The Sr/F co-doped CaP(Sr/F-CaP)coatings were prepared by micro-arc oxidation(MAO)under different voltages to modify the microstructure and corrosion behavior of Mg-4Zn-1Mn alloy.The surface and interface characteristi...The Sr/F co-doped CaP(Sr/F-CaP)coatings were prepared by micro-arc oxidation(MAO)under different voltages to modify the microstructure and corrosion behavior of Mg-4Zn-1Mn alloy.The surface and interface characteristics investigated using scanning electron microscopy(SEM)and energy dispersive X-ray spectrometer(EDS)showed that the MAO coatings displayed uneven crater-like holes and tiny cracks under lower voltage,while they exhibited relatively homogeneous crater-like holes without cracks under higher voltage.The thickness of MAO coatings increased with increasing voltage.The corrosion behavior of Mg-4Zn-1Mn alloy was improved by the MAO coatings.The MAO coatings prepared under 450 V and 500 V voltages possessed the best corrosion resistance with regard to the electrochemical corrosion tests and immersion corrosion tests,respectively.The MAO coatings fabricated under 450-500 V could provide a better corrosion protection effect for the substrate.展开更多
The microstructures and mechanical properties of as-cast Mg-5 Sn-1 Si magnesium alloy modified with trace elements Y,Bi,Sb and Sr were investigated and compared.Results show that the microstructure of the as-cast Mg-5...The microstructures and mechanical properties of as-cast Mg-5 Sn-1 Si magnesium alloy modified with trace elements Y,Bi,Sb and Sr were investigated and compared.Results show that the microstructure of the as-cast Mg-5 Sn-1 Si alloy consists ofα-Mg,Mg_(2) Si,Mg_(2) Sn and Mg_(2)(Si_xSn_(1-x))phases.After adding 0.8 wt.%Y,0.3 wt.%Bi,0.9 wt.%Sb and 0.9 wt.%Sr,respectively into the Mg-5 Sn-1 Si magnesium alloy,Mg_(24)Y_(5),Mg_(3) Bi_(2),Mg_(3) Sb_(2) and Mg_(2) Sr phases are precipitated accordingly.Trace elements can refineα-Mg grain and Chinese scriptshaped Mg_(2) Si phase.Refinement efficiency of different trace elements onα-Mg grain and Mg_(2) Si phase is varied.Sr element has the best refinement effect,followed by Sb and Bi,while Y has the least refinement effect.Mg-5 Sn-1 Si-0.9 Sr alloy has higher tensile properties than the other three modified alloys.The refinement mechanism of Y,Bi and Sr elements on Mg-5 Sn-1 Si magnesium alloy can be explained by the growth restriction factors and the solute undercooling.For Mg-5 Sn-1 Si-0.9 Sb alloy,the heterogeneous nuclei of Mg_(3) Sb_(2) phase is the main reason for the refinement of grains and second phases.展开更多
In this study, the influence of minor titanium(Ti) addition on the microstructure and tensile properties of Mg-8Sn-1Zn based alloys were investigated by means of optical microscopy, X-ray diffraction, scanning electro...In this study, the influence of minor titanium(Ti) addition on the microstructure and tensile properties of Mg-8Sn-1Zn based alloys were investigated by means of optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and tensile tests. The results showed that Ti can decrease the secondary dendrite arm spacing(SDAS). The tensile strength of the Mg-8Sn-1Zn-Ti alloys is initially increased by increasing the Ti content up to 0.09 wt.%, but subsequently decreased for further increase of Ti content. The improved tensile properties are attributed to the decreased SDAS and refi ned Mg_2Sn phases, as well as the increased fraction of tin(Sn) segregated regions. The tensile fracture surface of the studied alloys shows mixed characteristics of cleavage and quasi-cleavage fracture. Adding Ti does not significantly change the fracture mode of the studied alloys.展开更多
利用光学显微镜、X射线衍射仪、扫描电镜、电子背散射衍射、透射电镜、硬度以及力学性能测试等对挤压态和T5处理态的Mg-6Zn-1Mn-4Sn-1.5Nd镁合金的显微组织和力学性能进行研究。研究结果表明:合金铸态的相组成为α(Mg)、Mn、Mg7Zn3、Mg...利用光学显微镜、X射线衍射仪、扫描电镜、电子背散射衍射、透射电镜、硬度以及力学性能测试等对挤压态和T5处理态的Mg-6Zn-1Mn-4Sn-1.5Nd镁合金的显微组织和力学性能进行研究。研究结果表明:合金铸态的相组成为α(Mg)、Mn、Mg7Zn3、Mg2Sn和MgS nN d相。挤压过程中完成动态再结晶,再结晶晶粒的平均尺寸为7.2μm。T5热处理显著提高挤压态合金的强度。合金的屈服强度和抗拉强度分别增加94 MPa和34 MPa。显微组织分析表明,合金强度的提高主要是由于时效过程中析出高密度的β′1杆状相。展开更多
The effect of the quenching rate after solution treatment on the residual stress and precipitation behavior of a high strength Mg-5 Zn-3.5 Sn-1 Mn-0.5 Ca-0.5 Cu plate is studied.The simulation results show decreasing ...The effect of the quenching rate after solution treatment on the residual stress and precipitation behavior of a high strength Mg-5 Zn-3.5 Sn-1 Mn-0.5 Ca-0.5 Cu plate is studied.The simulation results show decreasing temperature gradient in the plate with decreasing quenching rate,which leads to weakened inhomogeneous plastic deformation and decreased residual stress.No dynamic precipitation on the grain boundary happens after either cold water cooling or air cooling,however,air cooling leads to dynamic precipitation of Mg-Zn phase on Mn particles around which a low-density precipitate zone develops after aging treatment.Moreover,the fine and densely distributed Mg-Zn precipitates observed after aging treatment of the cold water cooled alloy are replaced by coarse precipitates with low density for the air cooled alloy.Both the low-density precipitate zone near Mn particles and the coarsening of precipitates are the source of the decrease in hardness and tensile properties of the air cooled alloy.The residual stress drops faster than the hardness with decreasing quenching rate,which makes it possible to lower the residual stress without sacrificing too much age-hardening ability of the alloy.展开更多
The characteristics of fatigue crack initiation in Ti-5AI-4Sn-2Zr1Mo-O.7Nd-O.25Si alloy wereStudied. Two modes Of fatigue crack initiation were found. The Nd-rich phase particles displaybetter resistance to fatigue cr...The characteristics of fatigue crack initiation in Ti-5AI-4Sn-2Zr1Mo-O.7Nd-O.25Si alloy wereStudied. Two modes Of fatigue crack initiation were found. The Nd-rich phase particles displaybetter resistance to fatigue crack initiation than the matrix at lower stress.展开更多
In the as-cast Ti-55 alloy, the intragranular rare earth-rich phase particles are about 1. 0~14 μm in diameter, elliptical, and rich in Nd, Sn, and O. The contents of Nd and Sn on the grain boundaries are higher th...In the as-cast Ti-55 alloy, the intragranular rare earth-rich phase particles are about 1. 0~14 μm in diameter, elliptical, and rich in Nd, Sn, and O. The contents of Nd and Sn on the grain boundaries are higher than those at other sites. The intragranular phases grow preferably at the region on the grain boundaries, which causes the formation of the elliptical morphology of the intragranular phases.展开更多
In order to investigate the effect of extrusion on Mg-4Zn-1Y alloy, microstructure and mechanical properties were analyzed by optical microscopy(OM), scanning electron microscopy(SEM), transmission electron micros...In order to investigate the effect of extrusion on Mg-4Zn-1Y alloy, microstructure and mechanical properties were analyzed by optical microscopy(OM), scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), energy dispersive spectrum(EDS) and tensile testing.The results indicated that the microstructure was obviously refined by extrusion and dynamic recrystallization.The second phases were dynamic precipitated and distributed more dispersively through extrusion.W-Phases(Mg3Zn3Y2) were twisted and broken, while I-Phases(Mg3Zn6Y) were spheroidized by deformation.Twin bands were formed to achieve the large deformation and hinder the slip of dislocations effectively to improve tensile properties.The tensile strength and elongation of extruded Mg-4Zn-1Y alloy were 254.94 MPa and 17.9% respectively which were improved greatly compared with those of as-cast alloy.The strengthening mechanisms of the extruded alloy were mainly fine-grain strengthening and distortion strengthening.展开更多
文摘The Sr/F co-doped CaP(Sr/F-CaP)coatings were prepared by micro-arc oxidation(MAO)under different voltages to modify the microstructure and corrosion behavior of Mg-4Zn-1Mn alloy.The surface and interface characteristics investigated using scanning electron microscopy(SEM)and energy dispersive X-ray spectrometer(EDS)showed that the MAO coatings displayed uneven crater-like holes and tiny cracks under lower voltage,while they exhibited relatively homogeneous crater-like holes without cracks under higher voltage.The thickness of MAO coatings increased with increasing voltage.The corrosion behavior of Mg-4Zn-1Mn alloy was improved by the MAO coatings.The MAO coatings prepared under 450 V and 500 V voltages possessed the best corrosion resistance with regard to the electrochemical corrosion tests and immersion corrosion tests,respectively.The MAO coatings fabricated under 450-500 V could provide a better corrosion protection effect for the substrate.
基金the financial support by the Natioal Natural Science Foundation of China(Nos.:51571086 and 51271073)the financial support from the Natural Science Foundation of Henan Polytechnic University(No.:B2010-20)。
文摘The microstructures and mechanical properties of as-cast Mg-5 Sn-1 Si magnesium alloy modified with trace elements Y,Bi,Sb and Sr were investigated and compared.Results show that the microstructure of the as-cast Mg-5 Sn-1 Si alloy consists ofα-Mg,Mg_(2) Si,Mg_(2) Sn and Mg_(2)(Si_xSn_(1-x))phases.After adding 0.8 wt.%Y,0.3 wt.%Bi,0.9 wt.%Sb and 0.9 wt.%Sr,respectively into the Mg-5 Sn-1 Si magnesium alloy,Mg_(24)Y_(5),Mg_(3) Bi_(2),Mg_(3) Sb_(2) and Mg_(2) Sr phases are precipitated accordingly.Trace elements can refineα-Mg grain and Chinese scriptshaped Mg_(2) Si phase.Refinement efficiency of different trace elements onα-Mg grain and Mg_(2) Si phase is varied.Sr element has the best refinement effect,followed by Sb and Bi,while Y has the least refinement effect.Mg-5 Sn-1 Si-0.9 Sr alloy has higher tensile properties than the other three modified alloys.The refinement mechanism of Y,Bi and Sr elements on Mg-5 Sn-1 Si magnesium alloy can be explained by the growth restriction factors and the solute undercooling.For Mg-5 Sn-1 Si-0.9 Sb alloy,the heterogeneous nuclei of Mg_(3) Sb_(2) phase is the main reason for the refinement of grains and second phases.
基金supported by the National Natural Science Foundation of China(Grant no.51404166)Shanxi Province Science Foundation for Youths(2013021013-4)+2 种基金Research Project Supported by Shanxi Scholarship Council of China(2014-023)Technological Innovation Programs of Higher Education Institutions Shanxi(Grant no.2014120)the Advanced Programs of Department of Human Resources and Social Security of Shanxi Province for Returned Scholars(2013101)
文摘In this study, the influence of minor titanium(Ti) addition on the microstructure and tensile properties of Mg-8Sn-1Zn based alloys were investigated by means of optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and tensile tests. The results showed that Ti can decrease the secondary dendrite arm spacing(SDAS). The tensile strength of the Mg-8Sn-1Zn-Ti alloys is initially increased by increasing the Ti content up to 0.09 wt.%, but subsequently decreased for further increase of Ti content. The improved tensile properties are attributed to the decreased SDAS and refi ned Mg_2Sn phases, as well as the increased fraction of tin(Sn) segregated regions. The tensile fracture surface of the studied alloys shows mixed characteristics of cleavage and quasi-cleavage fracture. Adding Ti does not significantly change the fracture mode of the studied alloys.
基金Project(2013CB632200)supported by the National Great Theoretic Research,ChinaProject(2011BAE22B01-3)supported by the National Sci&Tech Support Program,ChinaProject(2010DFR50010)supported by the International Cooperation,Sharing Fund of Chongqing University’s Large-scale Equipment,China
文摘利用光学显微镜、X射线衍射仪、扫描电镜、电子背散射衍射、透射电镜、硬度以及力学性能测试等对挤压态和T5处理态的Mg-6Zn-1Mn-4Sn-1.5Nd镁合金的显微组织和力学性能进行研究。研究结果表明:合金铸态的相组成为α(Mg)、Mn、Mg7Zn3、Mg2Sn和MgS nN d相。挤压过程中完成动态再结晶,再结晶晶粒的平均尺寸为7.2μm。T5热处理显著提高挤压态合金的强度。合金的屈服强度和抗拉强度分别增加94 MPa和34 MPa。显微组织分析表明,合金强度的提高主要是由于时效过程中析出高密度的β′1杆状相。
基金supported by the National Key Research and Development Program of China[2016YFB0301105]the National Key Research and Development Plan[2017YFB0103904]
文摘The effect of the quenching rate after solution treatment on the residual stress and precipitation behavior of a high strength Mg-5 Zn-3.5 Sn-1 Mn-0.5 Ca-0.5 Cu plate is studied.The simulation results show decreasing temperature gradient in the plate with decreasing quenching rate,which leads to weakened inhomogeneous plastic deformation and decreased residual stress.No dynamic precipitation on the grain boundary happens after either cold water cooling or air cooling,however,air cooling leads to dynamic precipitation of Mg-Zn phase on Mn particles around which a low-density precipitate zone develops after aging treatment.Moreover,the fine and densely distributed Mg-Zn precipitates observed after aging treatment of the cold water cooled alloy are replaced by coarse precipitates with low density for the air cooled alloy.Both the low-density precipitate zone near Mn particles and the coarsening of precipitates are the source of the decrease in hardness and tensile properties of the air cooled alloy.The residual stress drops faster than the hardness with decreasing quenching rate,which makes it possible to lower the residual stress without sacrificing too much age-hardening ability of the alloy.
文摘The characteristics of fatigue crack initiation in Ti-5AI-4Sn-2Zr1Mo-O.7Nd-O.25Si alloy wereStudied. Two modes Of fatigue crack initiation were found. The Nd-rich phase particles displaybetter resistance to fatigue crack initiation than the matrix at lower stress.
基金Project (50271054) supported by the National Natural Science Foundation of ChinaProject (20070700003) supported by the Doctorate Programs Foundation of Ministry of Education of China+1 种基金Project (102102210031) supported by the Science and Technologies Foundation of Henan Province,ChinaProject (2010A430008) supported by the Natural Science Foundation of Henan Educational Committee of China
文摘In the as-cast Ti-55 alloy, the intragranular rare earth-rich phase particles are about 1. 0~14 μm in diameter, elliptical, and rich in Nd, Sn, and O. The contents of Nd and Sn on the grain boundaries are higher than those at other sites. The intragranular phases grow preferably at the region on the grain boundaries, which causes the formation of the elliptical morphology of the intragranular phases.
基金National Great Theoretic Research Project(2013CB632200)International Cooperation Project(2010DFR50010)Chongqing Science & Technology Support Project(CSTC2013jcyjC60001)
基金Project supported by General Program of Liaoning Province Committee of Education(L2012035)Liaoning Province Science and Technology Plan(2013201018)Liaoning Province University Innovation Team Support Plan
文摘In order to investigate the effect of extrusion on Mg-4Zn-1Y alloy, microstructure and mechanical properties were analyzed by optical microscopy(OM), scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), energy dispersive spectrum(EDS) and tensile testing.The results indicated that the microstructure was obviously refined by extrusion and dynamic recrystallization.The second phases were dynamic precipitated and distributed more dispersively through extrusion.W-Phases(Mg3Zn3Y2) were twisted and broken, while I-Phases(Mg3Zn6Y) were spheroidized by deformation.Twin bands were formed to achieve the large deformation and hinder the slip of dislocations effectively to improve tensile properties.The tensile strength and elongation of extruded Mg-4Zn-1Y alloy were 254.94 MPa and 17.9% respectively which were improved greatly compared with those of as-cast alloy.The strengthening mechanisms of the extruded alloy were mainly fine-grain strengthening and distortion strengthening.