Effects of rare earth Ce addition on microstructure and mechanical properties of impure copper containing Pb

The effects of rare earth Ce on the microstructure and mechanical properties of impure copper containing Pb were investigated using OM,SEM,EPMA,TEM and tensile testing.TEM and EDS analysis reveal that spherical CePb3 particles form after Ce addition.CePb3 particles,with average size of^3.6μm,homogenously distribute in the Cu matrix.Due to small lattice misfit(~4.62%)with Cu matrix,CePb3 particles can act as effective nucleation sites beneficial to the grain refinement.Pb at grain boundaries seriously deteriorates the mechanical properties of Cu.The tensile strength and the elongation of Cu-0.1 Pb are decreased by 43.1%and 56.7%compared with those of pure copper,respectively.Ce can purify grain boundaries,cause the precipitation of CePb3 particles and refine grain sizes,which contribute to significant improvement of the mechanical properties of Cu.Compared with Cu-0.1Pb,the tensile strength(179 MPa)and the elongation(38.5%)of Cu-0.1Pb-0.3Ce are increased by 117.6%and 151.6%,respectively.

Influence of Cerium Addition on Microstructure and Properties of Cu-Ag Alloy in Situ Filamentary Composites

The in situ filamentary composites based on the Cu-10Ag and Cu-10Ag-Ce alloys were prepared. The microstructure and properties of the composites were studied. The effects of Ce addition on the microstructure as cast, including refining Cu grains and the Ag filaments, increasing the proportion of (Cu+Ag) eutectic and decreasing the proportion of the Ag precipitate, were researched. The average size of the Ag filaments in the composites could be approached by a formula: d=C·exp(-0.228η), here C is a coefficient related to the size of the original grains and 1500 nm for Cu-10Ag and 800 nm for Cu-10Ag-Ce. A two-stage strain strengthening effect was found for the deformed composites, that is the dislocation strengthening at low strain stage and the ultra-fine Ag filaments or interface strengthening at the high strain stage. The intermediate heat treatment at lower temperature further refined the Ag filaments and therefore improved the properties. The high strengthening rate of Ce addition on Cu-10Ag alloy attributed the refining effect to Cu grains and Ag filaments. The typical properties of the heavy deformed composites with 1 IHT reached to UTS=1500 MPa with conductivity 62% IACS for the Cu-10Ag alloy and UTS=1550 MPa with conductivity 65% IACS for the Cu-10Ag-Ce alloy, respectively.

Influence of Rare Earth(Ce and La) Addition on the Performance of Al-3.0 wt%Mg Alloy

The influences of rare earth elements（cerium and lanthanum） on the microstructure and phases of Al-3.0 wt%Mg alloys used for electromagnetic shielding wire were characterized by scanning electron microscopy（SEM）, energy-dispersive spectroscopy（EDS）, X-ray diffraction（XRD） and differential scanning calorimetry（DSC）. The mechanical properties and electrical resistivity were also investigated. The results indicated that a certain content of rare earth could improve the purification of the aluminum molten, enhance the strength, and reduce the electrical resistivity of Al-3.0 wt%Mg alloys. The strength reached the top value when RE content was 0.3 wt% while the alloy with 0.2 wt% RE addition had the smallest electrical resistivity. The elongation varied little when RE addition was no more than 0.2 wt%. But the excessive addition of rare earth would be harmful to the microstructure and properties of Al-3.0 wt%Mg alloys.

Effect of Ce on the thermal stability of the Ω phase in an Al-Cu-Mg-Ag alloy

This paper studies the effect of Ce on the thermal stability of the Ω phase in an Al-Cu-Mg-Ag alloy by TEM and tensile testing. It has been shown that Ce substantially increases the nucleation density of the Ω phase by acting as the heterogeneous nucleation center. Most impor-tantly,Ce improves the thermal stability of the Ω phase by decreasing the diffusion velocity of Cu atoms and increasing the energy barrier of the thickening ledge nucleation,thus improving the strength of the Al-Cu-Mg-Ag alloy at both ...

EFFECTS OF IMPURITIES AND RARE EARTH ADDITION ON THE TOUGHENING LEVELS OF Al-Li BASED ALLOYS 2090 AND 1420

The effects of the impurities Fe, Si, Na, K and a rare earth addition, Ce, on the intrinsic and extrinsic toughening levels have been investigated for the Al-Li based alloys 2090 and 1420. 29K reduction in the toughening level for the alloy 2090 with impurities 0.42% Fe+Si or 0.0132% Na+K i4 identified to be caused by the impurities.An improvement on the fracture toughness can be made by adding 0.05%-0.25% Ce to the alloy 2090. The reason behind this is that Ce microalloying can not only enhance both the intrinsic toughening level and the extrinsic toughening level but also suppress the embrittling behavior of the impurities. However, 0.06%-0.15% Ce microalloying fails to bring about any beneficial effect to the toughening level for the alloy 1420.

Effect of cerium on microstructure,texture and properties of ultrahigh-purity copper

The effects of Ce addition(310 ppm and 1500 ppm)on the microstructure,texture and properties of ultrahigh-purity copper(99.99999%)were systematically studied using scanning electron microscopy(SEM),transmission electron microscopy(TEM)and electron backscattered diffraction(EBSD)analyses,combined with the microhardness and conductivity tests.Regarding the microstructure of the as-cast and as-extruded samples,the addition of Ce refines the grain size of the ultrahigh-purity copper and the refinement effect of 310Ce alloy is greater than that of 1500Ce alloy.This is due to the stronger compone nt supercooling and the accele rated recrystallization caused by lower Ce co ntent.In addition,Ce can react with Cu to form the Cu-Ce eutectic phases,which are deformable during the hot deformation.Furthermore,the added Ce can weaken the texture,showing a variation of brass recrystallization(BR),rotated cube,copper and S texture components,which depends on the recrystallization,the particle stimulated nucleation(PSN)as well as the stacking fault energy(SFE).Most remarkably,the introduction of Ce enhances the hardness of the ultrahigh-purity copper without obviously reducing its conductivity.The major{111}orientations and the stress distributions are responsible for such a superior conductivity of the Ce-containing alloys.

Microstructure and mechanical properties of Al-7Si-0.7Mg alloy formed with an addition of(Pr+Ce)

Effects of （Pr＋Ce） addition on the Al-7Si-0.7Mg alloy were investigated by optical microscope （OM）, energy diffraction spectrum （EDS）, X-ray diffraction （XRD） and tensile tests. The results showed that the Al-7Si-0.7Mg alloy was modified with （Pr＋Ce） addition. The needle-like eutectic silicon phase developed into rose form and the crystalline grains decreased in size and showed a high degree of spheroidization. When the amount of the （Pr＋Ce） addition reached 0.6 wt.%, the mean diameter was 31.8μm （refined by 50%）. The aspect ratio decreased to 1.35, and the tensile strength and ductility reached 192.4 MPa and 2.18%, respectively At higher levels of addition, over-modification occurred, as indicated by increased grain size and reduced mechanical properties. The poisoning effect of the （Pr＋Ce） addition on eutectic silicon and the constitutional supercooling caused by the （Pr＋Ce） addition were the major causes of alloy modification, grain refinement, and the improvement of mechanical properties.

Microstructure,tensile and creep properties of as-cast Mg-3.8Zn-2.2C_(a-x)Ce(x=0,0.5,1 and 2 wt.%) magnesium alloys

The microstructure and mechanical properties of as-cast Mg-3.8Zn-2.2Ca alloy with different Ce contents were investigated by both optical and electron microscopy, X-ray diffraction, differential scanning calorimetry analysis, tensile and creep tests. The results indi-cated that adding 0.41 wt.%-1.83 wt.% Ce could refine the grains of the alloy, and the grain size gradually decreased as the Ce content in-creased. Furthermore, addition of either 0.41 wt.% or 0.89 wt.% Ce caused the morphology of the Ca2Mg6Zn3 phase to change partially from semi-continuous block to discrete fine particles. However, after adding 1.83 wt.% Ce, portions of the Ca2Mg6Zn3 and Mg12Ce phases were mixed and this Ca2Mg6Zn3＋Mg12Ce eutectic changed to a different coarse semi-continuous morphology. In addition, addition of 0.41 wt.%-1.83 wt.% Ce improved the tensile and creep properties of the alloy. Amongst these Ce-containing alloys, the alloy with 0.89 wt.% Ce exhibited the best ultimate tensile strength and elongation while the alloy with 1.83 wt.% Ce had the best yield strength and creep properties.

Eutectic nucleation in Al-7 wt pct Si-Mg casting alloys

The nucleation of eutectic crystals of hypoeutectic A1-7 wt pct Si-Mg casting alloys modified by Ce and Sr was studied by using differential scanning calorimeter （DSC） and scanning electron microscope （SEM）. DSC results were applied to calculate the values of activity energy and nucleation work of eutectic nucleation for the alloys. These values were decreased and the eutectic nucleation frequency was increased with the addition of Ce and Sr to the alloys. Moreover, the morphology of eutectic silicon in the modified alloys was partially or fully modified as fine, fibrous or coral, and DSC plots show that the eutectic undercooling of A1-7 wt pct Si-Mg alloys were increased with additions of modified agents. The mechanism of eutectic modification is combined actions of the accelerated nucleation and the restricted growth.