Microstructure characteristics and mechanical properties of Al/Mg joints manufactured by magnetic pulse welding

The effective connection of 1050 Al and AZ31 Mg was realized by magnetic pulse welding.The maximum tensile-shear force of the dissimilar Al/Mg metal lap joint reached 97%of that of the 1050 Al alloy base material by optimizing the process parameters.The microstructure of dissimilar Al/Mg welded joints was analysed by Scanning Electron Microscope(SEM),Energy Dispersive Spectrometer(EDS)and Electron Backscattered Diffraction(EBSD).The results show that the key to obtaining high shear strength of Al/Mg dissimilar metal joints is mainly due to the following two reasons.On the one hand,grain refinement and element interdiffusion occur at the interface.On the other hand,no intermetallic compounds are formed at the interface.

Preparation and Mechanical Properties of a Novel Textile Pad for Wound Debridement

Various types of wound debridement approaches are currently available in clinical practice such as autolytie, enzymatic. biodebridement, mechanical, and surgical debridemenl techniques. A critical look at these various options can explain their potential but also their limitations. In this study, a novel textile pad, which is composed of polyester filaments on the fleecy side and a bioeompatible coating on the opposite side, was made to provide a safe, inexpensive, easier and especially more efficient debridement process that can be used in all healthcare settings by all healthcare practitioners. Eighteen kinds of samples were prepared with different pile density, ground yarn count and coating amount. Dimensional morphology, stitch density, mass per unit area and mechanical properties were investigated to study the intrinsic relationship of structure and properties of textile pad for wound debridement. Results showed that tensile strength and suturing strength at piped site increased obviously with the increment of ground yarn count, while the amount of coating could also have a slight impact on these two properties. However, compressive load was mainly affected by pile density, with no obvious relation to ground yarn count and coating amount.

Comparative study of β-Si_3N_4 powders prepared by SHS sintered by spark plasma sintering and hot pressing

β-Si3N4 powders prepared by self-propagating high-temperature synthesis （SHS） with additions of Y2O3 and Al2O3 were sintered by spark plasma sintering （SPS）. The densification, microstructure, and mechanical properties of Si3N4 ceramics prepared using this method were compared with those obtained by hot pressing process. Well densified Si3N4 ceramics with finer and homogeneous microstructure and better mechanical properties were obtained in the case of the SPS technique at 200°C lower than that of hot pressing. The microhardness is 15.72 GPa, the bending strength is 716.46 MPa, and the fracture toughness is 7.03 MPa·m1/2.

Effects of salinity on the nail-holding power of dimension lumber used in light-frame wood building

We studied the effect of salinity on nail-hold- ing power in wood construction. In saline solution, the holding power of nails was less than in purified water. With the increase of salt concentration, the surface and side nail- holding power of the wood specimens both declined, but the differences between salinity treatments were not sig- nificant. However, compared to the surface and side nail- holding power, the power on the edge was generally less and the difference was not obvious in different salt con- centrations. In the same salt concentration, with the extension of the processing cycle, the performance of holding power of nails showed a downward trend, expect the temporary rise in the middle.

Microstructural characterization and mechanical properties of self-reinforced Si_3N_4 ceramics containing high oxynitride glass

Self-reinforced Si_3N_4 ceramics containing high oxynitride glass have beenfabricated by the control of microstructure evolution and p-Si_3N_4 grain growth. The effects of thesize distribution of the elongated p-Si_3N_44 grains, and the p-Si_3N_4 grain growth as well as theoxynitride glass chemical characteristic on the microstructure and mechanical properties wereinvestigated. The experimental results show that the p-Si_3N_4 grains in high oxynitride glass growto elongated rod-like crystals and form the stereo-network structure. Under the sintering conditionsof 1800 deg C and 60 min, a quite uniform microstructure with an average aspect ratio of 6.5 and anaverage of 1 mu m can be obtained. A large amount of oxynitride glass phase with high nitrogencontent enhances the elevated temperature fracture toughness because of its high softeningtemperature and high viscosity. In the present material, the crack deflection and pullout of theelongated rod-like P-Si_3N_44 grains are the primary toughening mechanisms.

High-frequency induction heated sintering of ball milled Fe-WC nanocomposites

Fe-WC nanocomposites were successfully fabricated by high-frequency induction heated sintering of ball milled nanostructure powders. The ball milled powders were characterized by X-ray diffraction. Density measurements by the Archimedes method show that all sintered samples have the relative density higher than 95%. Studies on the effects of WC content, milling speed, and milling time indicate that a higher milling speed and a more WC content lead to the improvement of mechanical properties. There is a very good distribution of WC particles in the Fe matrix at the milling speed of 650 r/rain. For the sintered sample 20-5-650 （20wt% WC, milling time of 5 h, and milled speed of 650 r/min）, the maximum Brinell hardness and yield stress are obtained to be 3.25 GPa and 858 MPa, respectively. All sintered samples have brittle fracture during compression test except the sample 20-5-650.

EFFECT OF Fe_2O_3 ON WELDING TECHNOLOGY AND MECHANICAL PROPERTIES OF WELD METAL DEPOSITED BY SELF-SHIELDED FLUX CORED WIRE

Five experimental self-shielded flux cored wires are fabricated withdifferent amount of Fe_2O_3 in the flux. The effect of Fe_2O_3 on welding technology and mechanicalproperties of weld metals deposited by these wires are studied. The results show that with theincrease of Fe_2O_3 in the mix, the melting point of the pretreated mix is increased. LiBaF_3 andBaFe_(12)O_(19), which are very low in inherent moisture, are formed after the pretreatment. Themechanical properties are evaluated to the weld metals. The low temperature notch toughness of theweld metals is increased linearly with the Fe_2O_3 content in the flux due to the balance betweenFe_2O_3 and residual Al in the weld metal. The optimum Fe_2O_3 content in flux is 2.5 percent approx3.5 percent.

Experimental Study on the Influence Mechanism of Carbon Fiber/Epoxy Composite Reinforcement and Matrix on Its Fire Performance

The effects of the number of layers,the arrangement of carbon fiber(CF)tow and the epoxy resin(ER)matrix on the fire performance of carbon fiber/epoxy composites(CFEC)were studied by a variety of experimental methods.The results show that the number of layers of CF tow has influence on the combustion characteristics and fire propagation of the composites.The arrangement of CF tow has influence on flame propagation rate and high temperature mechanicalproperties.The mechanism of the influence of the number of layers of CF tow on the composite is mainly due to the different thermal capacity of ER matrix.The effect of the arrangement of CF tow on the fire performance of the composite is mainly due to the inhibition and obstruction of the tow on the combustion of ER matrix.The influence on the high temperature mechanicalproperties is mainly due to the different arrangement direction of CF tow.The fitting equation of the mechanicalproperties of the samples was obtained.This equation could be used to predict the samples’tensile strength from 25°C to 150℃by comparing with the experimental results.Taking the carbon fiber woven cloth(C)applied in the fuselage material as an example,combining the influencing factors of various parameters in the fire field,some suggestions are put forward combined with the research conclusion.

Effect of PLA Knitted Structure on the Mechanical Properties of Composite Vascular Scaffold

A new entire biodegradable scaffold has been developed which does not require precelluiarization before transplantation. This new kind of vascular scaffold prototype made from porous poly- e-caprolactone （PCL） membrane to provide three-dimensional environment for cell growth, and embedded with weft-knitted polylactic acid （PLA） fabric to support mechanics. The aim of this paper is to study the variation tendency of mechanical properties with the fabric spacing changing. The basic geometrical parameters were measured to characterize properties of the samples. The tensile and compressive elastic recovery of the samples were tested by the universal mechanical tester and radial compression apparatus, respectively. Both tensile and compressive properties enhanced when reducing the fabric spacing of the composite vascular scaffold.

Thermo-Mechanical Processing of Iron-Phosphorous-Carbon Alloys

Phosphorous is widely considered as an impurity in steels. Consequently, its role as an important alloying element in iron could never be established. The present paper deals with the exploitation of phosphorous as a useful alloying element in iron in conjunction with carbon by way of improved thermo-mechanical processing leading to a tough steel equivalent to high strength low alloy steels. It was observed that phosphorous is pushed towards ferrite grains by carbon which in turn forms pearlite along ferrite grains. Suitable adjustment in the amounts of carbon and phosphorous yields an attractive set of mechanical properties after appropriate processing. Typical chemistry and processing combinations yields UTS: 700 MPa and % El: 25% Area under the stress-strain curve: 60 Joules.

Investigation of Mechanical Behavior of Defective Carbon Nanotubes Using Molecular Dynamics Simulation

Carbon nanotubes （CNTs） having pristine structure （i.e., structure without any defect） hold very high mechanical properties. However, CNTs suffer from defects ＇which can appear at production stage, purification stage or be deliberately introduced by irradiation with energetic particles or by chemical treatment. In this article, mechanical properties of single-walled nanotubes with defects are studied under both compressive and tensile loads using molecular dynamics （MD） simulations. Two types of defectStone-Wales and vacancy defects with different defect densities are considered for present investigation. Molecular simulations are carried out using the classical MD method. The Brenner potential is used for carbon-carbon interaction in the CNT. Temperature of the system is controlled by velocity scaling. Simulation results show that the defects have negligible effect on the modulus of elasticity of nanotubes. However, they have significant effect on the failure stress and strain of the nanotubes.

Effects of Irradiation on the Structure-activity Relationship of Konjac Glucomannan Molecular Chain Membrane

To know the effects of irradiation on the konjac glucomannan （KGM） molecular chain membrane, KGM membrane solution was treated with the irradiation dose of 0-20 kGy in this study, and the structure and properties of KGM membrane were analyzed with Infrared spectrum, Raman spectrum, X-ray, SEM scanning and so on. The results revealed that the effects of different irradiation doses on the KGM molecular chain structure were different. Higher irradiation dose （20 kGy） resulted in partial damage against KGM membrane crystal structure, and there was no obvious change for the amorphous structure; with membrane property test, the tensile strength of KGM membrane gradually increased with the increase of irradiation dose and its elongation at break reduced, but these changes were not significant, WVP value reduced; with SEM, the membrane surface treated with irradiation was smoother even than the membrane without treatment. In addition, when increasing the irradiation dose, membrane surface became more even, and arrangement was more orderly and compact. KGM membrane nrooerties, and it is an ideal Irradiation modification could effectively improve the modification method.

EFFECTS OF RARE EARTH MIXTURE ON MECHANICAL PROPERTIES OF CuZnAl SHAPE MEMORY ALLOYS

With thehelpofquantitative metallograph ,tensiletest,electron probeandscan electron mi croscope,theinfluencesof mixture rareearth ( RE) on the grain size, dynamics of grain growth and mechanicalpropertiesof CuZnAlshape memoryalloys wereinvestigated . Theex perimentalresultsshowsthat REcanrefinegrainsgreatly,improvethe mechanicalpropertiesremarkably andchangethetensilefracturefrom brittletypebordered grainstoplastictypeinthecondition of maintainingshape memory properties. Moreover microstructuresrevealthatREwhich accumulates on the grain boundariescan restrain grains’growing. In addition, the mechanismsofrefininggrainsizeandimproving mechanicalpropertiesarealsodiscussed.

NOVEL OXIDATION RESISTANT CARBON SILICON ALLOY FIBRES

Anovel silicon containing carbon precursor was synthesised by reacting a petroleum pitchfraction and polydimethylsilane. The precursor containing about 26wt% Si was meltspunintofibresand then oxidativelystabilised in airto renderthefibresinfusiblebefore pyrolysisat1200℃underinertatmospheretoproduceC Sialloy( CSA) fibres. Theextentofstabili sation wasfoundto becriticalto the development of mechanicalstrength of thefibres which varied with heattreatmenttemperature, showing a maximum at 1200 ℃when thestrength was 1 4 1 6 GPa. Thesestrengthsareremarkably goodconsideringthelow modulus whichis duetothe quite high failurestrains. Thefibrescanshow excellentresistanceto oxidation if given an initialshortexposureto oxygen athigh temperature duetotheformation of an im perceptiblelayer of silica. CSAfibreshavethe advantagesof both carbon fibresand SiCfi bres,thusextended application areascan beenvisaged .

Research and development of nanocrystalline W/W-based materials: novel preparation approaches, formation mechanisms, and unprecedented excellent properties

Tungsten(W)has become the most promising plasma-facing material(PFM)in fusion reactor,and W still faces performance degradation caused by low-temperature brittleness,low recrystallization temperature,neutron irradiation effects,and plasma irradiation effects.The modification of wW-based materials in terms of microstructure manipulation is needed,and such techniques to improve the performance of materials are the topics of hot research.Researchers have found that refining the grain can significantly improve the strength and the irradiation resistance of Ww-based materials.In this paper,novel approaches and technique routes,including the"bottom-up"powder metallurgy method and"top-down"severe plastic deformation method,are introduced to the fabrication of nanocrystalline WW-based materials.The formation mechanisms of nanocrystalline WW-based materials were revealed,and the nanostructure stabilization mechanisms were introduced.The mechanical properties of nanocrystalline WW-based materials were tested,and the irradiation behaviors and performances were studied.The mechanisms of their high mechanical properties and excellent irradiation-damage resistance were illustrated.This article may provide an experimental and theoretical basis for the design and development of high-performance novel nanocrystallineW/W-based materials.

Effect of Ni Content on Mechanical Properties and Corrosion Behavior of Al/Sn－9Zn－xNi/Cu Joints

The effects of Ni content on the microstructure and the wetting behavior of Sn-9Zn-xNi solders on Al and Cu substrates, as well as the mechanical properties and electrochemical corrosion behavior of Al/Sn-9Zn-xNi/Cu solder joints, were investigated. The microstructure of Sn-gZn-xNi revealed that tiny Zn and coarsened Ni5Zn21 phases dispersed in theβ-Sn matrix. The wettability of Sn-9Zn-xNi solders on Al substrate was much better than that on Cu substrate. With increasing Ni content, the wettability on Cu substrate was slightly improved but became worse on Al substrate. In the Al/Sn-9Zn-xNi/Cu joints, an Al4.2Cu3.2Zn0.7 intermetallic compound （IMC） layer formed at the Sn-gZn-xNi/Cu interfaces, while an Al-Zn-Sn solid solution layer formed at the Sn-9Zn-xNi/Al interface. The mixed compounds of Ni3Sna and Al3Ni dispersed in the solder matrix and coarsened with increasing Ni content, thus leading to a reduction in shear strength of the Al/Sn-9Zn- xNi/Cu joints. Al particles were segregated at both interfaces in the solder joints. The corrosion potentials of Sn-9Zn-xNi solders continuously increased with increasing Ni content. The Al/Sn-9Zn-0.25Ni/Cu joint was found to have the best electrochemical corrosion resistance in 5% NaCl solution.

Processing, Microstructure and Mechanical Properties of Ti6Al4V Particles-Reinforced Mg Matrix Composites

Novel Ti6Al4V particles-reinforced AZ91 Mg matrix composites were successfully fabricated by stir casting method. The stirring time in semisolid condition directly affected the particle distribution and the quality of the ingots. Furthermore, the optimal speed of the heating and the liquid stirring could overcome particle settlement caused by the density difference between the matrix and the particles. Ti6Al4V particles distributed uniformly in the composites with different particle contents. The average grain size decreased with the increase in the particle contents. The Ti6A14V particles bonded pretty well with the alloy matrix. In addition, there were some interfacial reactions in the composites. There were rod-like A13Ti phases at the interface. The precipitates extended from the particle surface to the matrix, and they might improve the interfacial bonding strength. The ultimate tensile strength, yield strength and elastic modulus were enhanced as the particle contents increased, and the elongation was much better than that of the same matrix material reinforced with SiC particles. Thus, the novel composites exhibit better comprehensive mechanical properties.

Microstructure,Mechanical Properties and Die-Filling Behavior of High-Performance Die-Cast Al-Mg-Si-Mn Alloy

This work aims to reveal the relationships between the microstructure, mechanical properties and flow behavior of die-casting AlMg5Si2Mn alloy. Results indicated that the microstructure of the die-cast AlMgsSi2Mn consists of α1-Al grains, fine-size α2-Al grains and （Al ＋ Mg2Si） eutectic. The surface layer observed has the thickness in a range of 120-135 μm, while an ellipse-like surface layer edge is observed in the corner of the plateqike sample. Tensile strength and elongation （3） of the specimens are slightly decreased along the die-filling direction due to the backflow of melt. Pure （Al ＋ Mg2Si） eutectic layer and ultra-fine-size α2-Al grains observed are around the overflow channels. Mass feeding is predominantly responsible for the superior mechanical properties of the round bars as compared to those of plate-like samples.

Experimental research on physical and mechanical parameters of matured bottom stalk of the reed for harvester design

The compressing,stretching,bending,and shearing stress of reed stalk growing in the Yangtze River region were investigated by using a computer-controlled electronic universal testing machine.The results were as follows:the average maximum values of the stress resistance intensity,pulling resistance intensity,the average of maximum bending resistance intensity,and shearing resistance intensity were 22 MPa,152 MPa,118 MPa and 26 MPa,respectively,whereas the equivalent values of the modulus of elasticity were 45 MPa,321 MPa,77 MPa and 286 MPa,respectively.The stalk of reed is a kind of anisotropic material and it is different from Arundo donax L.,ramie and wheat.Thus,the traditional agricultural machine for cutting and processing is found to be inconvenient to use in reed harvesting.The data of the experiments provided an important foundation for determining the structural parameters of reed cutter.

Cooling Rate Sensitivity of RE-Containing Grain Refiner and Its Impact on the Microstructure and Mechanical Properties of A356 Alloy

The cooling rate sensitivities of A1TiB, RE and A1TiB-RE refiners were investigated using laboratory experiments and the actual industrial applications of A356 automotive wheel via low pressure die casting technology. Their impact mechanisms on the microstructure and mechanical properties of the A356 alloy were discussed. The results demonstrated that the AITiB-RE refiner possessed most effective and synergetic refinement effects compared to the individual A1TiB or RE refiners. The A1TiB-RE refiner exhibited the least sensitivity to the cooling rate changes than the other refiners. The comprehensive properties of alloy wheel refined by the A1TiB-RE refiner were improved significantly. The tensile strength, yield strength, and elongation of wheel spoke improved by approximately 11.3%, 10.8% and 44.1%, respectively. The property difference values of the tensile strength, yield strength, and elongation in different positions of the wheel decreased from 14.8%, 31.2% and 47.7% to 8.6%, 27.1% and 30.9%, respectively.