Extrusion Direction Research Articles

Abnormal texture formation and mechanical anisotropy of pre-aging extruded Mg-Gd-Y-Zn-Zr alloy with large-scale

In order to further explore the effect of pre-aging treatment on large-scale alloys, a pre-aging extruded Mg-9.32Gd-4.02Y-2.16Zn-0.48Zr (wt.%) alloy with large extrusion ratio (ER = 19.5) and extrusion temperature of 450 °C in large-scale (Φ308 mm × 800 mm) was investigated in this paper. It exhibited good properties and a more pronounced anisotropy. The comprehensive performance in the 45° direction was the best. The extrusion direction (ED) presented a high strength, while the transverse direction (TD) showed poor strength and ductility contemporaneously. The main results of strength anisotropy were the alignment orientation of the long-period stacking ordered (LPSO), fine grain strengthening, and texture strengthening. The c-axis of most of the grains in TD samples was perpendicular to the direction of applied stress because of the abnormal <0001>//ED texture, which reduced the ductility. In addition, the formation mechanism of abnormal texture has also been studied. The higher extrusion temperature reduced the critical shear stress (CRSS) of the non-basal slip system, and the higher strain promoted the rotation of the base plane along the principal stress axis under the operation of continuous non-basal slip, resulting in the abnormal <0001>//ED texture due to lattice rotation. On the other hand, dynamic recrystallization (DRX) also greatly affected the generation of the abnormal texture. Firstly, DRX produced a proportion of grains with a nucleation orientation of <0001>, then the subsequent preferential growth of DRX grains led to the vast majority of grains with an orientation tending towards <0001>. However, the former has less effect on abnormal texture than the latter.

Effect of Equal Channel Angular Pressing on the Microstructure and Mechanical Properties of an Mg–5Sn Alloy

An Mg–5Sn alloy was processed by equal channel angular pressing (ECAP) for different passes (4P, 8P, and 12P), and the microstructure evolution and mechanical properties were investigated. The grain size, amount of Mg2Sn precipitates, and texture of ECAP alloys depend on the number of passes. The ECAP 8P alloy has the finest grains and largest area fraction of Mg2Sn particles, followed by the ECAP 12P alloy. The ECAP 4P and 8P alloys exhibit basal textures tilted towards transverse direction (TD), whereas the ECAP 12P alloy shows basal texture with the c-axis of the grains parallel to the extrusion direction (ED). ECAP alloys show superior strengths compared to the as-cast alloy, mainly attributed to fine grain strengthening, precipitation strengthening, texture strengthening, and dislocation strengthening. The ultimate tensile strength (UTS) increases while the elongation (EL) decreases with increasing ECAP pass.

Influence of Ultrafine-Grained Microstructure and Texture Evolution of ECAPed ZK30 Magnesium Alloy on the Corrosion Behavior in Different Corrosive Agents.

Magnesium-Zinc-Zirconium (Mg-Zn-Zr) alloys have caught considerable attention in medical applications where biodegradability is critical. The combination of their good biocompatibility, improved strength, and low cytotoxicity makes them great candidates for medical implants. This research investigation is focused on providing further insight into the effects of equal channel angular processing (ECAP) on the corrosion behavior, microstructure evolution, and mechanical properties of a biodegradable ZK30 alloy. Billets of Mg-3Zn-0.6 Zr (ZK30) alloy were processed through ECAP up to 4 passes of route Bc (rotating the billets 90° in the same direction between the subsequent passes) at 250 °C. Electron back-scatter diffraction (EBSD) was utilized to investigate the microstructural evolution as well as the crystallographic texture. Several electrochemical measurements were carried out on both a simulated body fluid and a 3.5% sodium chloride (NaCl) solution. Mechanical properties such as Vicker’s hardness and tensile properties were also assessed. The as-annealed (AA) microstructure was dominated by equiaxed coarse recrystallized grains with an average grain size of 26.69 µm. After processing, a geometric grain subdivision took place due to the severe plastic deformation. Processed samples were characterized by grain refinement and high density of substructures. The 4-passes sample experienced a reduction in the grain size by 92.8% compared with its AA counterpart. The fraction of high-angle grain boundaries increased significantly after 4-passes compared to the 1-pass processed sample. With regards to the crystallographic texture, the AA condition had its {0001} basal planes mostly oriented parallel to the transversal direction. On the other hand, ECAP processing resulted in crystallographic texture changes, such as the shifting of the ZK30 shear plane to be aligned at 45° relative to the extrusion direction (ED). Furthermore, the maximum texture intensity was reduced from 14 times random (AA billets) to 8 times random after ECAP processing through 4-passes. The corrosion rate of the 4-passes sample was tremendously reduced by 99% and 45.25% compared with its AA counterpart in the simulated body fluid and the NaCl solution, respectively. The pitting corrosion resistance of ZK30 showed notable improvements in the simulated body fluid by 471.66% and 352% during processing through 1-pass and 4-passes, respectively, compared with the 3.5% NaCl findings. Finally, significant improvements in the tensile strength, hardness, and ductility were also achieved.

Mechanical properties and electrical conductivity of oriented-SiC-whisker-reinforced Al2O3/Cu composites

Oriented SiC whisker-reinforced Al2O3/Cu composites were fabricated by powder metallurgy and hot extrusion. The microstructure of the composites was characterized by scanning electron microscopy. The mechanical properties and electrical conductivity of the composites were measured. The results indicated that the SiC whiskers aligned along the extrusion direction, and the nano Al2O3 particles were uniformly dispersed in the Cu matrix with ideal interfacial bonding. Particle and whisker hybrid reinforcement significantly enhanced the mechanical properties. The yield strength and elongation of (1 vol.%SiCw + Al2O3)/Cu composites were 6% and 15.6% higher than those of the Al2O3/Cu composites, respectively. The experimental yield strength was consistent with the theoretical value associated with different strengthening mechanisms. The main strengthening mechanisms were fine grain strengthening, Orowan strengthening and load transfer strengthening. The electrical conductivity of all the composites was higher than 82.8% IACS; however, the SiC whiskers led to electrical conductivity anisotropy. In general, the electrical conductivity of composites is related to the volume fraction and type of reinforcement. Therefore, the influence of the hybrid composition on the electrical conductivity was studied, and an analytical model for the electrical conductivity of hybrid-reinforced copper matrix composites was established, including the characteristic parameters of the particles and whiskers. The model and presented findings can provide a design basis for hybrid-reinforced composites.

On the structure-properties relationship of amorphous and crystalline silica nanoparticles reinforced magnesium matrix nanocomposites

In this study, the structure-properties relationship of magnesium matrix nanocomposites was studied. Using an accumulative extrusion (AE) process, the matrix was reinforced by adding 0.25, 0.5 and 1 wt% crystalline and amorphous silica nanoparticles separately. The mechanical behavior of nanocomposite strips was investigated by hardness and uniaxial compression tests. The results indicated that the Mg/0.5%SiO2-Am had the best room temperature compressive properties. An increase of 28.5% in compressive yield strength after extrusion and 235% after annealing was measured. Ultimate compressive strength (UCS) was increased by 20% without reduction in the nanocomposite ductility compared to the pure magnesium strip. FESEM and OM were used for microstructural analysis and revealed no visible cracks or distinct defects between magnesium layers after AE passes. It is found from the EDS analysis that the reinforcement distribution after the AE process was uniform with few agglomerates. Texture analysis using X-ray diffraction and EBSD after the AE process for samples reinforced with 0.5 wt% of amorphous and crystalline silica nanoparticles indicated a negligible difference in the basal plane orientation of the monolithic and nanocomposite magnesium strips after the AE process along extrusion direction. On the other hand, increasing the basal plane peak intensity after annealing for the sample reinforced with amorphous silica compared to the sample reinforced with crystalline silica indicated a weakening of basal texture. Furthermore, the EBSD analysis showed that amorphous silica nanoparticles are more effective than crystalline silica in grain refinement.

Unveiling the mechanical response and deformation mechanism of extruded Mg-2.5Nd-0.5Zn-0.5Zr alloy sheet under high-temperature tensile

The microstructure evolution, mechanical response and deformation mechanism of the extruded Mg-2.5Nd-0.5Zn-0.5Zr alloy sheet by high-temperature (423–573 K) tensile were investigated. The results showed that the alloy exhibited excellent high-temperature mechanical properties at 523 K (extrusion direction (ED): ultimate tensile strength (UTS)~191.5 MPa, yield strength (YS)~154.5 MPa, elongation (EL)~30.1%; transverse direction (TD): UTS~190.5 MPa, YS~148.2 MPa, EL~35.2%). The YS of ED and TD of the alloy decreased linearly, and the anisotropy of the alloy decreased gradually (from 0.9261 to 1.009) with the increase of tensile temperature, which was beneficial to the subsequent processing of the alloy. Moreover, the decreased anisotropy was the result of grain size, second phase particles size and texture state. The microstructure showed obvious deformed structures at 423 K and it was gradually replaced by dynamic recrystallization with an average grain size of 3.3–4.2 µm and the texture strength weakened greatly (maximum pole density value reduced from 15.8 to 4.0) as the temperature increased to 573 K. Meanwhile, both the deformation models and the contributions of different deformation mechanisms at different tensile temperatures were roughly estimated. It was found that basal slip was always the main deformation mechanism at different tensile temperatures, but its contribution to deformation decreased with increased tensile temperatures (from 93.0% to 66.6%). With the increase of tensile temperature, the degree of prismatic slip (from 4.1% to 23.2%) and pyramidal slip (from 2.9% to 10.2%) in deformation gradually increased.

Microstructure evolution and ductility improvement mechanisms of magnesium alloy in interactive alternating forward extrusion

The microstructural evolution and mechanical properties of AZ31 magnesium alloy processed by the interactive alternating forward extrusion at different loading displacements (h=3, 6, 9 mm) were investigated. Optical microscopy (OM) and electron backscatter diffraction (EBSD) were used to analyze the evolution of microstructure, and the mechanical behavior was clarified by tensile tests and scanning electron microscopy (SEM). The results show that continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) can achieve grain refinement jointly in interactive alternating forward extrusion. With the decrease of the loading displacement h, the proportion of recrystallization increases from 23.4% to 66.7%. The fiber texture gradually tilts to the extrusion direction (ED), and the grain orientation randomization of DDRX further weakens the fiber texture intensity. When h=3 mm, the ultimate tensile strength (UTS) is 249.1 MPa and the elongation can reach 29.4%.

Effects of grains‘ morphology on strengthening mechanisms in ODM401 14Cr ODS steel at high temperatures

The effect of grain orientation on the mechanical behavior of the 14Cr ODS steel (ODM401) at temperatures 400–800 °C is analyzed. The tensile and stress relaxation tests are performed on tensile specimens with grain orientation parallel and perpendicular to the extrusion direction. The strengthening mechanisms are analyzed in terms of the internal and thermal stress component, dislocation glide and climb and grain boundary creep. Models of strengthening mechanisms are used for evaluation of their intensity for a given temperature, grain orientation and macroscopic plastic strain level (0.001, 0.01, 0.025). Both grain orientations provide similar strengthening up to 600 °C. The grain orientation parallel to the extrusion direction provides higher strength at temperatures 700–800 °C due to the reduced grain boundary creep and dislocations annihilation at grain boundaries.

Corrosion behaviors of hot-extruded Mg96Y2Zn2 alloy in transverse and longitudinal directions: Guidance for parameters selection

The hot-extruded Mg alloys containing long period stacking ordered (LPSO) phase suffered from the difference of corrosion behavior between transverse and longitudinal sections. To fathom out the mechanism of the difference and improve the overall corrosion resistance, the extruded Mg96Y2Zn2 alloys are prepared through different ram speed. Dynamic recrystallization was achieved in extruded Mg96Y2Zn2 alloys and the LPSO phases were elongated along the extrusion direction (ED). The results indicates that the basal texture can be strengthened by increasing the ram speed, since the volume fraction of dynamically recrystallized (DRXed) grains is reduced. As a result of the extruded Mg96Y2Zn2 alloys did not undergo passivation during corrosion, the decrease in grain size led to an increase in corrosion rate. The peeling off of LPSO strips with larger size caused more serious damage to the alloys. The existence of texture and huge LPSO strips lead to the difference of corrosion properties in the two directions. Therefore, larger DRXed grains with a higher volume fraction and finer scaled LPSO strips are beneficial to the corrosion properties of extruded Mg96Y2Zn2 alloys. Parameters have the same effects as low ram speed are conducive to improve corrosion resistance.

Tensile behavior at various temperatures of the Mg-Gd-Y-Zn-Zr alloys with different initial morphologies of LPSO phases prior to extrusion

The tensile behavior at (−100)-300 °C of the extruded and peak-aged Mg-5Gd-3Y-xZn-0.5Zr (x = 1 and 2 wt%, designated as VWZ531K and VWZ532K) alloys was investigated in the aspects of microstructural evolution, deformation modes, mechanical properties, etc. The higher Zn content endows the VWZ532K alloy with more intragranular lamellar LPSO phases and larger interdendritic ones at the initial homogenized status, which induces the lower DRX ratio, finer DRXed grain size, and negligible aging hardening response subsequently. During extrusion, precipitation of intragranular LPSO phases occurred in the VWZ531K alloy and partial DRXed grains formed a special texture component with the c-axis aligning parallel to the extrusion direction. However, the VWZ532K alloy experienced the dissolution of intragranular LPSO and dynamic precipitation of β phases. During tensile tests, deformation modes (including twinning, basal slip and non-basal slip) were modified by the testing temperature, grain orientation, LPSO morphology, etc. Compared with the β′ precipitates, LPSO phases are more thermostable to maintain the high-temperature strength, which induce the higher tensile yield strength of the peak-aged VWZ532K alloy (182 MPa) at 300 °C. The larger volume fraction of tension twins and lamellar LPSO phases result in the abnormal high elongation (17.9%) at −100 °C for the VWZ531K alloy.

Investigation on deformation of composite multi-bolted joints considering influences of hole-location errors and installation sequence

In this paper, deformation of composite multi-bolted joints considering hole-location error and installation sequence was investigated. Experiments were conduct to examine deformation and damage of joints with different hole-location error and installation sequence. Deformation of joints was measured by laser measurement system. Bolt-composite interfaces were examined microscopically to reveal damage caused by forced installation. Results showed that hole-location error caused vertical deformation of composite joint. Non-uniform extrusion of up and down hole was caused by forced installation. Besides, deformation mode of hole exit was dominated by deformation asymmetry. Damage distribution was influenced by radial extrusion direction of up and down holes. Thus, damage was distributed no-uniformly along depth of holes. During forced installation, deformation accumulation of multi-bolted joints was generating. Different installation sequences caused various deformation distribution of composite joints. Average deformation were reduced by more than 70% after changing the installation sequence. Conclusions of this paper are of significance for developing deformation model and deformation reduction of composite multi-bolted joints assembly.

A Superior High-Strength Dilute Mg-Bi-Ca Extrusion Alloy with a Bimodal Microstructure

Improving the mechanical properties of Mg alloys is of great significance for their wide application. A micro-alloyed Mg-1.45Bi-0.79Ca alloy (in wt.%) exhibiting a high tensile yield strength of 394 ± 5 MPa and a moderate elongation of 6.6 ± 0.6% was fabricated by single pass extrusion. The superior high strength is mainly attributed to the synergy effects of ultra-fine dynamic recrystallized grains; numerous Mg2Ca, Mg3Bi2, and Mg2Bi2Ca nano-precipitates; residual dislocations; sub-grain boundaries; as well as strong &lt;10-10&gt; fibre texture in the extrusion direction.

Mechanical properties and deformation mechanism in Mg-Gd alloy laminate with dual-heterostructure grain size and texture

Heterostructures can effectively break the traditional strength-ductility trade-off dilemma. However, how the texture of materials with heterostructure under hetero-deformation induced stress (including back stress and forward stress) influences the activation of the deformation mechanism is still not clear. In this paper, a Mg-1Gd/Mg-13Gd (wt.%) laminate with an alternating distribution of dual-heterostructure grain size and texture, where the coarse-grained (CG) layers presented a bimodal texture along the extrusion direction and the fine-grained (FG) layers showed random texture, exhibited an excellent strength-ductility synergy. Strain delocalization in the Mg-13Gd layer was realized by generating dispersed stable strain bands, which promoted the activation of ductile mechanisms. In the CG layers, the bimodal texture facilitated the activation of pyramidal <c + a> slip to maintain the continuity of strain at the interface. The lower level of geometric compatibility factor at the interface, with its heterogeneous texture, aggravated deformation incompatibility and boosted the back stress. The higher shear stress field at the interface generated by back stress led to the activation of pyramidal <c + a> slip and enhanced the strength of the CG layers. In the FG layers, the forward stress promoted the activation of prismatic <a> and pyramidal <c + a> slips at the interface; they acted together with the abundant basal <a> slips caused by the random texture to improve the ductility of the FG layers. The results of this work will promote the development of heterogeneous theory in textured Mg alloys.

Directional-dependent precipitate microstructure and mechanical properties of tensile and compressive stress-assisted aged Mg-Zn alloys

Aging aided by external elastic stress is of scientific interest and practical importance in improving the precipitation hardening response of magnesium alloys. In this work, fiber textured Mg-6 wt.% Zn alloys were subjected to tensile and compressive stress-assisted aging (TSA and CSA, respectively), in which stress is applied along the extrusion direction. Results reveal that the precipitate microstructure, including shape, size, distribution and even internal defect structures exhibits a stress directional dependence. Aberration-corrected scanning transmission electron microscopy shows that a high number density of Zn solute clusters is produced upon CSA, and relatively fine β1’ precipitates are predominantly formed under TSA. First-principles calculations indicate that the stress direction-dependent solute diffusion ability is the leading cause of such directional-dependent precipitate characteristics. Furthermore, TSA generates a higher yield strength than that of stress-free aging (SFA), owing to the relatively high density of fine β1’ precipitates. Compared with SFA and TSA alloys, the CSA alloy contains massive Zn solute clusters and has higher yield strength and better ductility due to the strong cluster-dislocation interactions without the generation of local high stress concentration at the coherent interface. This work offers further insights into altering the precipitation behavior of Mg alloys by applying external stress field and provides possible solutions to achieve high strength-ductility synergy in Mg alloys.

Microstructure evolution and enhanced mechanical properties in Al-Mn alloy reinforced by B-doped TiC particles

In this work, novel TiC particles doped by trace amounts of B, referred to as TiCB, were introduced to an Al-Mn alloy with the Al-TCB master alloy. The effects of the TiCB particles on the solidification microstructure, extrusion behavior, and mechanical properties of the Al-Mn alloy were systematically studied. The results showed that TiCB particles could significantly refine α-Al grains by providing heterogeneous nucleation substrates and hindering the growth of α-grains. For example, when the amount of added TiCB particles was 0.5 wt%, average α-Al grain size could be refined to a minimum of 40.2 μm from 410.1 μm when no particles were added. After hot extrusion, TiCB particles and fractured α-Al(Fe, Mn)Si formed streamlines along the extrusion direction. More importantly, TiCB particles could inhibit the dynamic recrystallization process during hot extrusion and retain numerous geometrically necessary dislocations. Consequently, the mechanical properties of the Al-Mn alloy at room temperature (25 °C) and elevated temperature (350 °C) were significantly improved after adding TiCB particles. When the amount of added TiCB particles was 1.5 wt%, the ultimate tensile strengths at 25 °C and 350 °C were increased by 25.6% and 32.4%. This work sheds light on the grain refinement and strengthening of non-heat-treatable wrought Al-Mn alloys.

Honeycomb-Structured Porous Films from Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate): Physicochemical Characterization and Mesenchymal Stem Cells Behavior.

Surface morphology affects cell attachment and proliferation. In this research, different films made of biodegradable polymers, poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB-co-HV), containing different molecular weights, with microstructured surfaces were investigated. Two methods were used to obtain patterned films—water-assisted self-assembly (“breath figure”) and spin-coating techniques. The water-assisted technique made it possible to obtain porous films with a self-assembled pore structure, which is dependent on the monomer composition of a polymer along with its molecular weight and the technique parameters (distance from the nozzle, volume, and polymer concentration in working solution). Their pore morphologies were evaluated and their hydrophobicity was examined. Mesenchymal stem cells (MSCs) isolated from bone marrow were cultivated on a porous film surface. MSCs’ attachment differed markedly depending on surface morphology. On strip-formed stamp films, MSCs elongated along the structure, however, they interacted with a larger area of film surface. The honeycomb films and column type films did not set the direction of extrusion, but cell flattening depended on structure topography. Thus, stem cells can “feel” the various surface morphologies of self-assembled honeycomb films and change their behavior depending on it.

Effect of Sm on microstructures and mechanical properties of Mg–Gd(–Sm)–Zr alloys by hot extrusion and aging treatment

We investigated the effect of Sm on microstructures and mechanical properties of Mg–Gd (–Sm)–Zr by hot extrusion and aging treatment. The dynamic recrystallization (DRX) and precipitation behavior were analyzed by the electron backscattering diffraction (EBSD) and transmission electron microscope (TEM). For as-extruded alloys, the addition of Sm promotes DRX and dynamic precipitation, and the dynamic precipitation can activate the particle-stimulated nucleation (PSN) mechanism to promote the nucleation of DRX. The DRX grains of the as-extruded Mg–Gd–Zr show a random texture, but the as-extruded Mg–Gd–Sm–Zr shows an abnormal texture (<0001>Mg was parallel to the extrusion direction). For the extruded-aged alloys, the matrix precipitates of the Mg–Gd–Zr and Mg–Gd–Sm–Zr were all β′. But the size of β′ in Mg–Gd–Sm–Zr was smaller. The grain boundaries precipitates of the two alloys were all β. The β phase of Mg–Gd–Zr was granular and distributed discontinuously, while that of Mg–Gd–Sm–Zr was continuous distribution. Furthermore, there was an obvious precipitation-free zone of extruded-aged Mg–Gd–Sm–Zr. The high-temperature mechanical properties of extruded-aged Mg–Gd–Sm–Zr were obviously improved by the addition of Sm. The tensile strength, yield strength and elongation at 200 °C were 336 MPa, 271 MPa and 7.4%, respectively. Finally, the strengthening mechanism of extruded-aged Mg–Gd–Sm–Zr was analyzed in detail.

Spark plasma extrusion of binder free hydroxyapatite powder

Abstract This work explores the possibility of manufacturing dense and nanocrystalline hydroxyapatite (HA) large monoliths by spark plasma extrusion (SPE). This method combines uniaxial mechanical compression, high temperature, and electromagnetic field to promote the extrusion and sintering of HA powder in one single step. The results show that the binder-free extrusion of pre-compacted HA powder is feasible at a temperature similar to the temperature at which nanocrystalline HA shows superplastic behavior. The extrusion continues throughout the sliding and rotation of the particles, and also due to the grain boundary sliding, up to the point where no more material is available, thus producing monoliths of nearly 30 mm in length and 10 mm in diameter. The dehydration and smooth surface of the powder appear as paramount factors to facilitate the HA extrusion without additives. The extruded HA preserved the stoichiometry and nanometric grain size and exhibited preferential microstructural alignment in the direction of extrusion. The material experiences local thermal and pressure gradients during extrusion, producing different densification and hardness along its length. The SPE of HA will benefit the healthcare field by offering new processing approaches of bone substitutes and osteosynthesis devices.

Texture, microstructure and mechanical properties of an extruded Mg-10Gd-1Zn-0.4Zr alloy: Role of microstructure prior to extrusion

The homogenized Mg-10Gd-1Zn-0.4Zr (wt.%) alloys with and without the LPSO phases were hot extruded, and then the texture evolution, microstructure and mechanical properties of the extruded alloys were investigated. The initial microstructure (prior to extrusion) containing no LPSO phases or only bulk/lamellar LPSO phases leads to a fully dynamically recrystallized (DRXed) grains, while that containing both the bulk and lamellar LPSO phases results in a bimodal structure with the coarse deformed grains and fine DRXed grains, indicating that the bulk LPSO phases can promote the DRX behavior via particle stimulated nucleation mechanism while the lamellar LPSO phases hamper the DRX behavior. An abnormal texture with <0001> parallel to the extrusion direction is observed in extruded alloys with a large average grain size, while a relatively weak basal texture is observed in small grains. The formation mechanism of this abnormal texture is due to the growth advantage of the DRXed grains with <0001> parallel to the extrusion direction over other grains. The contribution of each strengthening mechanism to the yield strength in four extruded alloys was calculated quantitatively, and the results show that grain refinement and solid solution strengthening mechanisms contribute the most to the yield strength in all extruded alloys. The contributions of dislocation strengthening and the secondary phase strengthening are enhanced in extruded alloys containing bulk LPSO phases, while that of texture strengthening is reduced. This work sheds light on controlling the mechanical properties of the extruded Mg alloys via the LPSO phases and texture.

Modeling of the Electrotransport Process in PP-Based and PLA-Based Composite Fibers Filled with Carbon Nanofibers.

Polypropylene and polylactide-based composite fibers have been produced by a melt technology. Long vapor-grown carbon fibers (CNFs) have been used as electrical conductivity fillers. It is clearly shown by experimental methods that the CNFs are evenly distributed in the polymer matrix, orienting themselves along the direction of fiber extrusion and retaining their initial dimensions. It is shown that for composites fibers based on crystallizing (polypropylene) and amorphous (polylactide acid) polymer matrix, the dependence of electrical resistance on the filler concentration is percolation character and can be described as a double Boltzmann function. Four sections are identified on the dependences of the electrical resistance on the filler concentration for composite fibers, and the reasons for this character of this dependence on the formation of electrically conductive circuits are analyzed. Investigated in this work are the PP-based and PLA-based composites filled with carbon nanofibers that can be used as antistatic, shielding materials, or as sensors.