Hot Hydrostatic Extrusion of Mechanically Alloyed Al-4.9Fe-4.9Ni Powders

Al-4.9 Fe-4.9 Ni alloy powders have been synthesized by mechanical alloying. The rnechanically alloyed powders are consolidated by hot hydrostatic extrusion. The results show that extrusion tempereture. extrusion ratio and lubricant have great effects on the quality of extruded rods and their mechanical properties, The mixture of graphite and glass powders as lubricant can prevent the oxidization of cold compacted billet by cladding the billet with this lubricant before heating. This technique greatly simplifies the conventional densification process of powders

Formation Mechanism of NiAl/TiB_2 Nanocomposite by Mechanical Alloying Elemental Powders

A NiAl/TiB2 nanocomposite is synthesized by mechanical alloying elemental powders. Upon milling for a certain time, an abrupt exothermic reaction occurs and a large amount of NiAl and TiB2 compounds form simultaneously. It is suggested that two separate chemical reactions,i.e. Ni+Al →NiAl and Ti+2B→TiB2, are involved during the exothermic reaction. Additionof Ti and B to Ni-Al system impedes the structural evolution of Ni and Al powders and delays the abrupt reaction. The final products are equilibrium phases without any metastable phases formed. This type of reaction is suggested to be suitable for alloy systems with two large heatrelease reactions.

Mechanical alloying characteristic and thermal stability of Al_(78)Fe_(20)Zr_2 amorphous powders

The powders of pure Al, Fe, and Zr for preparing Al78Fe20Zr2 were subject to a high-energy planetary ball milling.The microstructure evolution of the mixtures at the different intervals of milling was characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM） and differential scanning calorimetry（DSC）.It was found that a nearly complete amorphization could be achieved in the mixtures after ball milling for 23 h.Further ball milling led to the crystallization of the amorphous powders.A long time ball milling, e.g., 160 h, led to a complete crystallization of the amorphous powders and the formation of Al3Zr and Al13Fe4.The crystallization products caused by ball milling are almost the same as that produced by isothermal annealing of the amorphous powders in vacuum at 800 K for 1 h.

Role of Disclinations and Nanocrystalline State in the Formation of Quasicrystalline Phases on Mechanical Alloying of Cu-Fe Powders

Elemental powders of Cu and Fe were ball milled for various time durations up to 100 h. The various stages of forced alloying by ball milling, leading to instability of elemental crystalline phases and formation of quasicrystalline phases were monitored using X-ray diffraction. Diffusion of Fe into the Cu matrix is proposed as the cause which triggers the instability of crystalline phases and leads to the formation of quasicrystalline phases after 10 h of milling. Milling for 100 h resulted in two different quasicrystalline phases with different lattice constants. Role of the nanocrystalline microstructure as an important criterion for the destabilisation of crystalline phases is explained. It is suggested that the formation of nanocrystalline microstructure and their subsequent transformation into quasicrystalline phases may be associated with a continuous increase in the disclination content of the system, which had formed as a result of continued milling and mechanical deformation.

Curing Kinetics, Mechanical Properties and Thermal Stability of Epoxy/Graphene Nanoplatelets(GNPs) Powder Coatings

Epoxy/graphene nanoplatelets（GNPs） powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored by means of real-time Fourier transform infrared spectroscopy（FT-IR） with a heating cell. The mechanical properties of the epoxy/GNPs cured coatings had been investigated, by evaluating their fracture surfaces with field-emission scanning electron microscopy（FE-SEM） after three-point-bending tests. The thermal stability of the epoxy/GNPs cured coatings was studied by thermo-gravimetric analysis（TGA）. The isothermal curing kinetics result showed that the GNPs would not affect the autocatalytic reaction mechanism, but the loading of GNPs below 1.0 wt % additive played a prompting role in the curing of the epoxy/GNPs powder coatings. The fracture strain, fracture toughness and impact resistance of the epoxy/GNPs cured coatings increased dramatically at low levels of GNPs loading（1 wt %）, indicating that the GNPs could improve the toughness of the epoxy/GNPs powder coatings. Furthermore, from FE-SEM studies of the fracture surfaces, the possible toughening mechanisms of the epoxy/GNPs cured coatings were proposed. TGA result showed that the incorporation of GNPs improved the thermal stability of the cured coatings. Hence, the GNPs modified epoxy can be an efficient approach to toughen epoxy powder coating along with improving their thermal stability.

Effect of CF and RPP on the Mechanical and Electrical Properties of Smart Aggregate

By using redispersible polymer powder（RPP） and carbon fiber（CF） to adjust the flexibility and electrical properties of the smart aggregate, a new kind of smart aggregate with Z type structure was proposed. The study shows that Z type aggregate is more sensitive to the feedback of external force than the prism aggregate in the same loading environment, and it indicates that Z type aggregate is more suitable for the research and application of concrete health monitoring. Although the incorporation of RPP would cause the compressive strength of the aggregates and the elastic modulus of hardened cement mortar to reduce slightly within the dosage of RPP by 2.25% because of the polymer film formed in the internal system, this would improve the deformability of the aggregates. In the early loading stage（in the first 60 seconds）, the intelligent concrete specimens implanted with Z type smart aggregate do not show higher sensitivity as expected, although the resistance change rate changes a little bit more, the overall of it is still in balance. Adding RPP could improve the flexibility of smart aggregates exactly, and it plays an active role in prolonging the life of the smart aggregates. By implanting Z type aggregates the damage and failure of the concrete structure could be predicted accurately in this study. The results of this paper will help to promote further research and application of intelligent concrete.

Thermal Expansion and Mechanical Properties of Middle Reinforcement Content SiCp/Al Composites Fabricated by PM Technology

Middle reinforcement content SiCp/Al composites（Vp=30%, 35% and 40%） for precision optical systems applications were fabricated by powder metallurgy technology. The composites were free of porosity and SiC particles distributed uniformly in the composites. The mean linear coefficients of thermal expansion（20-100 ℃） of SiCp/Al composites ranged from 11.6×10-6 to 13.3×10-6 K-1 and decreased with an increase in volume fraction of SiC content. The experimental coeffi cients of thermal expansion agreed well with predicted values based on Kerner＇s model. The Brinell hardness increased from 116 to 147, and the modulus increased from 99 to 112 GPa for the corresponding composites. The tensile strengths were higher than 320 MPa, but no signifi cant increasing trend between tensile strength and SiC content was observed.

The Effect of Different Levels of Sunflower Head Pith Powder on Some Emulsion Attributes of Mechanically Deboned Chicken Meat

In this study, the effect of sunflower head pith powder at various concentrations （0.0, 0.5, 1.0, 1.5, 2.0%） on the emulsion properties of mechanically deboned chicken meat （MDCM） was investigated in a model system. For this purpose, fresh and frozen MDCM samples were used for preparing the oil/water （O/W） model emulsion systems, pH values of slurries and emulsions, emulsion capacity （EC）, stability （ES） and viscosity （EV） of the prepared model system emulsions were analyzed. Protein, fat, ash, dry matter contents and pH value of MDCM were 14.85, 14.93, 0.99, 30.45% and 6.7, respectively. It was found that the pith powder addition significantly （P 〈 0.01） decreased the pH values of slurries. On the other hand, the effect of pith powder addition on pH values of emulsions was insignificant （P 〉 0.01）. The highest EC value was reached when 1% of pith powder added. ES values of the emulsions reached a maximum level at 1.5% pith powder level. Fresh MDCM emulsions had higher EV values than did frozen MDCM emulsions at 10, 20, 50 rpm.

Characterization of Mo–Si–B Nanocomposite Powders Produced Using Mechanical Alloying and Powder Heat Treatment

Mo-Si-B nanocomposite powders with a composition of Mo-12Si-8.5B （in at.%） were processed using mechanical alloying under milling conditions for different milling time and powder-to-ball ratios. The Mo-12Si-8.5B alloy, which consists of α-Mo and intermetallic Mo3Si and T2 phases, was also synthesized by hot-pressed sintering the mechanically alloyed powders under a pressure of 50 MPa at 1600 ℃. The results demonstrated that the sizes and morphologies of the powder particles became gradually refined and uniform by both increasing the milling time and decreasing the powder-to-ball ratio. After 15 h of milling, the powders were completely homogenized at the 1：10 and the 1 ： 15 powder-to-ball weight ratios, and the homogenization was accelerated to rapidly stabilize the milling process because of their high milling energy. Annealing the Mo-Si-B milled powders could promote the growth of the intermetallic Mo3Si and the T2 phases, which formed even after low-temperature annealing at 900 ℃. Increasing the annealing temperature only improved the crystallinity of various phases. When the milled and annealed powders were hot-pressed sintered, the Mo-Si-B alloy exhibited a fine-grained microstructure, where the intermetallics Mo3Si and T2 were distributed in a continuous α-Mo matrix.

Effect of Powder Particle Shape on the Properties of In Situ Ti–TiB Composite Materials Produced by Selective Laser Melting

This work studied the preparation of starting powder mixture influenced by milling time and its effect on the particle morphology （especially the shape） and, consequently, density and compression properties of in situ Ti-TiB composite materials produced by selective laser melting （SLM） technology. Starting powder composite system was prepared by mixing 95 wt% commercially pure titanium （CP-Ti） and 5 wt% titanium diboride （TiB2） powders and subsequently milled for two different times （i.e. 2 h and 4 h）. The milled powder mixtures after 2 h and 4 h show nearly spherical and irregular shape, respectively. Subsequently, the resultant Ti-5 wt% TiB2 powder mixtures were used for SLM processing. Scanning electron microscopy image of the SLM-processed Ti-TiB composite samples show needle-shape TiB phase distributed across the Ti matrix, which is the product of an in-situ chemical reaction between Ti and TiB2 during SLM. The Ti-TiB composite samples prepared from 2 h and 4 h milled Ti-TiB2 powders show different relative densities of 99.5% and 95.1%, respectively. Also, the compression properties such as ultimate strength and compression strain for the 99.5% dense composite samples is 1421 MPa and 17.8%, respectively, which are superior to those （883 MPa and 5.5%, respectively） for the 95.1% dense sample. The results indicate that once Ti and TiB2 powders are connected firmly to each other and powder mixture of nearly spherical shape is obtained, there is no additional benefit in increasing the milling time and, instead, it has a negative effect on the density （i.e. increasing porosity level） of the Ti-TiB composite materials and their mechanical properties.

Superior Properties of Mg–4Y–3RE–Zr Alloy Prepared by Powder Metallurgy

Magnesium alloys are important materials for application in the automotive and aviation industries. During the last few years, the number of possible applications as biodegradable implants in medicine has grown. Mg-RE（rare earth） alloys belong to the most advanced group of products, offering the best combination of mechanical properties and corrosion resistance. Among these materials, WE43（Mg-Y-Nd）is a very well-known commercial alloy that has been extensively studied for applications at increased temperatures and also in organisms. Although this material has been described, there are still possibilities to improve its properties and subsequently expand its applicability. Powder metallurgy has already been used for the preparation of magnesium alloys with superior mechanical properties and occasionally superior corrosion properties. Therefore, the present paper is oriented toward the preparation of Mg-4Y-3RE-Zr（WE43） alloy by the powder metallurgy technique（WE43-PM） and comparison of the final properties with the product of extrusion of as-cast ingot（WE43-IM）. Our processing leads to a partial improvement in the mechanical properties and superior corrosion resistance of WE43-PM. The texture strength of WE43-PM was low, and therefore, anisotropy of mechanical properties was suppressed.

Flow behavior and deposition study of pollen-shape carrier particles in an idealized inhalation path model

Pollen-shape （spiked sphere） hydroxyapatite （HA） particles for drug carrier application are studied. The particle shape and size effect on flow characteristics and deposition are assessed. The pollen-shape HA particles are synthesized to have comparable size as typical carrier particles with mean diameter of 30-50 μm and effective density less than 0.3 g/cm^3. The flow behaviors of HA and commonly used lactose （LA） carrier particles are characterized by the Carr＇s compressibility index （CI）. The HA particles have lower CI than the LA particles for the same size range. The flow fields of HA and LA carrier particles are measured in an idealized inhalation path model using particle image velocimetry （PLY） technique. The particle streamlines indicate that a large portion of particles may deposit at the bending section due to inertial impaction and gravitational deposition. The flow field result shows that HA particles give smaller separation regions than the LA particles for the same size range. The pollen-shape HA particles are found to be able to follow the gas flow in the model and minimize undesired deposition. Deposition result confirms the bending section to have the most deposition. Deposition is found to be a function of particle properties. An empirical correlation is derived for the deposition efficiency of the pollen-shape particles as a function of particles Stokes number.

Structural Modification of Al65Cu16.5Ti18.5 Amorphous Powder through Annealing and Post Milling： Improving Thermal Stability

To improve thermal stability of the Al65Cu16.5Ti18.5 amorphous powder,structural modification of the amorphous powder was performed through annealing and post milling.Annealing above the crystallization temperature（Tx） not only induced nanoscale intermetallics to precipitate in the amorphous powder,but also increased Cu atomic percentage within the residual amorphous phase.Post milling induced the amorphization of the nanocrystal intermetallics and the formation of Cu9Al4 from the residual amorphous phase.Thus,a mixed structure consisting of amorphous phase and Cu9Al4 was obtained in the powder after annealing and post milling（the APMed powder）.The phase constituent in the APMed powder did not change during the post annealing,which exhibited significantly improved thermal stability in comparison with the as-milled amorphous powder.