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Good electrical conductivity, mechanical properties and electrochemical performance are required for aluminum alloys acting as cathode current collectors of lithium ion batteries (LIBs). The effect of La alloying on the microstructure, mechanical properties and the electrochemical performance of Al-Fe-Mn alloys were characterized by optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, tensile test, conductivity test and Tafel polarization curve test. The experiment results showed that Al13Fe4 and Al6(Mn, Fe) precipitates tended to nucleate and grow along the grain boundaries. The addition of La to the Al-Fe-Mn alloy could help to refine grains and spheroidize secondary phases. These changes in microstructure could improve the tensile strength and elongation at room temperature and a high temperature of 125°C and enhance the corrosion resistance of the alloy. However, the spheroidized precipitates tended to aggregate in the alloy with 0.15 wt.% La and this uneven aggregation resulted in a decrease in tensile strength and elongation in comparison to the alloy with 0.1 wt.% La, which suggested an optimal La content for the Al-Fe-Mn alloy.

Al&ndash, xFe&ndash, Si&ndash, La alloys (x = 0.07, 0.2, 0.4 wt. %) were designed as current collectors of positive electrodes in lithium ion batteries, and the microstructure, tensile strength, electrical conductivity and corrosion resistance of the alloys were investigated with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), a tensile test, an electrical conductivity test, and an electrochemical test. It was found that the amount of Fe content greatly affected the quantity of the second phases in the alloys. The higher the Fe content was, the more the second phases were. With increase of the Fe content, the tensile strength and corrosion resistance of the Al&ndash, La alloys were improved, and the electrical conductivity of the Al&ndash, La alloys could meet the application requirements. Compared to the Al&ndash, 0.07Fe&ndash, 0.1Si&ndash, 0.07La alloy, the strength of the Al&ndash, 0.4Fe&ndash, 0.07La alloy was greatly enhanced. The Al&ndash, 0.07La alloy also had a higher corrosion potential than that of the Al&ndash, 0.07La alloy.

Effect of Ce addition on the microstructures, mechanical properties and electrochemical properties of Al-Cu-Mn-Mg-Fe lithium battery alloy was investigated by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile testing and electrochemical testing. Experimental results indicate that Ce addition resulted in the formation of Al8Cu4Ce phase in the Al-Cu-Mn-Mg-Fe alloy. The Ce-containing precipitates nucleated and grew up along the surface of Al6(Mn, Fe) precipitates. Al6(Mn, Fe) precipitates could be remarkably refined by Ce alloying. The aging precipitation behavior of Sˈ phases could be promoted after Ce addition to the alloy. In comparison with Ce-free alloy, the Ce-containing alloy had higher tensile strength at both low temperature and elevated temperature. Especially at 200 °C, the yield strength and tensile strength of Ce-containing alloy substantially increased by 23.4% and 27.08%, respectively. Potentiodynamic polarization testing indicated that the Ce-containing alloy had a more positive corrosion potential and a lower corrosion current density.

The rapid development of new energy automobiles leads to an increasing demand for high-strength lithium battery shell alloy. The microstructures, electrical conductivity and mechanical properties o...

Development of high strength lithium battery shell alloy is highly desired for new energy automobile industry. The microstructures and mechanical properties of Al-Cu-Mn-Mg-Fe alloy with different CeLa additions were investigated through optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Rietveld refinement and tensile testing. Experimental results indicate that Al 8 Cu 4 Ce and Al 6 Cu 6 La phases formed due to CeLa addition. Addition of 0.25 wt.% CeLa could promote the formation of denser precipitation of Al 20 Cu 2 Mn 3 and Al 6 (Mn, Fe) phases, which improved the mechanical properties of the alloy at room temperature. However, up to 0.50 wt.% CeLa addition could promote the formation of coarse Al 8 Cu 4 Ce phase, Al 6 Cu 6 La phase and Al 6 (Mn, Fe) phase, which resulted in weakened mechanical properties.

The 304 austenitic stainless steel (ASS) undergone equal-channel angular pressing (ECAP) was annealed to achieve a strength-ductility balance through bi-modal microstructure (BMS) tailoring. The coarse grained ASS was first refined down to the nano-grained (NG) level by ECAP for eight passes. The NG microstructure with high dislocation density offers higher strength but lower ductility. The recrystallization curve of NG ASS exhibits three distinct regions including the recovery region below 650 °C, the recrystallization region from 650 °C to 800 °C, and the grain growth region above 800 °C. The results of microstructure observation and tensile test show that the annealing NG ASS at 750 °C for 30 min produces the BMS consisting of 62 v/v% ultrafine grains with average size 350 nm and 38 v/v% coarser grains with average size 1.4 µm. Consequently this BMS ASS presents high strength and high ductility with yield strength 725 MPa, tensile strength 930 MPa, uniform elongation 34.5% and total elongation 40.6%. The present study provides an easy route to enhance the mechanical properties of face center cubic metal and alloys, and thus is of wide application potential.

The increasing demand for high-performance current collectors of lithium ion secondary batteries requires that the employed aluminum alloys have better mechanical properties and superior electrochemical performance. The effect of Si addition on the microstructure, tensile and electrochemical performance of Al-Fe-Cu-La alloy was investigated by optical microscopy, X-ray diffraction, scanning electron microscopy, a tensile test, conductivity test and Tafel polarization curve test. Experimental results indicated that Si addition to the Al-Fe-Cu-La alloy helped to refine the longitudinal grain size of the alloy. The Si-containing phase (AlFeSi) nucleated and grew along the surface of the AlFeLa phase. The Si addition to the Al-Fe-Cu-La alloy could greatly increase the tensile strength in the temperature range of &minus, 20 &deg, C to 50 &deg, C and improve high temperature stability of the alloy. Also, the addition of Si promoted the formation of the AlFeSi ternary phase, which helped to improve the corrosion resistance of the alloy.

Al-xFe-La alloys (x = 0.07, 0.1, 0.2) for aluminum current collectors of lithium-ion batteries were prepared and the microstructure of Al-0.07Fe-0.07La, Al-0.1Fe-0.07La and Al-0.2Fe-0.07La aluminum alloys were observed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS). The experimental results showed that with the increase of Fe content, the size of the second phases in Al-xFe-0.07La alloys became finer and more dispersed and that the microstructure of the alloy had improved. The strength and corrosion resistance of Al-xFe-La alloys were studied by tensile tests and electrochemical tests and the morphological investigations of samples were also conducted by SEM and EDS. With the increase of Fe content, the strength and corrosion resistance of Al-xFe-La alloys became better. Compared to Al-0.07Fe-0.07La alloy, the yield strength and tensile strength of the Al-0.2Fe-0.07La alloy increased by 51.19% and 58.48% respectively, and the elongation increased by 88.41%. Moreover, Al-0.2Fe-0.07La alloy had much more positive corrosion potential and much smaller corrosion current than those of Al-0.07Fe-0.07La alloy.

Dense and porous nickel-free Ti–11Nb–4O (at.%) alloys with Af temperature closed to body temperature were fabricated by conventional powder metallurgy (sintering) method from elemental Ti and Nb powders. Their microstructure, phase transformation temperature, superelasticity and mechanical properties at room temperature were investigated by optical microscopy, X-ray diffraction, differential scanning calorimetry and compression testing. It has been found that the phase temperature of Ti–11Nb–4O alloy by sintering is different from that by smelting and cold-rolling method due to the introduction of oxygen during powder mixing and sintering, and the Af temperature can reach up about 40 °C by reducing Nb content and controlling oxygen. Near dense Ti–11Nb–4O alloys can exhibit more than 5.4% superelasticity, high cyclic stability up to 100 cycles, high yield strength of 1.48 GPa and small strain hysteresis of 0.14% at room temperature. Moreover, porous Ti–11Nb–4O alloys with 29.4% porosity also can show complete superelasticity of near 3%, yield strength of 800 MPa and elastic modulus of 24.5 GPa at room temperature, which can be considered as one of perfect bone replacement materials in conjunction with their excellent biocompatibility. Keywords: Ni-free shape memory alloys, Superelasticity, Porous alloys

The Ti-(11–15)Nb–18Zr (at.%) alloys with low oxygen content and fine grain microstructure were successfully prepared by low temperature sintering after dielectric barrier discharge plasma (DBDP) milling of hydride (TiH2, ZrH2) and Nb powders. Hydride powders effectively reduced the oxygen content and lower the sintering temperature of Ti- (11–15) Nb–18Zr alloys. DBDP milling quickly refined and activated the TH2-Nb-ZrH2 powders without increased contamination by oxygen. The decrease in sintering temperature (as low as 1000 °C) helped to reduce the grain size of the Ti-(11–15)Nb–18Zr alloys to 3–8 μm, which has significantly increased the strength of the alloys. The reduction of oxygen content (as low as 0.4 wt%) in the Ti-(11–15)Nb–18Zr alloys benefited the superelasticity of the alloys. Among them, the Ti–12Nb–18Zr alloys presents an excellent superelasticity of about 1.5%, which is the highest value ever reported in the sintered Ti–Nb based SMAs.

Al foil with high formability and corrosion resistance is highly desired for lithium-ion battery soft packaging. Annealing treatment has a significant impact on the performance of soft packaging Al foil. The effects of both La content and the annealing temperature on the microstructure, mechanical properties, and corrosion behavior of Al-1.5Fe-La alloy was investigated through optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile testing, potentiodynamic polarization testing, and electrochemical impedance spectroscopy (EIS) testing. A higher addition of La resulted in the formation of AlFeLa particles and a refinement of the Fe-rich second phase. The Al-1.5Fe-0.25La alloy had a higher formability and corrosion resistance than the Al-1.5Fe-0.1La alloy. Microstructure analysis indicated that recovery, recrystallization, and grain growth successively occurred in the Al-Fe-La alloy with the increase of the annealing temperature from 200 &deg, C to 250 and 380 &deg, C. After annealing at 250 &deg, C, the Al-Fe-La alloys had the highest corrosion resistance due to refined grain and a high fraction of small-angle grain boundaries.

The mechanism of microstructure evolution of 304 stainless steel (SS) during equal-channel angular pressing (ECAP) at 500 °C was investigated systematically by optical microscope (OM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The results show that the refining mechanism of microstructure of 304 SS during ECAP behaviors as a hybrid model consisting of dislocation-subdivision mechanism and twin fragmentation mechanism, resulting in three kinds of nanostructure domains: (1) the equiaxial nano-grains with curving grain boundaries (GBs) having high angles of misorientation resulted from the cross-slip and movement of dislocations; (2) the equiaxial nano-grains with smooth and distinct boundaries resulted from the intersection between primary deforming twin bundles; (3) the secondary nano-twins formed in the primary deforming twins. The average nano-grain size ultimately obtained is in the range of 80 nm to 120 nm and the nano-twins have a width of 20–40 nm and a length of 100 to a few hundred nm. A low content about 10% (V/V) of deformation-induced martensite (DIM) is obtained in the first pass and remains almost constant during further passes of ECAP. The refining mechanism of DIM is also a hybrid model, including the refinement of banded DIM by the intersection with slipping bands and the newly induced fine martensite in submicron and nanometer grained austenite matrix.

Effects of Zr addition on the microstructure, mechanical and electrochemical properties of Al–Mn–Si–Zn alloy were investigated. Transmission electron microscopy (TEM) observations reveal that, in as-annealled state, the precipitates in the Zr-containing alloy are finer and more dispersive than those in the Zr-free alloy. Whereas, in simulated brazing state, a weaker precipitation is found in the Zr-containing alloy. Tensile testing results indicate that, with Zr additon, comprehensive mechanical properties of the as-annealed alloys could be significantly improved but weakened for the simulated brazing alloy. Electrochemical testing results reveal that, with Zr addition, the corrosion resistance of the as-annealed alloy decreases. However, after the simulated brazing treatment, such a negative effect of Zr element on the corrosion behavior of the alloy could be negligible.

Due to severe application environment lithium battery shell of new-energy automotives requires increasing demands for using high performance aluminum alloys. In the present work, effect of Ce addition on the microstructure, tensile and electrochemical properties of an Al–Cu–Mn–Mg–Fe alloy were investigated through using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), tensile tests and electrochemical tests. The experimental results indicated that the addition of Ce element could promote the precipitation of second phases. With addition of 0.36% Ce, high melting point Al8Cu4Ce phase and many Al20Cu2Mn3 particles could be found. In addition, the precipitation of conventionally dominant phase of Al2Cu could be suppressed in alloy. The Ce addition was found to result in enhanced tensile strength and improved corrosion resistance.

The fine microstructure of the passive films on nanocrystalline (NC) and coarse crystalline (CC) 304 stainless steels (SSs) in 0.5 M H2SO4 were investigated by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The results indicate that the passive film on both CC and NC SSs exhibits a two-layer microstructure consisting of a compact inner layer and a porous outer layer. Some hydrated compounds (HC) were present in the porous outer layer of NC SS but not CC SS in 0.5 M H2SO4 solution. The pores in the outer layer of the NC SS were observed to be in the nanoscale by AFM. HC filling of the pores in the passive film on NC SS may occur due to capillary forces endowed by the nanosize pores. XPS analysis of the passive films on both CC and NC SSs, however, does not show such a composition difference which is attributed to dehydration occurring in the XPS vacuum chamber. Both the inner and outer layers of the NC SS were determined by EIS analysis to be more compact and protective than the corresponding films on CC SS as evidenced by the lower Q value, higher n, and much higher R value in the corresponding layer.

Effect of microstructure change on the corrosion behaviour of equal channel angular pressed (ECAPed) 304 stainless steel (SS) was investigated. Nanostructure (80–120 nm) was obtained after 4 and 8 passes ECAP and exhibited a higher corrosion resistance than as-received SS. However, thickness and composition of the passive film formed in air at room temperature on both as-received and 8-pass samples show little difference, indicating that Cr diffusion is not enhanced by the formation of nanostructure. The improved corrosion resistance of ECAPed SS is not caused by thickness or composition change, but by compactness and stability improving of the passive film.

The effect of Zn addition on the microstructure, tensile properties and electrochemical properties of as-annealed 3003 Al alloy was investigated through TEM observations, tensile tests and Tafel polarization analysis. High density precipitates are observed in the Zn-containing alloys and the alloy with 1.8% Zn addition also has rod-like precipitates. Tensile test results indicate that Zn has a great effect on tensile strength of 3003 Al alloy. The alloy with 1.5% Zn addition has the highest ultimate tensile strength. The electrochemical results indicate that Zn addition to 3003 Al alloy also has great impact on the corrosion potential of the 3003 Al alloy in 0.5% NaCl solution and ethylene glycol-water solution. The corrosion potential varies with the Zn content and shifts negatively.

Ni–P deposits of amorphous, nanocrystalline, and mixed structures were prepared by electroless deposition. The three deposits were hypoeutectic Ni–P alloys with different P concentrations. The overall transformation sequences of the deposits during post-deposition annealing were investigated using differential scanning calorimetry, x-ray diffraction, and transmission electron microscopy. It was found that there existed three heat-release peaks in a mixed-structure deposit during annealing. The first peak came from the precipitation of Ni nanocrystallites from an amorphous matrix, the second peak resulted from the decomposition of the retained amorphous matrix into Ni + Ni3P having a composition close to the eutectic point, and the third peak, newly found in hypoeutectic Ni–P alloys, was assumed to be caused by both grain growth and the precipitation of Ni3P from as-deposited supersaturated Ni(P) nanocrystals interspersed within the amorphous matrix. By comparing the transformation sequences of the amorphous deposit with that of the nanocrystalline deposits, it was concluded that the transformation sequence of the mixed-structure deposit was a superimposition of those of both the amorphous and nanocrystalline deposits.

Electroless Ni–P and Ni–Co–P deposits were obtained on Al substrate. Their surface morphology, microstructure and composition were analyzed using SEM and XRD. Their corrosion resistance was characterized by anodic polarization curves. Based on the measurement of the thickness, electrical conductivity and magnetic conductivity of the deposits, their electromagnetic shielding effect values were calculated and the influence of cobalt on the corrosion and electromagnetic shielding properties of Ni–Co–P deposits was revealed. The results showed that cobalt improved the corrosion resistance and greatly enhanced the electromagnetic shielding property of Ni–Co–P deposits. Electroless Ni–Co–P deposits on Al substrate would impart the product with high corrosion resistance, good electromagnetic shielding effect and light weight.