Microstructural evolution and strengthening mechanisms of Mg-3Sn-1Ca based alloys with additions of different amounts of Al N nanoparticles were investigated.It was found that with increasing the amount of AlN nano-pa...Microstructural evolution and strengthening mechanisms of Mg-3Sn-1Ca based alloys with additions of different amounts of Al N nanoparticles were investigated.It was found that with increasing the amount of AlN nano-particles the grain size decreases obviously.The existence of AlN nano-particles could refine the primary crystal phases CaMgSn,which provided more heterogeneous nucleation sites for the formation of magnesium.Moreover,such nano-particles could also restrict the grain growth during solidification.After adding AlN nano-particles,both the tensile properties at room temperature and high temperature 250℃and the hardness are largely improved.The improvement of strength is attributed to grain refinement and second phase refinement.展开更多
Zinc calcium phosphate （Zn-Ca-P） coating and cerium-doped zinc calcium phosphate （Zn-Ca-Ce-P） coating were prepared on AZ31 magnesium alloy. The chemical compositions, morphologies and corrosion resistance of coat...Zinc calcium phosphate （Zn-Ca-P） coating and cerium-doped zinc calcium phosphate （Zn-Ca-Ce-P） coating were prepared on AZ31 magnesium alloy. The chemical compositions, morphologies and corrosion resistance of coatings were investigated through energy-dispersive X-ray spectroscopy （EDS）, X-ray photoelectron spectroscopy （XPS）, X-ray diffraction （XRD）, electron probe micro-analysis （EPMA） and scanning electron microscopy （SEM） together with hydrogen volumetric and electrochemical tests. The results indicate that both coatings predominately contain crystalline hopeite （Zn3（PO4）2·4H2O）, Mg3（PO4）2 and Ca3（PO4）2, and traces of non-crystalline MgF2 and CaF2. The Zn-Ca-Ce-P coating is more compact than the Zn-Ca-P coating due to the formation of CePO4, and displays better corrosion resistance than the Zn-Ca-P coating. Both coatings protect the AZ31 Mg substrate only during an initial immersion period. The micro-galvanic corrosion between the coatings and their substrates leads to an increase of hydrogen evolution rate （HER） with extending the immersion time. The addition of Ce promotes the homogenous distribution of Ca and formation of hopeite. The Zn-Ca-Ce-P coating has the potential for the primer coating on magnesium alloys.展开更多
Previous investigations indicate that the creep resistance of magnesium alloys is proportional to the stability of precipitated intermetallic phases at grain boundaries.These stable intermetallic phases were considere...Previous investigations indicate that the creep resistance of magnesium alloys is proportional to the stability of precipitated intermetallic phases at grain boundaries.These stable intermetallic phases were considered to be effective to suppress the deformation by grain boundary sliding,leading to the improvement of creep properties.Based on this point,adding the alloying elements to form the stable intermetallics with high melting point became a popular way to develop the new creep resistant magnesium alloys.The present investigation,however,shows that the creep properties of binary Mg-Sn alloy are still poor even though the addition of Sn possibly results in the precipitation of thermal stable Mg_(2)Sn at grain boundaries.That means other possible mechanisms function to affect the creep response.It is finally found that the poor creep resistance is attributed to the segregation of Sn at dendritic and grain boundaries.Based on this observation,new approaches to improve the creep resistance are suggested for magnesium alloys because most currently magnesium alloys have the commonality with the Mg-Sn alloys.展开更多
Even though Mg alloys containing Mn and rare earth elements lead to higher ductility and lower yield asymmetry due to the weak texture after extrusion, plastic instability, commonly known as the Portevin–Le Chatelier...Even though Mg alloys containing Mn and rare earth elements lead to higher ductility and lower yield asymmetry due to the weak texture after extrusion, plastic instability, commonly known as the Portevin–Le Chatelier(PLC) effect, causes unexpected fragility in the service environment. In the present study, the PLC phenomenon and texture development during the deformation of Mg-Mn and Mg-Mn-Nd extruded alloys were investigated under various temperatures and strain rates. The addition of Nd causes not only texture weakening but also severe PLC phenomenon. The PLC phenomenon was significantly affected by the temperatures and the strain rates, which causes a difference in mechanical properties and development of texture. In the conditions of high temperature and low strain rate, the strength increased while the elongation decreased significantly, and obvious PLC phenomenon with severe serration and negative strain rate sensitivity. The initial texture was maintained even after deformation only under severe PLC conditions, and this is due to the restriction of basal slip and suppression of lattice rotation in PLC conditions. The series of results indicate that the PLC phenomenon causes a reduction of formability even at high temperature.展开更多
Mg-Al-Zn-Mn(AZ)system alloys have become widely used due to their good castability,excellent formability and outstanding corrosion resistance[1-6].However,their strength is still much lower than that of traditional Mg...Mg-Al-Zn-Mn(AZ)system alloys have become widely used due to their good castability,excellent formability and outstanding corrosion resistance[1-6].However,their strength is still much lower than that of traditional Mg-RE(rare earth)based alloys or even some new Mg-Li basedalloys[7-19].展开更多
Large-scale Mg-8Gd-4Y-1Zn-Mn(wt.%)alloy ingot with a diameter of 315 mm and a length of 2410 mm was prepared through semi-continuous casting.Chemical composition,microstructure and mechanical properties at different l...Large-scale Mg-8Gd-4Y-1Zn-Mn(wt.%)alloy ingot with a diameter of 315 mm and a length of 2410 mm was prepared through semi-continuous casting.Chemical composition,microstructure and mechanical properties at different locations of the samples with as-cast,T4 and T6 heat-treated states,respectively,were investigated.No obvious macro segregation has been detected in the high-quality alloy ingot.The main eutectic structures at all different locations are composed ofα-Mg,Mg3RE-type,Mg5RE-type and LPSO phases.At the edge of ingot,the unusual casting twins including 10-12 extension twins and 10-11 compression twins were observed due to the intensive internal stress.In T4 heat-treated alloy,the micro segregation was eliminated.The remained phases wereα-Mg and LPSO phase.Combined with the remarkable age-hardening response,T6 samples exhibits improved mechanical properties at ambient temperature,which derives from the dense prismaticβ'precipitates and profuse basalγ'precipitates.展开更多
基金financially supported by the Study Abroad Program by the Government of Shandong Province(201802005)Linyi Industrial Technology Research Institute and Shandong Yinguang Yuyuan Light Metal Precise Forming Co.,Ltd。
文摘Microstructural evolution and strengthening mechanisms of Mg-3Sn-1Ca based alloys with additions of different amounts of Al N nanoparticles were investigated.It was found that with increasing the amount of AlN nano-particles the grain size decreases obviously.The existence of AlN nano-particles could refine the primary crystal phases CaMgSn,which provided more heterogeneous nucleation sites for the formation of magnesium.Moreover,such nano-particles could also restrict the grain growth during solidification.After adding AlN nano-particles,both the tensile properties at room temperature and high temperature 250℃and the hardness are largely improved.The improvement of strength is attributed to grain refinement and second phase refinement.
基金Project(51571134)supported by the National Natural Science Foundation of ChinaProject(2014TDJH104)supported by the SDUST Research Fund+1 种基金the Joint Innovative Centre for Safe and Effective Mining Technology and Equipment of Coal Resources,Shandong Province,ChinaProject(cstc2012jj A50034)supported by the Natural Science Foundation of Chongqing,China
文摘Zinc calcium phosphate （Zn-Ca-P） coating and cerium-doped zinc calcium phosphate （Zn-Ca-Ce-P） coating were prepared on AZ31 magnesium alloy. The chemical compositions, morphologies and corrosion resistance of coatings were investigated through energy-dispersive X-ray spectroscopy （EDS）, X-ray photoelectron spectroscopy （XPS）, X-ray diffraction （XRD）, electron probe micro-analysis （EPMA） and scanning electron microscopy （SEM） together with hydrogen volumetric and electrochemical tests. The results indicate that both coatings predominately contain crystalline hopeite （Zn3（PO4）2·4H2O）, Mg3（PO4）2 and Ca3（PO4）2, and traces of non-crystalline MgF2 and CaF2. The Zn-Ca-Ce-P coating is more compact than the Zn-Ca-P coating due to the formation of CePO4, and displays better corrosion resistance than the Zn-Ca-P coating. Both coatings protect the AZ31 Mg substrate only during an initial immersion period. The micro-galvanic corrosion between the coatings and their substrates leads to an increase of hydrogen evolution rate （HER） with extending the immersion time. The addition of Ce promotes the homogenous distribution of Ca and formation of hopeite. The Zn-Ca-Ce-P coating has the potential for the primer coating on magnesium alloys.
文摘Previous investigations indicate that the creep resistance of magnesium alloys is proportional to the stability of precipitated intermetallic phases at grain boundaries.These stable intermetallic phases were considered to be effective to suppress the deformation by grain boundary sliding,leading to the improvement of creep properties.Based on this point,adding the alloying elements to form the stable intermetallics with high melting point became a popular way to develop the new creep resistant magnesium alloys.The present investigation,however,shows that the creep properties of binary Mg-Sn alloy are still poor even though the addition of Sn possibly results in the precipitation of thermal stable Mg_(2)Sn at grain boundaries.That means other possible mechanisms function to affect the creep response.It is finally found that the poor creep resistance is attributed to the segregation of Sn at dendritic and grain boundaries.Based on this observation,new approaches to improve the creep resistance are suggested for magnesium alloys because most currently magnesium alloys have the commonality with the Mg-Sn alloys.
基金financial support of German Research Foundation(DFG)(Grant Nr.Yi103/3-1 and AL1343/8-1)。
文摘Even though Mg alloys containing Mn and rare earth elements lead to higher ductility and lower yield asymmetry due to the weak texture after extrusion, plastic instability, commonly known as the Portevin–Le Chatelier(PLC) effect, causes unexpected fragility in the service environment. In the present study, the PLC phenomenon and texture development during the deformation of Mg-Mn and Mg-Mn-Nd extruded alloys were investigated under various temperatures and strain rates. The addition of Nd causes not only texture weakening but also severe PLC phenomenon. The PLC phenomenon was significantly affected by the temperatures and the strain rates, which causes a difference in mechanical properties and development of texture. In the conditions of high temperature and low strain rate, the strength increased while the elongation decreased significantly, and obvious PLC phenomenon with severe serration and negative strain rate sensitivity. The initial texture was maintained even after deformation only under severe PLC conditions, and this is due to the restriction of basal slip and suppression of lattice rotation in PLC conditions. The series of results indicate that the PLC phenomenon causes a reduction of formability even at high temperature.
基金financially supported by the Projects for Science and Technology of Jilin Province(Nos.20210402064GH and 20220402012GH)the National Natural Science Foundation of China(No.U21A20323)+3 种基金the Capital Construction Fund within the Budget of Jilin Province(No.2023C044-2)the Special High-Tech Industrialization Project of Science and Technology Cooperation between Jilin Province and Chinese Academy of Sciences(No.2021SYHZ0043)the Major science and technology projects of Jilin Province and Changchun City(No.20210301024GX)the Project for Jilin provincial department of education(No.JJKH20220760KJ)。
文摘Mg-Al-Zn-Mn(AZ)system alloys have become widely used due to their good castability,excellent formability and outstanding corrosion resistance[1-6].However,their strength is still much lower than that of traditional Mg-RE(rare earth)based alloys or even some new Mg-Li basedalloys[7-19].
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0301100)the Natural Science Foundation Commission of China(Nos.51571044 and 51874062)+2 种基金the Chongqing foundation and advanced research project(No.cstc2019jcyjzdxmX0010)the Fundamental Research Funds for the Central Universities(Nos.2018CDGFCL0005 and 2019CDXYCL0031)the financial support from the China Scholarship Council(No.201906050113)。
文摘Large-scale Mg-8Gd-4Y-1Zn-Mn(wt.%)alloy ingot with a diameter of 315 mm and a length of 2410 mm was prepared through semi-continuous casting.Chemical composition,microstructure and mechanical properties at different locations of the samples with as-cast,T4 and T6 heat-treated states,respectively,were investigated.No obvious macro segregation has been detected in the high-quality alloy ingot.The main eutectic structures at all different locations are composed ofα-Mg,Mg3RE-type,Mg5RE-type and LPSO phases.At the edge of ingot,the unusual casting twins including 10-12 extension twins and 10-11 compression twins were observed due to the intensive internal stress.In T4 heat-treated alloy,the micro segregation was eliminated.The remained phases wereα-Mg and LPSO phase.Combined with the remarkable age-hardening response,T6 samples exhibits improved mechanical properties at ambient temperature,which derives from the dense prismaticβ'precipitates and profuse basalγ'precipitates.
