Small addition of mischmetal （MM） into aluminum alloys can lead to grain refinement. However, it is still uncertain whether the same effect applies to Mg-Al alloys. This work indicated that small amount of mischmeta...Small addition of mischmetal （MM） into aluminum alloys can lead to grain refinement. However, it is still uncertain whether the same effect applies to Mg-Al alloys. This work indicated that small amount of mischmetal addition ranging from 0.1% to 1.2% （mass fraction） did not cause grain refinement in Mg-Al alloys. On the contrary, they tended to coarsen the grains. When added into Mg-Al alloys, MM reacted preferentially with Al to form Al11 MM3 phase. As Al11 MM3 phase mainly distributed within α-Mg grains than at grain boundaries, it had little effect in restricting grain growth. In addition, MM reacted with Al8（Mn, Fe）5 or ε-AlMn particles to form Al-MM-Mn compounds, thus it reduced the amount of heterogeneous nuclei in the melt and resulted in remarkable grain coarsening.展开更多
The effects of lanthanum-praseodymium-cerium mischmetal （LPC） on the microstructure and mechanical properties of Mg-Al alloy were investigated. With the addition of LPC, an additional rod-like Al11La3 phase was depo...The effects of lanthanum-praseodymium-cerium mischmetal （LPC） on the microstructure and mechanical properties of Mg-Al alloy were investigated. With the addition of LPC, an additional rod-like Al11La3 phase was deposited in the alloy. LPC greatly improves the tensile strength of cast Mg-Al alloys but negatively affects the elongation of cast alloys above 473 K. Cast alloys are strengthened by both precipitation strengthening and dispersion strengthening at ambient temperature. When the temperature exceeds 473 K, only the dispersion operates as a strengthening mechanism.展开更多
Mg-Zn-Zr(ZK)alloys exhibit notably high mechanical strength amongst all magnesium alloy grades.However,due to the formation of low melting point Mg_3Zn_7-precipitates,these alloys are susceptible to hot cracking,thus ...Mg-Zn-Zr(ZK)alloys exhibit notably high mechanical strength amongst all magnesium alloy grades.However,due to the formation of low melting point Mg_3Zn_7-precipitates,these alloys are susceptible to hot cracking,thus compromising their metallurgical processing.The addition of rare earths to ZK alloys is an alternative to form higher melting point intermetallic compounds,speed up dynamic recrystallization,refine grain size,enhance corrosion resistance and extend the service temperature due to improved creep resistance.This work deals with the effect of Ce-base mischmetal addition on the hot rolling behaviour of as-cast ZK60 alloy.The microstructure investigation conducted using electron microscopy and X-Ray diffraction shows that precipitation of Mg_(7)Zn_(3) intermetallics occur during hot rolling,whereas no further precipitation is observed for the ZK60-Mm alloys.The fragmentation of the intermetallic compounds occur during hot rolling and finer particles of Mg_(7)Zn_(3) are observed for the ZK60,whereas Mg_(7)Zn_(3) and Mg Zn_(2) Ce intermetallics are formed in the alloy modified with mischmetal addition.A higher fraction of dynamically recrystallized grains is observed for the ZK60-Mm in comparison to the ZK60.Continuous recrystallization takes place in ZK60 with the formation of sub-grains near to the intermetallics and the addition of mischmetal promotes the occurrence of discontinuous recrystallization with the nucleation of new grains close to the precipitates.The mechanical strength and,in particular,the ductility of the hot-rolled alloys are notably improved when compared to the same alloys in the as-cast condition.The mechanical strength is,however,higher for the ZK60 alloy.Less solid solution strengthening,softer Mg Zn_(2) Ce intermetallics and more extensive recrystallization contribute to reduce the mechanical strength of ZK60-Mm.Failure in both alloys are initiated at coarse intermetallics and propagate through intermetallic-rich regions.展开更多
The effect of yttrium and mischmetal(MMs) on the as-cast and solid solution treated structures of Mg-Al alloys with different Al-contents was investigated. The results show that the MMs in Mg-Al alloy existed in rod A...The effect of yttrium and mischmetal(MMs) on the as-cast and solid solution treated structures of Mg-Al alloys with different Al-contents was investigated. The results show that the MMs in Mg-Al alloy existed in rod Al 4(Ce, La)compound while Y in Mg-Al alloy in polygonal Al 2Y compound. The amount of Mg 17Al 12 in Mg-Al alloy is decreased with increasing Y or MMs addition, and Mg 17Al 12 intermetallic compound is changed from continuous network to discontinuous one. The Al 4(Ce, La) and Al 2Y compounds are not dissolved into Mg-Al alloy matrix during solid solution treatment so that their high heat stability can be exhibited. The experiment of mechanical properties indicate that elongation and impact toughness of the Mg-Al-Y alloy with polygonal Al 2Y compound are higher than those of Mg-Al-MMs alloy with rod Al 4(Ce, La) compound.展开更多
The physical,mechanical properties and microstructures of three 2618 Aluminum alloys containing less than 0.046 wt.-%mischmetal have been studied.lt has been shown that the trace mischmetal has no obvious influence on...The physical,mechanical properties and microstructures of three 2618 Aluminum alloys containing less than 0.046 wt.-%mischmetal have been studied.lt has been shown that the trace mischmetal has no obvious influence on the physical properties of the.alloy,but can clearly improve plasticity and toughness,and slightly raise the thermal stability.展开更多
The influence of mischmetal addition on physicochemical properties of PtSnNa/ZSM-5 catalyst was studied by means of XRF,H 2 chemisorption,XRD,TPR,NH 3-TPD and TPO techniques.The results showed that the presence of mis...The influence of mischmetal addition on physicochemical properties of PtSnNa/ZSM-5 catalyst was studied by means of XRF,H 2 chemisorption,XRD,TPR,NH 3-TPD and TPO techniques.The results showed that the presence of mischmetal had an obvious impact on the catalytic performance of the PtSnNa/ZSM-5 catalyst.A suitable content of mischmetal not only could enhance the interactions between Pt species and the support,but also inhibit the formation of coke during the reaction,thus improving the catalytic activity and stability.In our experiments,when the content of mischmetal was 3m%,the catalyst exhibited best catalytic performance.However,the continuous addition of mischmetal could promote the reduction of Sn species to metallic tin,which was disadvantageous to the reaction.展开更多
In molten salt electrolysis of mixed rare earth chlorides,the influence of the amount of samarium and neodymium containing in the raw material is experimented and discussed.The process of the formation of oxychloride,...In molten salt electrolysis of mixed rare earth chlorides,the influence of the amount of samarium and neodymium containing in the raw material is experimented and discussed.The process of the formation of oxychloride,which is harmful to the production of mischmetal,is described.展开更多
The effect of mischmetal addition on lead segregation in high lead bronze(grade ZQPb25-5)is studied in this paper.The testing results confirm that 0.5 to 1.0% misehmetal addition can effectively prevent lead from grav...The effect of mischmetal addition on lead segregation in high lead bronze(grade ZQPb25-5)is studied in this paper.The testing results confirm that 0.5 to 1.0% misehmetal addition can effectively prevent lead from gravity and inverse segregation.The results of preventing lead from segregation respectively by mischmetal and nickel are also compared in the paper.The mischmetal addition in high lead bronze is distributed in the copper matrix mainly in the form of a compound which promotes early precipitation and refinement of α-dendrites, thus restraining the Pb-rich melt from either sinking to the bottom or escaping to the surface layer of the casting.As a result,the tendency of lead segregation is significantly decreased.Proper addition of mischmetal can also improve the mechanical properties,especially the ductility of high lead bronze.In addition,the contents of tin in high lead bronze can partially be substituted by mischmetal addition.展开更多
The wetting of steel sheet by liquid Zn+5 wt%Al alloy has been measured by the Meniscograph. The result shows that the addition of mischmetal in Zn+5 wt%Al alloy decreases the surface tension of the alloy,reduces the ...The wetting of steel sheet by liquid Zn+5 wt%Al alloy has been measured by the Meniscograph. The result shows that the addition of mischmetal in Zn+5 wt%Al alloy decreases the surface tension of the alloy,reduces the wetting angle of the liquid alloy raising in steel substrate surface and enhances the adhesive power and wettability between them.It is concluded that the mischmetal addition in baths influences the reac- tion between steel sheet and liquid Zn+5 wt%Al alloy and thus improves the wettability of them.展开更多
A conversion film was obtained on zinc deposit by immersing zinc coated specimens in a mischmetal salt solution. Several factors affecting the anticorrosive efficiency of the conversion film were studied. The suitabl...A conversion film was obtained on zinc deposit by immersing zinc coated specimens in a mischmetal salt solution. Several factors affecting the anticorrosive efficiency of the conversion film were studied. The suitable technological conditions were established. The composition and the thickness of the conversion film were determined by Auger electron spectroscopy(AES).展开更多
The quality of mischmetal wire and rod and the method of adding rare earth into steel are quite important for making high quality steel. This paper proposes a quality specification of wire and rod as well as related a...The quality of mischmetal wire and rod and the method of adding rare earth into steel are quite important for making high quality steel. This paper proposes a quality specification of wire and rod as well as related adding method. The paper also provides principles for selecting raw material and adding method.展开更多
To improve the comprehensive mechanical properties of Mg-10Zn-5Al-0.1Sb magnesium alloy,different amount of Ce-rich rare earth(RE)was added to the alloy,and the effect of RE addition on the microstructure and mechanic...To improve the comprehensive mechanical properties of Mg-10Zn-5Al-0.1Sb magnesium alloy,different amount of Ce-rich rare earth(RE)was added to the alloy,and the effect of RE addition on the microstructure and mechanical properties of Mg-10Zn-5Al-0.1Sb alloy was investigated by means of Brinell hardness measurement, scanning electron microscopy(SEM),energy dispersive spectroscope(EDS)and X-ray diffraction(XRD).The results show that an appropriate amount of Ce-rich rare earth addition can make the Al4Ce phase particles and CeSb phase disperse more evenly in the alloy.These phases refine the alloy's matrix and make the secondary phases[?-Mg 32 (Al,Zn)49 phase and?-Al 2 Mg5Zn2 phase]finer and more dispersive,therefore significantly improve the mechanical properties of the Mg-10Zn-5Al-0.1Sb alloy.When the RE addition is 1.0 wt.%,the tensile strengths of the alloy both at room temperature and 150oC reach the maximum values while the impact toughness is slightly lower than that of the matrix alloy.The hardness increases with the increase of RE addition.展开更多
The influence of Ce-rich mish metal（MM） and electromagnetic stirring（EMS） on microstructure evolution of AZ91D magnesium alloy was investigated by optical microscopy, scanning electron microscopy（SEM）, energy di...The influence of Ce-rich mish metal（MM） and electromagnetic stirring（EMS） on microstructure evolution of AZ91D magnesium alloy was investigated by optical microscopy, scanning electron microscopy（SEM）, energy dispersion spectrum（EDS） and X-ray diffraction（XRD）. The microstructure of AZ91D and alloying AZ91D is different. Except dominant primary α（Mg） and β-Mg 17Al 12 in AZ91D, a new phase Al 11MM3 is observed in alloyed AZ91D. Increasing Ce-rich MM, primary α grains can be refined, the content and grain size of β obviously decrease, furthermore, its morphology degrades from discontinuous network to separated particles, and Al 11MM3 amount substantially increases and acicular Al 11MM3 aggregates into clusters at grain boundaries. In EMS process, α morphology evolves from rosette to sphere, and then spherical-like with the decrease of isothermal stirring temperature. Moreover, Al 11MM3 mainly distributes inside primary grains and eutecticum in form of short-rod. EMS can alter not only the primary morphology but Al 11MM3.展开更多
基金Project supported by Beijing Municipal Science & Technology Research Project (Y0405004040211)
文摘Small addition of mischmetal （MM） into aluminum alloys can lead to grain refinement. However, it is still uncertain whether the same effect applies to Mg-Al alloys. This work indicated that small amount of mischmetal addition ranging from 0.1% to 1.2% （mass fraction） did not cause grain refinement in Mg-Al alloys. On the contrary, they tended to coarsen the grains. When added into Mg-Al alloys, MM reacted preferentially with Al to form Al11 MM3 phase. As Al11 MM3 phase mainly distributed within α-Mg grains than at grain boundaries, it had little effect in restricting grain growth. In addition, MM reacted with Al8（Mn, Fe）5 or ε-AlMn particles to form Al-MM-Mn compounds, thus it reduced the amount of heterogeneous nuclei in the melt and resulted in remarkable grain coarsening.
文摘The effects of lanthanum-praseodymium-cerium mischmetal （LPC） on the microstructure and mechanical properties of Mg-Al alloy were investigated. With the addition of LPC, an additional rod-like Al11La3 phase was deposited in the alloy. LPC greatly improves the tensile strength of cast Mg-Al alloys but negatively affects the elongation of cast alloys above 473 K. Cast alloys are strengthened by both precipitation strengthening and dispersion strengthening at ambient temperature. When the temperature exceeds 473 K, only the dispersion operates as a strengthening mechanism.
基金funding of FAPESP,processes 2010/11391-2,2011/09324-8,2011/19218-0FAPESP and CNPQ for the scholarshipsthe funding provided by CAPES(PROBRAL project 88881.143948/2017-01)。
文摘Mg-Zn-Zr(ZK)alloys exhibit notably high mechanical strength amongst all magnesium alloy grades.However,due to the formation of low melting point Mg_3Zn_7-precipitates,these alloys are susceptible to hot cracking,thus compromising their metallurgical processing.The addition of rare earths to ZK alloys is an alternative to form higher melting point intermetallic compounds,speed up dynamic recrystallization,refine grain size,enhance corrosion resistance and extend the service temperature due to improved creep resistance.This work deals with the effect of Ce-base mischmetal addition on the hot rolling behaviour of as-cast ZK60 alloy.The microstructure investigation conducted using electron microscopy and X-Ray diffraction shows that precipitation of Mg_(7)Zn_(3) intermetallics occur during hot rolling,whereas no further precipitation is observed for the ZK60-Mm alloys.The fragmentation of the intermetallic compounds occur during hot rolling and finer particles of Mg_(7)Zn_(3) are observed for the ZK60,whereas Mg_(7)Zn_(3) and Mg Zn_(2) Ce intermetallics are formed in the alloy modified with mischmetal addition.A higher fraction of dynamically recrystallized grains is observed for the ZK60-Mm in comparison to the ZK60.Continuous recrystallization takes place in ZK60 with the formation of sub-grains near to the intermetallics and the addition of mischmetal promotes the occurrence of discontinuous recrystallization with the nucleation of new grains close to the precipitates.The mechanical strength and,in particular,the ductility of the hot-rolled alloys are notably improved when compared to the same alloys in the as-cast condition.The mechanical strength is,however,higher for the ZK60 alloy.Less solid solution strengthening,softer Mg Zn_(2) Ce intermetallics and more extensive recrystallization contribute to reduce the mechanical strength of ZK60-Mm.Failure in both alloys are initiated at coarse intermetallics and propagate through intermetallic-rich regions.
文摘The effect of yttrium and mischmetal(MMs) on the as-cast and solid solution treated structures of Mg-Al alloys with different Al-contents was investigated. The results show that the MMs in Mg-Al alloy existed in rod Al 4(Ce, La)compound while Y in Mg-Al alloy in polygonal Al 2Y compound. The amount of Mg 17Al 12 in Mg-Al alloy is decreased with increasing Y or MMs addition, and Mg 17Al 12 intermetallic compound is changed from continuous network to discontinuous one. The Al 4(Ce, La) and Al 2Y compounds are not dissolved into Mg-Al alloy matrix during solid solution treatment so that their high heat stability can be exhibited. The experiment of mechanical properties indicate that elongation and impact toughness of the Mg-Al-Y alloy with polygonal Al 2Y compound are higher than those of Mg-Al-MMs alloy with rod Al 4(Ce, La) compound.
文摘The physical,mechanical properties and microstructures of three 2618 Aluminum alloys containing less than 0.046 wt.-%mischmetal have been studied.lt has been shown that the trace mischmetal has no obvious influence on the physical properties of the.alloy,but can clearly improve plasticity and toughness,and slightly raise the thermal stability.
基金the Specialized Research Fund for the Doctoral Program of Higher Education of China (No.20100092120047)the Production and Research Prospective Joint Research Project (No.BY2009153)the National Nature Science Foundation of China (No.50873026) for financial supports
文摘The influence of mischmetal addition on physicochemical properties of PtSnNa/ZSM-5 catalyst was studied by means of XRF,H 2 chemisorption,XRD,TPR,NH 3-TPD and TPO techniques.The results showed that the presence of mischmetal had an obvious impact on the catalytic performance of the PtSnNa/ZSM-5 catalyst.A suitable content of mischmetal not only could enhance the interactions between Pt species and the support,but also inhibit the formation of coke during the reaction,thus improving the catalytic activity and stability.In our experiments,when the content of mischmetal was 3m%,the catalyst exhibited best catalytic performance.However,the continuous addition of mischmetal could promote the reduction of Sn species to metallic tin,which was disadvantageous to the reaction.
文摘In molten salt electrolysis of mixed rare earth chlorides,the influence of the amount of samarium and neodymium containing in the raw material is experimented and discussed.The process of the formation of oxychloride,which is harmful to the production of mischmetal,is described.
文摘The effect of mischmetal addition on lead segregation in high lead bronze(grade ZQPb25-5)is studied in this paper.The testing results confirm that 0.5 to 1.0% misehmetal addition can effectively prevent lead from gravity and inverse segregation.The results of preventing lead from segregation respectively by mischmetal and nickel are also compared in the paper.The mischmetal addition in high lead bronze is distributed in the copper matrix mainly in the form of a compound which promotes early precipitation and refinement of α-dendrites, thus restraining the Pb-rich melt from either sinking to the bottom or escaping to the surface layer of the casting.As a result,the tendency of lead segregation is significantly decreased.Proper addition of mischmetal can also improve the mechanical properties,especially the ductility of high lead bronze.In addition,the contents of tin in high lead bronze can partially be substituted by mischmetal addition.
文摘The wetting of steel sheet by liquid Zn+5 wt%Al alloy has been measured by the Meniscograph. The result shows that the addition of mischmetal in Zn+5 wt%Al alloy decreases the surface tension of the alloy,reduces the wetting angle of the liquid alloy raising in steel substrate surface and enhances the adhesive power and wettability between them.It is concluded that the mischmetal addition in baths influences the reac- tion between steel sheet and liquid Zn+5 wt%Al alloy and thus improves the wettability of them.
文摘A conversion film was obtained on zinc deposit by immersing zinc coated specimens in a mischmetal salt solution. Several factors affecting the anticorrosive efficiency of the conversion film were studied. The suitable technological conditions were established. The composition and the thickness of the conversion film were determined by Auger electron spectroscopy(AES).
文摘The quality of mischmetal wire and rod and the method of adding rare earth into steel are quite important for making high quality steel. This paper proposes a quality specification of wire and rod as well as related adding method. The paper also provides principles for selecting raw material and adding method.
基金supported by the National Natural Science Foundation of China(Grant Nos.51001079,51044007,and 50571073)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20111402110004)the National Natural Science Foundation of Shanxi Province,China(Grant No.2009011028-3)
文摘To improve the comprehensive mechanical properties of Mg-10Zn-5Al-0.1Sb magnesium alloy,different amount of Ce-rich rare earth(RE)was added to the alloy,and the effect of RE addition on the microstructure and mechanical properties of Mg-10Zn-5Al-0.1Sb alloy was investigated by means of Brinell hardness measurement, scanning electron microscopy(SEM),energy dispersive spectroscope(EDS)and X-ray diffraction(XRD).The results show that an appropriate amount of Ce-rich rare earth addition can make the Al4Ce phase particles and CeSb phase disperse more evenly in the alloy.These phases refine the alloy's matrix and make the secondary phases[?-Mg 32 (Al,Zn)49 phase and?-Al 2 Mg5Zn2 phase]finer and more dispersive,therefore significantly improve the mechanical properties of the Mg-10Zn-5Al-0.1Sb alloy.When the RE addition is 1.0 wt.%,the tensile strengths of the alloy both at room temperature and 150oC reach the maximum values while the impact toughness is slightly lower than that of the matrix alloy.The hardness increases with the increase of RE addition.
文摘The influence of Ce-rich mish metal（MM） and electromagnetic stirring（EMS） on microstructure evolution of AZ91D magnesium alloy was investigated by optical microscopy, scanning electron microscopy（SEM）, energy dispersion spectrum（EDS） and X-ray diffraction（XRD）. The microstructure of AZ91D and alloying AZ91D is different. Except dominant primary α（Mg） and β-Mg 17Al 12 in AZ91D, a new phase Al 11MM3 is observed in alloyed AZ91D. Increasing Ce-rich MM, primary α grains can be refined, the content and grain size of β obviously decrease, furthermore, its morphology degrades from discontinuous network to separated particles, and Al 11MM3 amount substantially increases and acicular Al 11MM3 aggregates into clusters at grain boundaries. In EMS process, α morphology evolves from rosette to sphere, and then spherical-like with the decrease of isothermal stirring temperature. Moreover, Al 11MM3 mainly distributes inside primary grains and eutecticum in form of short-rod. EMS can alter not only the primary morphology but Al 11MM3.
