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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 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.

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...

Optimizing alloy composition is an effective way to improve physical and chemical properties of automobile heat exchanger materials.A Sm-containing Al-Mn-Si-Fe-Cu alloy was investigated through transmission electron microscopy,scanning electron microscopy,and electrochemical measurement.Experimental results indicated that main phases distributed in the alloy wereα-Al(Mn,Fe)Si,Al2Sm and Al10Cu7Sm2.Alloying with Sm element could refine the precipitated α-Al(Mn,Fe)Si phase.Polarization testing results indicated that the corrosion surfacewas mainly composed of pitting pits and corrosion products.Sea water acetic acid test(SWAAT) showed that corrosion loss increased first and then slowed downwith increase of the corrosion time.

Effects of CeLa addition on the localized corrosion and electrochemical corrosion behavior of Al-Cu-Mn-Mg-Fe lithium battery shell alloy were investigated by immersion testing and electrochemical testing in 0.6 M NaCl solution at different temperatures. Experimental results indicated that CeLa addition resulted in the formation of AlCuCe/La (Al 8 Cu 4 Ce and Al 6 Cu 6 La) local cathodes and corrosion activity of the main intermetallic particles decreased in the order of Al 2 CuMg, AlCuCe/La, Al 6 (Mn, Fe). Corrosion potential shifted positively due to CeLa alloying. Corrosion current density of the CeLa-containing alloy was lower than that of the CeLa-free alloy at room temperature. At room temperature, there was no obvious surface passivation for both alloys. At 80 °C CeLa addition resulted in a wide passive region at the anode polarization region. Electrochemical impedance spectroscopy (EIS) analysis also indicated that corrosion resistance of the CeLa-containing alloy was much higher than that of the CeLa-free alloy.

The structural evolution of the oxide films at 25–450 °C on nanocrystalline (NC) and coarse crystalline (CC) 304 stainless steels (SS) was investigated. The structure of the oxide film on both NC and CC SSs was observed to undergo transient processes from a bi-layer to a single-layer and then back to a bi-layer when the temperature changed from the low range (25–150 °C) to the medium range (150–300 °C) and subsequently to the high range (300–450 °C), respectively. These formation mechanisms of the oxide films on SS were attributed to the different diffusion properties of Cr and Fe in the three temperature ranges. The thickness of the oxide films was similar between the NC and CC SSs below 300 °C due to their similar Cr ox /Fe ox concentration ratios in their oxide films at this temperature. Above 300 °C, Cr diffusion enhancement in the NC matrix led to a higher Cr ox /Fe ox ratio and better compactness of the oxide film, which resulted in a slower atomic diffusion rate in the oxide film and a thinner oxide film. Therefore, the temperature of 300 °C was concluded to be the critical temperature of the detectable Cr diffusion enhancement in the NC SS compared to the CC SS.

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.

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.

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 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.

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 structure and compactness of the passive films on nanocrystalline (NC) and coarse crystalline (CC) 304 stainless steels (SSs) are investigated. A bi-layer passive film composed of an inner Cr2O3-rich layer and an outer Fe2O3-rich layer is obtained on both NC and CC 304SSs. The lower oxide formation potential Uox(Cr) of chromium causes the Cr2O3-rich inner layer to form initially, and when the surface potential of the passive film increases due to Cr2O3 formation, Fe2O3 with a higher formation potential Uox(Fe) forms and predominates in the outer layer as a result of the higher diffusion rate of Fe than that of Cr across the inner layer. Compared with the CC-304SS, the inner layer of the passive film on the NC-304SS possesses a higher Cr2O3 content, which is attributed to the greater nucleation sites and faster growth rate of Cr2O3 in NC-304SS and is believed to be responsible for the higher compactness of the passive film on NC-304SS.

Nickel-free Ti–Nb alloys were fabricated by conventional powder metallurgy sintering method. The oxygen content of sintered Ti–Nb alloys were successfully decreased to around 0.8 wt.% by putting TiH2 powders aside the samples during the sintering process. For the first time, the phase transformation behaviors of these sintered Ti–Nb alloys were observed by differential scanning calorimetry (DSC) measurement. The relationship between martensitic transformation start temperature (Ms) and mechanical properties, including elastic modulus and recoverable strain, was established by compression tests carried out at room temperature. While Ms was close to test temperature, an obvious drop of elastic modulus was observed, which was related to the “β-α” transformation. In the meantime, a remarkable recoverable strain as high as 5% was obtained at room temperature, which is the highest value reported in sintered Ti–Nb alloys until now. The results of this study reveal that the recoverable strain can be further improved by adjusting Ms close to the service temperature, which was neglected in the reported studies before and will provide some guidance for the future design and fabrication of porous Ni-free Ti-based shape memory alloys for biomedical application. Keywords: Sintered titanium alloy, Superelasticity, Oxygen content, Martensitic transformation, Biomedical alloy

In this work, an attempt was made to further promote the wear and friction behavior of dual-scale structured Al–12 wt% Sn bearing alloys by coupling with a nano-Si@Sn composite. A so-called tri-modal Al–Sn–Si (denoted as CG-30 Si-containing alloy), which exhibited increased bulk hardness and improved distribution and refinement of the Sn phase, was produced by combining mechanical alloying and conventional powder sintering. The wear performance of the Si-containing and Si-free alloys was differentiated by performing both block-on-ring and ball-on-disk testing. Moreover, the addition of nano-Si@Sn composites to the dual-scale Al–Sn matrix resulted in significant reductions of the friction coefficient and wear volume. These improvements in wear behavior stemmed from the polishing effect of fine Si particles on the counterface, and Sn-rich clusters that acted as lubricants on the worn surface; together, the polishing effect and lubrication led to the formation of a smooth tribolayer, and hence, a decrease in the tendency for abrasive wear. Abrasive wear was also reduced by an increase in the alloy hardness with the addition of Si. As such, Sn-phase modification via Si addition constitutes a promising method for preparing self-lubricating Al-based alloys.

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.