Effects of Rare Earths on Electrical Conductivity, Melting-Welding and Corrosion Resistance by Electric Arc of Copper-Based Alloys

The effects of rare earths on electric conductivity fusion welding-resistance and erosion-resistance by electric arc of copper-based compound material by adding different amount of rare earths to copper base to get copper based compound materials were studied. Rare earths improve active ability among interfaces and optimize organizational structures. The conductivity of samples with rare earths is obviously better than that of materials without them. Moreover, wear ability and oxidization resistance of materials with rare earths can be improved greatly. For copper contact head with rare earths, electric arc corrosion resistance and welding-melting resistance are improved. Such alloys also decrease resistance change with increasing temperature. But the adding quantity of rare earths should be appropriate and formed handicraft should be properly regulated.

Microstructure and corrosion resistance of sintered NdFeB magnet modified by intergranular additions of MgO and ZnO

Microstructure and corrosion resistance of sintered Nd15Dy1.2Fe77Al0.8B6 and Nd22Fe71B7 magnets modified by intergranular addition of MgO and ZnO were investigated. Both the remanence and sintering density of the magnets increased slightly with intergranular additions of MgO and ZnO. There was a remarkable increase in coercivity of Nd22Fe71B7 after addition. Besides, the effects on magnetic properties and an improved corrosion resistance were observed. Compared with the native magnets without addition, corrosion potential of the magnets with MgO and ZnO additives was more positive and the current density in the anodic branch of the polarization curve was reduced. Corrosion resistance resulting from autoclave testing （2×10^5 Pa of steam pressure, 120 ℃） showed that the corrosion rate of NdFeB magnets reduced with the increase of additive amount. Microstructure observation revealed that MgO and ZnO additives were incorporated into the intergranular phases in the magnets. With the introduction of MgO and ZnO, more intergranular phase with high oxygen content was formed while keeping the volume fraction of all the intergranular phases almost unchanged, which may contribute to improved corrosion resistance. Furthermore, addition of MgO and ZnO refined the grain size of Nd22Fe71B7.

Microstructure and corrosion behavior of as-cast ADC12 alloy with rare earth Yb addition and hot extrusion

The effects of rare earth ytterbium(Yb)addition and hot extrusion on the microstructure and corrosion behavior of as-cast ADC12 were studied by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD).The experimental results demonstrate that both the Si phase andβ-Al5FeSi phase in the alloy with 0.9 wt%Yb have been remarkably refined,and the Al3Yb intermetallic compound has also been obtained.The Si,β-Al5FeSi,and rare earth phases are further refined in the alloy at 0.9 wt%Yb and hot extrusion.The results of the immersion corrosion tests and electrochemical experiments show that the corrosion current density(8.56μA/cm2)of the alloy with 0.9 wt%Yb addition and hot extrusion is 50.6%lower than the untreated alloy(17.33μA/cm2),and the polarization resistance(9252Ω·cm2)was 71.3%higher than the untreated alloy(2654Ω·cm2).The corrosion in the cathode phase in the micro-battery was refined to varying degrees attributable to the addition of Yb and hot extrusion,where the cathode reaction in the corrosion process caused a decrease of the corrosion rate.

Effect of Heat Treatment on the Microstructure and Corrosion Resistance of Cu-Zn Alloy

The microstructure of Cu-Zn alloy with different heat treatment conditions in 3.5%NaCl+NH3 solution were observed, and the average corrosion rates and electrochemical data of Cu-Zn alloy were measured, as well as the effect of heat treatment on microstructure and corrosion resistance of Cu-Zn alloy was analyzed. The results show that the microstructure of Cu-Zn alloy has been changed due to the heat treatment. As a results, the better corrosion resistance can be obtained for the Cu-Zn alloy quenched from 900 ℃ for 0.5 h followed by tempered at 100 ℃ for 2 h.

Effect of rare earth content on microstructure and corrosion resistance of hot-dip Zn-5Al alloy coated steel wire for bridge cables

The effects of the content of rare earth elements on the microstructure and properties of hot-dip Zn-5 Al alloy steel wire for bridge cables were investigated.The microstructure of the hot-dip coating was analyzed using an optical microscope and a scanning electron microscope equipped with an energy-dispersive spectrometer.The bonding force between the hot-dip coating and steel wire was determined by the winding test.The corrosion resistance of the steel wire hot-dip coating was tested by the electrochemical workstation.The hot-dip Zn-5A1 alloy coating has a corrosion-resistant structure composed of a zinc-rich phase and an aluminum-rich phase.Due to the enhanced bonding force,the micro structure of the hot-dip coating of the Zn-5A1 alloy with rare earth elements is more compact and uniform than that without rare earth elements.The addition of rare earth elements improves the corrosion resistance of Zn-5A1 alloy coated steel wire.Due to the rare earth segregation,which prevents the corrosion of the grain boundary and enhances the anti-intergranular corrosion performance,steel wire exhibits the optimum corrosion resistance when the content of rare earth elements is 0.08 wt.%.

Influence of adding various rare earths on microstructures and corrosion resistance of chromizing coatings prepared via pack cementation on P110 steel

In order to improve the corrosion resistance and increase the service lifetime of P110 steel during operation,four chromizing coatings were formed onto its surface with/without addition of rare earths via pack cementation process.The surface morphologies and microstructures of the chromizing coatings were observed using scanning electron microscopy(SEM),and the phase constitutions were investigated by X-ray diffraction(XRD).Electrochemical corrosion behavior of the chromizing coatings in simulated oilfield ...

Effect of rare earth addition on microstructure and corrosion behavior of plasma nitrocarburized M50NiL steel

M50NiL steel was plasma nitrocarburized at 480 °C with and without rare earth （RE） addition. The microstructures of the surface layer were characterized by optical microscopy, X-ray diffraction and scanning electron microscopy. The mechanical proper-ties and corrosion resistances of the surface layer were studied by Vickers microhardness measurements and polarization tests in 3.5% NaCl solution. The results showed that RE atoms could diffuse into the surface layer of the steel and inhabit the formation ofε-Fe2–3（N,C） phase. As compared to the treatment without RE addition, RE addition further increased the surface hardness by 143 HV0.1, and further increased the thickness of the nitrocarburized layer by 39μm. Compared with the quenched bearing steel, the cor-rosion resistance of the samples nitrocarburized with and without RE addition could be significantly improved. Especially, the sample plasma nitrocarburized with RE addition exhibited the highest corrosion resistance.

Effects of rare earths on the microarc oxidation of a magnesium alloy

The effects of rare earths on the properties of the microarc oxidation（MAO） coating on a magnesium alloy were investigated by means of scanning electron microscopy（SEM）,energy dispersive X-ray spectroscopy（EDS）,and electrochemistry methods.The results show that a nice and compact MAO coating was successfully obtained when the magnesium alloy was treated in nitrate solutions as the pre-treatment of MAO.However,the MAO was not successfully completed for the silicate electrolytes with the addition of rare earths.After the magnesium alloy being treated by rare earth nitrate,the obtained MAO coating has advantages such as uniform distribution of thickness,improved corrosion resistance,and nice-uniform surface,as compared with the untreated magnesium alloy.In addition,the time of non-ESP,the voltage and current density of the MAO process obviously decrease.Cerium oxide doped on the surface of the magnesium alloy can significantly improve the corrosion resistance of the MAO coating and decrease the current density of the MAO process,as compared with lanthanum oxide,whereas the doped rare earths have no significant effect on the components of the MAO coating.

Influence of heat treatment on corrosion behavior of hot rolled Mg5Gd alloys

The influence of heat treatment on the corrosion behavior of rolled Mg5 Gd alloys in 3.5 wt.% Na Cl solution saturated with Mg(OH)2 was characterized by immersion test, electrochemical test, scanning electrochemical microscopy(SECM) and corrosion morphology analysis in order to improve the corrosion resistance of Mg alloys. The results showed that solution treatment reduced the corrosion rate of the Mg5 Gd significantly, resulting in relatively uniform corrosion and shallow corrosion cavities due to the dissolution of Cd-containing particles. The following aging process could further decrease the corrosion rate. Precipitation of nano-sized Cd-containing particles did not cause apparent micro-galvanic corrosion, which could be attributed to the formation of a protective corrosion product film fully covering the particles.

Effect of samarium on microstructure and corrosion resistance of aged as-cast AZ92 magnesium alloy

The effects of samarium（Sm） on microstructure and corrosion resistance of AZ92 magnesium alloy were characterized and analyzed by scanning electronic microscopy, X-ray diffraction, mass loss test, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy and potentio-dynamic polarization test. The results showed that the added Sm could promote continuous precipitation of β-Mg17Al12 phase in grains, and meanwhile restrain discontinuous precipitation of the same phase along the grain boundaries. Thus, the precipitations distributed more uniformly in the aged AZ92 magnesium alloys. When the content of Sm was 0.5 wt.%, the corrosion resistance of aged AZ92 alloy tended to be the best, which was due to the β-phase distributes more homogeneous reducing the galvanic corrosion. The corrosion product film had more integrality and compactness than AZ92 alloys without Sm. However, it resulted in worse corrosion resistance of AZ92 alloy because of the formation of mass cathodic Al2 Sm phase coming from excess Sm in AZ92 alloy.

Improvement in magnetic properties,corrosion resistance and microstructure of Nd-Fe-B sintered magnets through intergranular addition of Tb_(68)Ni_(32)

New energy vehicles and offshore wind power industries have a high demand for sintered Nd-Fe-B magnets with high intrinsic coercivity and high corrosion resistance.In this study,the magnetic properties,anticorrosion properties,and micro structure of Nd-Fe-B sintered magnets with the intergranular addition of low-melting-point eutectic Tb_(68)Ni_(32) alloy powders were investigated.The aim is to determine if the addition of Tb_(68)Ni_(32) can improve these properties.A low melting-point eutectic alloy Tb_(68)Ni_(32) powders was prepared as a grain boundary additive and blended with the master alloy powders prior to sintering.The coercivity of the resultant magnets gradually increases from 1468 to 2151 kA/m by adding increasing amounts of Tb_(68)Ni_(32).At the same time,the remanence first increases and then slightly decreases.After studying the microstructure and elemental composition of the Tb_(68)Ni_(32) added magnets,it is found that the significant increase in coercivity and the negligible reduction in remanence is due to densificatio n,improved grain orientation,a unifo rm and continuous boundary phase distribution,as well as the generation of a(Nd,Pr,Tb)_(2) Fe_(14)B "core-shell" structure surrounding the main-phase grain.Moreover,the corrosion resistance of the magnet is greatly improved owing to the enhancement of electrochemical stability,as well as the optimization of the distribution and morphology of the intergranular phase.

Microstructure and properties of TP2 copper tube with La microalloying by horizontal continuous casting

The TP2 copper tube was prepared with La microalloying by horizontal continuous casting(HCC). The absorptivity of La and its effects on microstructure, tensile and corrosion properties of HCC TP2 copper tube were studied by means of the inductively coupled plasma optical emission spectrometer(ICP-OES), optical microscope(OM), scanning electron microscope(SEM) and potentiodynamic polarization measurements. The results show that the absorptivity of La in the HCC TP2 copper tube is about 15% under antivacuum conditions due to the good chemical activities of La. The impurity elements in copper tube such as O, S, Pb and Si can be significantly reduced, and the average columnar dendrite spacing of the copper tube can also be reduced from 2.21 mm to 0.93 mm by adding La. The ultimate tensile strength and the elongation with and without La addition are almost unchanged. However, the annual corrosion rate of the HCC TP2 copper tube is reduced from 10.18 mm·a^(-1) to 9.37 mm·a^(-1) by the purification effect of trace La.

含铈半固态ZL105合金组织及耐腐蚀性能研究

通过光学显微镜、扫描电子显微镜、能谱分析仪、显微硬度测试、盐溶液浸泡腐蚀及电化学工作站等分析测试方法研究了不同稀土铈添加量对半固态ZL105合金微观组织形貌及耐腐蚀性能的影响。研究结果表明:随着稀土铈含量的不断提高,ZL105合金组织内的初生α-Al相的尺寸逐渐缩小;当铈的含量为0.6%时,合金中初生α-Al相晶粒尺寸为65.77μm,晶粒平均形状因子为0.74,与不添加稀土铈的ZL105合金相比α-Al相晶粒尺寸(115.37μm)降低了42.99%,晶粒平均形状因子(0.42)提高了76.19%。与不含稀土铈的ZL105合金相比,添加了0.6%稀土铈的合金维氏硬度提高了31.64%。稀土铈的添加也大幅提高了合金的耐腐蚀性能,铈的含量为0.6%时合金的失重腐蚀速率为10.85 mg·cm^(-2)·d^(-1),相比于不含稀土铈的合金降低了50.93%,合金的腐蚀电位有所增大并且腐蚀电流密度有所减小。通过腐蚀表面形貌观察可知添加稀土铈的合金的腐蚀凹坑及腐蚀裂纹明显减少,腐蚀表面逐渐变得平整且光滑,腐蚀形貌得到了极好的改善。

稀土CeO_(2)增强65Mn钢渗硼层的耐蚀性与抗磨性能

在700℃下对65Mn钢进行稀土硼共渗处理,利用金相显微镜以及能量散射光谱(EDS)研究其表面渗层的微观结构特征,分析其对耐蚀性和耐磨性的影响,并与常规850℃下渗硼处理进行对比。采用腐蚀实验和磨损实验,评估了CeO_(2)增强的65Mn钢渗硼层在含肥土壤环境中的耐蚀性和抗磨性能。实验结果表明,引入CeO_(2)纳米颗粒后渗层的结构更加均匀致密,这对提升渗硼层的耐蚀性和抗磨性能具有显著的改善效果。腐蚀测试结果表明,稀土硼共渗渗层表面没有出现裂纹,保持完整且致密,界面未见腐蚀迹象。磨损测试结果表明,稀土硼共渗渗层体积磨损量为常规渗硼处理的18.09%。

稀土Ce对铝硅合金组织、力学及耐腐蚀性能的影响

研究熔铸工艺条件下制备的不同稀土铈含量(w(Ce)分别为0%、0.3%、0.6%和0.9%)的Al-Si合金微观组织、力学性能及耐腐蚀性能。研究结果表明:稀土Ce的添加极大的优化了Al-Si合金的微观结构,α-Al枝晶明显被细化,枝晶变得十分圆整且规则。共晶Si相也变得非常细小,颗粒状的共晶Si相边缘圆润,且排布有序。随着稀土Ce添加量的逐渐增大,Al-Si合金的拉伸性能及显微硬度均逐渐增大,当稀土Ce的含量为0.6%时,合金的抗拉强度、伸长率及显微硬度达到峰值,分别为228.96 MPa、5.1%和109.5 HV,比未添加稀土Ce的合金分别提高了24.59%、54.55%和40.74%。并且此时合金的抗腐蚀性能达到最佳,通过浸泡测试可知合金的失重腐蚀速率仅为11.36 mg/(cm^(2)·d),相比于未变质的Al-Si合金基体降低了50%。

Effect of cerium on microstructure,mechanical properties and corrosion properties of Al-Zn-Mg alloy

The effects of trace Ce on the microstructure,mechanical properties and corrosion resistance of Al-Zn-Mg alloy were studied by means of metallographic analysis,scanning electron microscopy(SEM),mechanical tensile test,slow strain rate tensile test,cyclic polarization curve test,electrochemical impedance spectroscopy test and anodic oxidation test.The results show that the addition of trace Ce has little effect on the strength of Al-Zn-Mg alloy,but can significantly improve the corrosion resistance of the alloy;The mechanical properties and corrosion resistance of the alloys decrease significantly with the addition of excessive Ce;the addition of 0.04 wt%Ce can reduce significantly the self-corrosive current density of AlZn-Mg alloy and increase obviously passivation film resistance of the alloy.The stress corrosion sensitivity index decreases from 0.612 to 0.219,which improves the corrosion resistance properties significantly.

Concurrent improvements of corrosion resistance and coercivity in Nd-Ce-Fe-B sintered magnets through engineering the intergranular phase

Usually the improved coercivity of rare earth(RE)based 2:14:1-type permanent magnets via RE-rich intergranular additives is achieved at the cost of more corrosion channels and deteriorated corrosion resistance,which remains a challenging hurdle in the RE-Fe-B community.Distinctly,here we report the concurrent improvements of corrosion resistance and coercivity in 40 wt.%Ce-substituted Nd-Ce-Fe-B sintered magnets through engineering the intergranular phase using simple(Nd,Pr)H_(x)additive.The dehydrogenated Nd/Pr changes the RE concentration gradients between 2:14:1 matrix and intergranular phases during sintering and enlarges the fraction of corrosion-resistant REFe_(2) phase,rather than the conventionally assumed Nd/Pr-rich intergranular phase with high chemical vulnerability.The spontaneous formation of REFe_(2) intergranular phase after(Nd,Pr)H_(x) addition generates the uniquely enhanced corrosion resistance against the hot/humid and acidic environments,and counts as one peculiar feature of Nd-Ce-Fe-B magnets at high Ce substitution level,being distinct from previously reported Ce-free/lean RE-Fe-B.Simultaneously,the formation of continuous grain boundaries enhances the coercivity from 8.7to 12.5 k Oe with trace addition of(Nd,Pr)H_(x).Above findings may spur progress towards developing a high-performance Nd-Ce-Fe-B permanent magnet.

Corrosion resistance and mechanical properties of (Ho,Nd)FeB magnets

(Ho,Nd)FeB magnets with different Ho contents were prepared by Ho substitution for part of Nd during the casting process.Effects of Ho contents on the corrosion resistance and mechanical properties of(Ho,Nd)FeB magnets were analyzed by a highly accelerated aging tester,an electrochemical workstation,a microhardness tester,a bending tester,a scanning electron microscope and an X-ray diffractometer.Results show that the addition of Ho can change the main phase structure,optimize the distribution of rare-earth rich(RE-rich) phases in grain boundary,and improve the corrosion resistance and mechanical properties of NdFeB magnets.When the content of Ho increases from 0 to 21.0 wt%,the weight loss of magnets decreases from 2.672 to 0.933 mg/cm^(2),and the microhardness and bending strength increase from 528.74 HV and 374.92 MPa to 633.84 HV and 459.80 MPa,respectively.

稀土对热镀锌层耐蚀性的影响

实验研究了稀土元素对GI镀锌液的流动性、镀层厚度、镀层微观结构以及耐蚀性能的影响,初步探讨了稀土提高GI镀层耐蚀性的作用机理.结果表明：添加稀土具有细化镀层表面树枝晶、提高镀液流动性、降低镀层厚度和改善镀层耐蚀性的作用;镀层的耐腐蚀性随着稀土含量的增加先增后减,即稀土对镀层耐蚀性的影响存在一个最佳范围;实验条件下,稀土含量w=0.045%-0.069%时,镀层的耐盐雾腐蚀性能约为纯锌层的2.8倍.

RE对热浸镀铝镀层组织及耐腐蚀性能的影响

研究了混合稀土(RE)对45钢热浸镀铝镀层微观组织和耐蚀性能的影响。结果表明,45钢热浸镀铝镀层由外层的Al层和内层的过渡层组成,过渡层与基体呈锯齿状冶金结合。当RE加入量不超过0.5%时,随RE加入量增加Al层厚度逐渐减小,当RE加入量超过0.5%后Al层厚度又增加。过渡层厚度则先增加(0.0%～0.1%RE)后逐渐降低。RE能细化热浸镀铝层中FeAl3相。动电位极化曲线测试及耐蚀性试验表明,RE加入量0.5%的热浸镀试样耐蚀性效果最好,耐盐水腐蚀失重试验中其耐蚀性约为45钢基底的4倍,热浸镀纯铝的2倍。