镁-镍基纳米/非晶储氢材料的研究进展及发展趋势

从制备方法、改性处理、性能研究方法等方面介绍了镁-镍基纳米/非晶储氢材料近年来的研究进展,并对其发展趋势及今后研完方向进行了探讨.     

Toward a Quantitative Understanding of the Mechanical Alloying Process

The mechanical alloying behavior of transition metal-based mixtures and the amorphization of equilibrium intermetallic compounds by milling were characterized on a quantitative basis as a function of the processing parameters. Different kinetic mechanisms rule the two processes. The former giving rise to a sigmoidal-shaped trend, while the latter is characterized by a continuous, gradual decrease of the conversion rate. It was found that the extent of the microstructure refinement determines the overall transformation rates and that the mechanical energy dose required to transform a given amount of the parent phases is a characteristic invariant quantity of the system undergoing amorphization. The atom fluxes at the impact, the sublayer distance affected, and the dimension of the amorphous domains formed were also determined. The emerged framework supports the view that diffusive phenomena and chemical driving forces play a minor role in the mechanical alloying processes. Conversely, the thermodynamic qualities of the reacting systems and the enthalpy gain remain the main factors in mechanically induced combustion reactions, provided a critical dispersion of the reactants is reached under milling.     

热喷涂纳米粉体材料及其涂层制备

介绍了国外喷涂用纳米结构喂料的制备方法，以及采用几种先进的热喷涂技术制备的纳米结构涂层，并指出非晶/纳米晶涂层是该领域研究的重中之重。与传统喷涂层相比，纳米结构涂层在耐磨、防腐性能方面呈现出优异性能和良好的发展前景。     

金属纳米块体材料制备加工技术和应用

综述了国内外块状纳米材料的制备技术进展及存在的问题 ,提出了超短时脉冲电流直接晶化法和深过冷直接晶化法两类潜在的块状金属纳米晶制备技术 ,并对今后的研究及发展前景进行了展望。同时对大块纳米材料的性能特点及应用前景做了展望     

Controlling the length scale and distribution of the ductile phase in metallic glass composites through friction stir processing

We demonstrate the refinement and uniform distribution of the crystalline dendritic phase by friction stir processing (FSP) of titanium based in situ ductile-phase reinforced metallic glass composite. The average size of the dendrites was reduced by almost a factor of five (from 24 μm to 5 μm) for the highest tool rotational speed of 900 rpm. The large inter-connected dendrites become more fragmented with increased circularity after processing. The changes in thermal characteristics were measured by differential scanning calorimetry. The reduction in crystallization enthalpy after processing suggests partial devitrification due to the high strain plastic deformation. FSP resulted in increased hardness and modulus for both the amorphous matrix and the crystalline phase. This is explained by interaction of shear bands in amorphous matrix with the strain-hardened dendritic phase. Our approach offers a new strategy for microstructural design in metallic glass composites.     

Electron microscopy of metastable phases in rapidly solidified Al-Co alloys

Four binary Al-Co alloys containing 2·4, 14, 20 and 25 at.% Co and a ternary Al-Co-Si alloy with 20 at.% Co and 5 at.% Si were rapidly solidified from the liquid state by melt spinning. It has been shown that the solid solubility of Co in Al can be increased up to at least 1·7at.% from the negligible value under equilibrium conditions. Two metastable crystalline intermediate phases and a D1 _a -type ordered phase were observed in localized regions in the rapidly solidified Al-2·4at.%Co alloy. A quasicrystalline decagonal phase has been observed in all the other rapidly solidified alloys. This decagonal phase was shown to contain dislocations, dislocation loops and also twin-like defects. The phenomenon of polytypism was also observed in this decagonal quasicrystalline phase. In extremely thin areas of the Al-14at.% Co alloy ribbons on amorphous phase was detected. Transmission electron microscopy was used to extensively characterize the phases in the as-solidified condition and also those produced during and after transformation to the equilibrium constitution. Work carried out when both the authors were in the Department of Metallurgical Engineering, Banaras Hindu University, Varanasi 221 005, India     

现代椅子设计中材料工艺的嬗变

以现代椅子设计的发展为线索,讨论木材、金属、塑料、复合材料等工业化材料及其工艺运用于椅子设计制造的过程与变迁,并结合工业设计发端以来各阶段的典型案例,分析每一个历史时期特定的材料工艺得以规模应用的原因,论述了在现代椅子设计和材料工艺之间,存在显性关联的历史线索,并指出当前材料工艺以加速度多方向发展,椅子设计也同样呈现明显的多元化趋势。     

纺织纤维材料在包装装潢设计中的创新应用分析

随着包装装潢设计领域不断发展,人们对设计的需求观念发生转变,呈现多样化。人们环保意识逐渐提升,这就要求在具体包装装潢设计中融入生态环保的理念。纺织纤维材料是环保材料,将其科学运用在包装装潢设计中比较重要。基于此,文章主要针对包装装潢设计中纺织纤维材料特点和类型进行阐述,然后就纺织纤维材料在包装装潢设计中应用和创新详细探究,只有融入创新的设计理念,才能保障包装装潢设计质量。     

Advances in Rational Design and Materials of High‐Performance Stretchable Electromechanical Sensors

Stretchable and wearable sensor technology has attracted significant interests and created high technological impact on portable healthcare and smart human–machine interfaces. Wearable electromechanical systems are an important part of this technology that has recently witnessed tremendous progress toward high‐performance devices for commercialization. Over the past few years, great attention has been paid to simultaneously enhance the sensitivity and stretchability of the electromechanical sensors toward high sensitivity, ultra‐stretchability, low power consumption or self‐power functionalities, miniaturisation as well as simplicity in design and fabrication. This work presents state‐of‐the‐art advanced materials and rational designs of electromechanical sensors for wearable applications. Advances in various sensing concepts and structural designs for intrinsic stretchable conductive materials as well as advanced rational platforms are discussed. In addition, the practical applications and challenges in the development of stretchable electromechanical sensors are briefly mentioned and highlighted.     

Microstructural and mechanical characterisation of ODS ferritic alloys produced by mechanical alloying and spark plasma sintering

Abstract

Powders with nominal composition Fe–14Cr–2W–0·4Ti were mechanically alloyed (MA) with Y₂O₃ in a planetary ball mill at two different rotational speeds. Consolidation of the as milled powders was performed by spark plasma sintering (SPS). As milled powders showed a highly deformed microstructure with elongated nanometre grains and, depending upon the rotational speed, different stages of the nanocluster evolution were observed to be produced. In the case of consolidated materials, grain growth occurred during the SPS process and it was possible to observe the influence of the MA parameters, with larger and more homogeneously distributed grains at the higher rotational speed. Additionally, Ti was observed to be incorporated to the nanoclusters after SPS, indicating a further step in their evolution during consolidation. The mechanical behaviour of the SPS compacts was evaluated by tensile and small punch testing also showing the influence of the MA parameters in the material behaviour.     

外科植入物用新型医用钛合金材料设计、开发与应用现状及进展

介绍了生物医用钛合金材料的定义、分类与基本特性,综述了国内外生物医用钛合金材料的发展历程,针对改善和提高医用钛合金材料的生物相容性和力学相容性问题,重点分析和讨论了医用钛合金在合金设计、显微组织和相变控制以及表面状态优化等方面存在的不足和未来研究方向,最后介绍了新型介稳定β型钛合金在设计、开发与应用方面的最新进展。     

Laser Gas Nitriding of Ti-6Al-4V Part 1: Optimization of the Process

A multi-variable test method, known as the Orthogonal Array, was used to optimize the parameters for the laser gas nitriding process (LGNP) to avoid surface cracking. Based on the fundamental requirement of a crack-free condition, the processing parameters were further optimized to improve the surface finish and to obtain a reasonable hardened depth. The effects of processing parameters have also been investigated with respect to the characteristics of the laser nitrided layer. Two types of lasers, i.e., CO₂ and Nd:YAG lasers were used. The CO₂ laser was operated in both the continuous as well as the pulse mode, while the Nd:YAG laser was used only in the pulse mode. A Nd:YAG laser in the pulse mode provided a better surface finish and lower cracking severity.     

Functionally Graded AA7075 Components Produced via Hot Stamping: A Novel Process Design Inspired from Analysis of Microstructure and Mechanical Properties

Herein, functionally graded AA7075 components manufactured via hot stamping are investigated by focusing on the effect of different process variables on localized microstructure evolution. To realize gradation through stamping, an active tool is designed and applied. The design of experiments allows to assess the impact of transfer time from the furnace to the tool, quenching time in the tool, and final quenching media. Related characteristics of mechanical properties throughout the hat-shaped profile are assessed via hardness and tensile tests. As expected, the sections of the samples formed in the cooled part of the tool are characterized by higher mechanical strength following subsequent aging, while sections formed in the heated part exhibit higher ductility. Moreover, the microstructural analysis reveals that fine precipitates with minimum interparticle distances only form in the cooled section of the samples. Increasing the tool temperature at the heated side to 350 °C results in the formation of coarse precipitates in the grain interior and along the grain boundaries. A sharp gradient in terms of microstructural and mechanical properties is found between these conditions. After reducing the transfer time, an increased volume fraction of fine precipitates leads to further improvements in hardness and mechanical strengths.     

Synthesis,structure, and mechanical response of Cr0.26Fe0.24Al0.5 and Cr0.15Fe0.14Al0.30Cu0.13Si0.28 nanocrystallite entropy alloys

The present research work has concentrated to synthesize nanocrystalline (NC) Cr_0.26Fe_0.24Al_0.5 (medium entropy alloy, 3E-MEA) and Cr_0.15Fe_0.14Al_0.30Cu_0.13Si_0.28 (high-entropy alloy, 5E-HEA) non-equiatomic (equal weight fraction) alloys through mechanical alloying (MA); which studied the influence of entropy effect on structural properties, microstructural characterization, and mechanical behaviour. Further, the same non-equiatomic ratio of two coarse grain alloys (CGAs) was manufactured by conventional powder metallurgy (PM) route (blending method, 3E-CGA, 5E-CGA) for comparison. All synthesized powders were hot-pressed (HPed) at 723 k for 30 min subsequently mechanical properties in terms of compressive stress-strain and hardness were examined. The samples of as-milled powders, HPed, and fractured were investigated using X-ray diffraction (XRD) and advanced electron microscopes. The HPed sample of 3E-MEA of Cr_0.26Fe_0.24Al_0.5 produced 94% BCC and 6% FCC crystal structures due to more dissolution of Al atoms in the stronger bonding atoms of Cr-Fe lattice. Whereas 5E-HEA of Cr_0.15Fe_0.14Al_0.30Cu_0.13Si_0.28 sample has exhibited 72.1% FCC phase and 27.9% BCC phase due to balance between the dissolution of FCC elements (Al, Cu, Si) and BCC elements (Cr, Fe). Further, 3E-MEA and 5E-HEA have exhibited the ultimate compressive strength (UCS) of 1278 ± 6.75 MPa and 2060 ± 2.8 MPa respectively whereas the corresponding conventionally blended alloys produced 268 ± 5 MPa and 615 ± 3 MPa for 3E-CGA and 6E-CGA respectively. Vicker’s hardness strength (VHS) of 5E-HEA of Cr_0.15Fe_0.14Al_0.30Cu_0.13Si_0.28 has exhibited 68% more when compared to 3E-MEA of Cr_0.26Fe_0.24Al_0.5, 3.26 times higher compared to blended alloys. Further, several strengthening mechanisms on the mechanical behaviour of MEA and HEA were investigated in which dislocation strengthening mechanisms followed by solid solution strengthening mechanisms have influenced more as compared to grain boundary strengthening mechanisms.