscopy(EIS) and hydrogen evolution experiments. EIS results revealed that, after 48 h immersion, a diffusion process controlled hydration of the ceramic coatings. Comparison of the collected hydrogen after 15 days of immersion in the quasi-in vivo environment revealed that the PEO and PCT ceramic coatings decreased hydrogen generation by up to 74% and 91%, respectively, compared to non-coated alloy.PCTPCL6 coating exhibited the lowest amount of collected hydrogen(0.2 m L/cm^(2)). The thick PCL layer delayed the onset of substrate corrosion for at least 120 h, reducing the corrosion rate by 85% compared with the PCT.
