原位观察铜网格增强Al/Cu复合材料的断裂行为

将一种按正交法编织的铜网格作为增强体引入到铝基体中制备了Al/Cu复合材料,再借助原位拉伸扫描电镜(SEM),观察了铝铜复合材料的组织演变,研究了其断裂机理与力学性能之间的关系.结果表明:在相同轧制变形量下,25 ℃冷轧和400 ℃热轧均可破碎增强体铜网格,并使其均匀分布于基体铝板.复合板原位拉伸下的载荷-位移曲线均表现出明显的弹性阶段、塑性阶段和失效阶段,微裂纹在Cu颗粒周围和应力集中处萌生,主裂纹及其扩展主要是Cu颗粒周围界面分层开裂与微裂纹沿滑移线方向的扩展共同作用下形成的,并且最终沿滑移线的断裂路径与单轴拉伸方向呈45°.发生在Al层的塑性断裂和Al/Cu结合界面上的界面分层断裂是Al/Cu复合板两种主要的失效方式.     

累积叠轧Al/Cu复合板界面反应层核-壳结构形成机制

采用累积叠轧(ARB)结合多次退火处理制备了Al/Cu复合板,重点研究了Al/Cu界面反应层核-壳结构形成机制. 结果表明:Al/Cu界面反应层的形成主要依赖于退火过程中铜原子在界面处的扩散,反应产物包括Al₂Cu、AlCu、Al₄Cu₉. 轧制变形致使反应层破碎并在基体中均匀分布,轧后退火处理导致新的反应层不断形成.最终经多次叠轧及退火处理,原始铜板材全部转变为椭球状具有核-壳结构的Al/Cu金属间化合物颗粒. 8道次复合板抗拉强度最高,达到176.8 MPa,是退火态1060抗拉强度的1.74倍;0道次复合板延伸率较好,主要是Al/Cu界面分层后铝层均匀塑性变形,应力缓慢释放所致.     

Creep behavior and dislocation mechanism of Ni3Al based single crystal alloy IC6SX at 760°C

The creep behavior and dislocation mechanism of Ni₃Al-based single crystal alloys IC6SX with crystal orientation [001] which was prepared by seed crystal method under the testing conditions of 760 ​°C/500 ​MPa,760 ​°C/540 ​MPa and 760 ​°C/580 ​MPa were investigated. The experimental results showed that the creep properties, dislocation morphology and mechanism of this alloy were different under different stress conditions. With the stress increasing from 500 ​MPa to 580 ​MPa, the creep life decreased from more than 1000h to 32.64h. The cubic degree of γ′ phase in single crystal alloy decreased obviously and the size of γ′ phase increased. The mechanism of dislocation movement also changed with the increasing stress. It was found that after the specimen was tested under the condition of 760 ​°C/500 ​MPa the dislocation network prevented the movement of dislocations and it was difficult for dislocations to enter the γ′ phase from the γ/γ′ interface. When the stress was 540 ​MPa, the dislocations cut into the γ′ phase by stacking fault. Furthermore, with the stress increasing to 580 ​MPa, the dislocation entered the γ′ phase in the form of extended dislocation and Lomer-Cottrell dislocation.     

Flexible free-standing polyaniline/poly(vinyl alcohol) composite electrode with good capacitance performance and shape memory behavior

The increasing demand for portable and flexible energy storage devices drives the development of flexible electrodes and electrolytes. The aim of this work is to fabricate the flexible free-standing polyaniline/poly (vinyl alcohol) (PANI/PVA) composite electrode with good capacitance performance and shape memory behavior. The electrodes were fabricated by chemical oxidation polymerization of aniline in porous PVA (P-PVA) films. The morphology, electrochemical and mechanical properties of PANI/P-PVA electrodes were studied by scanning electron microscope, cyclic voltammetry, galvanostatic charge-discharge, and tensile test etc. The results revealed that the flexible PANI/P-PVA-1 electrode had good specific capacitance of 173.86 ​mF ​cm⁻² at 1 ​mA ​cm⁻², with the capacitance retention of 70.16% after 4000 charge-discharge cycles. Besides, it had excellent heat-induced shape memory effect. The fixed shape could completely recover to its original shape within 10 ​s at 80 ​°C, which is above the glass transition temperature (75.89 ​°C) of PANI/P-PVA-1. The comparatively tensile strength (2.86 ​MPa) and high elongation at break (315.72%) indicated its outstanding flexibility. Up to 200 times folding had no effect on the electrochemical properties. The free-standing polymer electrodes with excellent comprehensive performance provide potential applications in flexible energy-storage devices, electronic encapsulation and high stretchable electric devices etc.     

Ameliorating mechanical properties and reducing anisotropy of as-extruded Mg-1.0Sn-0.5Ca alloy via Al addition

Effects of Al addition to a Mg–Sn–Ca ternary alloy on its microstructure and tensile properties after extrusion were studied via extrusion of Mg-1.0Sn-0.5Ca-xAl (x ​= ​0, 0.8, 2.4 ​wt%) sheets and analysis of the extruded materials. The results showed that Al addition not only refined the grain size (from 9.8 ​± ​0.7 ​μm to 8.3 ​± ​0.4 ​μm and 7.6 ​± ​0.5 ​μm) but also accelerated the generation of more second phase (from 0.98 to 1.72 and 4.32%). Except for the CaMgSn and Mg₂Ca in Mg-1.0Sn-0.5Ca alloy, new phase (Mg, Al)₂Ca appeared after Al addition. The addition of Al into Mg–Sn–Ca alloy induced the textural variation from an initially ED-split double-peaked texture to a weakened texture, i.e., divergent elliptical texture, due to the effect of particle stimulated nucleation. This eventually contributed to the improvement of mechanical anisotropy as well as the higher Hc value and n-value. For the strain hardening behavior when tension along the TD, the prolonged stage Ⅱ of Al-modified alloys was closely connected with the additional TD textural components, accelerating the activation of more basal slip. The decreased θⅢ0 in stage Ⅲ of Al-modified alloys is beneficial to the grain refinement and the emergence of more second phase.     

Effect of carbon addition on microstructure and mechanical properties of a typical hard-to-deform Ni-base superalloy

In this paper, the as-cast microstructure, microsegregation, and mechanical properties of GH4151 superalloys with a carbon addition were studied by scanner electron microscopy(SEM), transmission electron microscope(TEM), electron probe microanalysis(EPMA), differential thermal analyzer(DSC), and electron backscattered diffraction(EBSD). The results show that the solid solution effect of carbon in alloys is limited, the addition of C from 0.01 to 0.08 wt% significantly refines the secondary dendr...     

Stability of thermal cycling and high temperature mechanical properties for Ti–V–Al–B lightweight shape memory alloy

The microstructure of the Ti–V–Al shape memory alloy with refined grain and in-situ TiB phase was modified by doping minor Boron (B), which contributes to the superior mechanical performances and strain recovery characteristics. Compared with other quaternary Ti–V–Al-X alloys, the Ti–V–Al–B alloy showed the largest ultimate tensile stress due to the solution strengthening, grain refinement and precipitation strengthening of in-situ TiB phase. Moreover, the Ti–V–Al alloy added 0.1 ?at.%B possessed the maximum yield stress of 701 ?MPa and the largest tensile fracture strain of 27.6% at the temperature of 150 ?°C. Meanwhile, the excellent strain recovery characteristics with fully recoverable strain of 4% could be obtained due to B addition. Besides, B addition suppressed the precipitation of ω phase during thermal cycling and further improved the thermal cycling stability of the Ti–V–Al alloy.     

Effects of heat treatment on microstructure and mechanical properties of SLMed Sc-modified AlSi10Mg alloy

The influence of heat treatments on the microstructures and mechanical properties of the selective laser melting manufactured AlSi10Mg alloy modified with Sc was systematically investigated. The results showed that the addition of Sc element introduced primary Al₃Sc, which increased the heterogeneous nucleation during the solidification of AlSi10Mg alloy, and then the ultrafine network eutectic structure was obtained, and hence the tensile strength was improved significantly (nearly 23 ​%). During the heat treatment process, the network eutectic structure transformed from continuous to discontinuous, and the grain refinement was weakened with an increasing heating temperature, both of which affected the mechanical properties of the Sc modified AlSi10Mg alloy. The tensile strength decreased from 438 ​± ​10 ​MPa for the Sc-modified alloy to 208 ​± ​6 ​MPa, while the fracture strain significantly increased from 6 ​± ​0.2 ​% to 30.2 ​± ​1.2 ​% when the Sc-modified alloy was heat-treated at 325 ​°C for 12 ​h. It has been found that the desirable microstructure and mechanical properties of SLM Sc-modified AlSi10Mg alloy can be realized by controlling the heat treatment process parameters.     

铜铝冷轧复合薄带热处理工艺研究

利用金相显微镜和万能材料试验机,通过界面组织观察和力学性能测试,系统研究了铜/铝/铜冷轧复合薄带的热处理工艺,并讨论了热处理工艺参数对铜铝冷轧复合薄带界面组织和力学性能的影响规律.通过研究,得出如下结论:随退火温度升高或保温时间的延长,复合带强度降低,塑性增强;退火后复合带界面宽度为2～5μm,界面有脆性化合物CuAl2,CuAl和Cu9Al4生成;410℃退火,保温10 min时复合带综合性能最佳,为复合薄带的最佳热处理工艺.     

铜/铝异步轧制复合带的界面反应与强化机制

采用同步和异步轧制复合工艺制备铜/铝复合带,研究退火过程中的界面反应和异步轧制工艺的强化机制.利用扫描电镜观察界面微观组织和拉伸断口形貌,通过线扫描和电子探针分析界面元素分布,采用XRD进行界面物相分析,通过剥离和拉伸实验研究复合带的力学性能.结果表明,经400℃保温1h后界面形成具有三个亚层的扩散层组织,各亚层内元素含量存在突变;铝剥离表面检测到大量铜元素,化合物相包括CuAl₂,Cu₉Al₄,CuAl和Cu₄Al,而铜剥离表面只检测到Cu₉Al₄和Cu₄Al;异步轧制工艺可以提高界面结合强度和复合带的拉伸性能,使界面层在拉伸断裂后破坏程度降低.     

Near-microscopic grain boundary facilitates fatigue crack propagation in a polycrystalline Al–Zn–Mg–Cu alloy

In present study, grain characteristics with sizes within 10–30 μm were fabricated from a same Al–Zn–Mg–Cu alloy, FCP behaviors of the alloys with small grain(SG alloy), medium grain(MG alloy) and large grain(LG alloy)were investigated and related fatigue fracture morphology was analyzed. With the enhancement of stress intensity factor range(ΔK), the alloy with larger grains possessed faster FCP rate, which were successively arranged as SG alloy > MG alloy > LG alloy at initial stage while...     

Zr-xNb-4Sn alloys with low Young’s modulus and magnetic susceptibility for biomedical implants

The microstructure, mechanical and magnetic properties of Zr–x (8, 9, 10, wt.%)Nb–4Sn alloys were investigated to obtain novel Zr-based alloy with low Young’s modulus and magnetic susceptibility for biomedical implants. After homogenization annealing, hot forging and solution annealing, Zr–8Nb–4Sn, Zr–9Nb–4Sn and Zr–10Nb–4Sn alloys were composed of β+α″ phase, β+α″ phase, β+ω phase, respectively. The temperature at which the α" and ω phase were transformed into β phase during the heating process was about 200 ​°C, and the phase transformation temperature decreased with the increase of Nb element. Among all the Zr–x (x ​= ​8,9,10)Nb–4Sn(wt.%) alloys, Zr–9Nb–4Sn alloy had the lowest Young's modulus of 46.6 ​GPa and the low magnetic susceptibility of 1.294 ​× ​10⁻⁶ cm³g⁻¹, which has a good application prospect for biomedical applications.     

Bulk Al-Al3Zr composite prepared by mechanical alloying and hot extrusion for high-temperature applications

Bulk Al/Al₃Zr composite was prepared by a combination of mechanical alloying (MA) and hot extrusion processes. Elemental Al and Zr powders were milled for up to 10 h and heat treated at 600℃ for 1 h to form stable Al₃Zr. The prepared Al₃Zr powder was then mixed with the pure Al powder to produce an Al-Al₃Zr composite. The composite powder was finally consolidated by hot extrusion at 550℃. The mechanical properties of consolidated samples were evaluated by hardness and tension tests at room and elevated temperatures. The results show that annealing of the 10-h-milled powder at 600℃ for 1 h led to the formation of a stable Al₃Zr phase. Differential scanning calorimetry (DSC) results confirmed that the formation of Al₃Zr began with the nucleation of a metastable phase, which subsequently transformed to the stable tetragonal Al₃Zr structure. The tension yield strength of the Al-10wt%Al₃Zr composite was determined to be 103 MPa, which is approximately twice that for pure Al (53 MPa). The yield stress of the Al/Al₃Zr composite at 300℃ is just 10% lower than that at room temperature, which demonstrates the strong potential for the prepared composite to be used in high-temperature structural applications.     

Synthesis of amorphous SeP2/C composite by plasma assisted ball milling for high-performance anode materials of lithium and sodium-ion batteries

To promote substantially the performances of red phosphorous (P) anode for lithium and sodium-ion batteries, a simple plasma assisted milling (P-milling) method was used to in-situ synthesize SeP₂/C composite. The results showed that the amorphous SeP₂/C composite exhibits the excellent lithium and sodium storage performances duo to the small nano-granules size and complete combination of selenium (Se) and phosphorous (P) to generate Se–P alloy phase. It was observed that inside the granules of SeP₂/C composite the nanometer size of the SeP₂ particles ensured the fast kinetics for Li⁺ and Na⁺ ​transfer, and the amorphous carbon wrapping the SeP₂ particles relieved volume expansion during lithium/sodium storage processes and enhances electric conductivity. Therefore, the SeP₂/C electrode retained reversible capacities of 700 ​mA ​h ​g⁻¹ at 2 ​A ​g⁻¹ after 500 cycles and 400 ​mA ​h ​g⁻¹ at 0.5 ​A ​g⁻¹ after 400 cycles as anode for LIBs and SIBs, respectively. The result proves that the amorphous SeP₂/C composite can be a new type of anode material with great potential for lithium and sodium-ion batteries.     

Mechanisms of two-stage martensitic transformation in Ti-Ni-Hf alloy powder

The Ti-Ni-Hf shape memory alloy powders were prepared by plasma rotating electrode process. And the powders were featured with the perfect sphericity and smooth surface. Moreover, the grain size was refined in the Ti-Ni-Hf alloy powders due to the rapid cooling rate during plasma rotating electrode process. It was found that the Ti-Ni-Hf alloy powders had the typical self-accommodation configuration including spear-like, mosaic-like and lath-like martensite. Various twins, such as (001) compound twin, (011) type I twin as well as {111} type I twin, were observed in Ti-Ni-Hf alloy powders. Differing from the bulk Ti-Ni-Hf alloy, two-stage transformation corresponding to B2⇌B19’ martensitic transformation was detected in the as-received Ti-Ni-Hf alloy powders. In addition, the martensitic transformation behaviors were closely related to the annealing temperatures. The Ti-Ni-Hf alloy powders with low annealing temperature of 500 ​°C still exhibited two-stage martensitic transformation, while two-stage martensitic transformation changed into single martensitic transformation in the Ti-Ni-Hf alloy powders with the higher annealing temperature of 900 ​°C. And finally the possible mechanisms for the evolution of martensitic transformation behaviors were discussed.     

Microstructure and elevated-temperature mechanical properties of dispersoid-strengthened Al-Mg-Si-Mn alloys produced by twin roll casting

The microstructure and elevated-temperature mechanical properties of dispersoid-strengthened Al-Mg-Si-Mn alloys produced by twin roll casting (TRC) and conventional mold casting (MC) were studied. A specific heat treatment at 430 ​°C for 6 ​h was applied, followed by rolling. Tensile tests were carried out at 300 ​°C. The results show that in the as-cast microstructures, equiaxed grains formed in the MC sample while elongated grains with substructures formed in the TRC sample. The eutectics in the TRC sample were much finer than those in the MC sample. Upon heat treatment, large numbers of α-Al(Fe, Mn)Si dispersoids precipitated, and the TRC sample had a greater number density of dispersoids than those in the MC sample. During the tensile test after rolling, the TRC samples exhibited higher strength than the MC samples, which resulted from the combination of the strengthening effect of the stronger dispersoids and the greater substructure hardening effect in the TRC sample; the TRC sample exhibited better ductility due to its finer initial eutectic than that in the MC sample, which depressed the stress concentration and delayed the occurrence of microcracks and fracture in the TRC sample.     

Bulk Al–Al3Zr composite prepared by mechanical alloying and hot extrusion for high-temperature applications

Bulk Al/Al3Zr composite was prepared by a combination of mechanical alloying (MA) and hot extrusion processes. Elemental Al and Zr powders were milled for up to 10 h and heat treated at 600°C for 1 h to form stable Al3Zr. The prepared Al3Zr powder was then mixed with the pure Al powder to produce an Al–Al3Zr composite. The composite powder was finally consolidated by hot extrusion at 550°C. The mechanical properties of consolidated samples were evaluated by hardness and tension tests at room and elevated temperatures. The results show that annealing of the 10-h-milled powder at 600°C for 1 h led to the formation of a stable Al3Zr phase. Differential scanning calorime-try (DSC) results confirmed that the formation of Al3Zr began with the nucleation of a metastable phase, which subsequently transformed to the stable tetragonal Al3Zr structure. The tension yield strength of the Al?10wt%Al3Zr composite was determined to be 103 MPa, which is approximately twice that for pure Al (53 MPa). The yield stress of the Al/Al3Zr composite at 300°C is just 10% lower than that at room tem-perature, which demonstrates the strong potential for the prepared composite to be used in high-temperature structural applications.     

Sintering mechanism of Cu-9Al alloy prepared from elemental powders

The sintering behavior of Cu-9Al alloys prepared from die pressing of elemental powders was investigated. The experimental results and kinetic analysis showed the formation of three consecutive layers of Al₂Cu, Al₄Cu₉, and AlCu phases, with Al₂Cu appearing first in the initial solid phase sintering stage. A liquid phase formed in the intermediate stage, resulting from the eutectic reaction between Al and Al₂Cu phases at 500 °C, which is 47 °C lower than the equilibrium reaction temperature. Swelling occurred when the liquid phase infiltrated the gaps between the copper particles, leaving pores at the original sites of Al particles and Al₂Cu. In the final stage of sintering, the Al-rich phases (Al₂Cu and AlCu) transformed to Al-poor phases (Al₄Cu₉ and α-Cu) in the temperature range of 500–565 °C. Al₄Cu₉ and α-Cu then transformed to AlCu₃ (β) above the eutectoid reaction temperature (565 °C), whereas AlCu₃ transformed to α-Cu and eutectoid phases (α-Cu + Al₄Cu₉) during cooling. The pure copper transformed to AlCu₃, and the pore volume decreased at 1000 °C. The microstructure study helps manipulate precisely the sintering process of Cu-Al alloys and optimize the microstructure with a high dimensional accuracy.     

Corrosion resistance and thermal stability of sputtered Fe44Al34Ti7N15 and Al61Ti11N28 thin films for prospective application in oil and gas industry

Fe-and Al-based thin-film metallic glass coatings (Fe₄₄Al₃₄Ti₇N₁₅ and Al₆₁Ti₁₁N₂₈) were fabricated using magnetron co-sputtering technique, and their corrosion performances compared against wrought 316L stainless steel. The results of GI-XRD and XPS analyses demonstrated amorphous structure and oxide layer formation on the surface of the fabricated thin films, respectively. The potentiodynamic (PD) polarization test in chloride-thiosulfate (NH₄Cl ​+ ​Na₂S₂O₃) solution revealed lower corrosion current (I_corr) (0.42 ​± ​0.02 ​μA/cm² and 0.086 ​± ​0.001 ​μA/cm² Vs. 0.76 ​± ​0.05 ​μA/cm²), lower passivation current (I_pass) (1.45 ​± ​0.03 ​μA/cm² and 1.83 ​± ​0.07 ​μA/cm² Vs. 1.98 ​± ​0.04 ​μA/cm²), and approximately six-fold higher breakdown potential (E_bd) for Fe- and Al-based coatings than those of wrought 316L stainless steel. Electrochemical Impedance Spectroscopy (EIS) of both films showed 4- and 2-fold higher charge transfer resistance (R_ct), 7- and 2.5-times higher film resistance (R_f), lower film capacitance values (Q_f) (10 ​± ​2.4 ​μS-s^acm^-2, and 5.41 ​± ​0.8 ​μS-s^acm^-2 Vs. 18 ​± ​2.21 ​μS-s^acm^-2), and lower double-layer capacitance values (Q_dl) (31.33 ​± ​4.74 ​μS-s^acm^-2, and 15.3 ​± ​0.48 ​μS-s^acm^-2 Vs. 43 ​± ​4.23 ​μS-s^acm^-2), indicating higher corrosion resistance of the thin films. Cyclic Voltammetry (CV) scan exhibited that the passive films formed on the Fe- and Al-based coatings were more stable and less prone to pitting corrosion than the wrought 316L stainless steel. The surface morphology of both films via SEM endorsed the CV scan results, showing better resistance to pitting corrosion. Furthermore, the thermal analysis via TGA and DSC revealed the excellent thermal stability of the thin films over a wide temperature range typically observed in oil-gas industries.     

Al,Zr dual-doped cobalt-free nickel-rich cathode materials for lithium-ion batteries

Nickel-rich and cobalt-free cathode materials have obvious advantages in the aspects of energy density and economic efficiency. However, these materials are restricted from being used in commercial lithium-ion batteries due to the problems of poor structural stability and rate capability. In this study, the aluminum and zirconium dual-doped Co-free Ni-rich LiNi_0.96Mn_0.04O₂cathode material(NMAZ) is prepared by a facile high-temperature solid-phase method. The obta...