金属纤维多孔材料力学性能研究现状

详细论述了金属纤维多孔材料的拉伸性能、剪切性能、压缩性能和冲击性能等力学性能的研究进展,并简要叙述了应力波在多孔材料内部传播的研究现状,最后指出未来应加强金属纤维多孔材料的动态冲击性能及应力波在多孔材料内部的传播、衰减机制研究,从而进一步扩大金属纤维多孔材料的应用领域。     

Microstructure and mechanical properties of porous yttria stabilized zirconia ceramic using poly methyl methacrylate powder

Porous t-ZrO₂ ceramic was fabricated by pressureless sintering, using commercial t-ZrO₂ and different volume percentages of poly methyl methacrylate (PMMA) powders (20–80%). The spherical pores ranged from about 120 to 170 μm in diameter. By increasing the PMMA content, the number of pores, material properties and pore morphology were changed dramatically. The values of relative density, elastic modulus, bending strength and hardness of the 60 vol.% PMMA content sample, sintered at 1550 °C, were about 43%, 40 GPa, 170 MPa and 248 Hv, respectively.     

Syntheses and mechanical properties of Cr-Mo-N coatings by a hybrid coating system

Effects of Mo content up to 30.4 at.% on the microstructure and mechanical properties of CrN coatings are reported in this study. Ternary Cr-Mo-N coatings were deposited onto steel substrates (AISI D2) using a hybrid coating method of arc ion plating (AIP) using Cr target and DC magnetron sputtering technique using Mo target in N₂/Ar gaseous mixture. The synthesized Cr-Mo-N coatings formed a substitutional solid solution of (Cr,Mo)N where larger Mo atoms replaced Cr in CrN crystal. The Cr-Mo-N coatings showed increased hardness value of approximately 34 GPa at 21 at.% Mo, compared with 18 GPa for pure CrN. The friction coefficient decreased from 0.49 for pure CrN coating to 0.37 for Cr-Mo-N with 30.4 at.% Mo. This result is believed to be due to tribo-layer formation of MoO₃ which is known to function as a solid lubricant.     

Syntheses and mechanical properties of Mo-Si-N coatings by a hybrid coating system

In this work, comparative studies on microstructure and mechanical properties between Mo₂N and Mo-Si-N coatings were conducted. Ternary Mo-Si-N coatings were deposited on steel substrates (AISI D2) and Si wafers by a hybrid method, where arc ion plating (AIP) technique was combined with a magnetron sputtering technique. Instrumental analyses of X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS) revealed that the Mo-Si-N coatings must be a composite consisting of fine Mo₂N crystallites and amorphous Si₃N₄. The hardness value of Mo-Si-N coatings significantly increased from 22 GPa of Mo₂N coatings to about 37 GPa with Si content of 10 at.% due to the refinement of Mo₂N crystallites and the composite microstructure characteristics. The average friction coefficient of the Mo-Si-N coatings gradually decreased from 0.65 to 0.4 with increasing Si content up to 15 at.%. The effects of Si content on microstructure and mechanical properties of Mo-N coatings were systematically investigated.     

Zr基非晶合金多孔材料的制备与性能

采用液态金属渗流法制备直径为6 mm 的Zr基块体多孔非晶合金,采用扫描电镜(SEM)和X射线衍射仪(XRD)分析多孔材料的结构、形貌、断口特征和相组成,同时对多孔非晶合金的孔隙结构和力学特点进行分析.结果表明:采用CaC2作为孔隙支撑材料,能够制备出孔隙分布均匀、孔隙直径为0.2～0.8 mm的多孔非晶合金,其密度和孔隙率分别为3.57 g/cm3和47%.压缩力学性能实验表明:该多孔非晶合金的应力-应变曲线具有锯齿状变化规律,应力逐渐降低,其最大强度和应变分别为383 MPa和18.6%,应变量远大于单相非晶合金的应变量.     

Optimization of mechanical properties of recycled plastic products via optimal processing parameters using the Taguchi method

The large amount of plastic products presently produced necessitates recycling and reuse of these non-biodegradable materials. However, the degradation in the mechanical properties of products made from recycled plastic is a major drawback that limits their use. This study aims to improve the mechanical properties of products made from recycled plastic by utilizing the Taguchi optimization method, instead of coupling the products with additives. By adopting L₉ Taguchi OA, products made from various compositions of virgin and recycled plastic are produced by injection moulding. Four controllable factors (i.e., melt temperature, packing pressure, injection time, and packing time), each at three levels, are tested to determine the optimal combination of factors and levels in the manufacturing process. By determining the optimal combination of factors and levels, the appropriate blending ratio of virgin and recycled plastic can be evaluated from the mechanical performance exhibited by the compound. The effects of the optimal processing parameters and the addition of recycled plastic in various compositions on the mechanical properties and melt flow index of the produced parts are also investigated. The results reveal that the product made of 25% recycled polypropylene (PP) and 75% virgin PP exhibits a better flexural modulus compared to the virgin form. The same product exhibits a 3.4% decrease in flexural strength. The degradation in mechanical properties of products produced from recycled plastic can be improved by optimizing the influence processing parameters during the manufacturing process.     

Processing and mechanical properties of porous silica-bonded silicon carbide ceramics

A simple processing route for manufacturing highly porous, silica-bonded SiC ceramics with spherical pores has been developed. The strategy adopted for making porous silica-bonded SiC ceramics entails the following steps: (i) fabricating a formed body through a combination of SiC and polymer microbeads (employed as sacrificial templates) and (ii) sintering the formed body in air. SiC particles are bonded to each other by oxidation-derived SiO₂ glass. By controlling the microbead content and the sintering temperature, it was possible to adjust the porosity such that it ranged from 19 to 77%. The flexural and compressive strengths of the porous silica-bonded SiC ceramics with ≈40% porosity were ≈65 MPa and ≈200 MPa, respectively. The superior strengths were attributed to the homogeneous distribution of small (≤30 μm), spherical pores with dense struts in the porous silica-bonded SiC ceramics.     

Porosity and mechanical properties of porous titanium fabricated by gelcasting

Porous Ti compacts with large size and complex shape for biomedical applications were fabricated in the porosity range from 40.5% to 53.8% by controlling gelcasting parameters and sintering conditions. The experimental results show that the total porosity and open porosity of porous titanium compacts gelcast from the Ti slurry with 34 vol.% solid loading and sintered at 1100℃ for 1.5 h are 46.5% and 40.7%, respectively, and the mechanical properties are as follows： compressive strength 158.6 MPa and Young＇s modulus 8.5 GPa, which are similar to those of human cortical bone and appropriate for implanting purpose.     

Microstructure and mechanical properties of porous Ti3SiC2

A ≈43 vol.% porous Ti₃SiC₂ ternary compound was fabricated by the reactive sintering of elemental powders. Under cyclic compression, the first loading cycle resulted in a measurable deformation, but subsequent cycles to the same load resulted in fully reversible, closed hysteresis loops that were smaller in area than the first loop. Cyclic nanoindentation loadings on solid bridges separating pores displayed behavior that was qualitatively similar to the uniaxial compression testing results. The results are interpreted in light of our kink band formation model. The significantly larger areas associated with the porous material than the fully dense sample with comparable grain size are ascribed to the formation of more incipient and regular kink bands as a consequence of the lack of constraint due to the presence of pores. The technological implications of having a porous material that dissipates more energy – on an absolute scale – than its fully dense counterpart are discussed.     

Binder influence on the structural and mechanical properties of porous silicate ceramics

The influence of aluminum- and silicon-based binders on the structural and mechanical properties of porous silicate ceramics constructed from powdery structural elements was studied. Data from x-ray powder diffraction analysis, differential thermal analysis, IR spectroscopy, and scanning electron microscopy allowed to propose a structuration mechanism during high-temperature treatment of ceramic samples composed of crystalline silica and an aluminosilicate binder.     

Optimization of friction welding of tube to tube plate using an external tool by hybrid approach

Several developments have been observed in the field of materials processing and welding is a vital metal joining process that has potential industrial applications. Friction welding of tube to tube plate using an external tool (FWTPET) is a relatively newer solid state welding process used for joining tube to tube plate of either similar or dissimilar materials with enhanced mechanical and metallurgical properties. Generally, welding is a multi-input and multi-output process in which there exists a close relationship between the quality of joints and the welding parameters. In the present study, Artificial Neural Network (ANN) has been used to predict the strength behavior of FWTPET process. Several Neural Network architectures have been subjected to analysis and the optimal architecture has been determined. The optimal architecture has been used to predict the output process parameter. The predicted output and input parameters have been optimized using Genetic Algorithm (GA). GA optimized and experimentally determined process parameters were compared and the deviation is found to be minimal. Besides, the most influential process parameter has been determined using statistical analysis of variance (ANOVA).     

Effects of porosity on tensile mechanical properties of porous FeAl intermetallics

Uniaxial tensile tests and scanning electron microscopy (SEM) experiments were carried out on the porous FeAl intermetallics (porosities of 41.1%, 44.2% and 49.3%, pore size of 15–30 μm) prepared by our research group to study the macroscopic mechanical properties and microscopic failure mechanism. The results show that the tensile σ–ɛ curves of the porous FeAl with different porosities can be divided into four stages: elasticity, yielding, strengthening and failure, without necking phenomenon. The elastic modulus, ultimate strength and elongation decrease with the increase of porosity and the elongation is much lower than 5%. A macroscopic brittle fracture appears, and the microscopic fracture mechanism is mainly intergranular fracture, depending on the Al content in the dense FeAl intermetallics. In addition, the stochastic porous model (SPM) with random pore structure size and distribution is established by designing a self-compiling generation program in FORTRAN language. Combined with the secondary development platform of finite element software ANSYS, the effective elastic moduli of the porous FeAl can be determined by elastic analysis of SPM and they are close to the experimental values, which can verify the validity of the established SPM for analyzing the elastic properties of the porous material.     

烧结颈对多孔钛压缩力学性能的影响(英文)

为了研究烧结颈在螺旋孔隙多孔钛中所起的作用,利用数值模拟的方法对烧结颈尺寸和烧结颈位置对多孔钛单胞压缩力学性能的影响进行研究。结果表明:多孔钛单胞的压缩力学性能由单胞的螺旋孔隙结构和烧结颈决定,烧结颈的贡献系数约是螺旋孔结构贡献系数的3.5倍;随着相对烧结颈尺寸的增加,多孔钛单胞的压缩屈服强度和弹性模量增加;单胞中C1烧结点是最重要的烧结位置;在相同条件下,增加C1处的烧结颈尺寸对压缩性能的提高更有效。     

Optimization of the strain rate to achieve exceptional mechanical properties of 304 stainless steel using high speed ultrasonic surface mechanical attrition treatment

Surface mechanical attrition treatment (SMAT), an efficient way to create nanostructured surface/subsurface layers, has been extensively exploited in the last decade. However, the impact velocity of the balls in the treatment has not yet been measured in detail. The motivation of the present paper was to investigate the ball velocity and the effect of the number of balls on the resulting mechanical properties and the associated microstructures. Employing a high-speed camera, the maximum impact velocities of balls were quantified. This velocity is affected by the density and size of the ball. In the present paper an optimum number of balls for SMAT was also identified. With a detailed knowledge of the ball velocity we were able to accurately estimate the strain rate at different depths by analytical modeling and to study the correlation between the resulting microstructures and the strain/strain rate history of the material.     

Pore structure and mechanical properties of directionally solidi ed porous aluminum alloys简

Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen,and to carry over melt to a tailor-made apparatus that ensures directional solidification.Hydrogen is driven out of the melt,and then the quasi-cylindrical pores normal to the solidification front are usually formed.In the research,the effects of processing parameters （saturation pressure,solidification pressure,temperature,and holding time） on the pore structure and porosity of porous aluminum alloys were analyzed.The mechanical properties of Al-Mg alloys were studied by the compressive tests,and the advantages of the porous structure were indicated.By using the GASAR method,pure aluminum,Al-3wt.％Mg,Al-6wt.％Mg and Al-35wt.％Mg alloys with oriented pores have been successfully produced under processing conditions of varying gas pressure,and the relationship between the final pore structure and the solidification pressure,as well as the influences of Mg quantity on the pore size,porosity and mechanical properties of AlMg alloy were investigated.The results show that a higher pressure of solidification tends to yield smaller pores in aluminum and its alloys.In the case of Al-Mg alloys,it was proved that with the increasing of Mg amount,the mechanical properties of the alloys sharply deteriorate.However,since Al-3％Mg and Al-6wt.％Mg alloys are ductile metals,their porous samples have greater compressive strength than that of the dense samples due to the existence of pores.It gives the opportunity to use them in industry at the same conditions as dense alloys with savings in weight and material consumption.     

6005铝合金中厚板等离子-MIG复合焊接头组织与力学性能

采用等离子-MIG复合焊工艺对16 mm厚6005铝合金进行双面焊接,研究焊接接头的显微组织和力学性能。结果表明,焊缝区为等轴树枝晶,熔合线附近为柱状晶组织,热影响区相比母材组织粗化;接头各区显微硬度值均低于母材;接头的侧弯试验可达180°;抗拉强度201 MPa,为母材强度的77.31%,断裂位置在热影响区内。     

Optimization of electrical discharge machining process parameters for Al6061/cenosphere composite using grey-based hybrid approach

Fly ash has congregated considerable attention as a potential reinforcement for aluminum matrix composites (AMCs) to enhance selective properties and reduce the cost of fabrication. However, poor machinability of such AMCs limits their application. The present study focuses on the preparation of cenosphere fly ash reinforced Al6061 alloys by compo casting method. X-ray diffraction analysis of the prepared AMCs exposes the presence of cenosphere particles without any formation of other intermetallic compounds. In this study, electrical discharge machining (EDM) was engaged to examine the machinability of the prepared metal matrix composite (MMCs). The measured performance characteristics for the various combinations of input process parameters were considered to be MRR, EWR and SR. Face centered central composite design (CCD) of response surface method (RSM) was employed to design the number of experimental trials required and a hybrid approach of grey-based response surface methodology (GRSM) was imposed for predicting the optimal combination of processing parameter in EDM process. Generous improvement was observed in the performance characteristics obtained by employing both the optimal setting of machining parameters. The optical 3D surface profile graphs of the ED machined surface also revealed the improvement in surface quality and texture employing the optimal processing conditions proposed by hybrid GRSM approach.     

混合铝基复合材料的力学性能和耐磨性

混合金属基复合材料是重要的工程材料,因为他们比纯铝具有更低的密度、更高的比强度和更好的物理力学性能而广泛应用于汽车、航空航天等方面。研究了混合铝金属基复合材料的力学性能和磨损性能。通过搅拌铸造将云母和SiC颗粒加入到Al 356合金中。采用扫描电子显微镜(SEM)研究样品的显微组织,用能谱分析(EDX)其化学成分。结果表明,所制备的Al/10SiC?3云母复合材料具有较好的强度和硬度。增加复合材料中云母含量能提高复合材料的耐磨性。     

Pore structure and mechanical properties of directionally solidi ed porous aluminum alloys

Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen, and to carry over melt to a tailor-made apparatus that ensures directional solidif ication. Hydrogen is driven out of the melt, and then the quasi-cylindrical pores normal to the solidif ication front are usually formed. In the research, the effects of processing parameters(saturation pressure, solidif ication pressure, temperature, and holding time) on the pore structure and porosity of porous aluminum alloys were analyzed. The mechanical properties of Al-Mg alloys were studied by the compressive tests, and the advantages of the porous structure were indicated. By using the GASAR method, pure aluminum, Al-3wt.%Mg, Al-6wt.%Mg and Al-35wt.%Mg alloys with oriented pores have been successfully produced under processing conditions of varying gas pressure, and the relationship between the f inal pore structure and the solidif ication pressure, as well as the inf luences of Mg quantity on the pore size, porosity and mechanical properties of AlMg alloy were investigated. The results show that a higher pressure of solidif ication tends to yield smaller pores in aluminum and its alloys. In the case of Al-Mg alloys, it was proved that with the increasing of Mg amount, the mechanical properties of the alloys sharply deteriorate. However, since Al-3%Mg and Al-6wt.%Mg alloys are ductile metals, their porous samples have greater compressive strength than that of the dense samples due to the existence of pores. It gives the opportunity to use them in industry at the same conditions as dense alloys with savings in weight and material consumption.