Effect of composition on the texture and deformation behaviour of wrought Mg alloys

The microstructure and mechanical response of three extruded magnesium alloys, Mg-3Al-1Zn (AZ31), Mg-1.5Mn (Ml) and Mg-lMn-0.4RE (ME10) are examined. The tensile yield strength of ME10 was nearly half that of AZ31 and Ml. The tensile elongations were 6%, 11% and 19% for Ml, AZ31 and ME10, respectively. This range of properties is large and is attributed to the unique extrusion texture produced in ME10, and the high density of fine particles in Ml.

The origin of "Rare Earth" texture development in extruded Mg-based alloys and its effect on tensile ductility

The extrusion behaviour, texture and tensile ductility of five binary Mg-based alloys have been examined and compared to pure Mg. The five alloying additions examined were Al, Sn, Ca, La and Gd. When these alloys are compared at equivalent grain size, the La- and Gd-containing alloys show the best ductilities. This has been attributed to a weaker extrusion texture. These two alloying additions, La and Gd, were found to also produce a new texture peak with View the MathML source parallel to the extrusion direction. This “rare earth texture” component was found to be suppressed at high extrusion temperatures. It is proposed that the View the MathML source texture component arises from oriented nucleation at shear bands.

Effect of microalloying with rare-earth elements on the texture of extruded magnesium-based alloys

A series of alloys have been produced with microalloying additions of rare-earth (RE) elements in the range of 0.1–0.4 wt.%. The alloys have been extruded to produce grain sizes of 23 ± 5 μm. The texture of the extruded alloys was measured, and it was found that the extrusion texture was weakened by the addition of RE elements. The samples with weakened extrusion textures exhibited an increase in the tensile elongation.

Investigation of deformation mechanisms involved in the plasticity of AZ31 Mg alloy: in situ neutron diffraction and EPSC modelling

In situ neutron diffraction and Elasto-Plastic Self-Consistent (EPSC) polycrystal modelling have been employed to investigate which deformation mechanisms are involved in the plasticity of extruded AZ31 Mg alloy during the tensile loading along the extrusion direction. On the basis of this study we were able to determine the relative activity of the slip and twinning deformation modes. By tuning the parameters of the EPSC model (i.e. the critical resolved shear strengths and hardening parameters), excellent agreement with the experimental data has been achieved. It is shown that the strain in the crystallographic ⟨c ⟩direction is accommodated mainly by ⟨c + a ⟩ dislocation slip on second-order pyramidal planes. The results further indicate that either slip of ⟨a ⟩dislocations occurs on {10.1} pyramidal planes or cross-slip from basal and prismatic planes takes place.

Extruded products with Fenugreek (Trigonella foenum-graecium) chickpea and rice: Physical properties, sensory acceptability and glycaemic index

The present study investigated the effects of fenugreek flour (Trigonella foenum-graecum) and debittered fenugreek polysaccharide (FenuLife^®) inclusion on the physical and sensory quality characteristics, and glycaemic index (GI) of chickpea–rice based extruded products. Based on preliminary evaluation with different proportions of chick pea and rice, a blend of 70:30 chickpea and rice was chosen as the control for further studies. The control blend, replaced with fenugreek flour at 2%, 5% and 10%, or fenugreek polysaccharide at 5%, 10%, 15% and 20%, was extruded at the optimum processing conditions as specified in the detailed study. The extruded products were evaluated for their physical (moisture retention, expansion, hardness, water solubility index (WSI) and water absorption index (WAI)), sensory (flavor, texture, color and overall acceptability) characteristics and in vitro GI to evaluate their suitability as extruded snack products.

Due to the distinct bitter taste, inclusion of fenugreek flour was not acceptable at levels more than 2% in extruded chickpea based products. Addition of fenugreek polysaccharide resulted in slight reduction in radial expansion (P < 0.05), while longitudinal expansion increased. WAI increased while WSI decreased compared to the control (P < 0.05). The mean scores of sensory evaluation indicated that all products containing fenugreek polysaccharide up to 15% were within the acceptable range. There were no significant differences (P > 0.05) between products containing 5–15% fenugreek polysaccharide in their color, flavor, texture and overall quality.

Fenugreek, in the form of debittered polysaccharide (FenuLife^®) could be incorporated up to a level of 15% in a chickpea–rice blend to develop snack products of acceptable physical and sensory properties with low GI Index.

Bleaching and dyeing of superfine wool powder/polypropylene blend film

Fibers based regenerated protein draw much attention for recycling discarded protein resources and can produce biodegradable and environmental friendly polymers. In this study, superfine wool powder is blended with polypropylene (PP) to produce wool powder/PP blend film through extrusion and hot-pressing. Hydrogen peroxide is used to bleach the black colored surface of the blend films. The effects of peroxide concentration, bleaching time and powder content on the final whiteness and mechanical properties of the blend films are investigated.

The bleached films are dyed with acid red dyes and the dyed color is evaluated using a Computer Color Matching System. Color characters of dyed films, such as L*, a*, b*, ΔE*ab, C*ab and K/S values are measured and analyzed. The study not only reuses discarded wool resources into organic powder, widens the application of superfine wool powder on polymers, but also improves the dyeing properties of PP through the addition of protein content.

Needleless electrospinning. I. A comparison of cylinder and disk nozzles

In this study, we demonstrated the needleless electrospinning of poly(vinyl alcohol) (PVA) nanofibers with two nozzles, a rotating disk and a cylinder, and examined the effect of the nozzle shape on the electrospinning process and resultant fiber morphology. The disk nozzle needed a relatively low applied voltage to initiate fiber formation, and the fibers were mainly formed on the top disk edge. Also, the PVA concentration had little influence on the disk electrospinning process (up to 11 wt %). In comparison, the cylinder electrospinning showed a higher dependence on the applied voltage and polymer concentration. The fibers were initiated from the cylinder ends first and then from the entire cylinder surface only if the applied voltage were increased to a certain level. With the same polymer solution, the critical voltage needed to generate nanofibers from the disk nozzle was lower than that needed to generate nanofibers from the cylinder. Both electrospinning systems could produce uniform nanofibers, but the fibers produced from the disk nozzle were finer than those from the cylinder when the operating conditions were the same. A thin disk (8 cm in diameter and 2 mm thick) could produce nanofibers at a rate similar to that of a cylinder of the same diameter but 100 times wider (i.e., 20 cm long). Finite element analysis of electric field profiles of the nozzles revealed a concentrated electric field on the disk edge. For the cylinder nozzle, an uneven distribution of the electric field intensity profile along the nozzle surface was observed. The field lines were mainly concentrated on the cylinder ends, with a much lower electric field intensity formed in the middle surface area. At the same applied voltage, the electric field intensity on the disk edge was much higher than that on the cylinder end. These differences in the electric field intensity profiles could explain the differences in the fiber fineness and rate of the nanofibers produced from these two nozzles. These findings will benefit the design and further development of large-scale electrospinning systems for the mass production of nanofibers for advanced applications.

Novel nanocomposite fibres for technical textile applications

Technical textiles, based on advanced polymeric materials, are an important segment of the synthetic textile market. This area has seen considerable growth in recent times, now accounting for almost 25% of all manufactured synthetic fibres, and has driven the recent development of a range of specialist high performance polymer fibres that are stronger, lighter or have improved heat and fire resistance. However, the increasing size of the market has highlighted the need for materials that have improved performance whilst maintaining low manufacturing costs. These factors have resulted in a change in how new specialty fibres are developed and the emphasis in this field is now on the upgrading or improving of the properties of commodity (conventional) fibres by modifying their properties to suit specific applications.

This paper will describe our work on preparing novel polymer nanocomposite fibres by the addition of clay nanoparticles during melt extrusion. The effect of the nanoparticles on the processing of the fibres and the result on the physical morphology and mechanical properties will be described.

Influence of alloying additions on the extrudability of magnesium

The extrusion behaviour of a series of magnesium alloys was investigated and compared to a common aluminium alloy using limit diagrams. The variation in the limits was related to the different flow stress and solidus temperature of each alloy. The findings of this work have enabled predictions of the relative extrudability of new prototype alloys.

Effect of cold drawing on subsequent surface strain path and ductility during upsetting

Cold drawing is a process that sizes and smooths the surface of steel before it is cold headed to produce bolts. The effect of the changes in the mechanical properties due to cold drawing on the surface strain and ductility during the upsetting process was analysed showing that the stress and strain state can be more readily altered by changes in the process conditions (friction and height-to-diameter ratio) to cause greater increase in the failure strains than can be achieved by pre-drawing.

Performance of wrought aluminium and magnesium alloy tubes in three-point bending

This present work examines the load carrying capacity, energy absorption and fracture characteristics of wrought magnesium and aluminium alloy tubes in three-point bending. Magnesium alloy AZ31, and aluminium alloys 6063 and 7075, were extruded into cylindrical tubes of both equivalent thickness and mass. A strong thickness effect was present meaning that the AZ31 tube had significantly higher load and energy absorption performance than an equivalent mass 6063 tube, albeit not as high as the 7075 tube. Hinge formation and maximum load was delayed for the magnesium alloy, meaning that a high energy absorption rate persisted to higher deformation displacements than the aluminium alloys. It was also found that fracture during deformation was dependent on the indenter diameter, tube thickness and lower support separation.

The Challenge of inhomogeneous deformation in magnesium and its alloys

It is shown that wrought magnesium alloys display a number of significant types of deformation inhomogeneities. These are influenced by the variation in the ease of basal slip amongst grains, micro-textures, shear banding, twinning and grain boundary sliding. Key features of each of these effects are examined and their engineering consequences and challenges are identified.

Effect of grain size on the performance of extruded magnesium alloy tubes in three-point bending

The performance of extruded AZ31, AZ61 and AM-EX1 tubes was examined in three-point bending. Different extrusion temperatures were used to investigate the effect of grain size on the load-carrying capacity, energy absorption and fracture propensity of the tubes. Results showed that while the peak load increased with a smaller average recrystallised grain size, the retention of large elongated un-recrystallised grains in the microstructure reduced the load. The presence of the large elongated grains also appeared detrimental to the ability of the tube to deform before fracture.

Structural and functional properties of human multidrug resistance protein 1 (MRP1/ABCC1)

Multidrug ABC transporters such as P-glycoprotein (P-gp/MDR1/ABCB1) and multidrug resistance protein 1 (MRP1/ABCC1) play an important role in the extrusion of drugs from the cell and their overexpression can be a cause of failure of anticancer and antimicrobial chemotherapy. Recently, the mouse P-gp/Abcb1a structure has been determined and this has significantly enhanced our understanding of the structure-activity relationship (SAR) of mammalian ABC transporters. This paper highlights our current knowledge on the structural and functional properties and the SAR of human MRP1/ABCC1. Although the crystal structure of MRP1/ABCC1 has yet to be resolved, the current topological model of MRP1/ABCC1 contains two transmembrane domains (TMD1 and TMD2) each followed by a nucleotide binding domain (NBD) plus a third NH2-terminal TMD0. MRP1/ABCC1 is expressed in the liver, kidney, intestine, brain and other tissues. MRP1/ABCC1 transports a structurally diverse array of important endogenous substances (e.g. leukotrienes and estrogen conjugates) and xenobiotics and their metabolites, including various conjugates, anticancer drugs, heavy metals, organic anions and lipids. Cells that highly express MRP1/ABCC1 confer resistance to a variety of natural product anticancer drugs such as vinca alkaloids (e.g. vincristine), anthracyclines (e.g. etoposide) and epipodophyllotoxins (e.g. doxorubicin and mitoxantrone). MRP1/ABCC1 is associated with tumor resistance which is often caused by an increased efflux and decreased intracellular accumulation of natural product anticancer drugs and other anticancer agents. However, most compounds that efficiently reverse P-gp/ABCB1-mediated multidrug resistance have only low affinity for MRP1/ABCC1 and there are only a few effective and relatively specific MRP1/ABCC1 inhibitors available. A number of site-directed mutagenesis studies, biophysical and photolabeling studies, SAR and QSAR, molecular docking and homology modeling studies have documented the role of multiple residues in determining the substrate specificity and inhibitor selectivity of MRP1/ABCC1. Most of these residues are located in the TMs of TMD1 and TMD2, in particular TMs 4, 6, 7, 8, 10, 11, 14, 16, and 17, or in close proximity to the membrane/cytosol interface of MRP1/ABCC1. The exact transporting mechanism of MRP1/ABCC1 is unclear. MRP1/ABCC1 and other multidrug transporters are front-line mediators of drug resistance in cancers and represent important therapeutic targets in future chemotherapy. The crystal structure of human MRP1/ABCC1 is expected to be resolved in the near future and this will provide an insight into the SAR of MRP1/ABCC1 and allow for rational design of anticancer drugs and potent and selective MRP1/ABCC1 inhibitors.