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Ultrafine-grained Al samples were fabricated by spark plasma sintering (SPS) of a mechanically milled nanocrystalline powder. The effects of annealing and extrusion on the microstructure and tensile properties of the as-SPSed samples were investigated. Annealing removed the nanopores and caused significant coarsening of Al grains in the interparticle boundary (IPB) regions, leading to the formation of a heterogeneous structure consisting of coarse grains, ultrafine grains and Al4C3/Al2O3 nanoparticles. Hot extrusion also eliminated the nanopores and resulted in the formation of a heterogeneous structure containing enhanced volume fraction of ultrafine grains and finer nanoparticles. These microstructural changes rendered a much improved YS and UTS of 251 and 288 MPa, respectively, and excellent tensile ductility (elongation to fracture: 12.7%). The improvement in mechanical properties can be attributed to grain boundary and nanoparticle strengthening, strain delocalisation of the heterogeneous structure and improvement of the bonding strength of IPBs. [ABSTRACT FROM AUTHOR]

One of the main challenges in processing of metal matrix nanocomposites through the powder metallurgy method is achieving a dense compact with minimum internal porosity. Pores act as stress risers and deteriorate the mechanical properties of nano-materials. In the present investigation, powder mixtures of commercially pure Al (CP-Al) and 5252 Al alloy reinforced with nanometric SiC particles (0-7 wt.%) were produced by in situ powder metallurgy (IPM) method. These powders were consolidated through cold compaction, sintering and hot extrusion processes and subjected to density measurements, microstructural studies and thermal analysis. Microstructural studies showed that SiC nanoparticles formed a continuous network around the CP-Al powders, restricting effective densification during the cold compaction stage. This network was also shown to prevent metal-to-metal contact during sintering, especially at higher SiC contents. Therefore, a remarkable decrease in the sintered relative density was observed with increasing SiC contents in the CP-Al/SiC compacts. However, in the 5252 Al/SiC composite powders, the SiC nanoparticles embedded within the alloy matrix during the IPM process. As a result, a more homogeneous SiC particle distribution was attained. This led to enhanced cold densification and improved sinterability compared with those of CP-Al/SiC powder mixture. Besides, the presence of Mg in the 5252 alloy matrix was effective in reducing the oxide film covering the Al particles. The differential scanning calorimetry (DSC) revealed the formation of liquid phase during the sintering of 5252 Al/SiC powder compacts. As a result, mass transfer promoted through the liquid phase sintering enhancing densification. However, improved densification was obtained after hot extrusion of the nano-SiC reinforced composites. Results showed that the pressure required for extrusion increased with increasing SiC content. This was attributed to the enhanced redundant work induced by SiC particles. [ABSTRACT FROM AUTHOR]

Extrusion technology allows the preparation of analog rice, an artificial product made of carbohydrate sources other than rice, with characteristics similar to natural rice. In this study, we aimed at determining the effect of composition and temperature on the nutritional content of analog rice obtained using heat extrusion technology. The physical properties and acceptability of the resulting product were also studied. Skim milk, sago, mung bean, and corn flour as well as the binder carboxymethyl cellulose (CMC) were used. The procedure was conducted in four stages: raw-material preparation, formulation, physicochemical evaluation, and sensory property evaluation. The best analog rice formula was established as 50% sago flour, 30% corn flour, 19.2% mung bean flour, 0.4% skim milk, and 0.4% CMC. The panelists’ most preferred rice analog formula was the one with the highest sago starch and skim milk content. The extrusion temperature did not significantly affect the nutrient content. However, it had a considerable impact on the thermal profile and physical properties, such as appearance and granular morphology [ABSTRACT FROM AUTHOR]

In the present study, a new biodegradable Mg-Zn-Cu magnesium alloy was introduced for biological applications. The microstructural analysis showed the formation of MgZnCu intermetallics for the Mg-2Zn-0.1Cu alloy and also the Mg(Zn,Cu) 2 compounds for the Mg-2 Zn alloys with higher Cu contents. Moreover, the hot extrusion was applied for the grain refinement and changing the distribution of intermetallics. In vitro immersion tests, electrochemical and corroded surface analyses represented the enhancement of corrosion resistance with 0.1 wt.% Cu addition. Furthermore, the extruded alloys demonstrated more corrosion resistance behavior than that of the cast alloys. By considering the improved tensile properties of Mg-2Zn-0.1Cu alloy, this alloy was regarded as the potential candidate for use as the biodegradable magnesium implant. [ABSTRACT FROM AUTHOR]

The prior particle boundaries (PPBs), as one of the typical defects in the nickel-based powder metallurgy superalloy, largely affect the microstructure and thus properties/performance of alloys. However, the effect of PPBs on the microstructure evolution in nickel-based powder metallurgy superalloy during heat treatment is still unclear. In this paper, a comparative study of PPBs and their influence on grain growth during solution treatment in a novel nickel-based powder metallurgy superalloy FGH4113A (i.e., WZ-A3 from Shenzhen Wedge, China) with/without hot extrusion (HEX) was conducted. Firstly, through a combination of scanning electron microscope (SEM), electron probe microanalyzer (EPMA) and transmission electron microscope (TEM) techniques, PPBs in FGH4113A alloys were characterized to be Al2O3, carbides (TiC, M6C, M23C6) and large-size γ′ particles. After HEX, the oxides broke, carbides deformed, and γ′ phase redistributed. After solution treatment at 950 °C, the TiC decomposed to M6C and M23C6, while no such decomposition occurred in FGH4113A alloys after solution treated at 1050 °C and 1150 °C. Secondly, the evolution of grain size in FGH4113A alloys was analyzed using the electron backscattered diffraction (EBSD) technique. At 950 °C, the decomposition of carbide TiC resulted in the increase of PPBs and the enhancement of their pinning effect on grain boundaries, thus inhibiting grain growth. At 1050 °C, the nucleation rate due to recrystallization is comparable to the grain growth rate, leading to the stable distribution of grain size. While at 1150 °C, the higher temperature can induce a higher content of PPBs. However, the driving force for grain growth surpassed the pinning force of PPBs, making the grains quickly coarsen. Finally, it was concluded that the HEX process is an effective method to modify the microstructure of powder metallurgy superalloy after HIP that can heavily refine the grains in the powder metallurgy superalloys. Furthermore, based on the present experiment and analysis, an appropriate solution treatment mechanism (i.e., 1050 °C for 2 h) was proposed for FGH4113A alloys.

In this work, Mg-4Zn-1Ca (wt. %) alloy was primarily processed by disintegrated melt deposition. The resulting ingots were further pre-processed by the turning induced deformation technique (TID), and the turnings were subsequently consolidated by the hot extrusion process and sinterless powder metallurgy. A range of extrusion temperatures (200, 250 and 300 °C) was tested to understand the effect of the extrusion temperature on tailoring the microstructure and properties of TID-processed Mg-4Zn-1Ca (wt. %) alloys. The results indicated that the combined effect of TID and extrusion temperature plays a significant role in grain refinement, specifically at 200 °C. Overall, the sample extruded at 300 °C showed the best microhardness and compressive yield strength values. The resistance to ignition and wet corrosion increased and decreased, respectively, when the extrusion temperature was increased. Variations of basal texture and fine grain strengthening due to variations of extrusion temperature led to different properties peaking at different extrusion temperatures. Microstructure-property relationships are therefore discussed, highlighting that different extrusion temperatures have characteristic effects in improving and lowering the properties. Many of the investigated properties of TID-processed alloys exceed that of commercial Mg alloys, suggesting the capability of the sinterless TID technique to develop as an economical industrial way of recycling and manufacturing magnesium-based materials.

• Highly c -axis textured β-silicon nitride (β-Si 3 N 4) ceramics without seeding was prepared by a new method of hot extrusion using spark plasma heating at 1800 °C in 10 min. • The (002) pole figure showed a characteristic of center rotational symmetry and an average cline angle between hot extruding direction and [ 00l ] direction of β-Si 3 N 4 grains as low as 8.7°. • Higher hardness was achieved mainly due to the finer grain size compared to that of c -axis textured Si 3 N 4 ceramics with seeding. Highly c -axis textured β-silicon nitride (β-Si 3 N 4) ceramic with fine grains was prepared by a new method of hot extrusion for the first time. The (002) pole figure on the section plane vertical to extruding direction showed a characteristic of center rotational symmetry. The average cline angle between elongated β-Si 3 N 4 grains and hot extruding direction was about 14.4°. The degree of c -axis texturing by hot extrusion was comparable to that achieved by rotating magnetic field. The hardness and toughness anisotropy in different direction was apparent and relatively higher hardness was achieved in the present work mainly due to the finer grain size. Therefore, many different compositions of c -axis aligned Si 3 N 4 -based ceramics with tailored mechanical properties could be achieved by the strategy of hot extrusion. [ABSTRACT FROM AUTHOR]

TiB whisker (TiBw) and nitrogen (N) solid‐solution synergistic‐strengthened titanium matrix composites (TMCs) are prepared by in situ reaction of Ti–BN system via spark plasma sintering (SPS) and hot extrusion. The effects of the in situ‐synthesized TiBw and N solid solution on the microstructure and mechanical properties of TMCs are studied. Results show that TiBw is broken into several short fragments and distributed parallel to the extrusion direction after hot extrusion, whereas N atoms are all dissolved into the Ti matrix. The BN additive dispersion method and hot extrusion process can greatly eliminate TiBw aggregates and reduce the mean size of TiBw. Tensile test results reveal that the Ti with only 0.4 wt.% BN exhibits an exceptional ultimate tensile strength of 879 MPa and 16.6% elongation at room temperature. On this basis, the main strengthening mechanism of TiBw reinforcement and N solid solution at room and high temperature are studied based on the Hall–Petch equation, load transfer mechanism, and Labusch model. [ABSTRACT FROM AUTHOR]

From the viewpoints of grain refinement and preferred orientation, a mechanical alloying (MA) and hot-extrusion technique has been proposed to fabricate Bi2Te3-based bulk materials. In this paper, the MA and hot-extrusion process, microstructure and texture, thermoelectric and mechanical properties of extruded samples, and the effect of Cu-doping in n-type samples have been reviewed. The extruded samples exhibited fine-grained microstructure, and their basal planes were predominantly oriented parallel to the extrusion direction. The p-type Bi0.4Sb1.6Te3 samples showed significant enhancements in both thermoelectric and mechanical properties. For example, the sample extruded at 400°C had a maximum value of ZT = 1.2 at room temperature and a much higher hardness than unidirectionally solidified samples. However, the n-type Bi2Te2.85Se0.15 samples showed lower thermoelectric properties due to their higher carrier concentrations and smaller fractions of twin boundaries. Cu-doping in n-type samples resulted in a reduction in carrier concentration, and thus increases in related Seebeck coefficient and electrical resistivity and decrease in carrier thermal conductivity. The resulting ZT value of 0.86 for Cu0.05Bi2Te2.85Se0.15 sample was obtained. [ABSTRACT FROM AUTHOR]

Synergistic effects of partial replacement of Al with Ca, homogenization heat treatment, and hot extrusion on the microstructure and mechanical properties of Mg–(7-x)Al–xCa magnesium alloys were studied. The Mg17Al12 compound in Mg–7Al alloy, Mg17Al12 and Al2Ca compounds in AX52 alloy, Al2Ca and Mg–Al–Ca compounds in AX43 alloy, and Mg–Al–Ca compound in AX25 were characterized. The as-cast alloys were quite brittle with low strength values due to the deleterious effects of the continuous intergranular brittle constituents that completely masked the alloying effect. Homogenization resulted in the spheroidization of the eutectic constituents and gave the alloys some tensile ductility, which was remarkable for the AX43 alloy due to its fine grain size. Hot extrusion resulted in the fragmentation and dispersion of particles as well as formation of equiaxed, fine microstructures by the recrystallization processes, which led to the profound enhancements of the tensile properties in terms of both strength and elongation to failure. The product of strength and ductility of ~ 5500 MPa.% for the extruded AX43 alloy was far better than the value of ~ 314 MPa.% for the as-cast counterpart. [ABSTRACT FROM AUTHOR]

Magnesium alloys and composites, because of their notable properties, are currently being investigated to open out widespread applications for different industries. In this study, Mg–6Zn–1Ca alloy matrix composite, with different volume percentages of Al2O3 reinforcing particles, was produced by stir casting followed by hot extrusion. The microstructure of the cast and extruded alloys and composites was characterized using optical and scanning electron microscopes, energy-dispersive X-ray and X-ray diffraction spectroscopies. All produced samples were then undergone hardness and wear experiments. Microstructural observations indicated that Ca2Mg6Zn3 precipitates are often located at the grain boundaries of the α-Mg matrix. The observations also showed that increasing the amount of Al2O3 not only increases the hardness but also improves the wear resistance of both the cast and extruded samples, although wear resistance of the extruded composites was much higher than that of the cast samples. Besides, increasing the extrusion temperature from 350 °C to 400 °C increased the wear rate, and the composites extruded at 350 °C possessed the best wear resistance among samples. The results also showed that a combination of the abrasive, delamination and adhesive wear mechanisms takes place in composites, although abrasion is the predominant mechanism in the composites extruded at 350 °C. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Effect of extrusion temperature on properties of Mg–Zn–Ca–(Mn) alloys was studied. • Addition of Mn and decrease in extrusion temperature caused grain refinement. • Addition of Mn significantly reduced the corrosion rate of the alloys. • Mg–2 wt% Zn–0.7 wt% Ca–1 wt% Mn showed excellent mechanical and corrosion properties. Biodegradable Mg-based implants are widely used in clinical applications because they exhibit mechanical properties comparable to those of human bone and require no revision surgery for their removal. Among Mg-based alloys, Mg–Zn–Ca–(Mn) alloys have been extensively investigated for medical applications because the constituent elements of these alloys, Mg, Zn, Ca, and Mn, are present in human tissues as nutrient elements. In this study, we investigated the effect of the hot extrusion temperature on the microstructure, mechanical properties, and biodegradation rate of Mg–Zn–Ca–(Mn) alloys. The results showed that the addition of Mn and a decrease in the extrusion temperature resulted in grain refinement followed by an increase in the strength and a decrease in the elongation at fracture of the alloys. The alloys showed different mechanical properties along the directions parallel and perpendicular to the extrusion direction. The corrosion test of the alloys in the Hanks' solution revealed that the addition of Mn significantly reduced the corrosion rate of the alloys. The Mg–2 wt% Zn–0.7 wt% Ca–1 wt% Mn alloy hot-extruded at 300 °C with an ultimate tensile strength of 278 MPa, an yield strength of 229 MPa, an elongation at fracture of 10%, and a corrosion rate of 0.3 mm/year was found to be suitable for orthopedic implants. [ABSTRACT FROM AUTHOR]

Antifriction tin bronzes and, in particular, C92900 bronze are used in mechanical engineering to manufacture parts subject to friction. Permanent mold casting into steel molds is commonly used to produce parts from C92900 bronze. The feasibility of producing C92900 bronze rods by hot extrusion and upward casting methods is explored. The hot extrusion temperature and ram speed, as well as the upward casting speed at which defects do not emerge in rods is determined. Hot extrusion is shown to result in a significant refinement of grains down to 1.7 μm, while upward casting, on the contrary, results in an increase in the grain size in comparison with permanent mold casting. Regarding microstructure, γ-Cu3Sn intermetallic phase crystals are refined in hot extrusion and continuous upward casting. Large agglomerations of Pb particles can be observed in the extruded bronze microstructure, which presumably lead to a decrease in the coefficient of friction. Maximum hardness and tensile strength are characteristic of the rods produced by hot extrusion at 600°C, while the highest elongation at fracture is obtained in the rods produced by upward casting. Tribological studies conducted using the "shaft–partial insert" setup in a kerosene medium with a steel counter body show that hot extrusion leads to a tenfold increase in wear resistance and a threefold decrease in the coefficient of friction in comparison with the rods obtained by permanent mold casting. The rods obtained by the upward casting method, on the contrary, exhibit a decrease in wear resistance. Given these results, hot extrusion may be recommended along with the casting technique for manufacturing bronze C92900 rods. [ABSTRACT FROM AUTHOR]

During hot extrusion of copper, the material tends to stick to the extrusion die due to strong adhesive forces between hot working steel and copper at high temperatures. In this context, surface modifications like nanocomposite coatings deposited by plasma enhanced chemical vapor deposition or boriding of nickel-based alloy 718 (DIN 2.4668) create hard and wear resistant thin solid films that offer high temperature stability. Ti–Si–B– C –N nanocomposite coatings consist of nanocrystalline grains embedded in a thin amorphous matrix. Due to this particular nanostructure, hardness values of up to 39.3 GPa were reached. Boriding of alloy 718 leads to formation of phases consisting of alloying elements like nickel, iron, and chromium and the diffusing element boron. The borides form a boriding zone that offers high hardness. Extrusion of Ø122 mm × 300 mm copper billets preheated to 850 °C was carried out and adhesive wear on tool's surfaces was analyzed. The comparison between hot working steel DIN 1.2367 without surface modification and with Ti–Si–B– C –N coating or borided alloy 718 showed remarkable differences between conventional tools made of hot working steels/alloy 718 and tools with surface modification. A strong decrease particle adhesion was observed. [Display omitted] • Extrusion dies' surfaces were modified to increase thermal stability and hardness. • Extrusion experiments with Cu showed decrease in adhesive wear on extrusion dies. • Boriding of alloy 718 was carried out during precepitation hardening. [ABSTRACT FROM AUTHOR]

Multi-pass hot extrusion was used to prepare the Al2O3/AZ31 composite.The microstru-cture was characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy, and mechanical properties were tested by Vickers hardness tester and electron universal strength tester. The results show that Al2O3 particles are uniformly distributed in AZ31 magnesium matrix by multi-pass hot extrusion. The grain refining effect of Al2O3 particles on the matrix is enhanced, and the grain size of the composite decreases significantly with the increase of the pass. During the hot extrusion process, the dislocation density around the Al2O3 particles increases, and the high-density dislocation region facilitates the dynamic recrystallization nucleation, so that the grains of the Al2O3/AZ31 composite are significantly refined. The Al2O3 particles are gradually distributed into a long strip from the initial island distribution, then distributed in a linear pattern, and finally distributed uniformly in the form of particles in the AZ31 magnesium matrix. After fourth-pass hot extrusion, the mechanical properties of Al2O3/AZ31 composite are significantly improved, and hardness, tensile strength and yield strength are 89HV, 305MPa and 198MPa, respectively. The hardness, tensile strength and yield strength increase by 19.2%, 14.8%, and 14.1%, respectively, compared with the first-pass hot extrusion.

The publication presents a novel concept of the process of plastic forming of variable longitudinal-section cylindrical products, being the subject of Patent Application P.427426 [1]. Additionally, these products are provided with a connection stub pipe. The plastic forming method proposed in the article combines many advantages and utilitarian benefits associated with the manufacturing technology itself, as well as with its further implementation. Using stock in the form of normalized bar commonly available in the metal product market as a finished product obviously reduces the process costs involved with stock preparation, i.e. casting, rolling, machining, etc. It also results in obtaining a much smaller surface area of stock contact with the tool and, as a consequence, a smaller surface of stock friction against the tool, which contributes to a reduction of force needed for the plastic forming of the product. The smaller contact surface area and the shorter time of stock contact with the cooler tool cause, above all, less intensive heat exchange and stock chilling. This has a significant effect on the plasticity of the cast material and, as a consequence, the plastic forming force. The proposed method enables also manufacturing cylinders with either a closed or open stub pipe with a regulated length and a varying section. In addition, unlike the method known from Polish Patent Specification PL 212062 [2], the proposed method does not require using a multi-tool press. The upper punch is furnished with a flange, whose job is to start the stock extruding sleeve at the next process stage.

The large-sized (?300 mm) nickel based superalloy GH738 billet was fabricated by spray forming followed by hot isostatic press (HIP) and hot extrusion (HEX) within varied deformation temperatures. The micro-defect, carbonitride distribution, γ/γ′ evolution during the hot processes were investigated by the relevant approaches including XRD, SEM, TEM, EBSD and phase analysis technique respectively. The results show that the porosities in γ matrix of spray deposited billet are welded up to closure after HIP process. The difference of characteristic microstructure after dynamic recrystallization obtained after the hot extrusion is mainly based on the varied deformation conditions including temperature and strain-stress state. The grain-boundary-distributed carbonitrides in HIPed billiet are transformed into extrusion-direction-along distribution after hot extrusion. The effects of temperature field delivered and cooling condition on elements constitution, mass fraction, morphology, size and distribution of γ′ in GH738 are validated during different hot processes as well.

Nickel-base superalloy 617B is one of the most promising candidates for superheater and reheater pipes of advanced ultra-supercritical (AUSC) power plants.Hot extrusion is a key process during the manufacturing of superalloy 617B pipes.However, the high content of alloying elements in superalloy 617B makes microstructure control difficult during the hot extrusion process.Furthermore, to date, no systematical theoretical investigation has been conducted in the hot extrusion process control of superalloy 617B.Hence, in this work, the hot extrusion process of superalloy 617B tube was studied by finite element simulation using DEFORM-2D finite element software.The microstructure evolution during hot extrusion was considered by combining the microstructure evolution model of superalloy 617B and finite element simulation software.The microstructure evolution model was programmed using FORTRAN language and was developed using the finite element simulation software.The hot extrusion characteristics of superalloy 617B were systematically analyzed by the simulation.As a result, the evolution of temperature, grain size, and loading could be predicted quantitatively.At the same time, to optimize the hot extrusion parameters, microstructure-based hot extrusion control principles, including temperature principle, loading principle, precise microstructure control principle, were proposed considering practical hot extrusion process.Moreover, the control mechanism and application process of these principles were elaborated in detail in this paper.The hot extrusion parameters of superalloy 617B tube were optimized based on the proposed microstructure-based hot extrusion control principles.Under the guidance of the microstructure-based hot extrusion control principles, superalloy 617B tube with uniform axial dimension and good surface quality was extruded successfully in the factory.The practical extrusion result agrees well with the simulated one.Therefore, the establishment and validation of the simulation method and microstructure-based hot extrusion control principles can provide theoretical guidance for the hot extrusion process optimization of nickel-base superalloy tube in practical applications.

Metal matrix nanocomposites are attracting attention because of their great potential for improved mechanical properties and possible functionalization. These hybrid materials are often produced by casting processes, but they can also develop their property profile after hot working, e.g., by forging or extrusion. In this study, a commercial cast magnesium alloy AM60 was enriched with 1 wt.% AlN nanoparticles and extruded into round bars with varied extrusion rates. The same process was carried out with unreinforced AM60 in order to determine the influences of the AlN nanoparticles in direct comparison. The influence of extrusion speed on the recrystallization behavior as well the effect of nanoparticles on the microstructure evolution and the particle-related strengthening are discussed and assessed with respect to the resulting mechanical performance.

(AlFeNiCrCoTi0.5)p/6061Al matrix composites were prepared by cold isostatic pressing combined with equal-diameter angular extrusion. The microstructure and properties of the extruded materials after adding high-entropy alloys were studied. The FCC + BCC dual-phase high-entropy alloy particles mechanically alloyed for 90 h were added to the aluminum matrix, while the composite material formed a diffusion interface after equal-diameter angular extrusion. Compared with the 6061Al matrix, when the content of AlFeNiCrCoTi0.5 was 10%, by two passes, the hardness increased from 52.5 HV to 70.3 HV, the tensile strength increased from 158 MPa to 188 MPa, and the elongation changed from 14.9% to 14.1%. The material had good comprehensive mechanical properties.

Compared to the recycling process by remelting, hot extrusion significantly reduces the energy consumption and CO2 emission and ensures good mechanical and microstructural properties. This study investigates the effects of reinforcing aluminium AA6061 chips with mixed boron carbide (B4C) and zirconia (ZrO2) particles by employing a design of experiment (DOE) under 550 °C processing temperature and three hours preheating time. The findings showed that compressive strength (CS) and hardness increased with up to 5% added particles, and beyond 5%, the yielded values decreased because of materials agglomeration. However, the decreasing density was dependent on the addition of ZrO2 particles. The distribution of particles with different volume fractions of mixed particles was investigated by employing SEM, AFM, and EDS tests. Thus, the process can produce a net shape structure that utilises material-bonding consolidation to provide sufficient support to reuse the recovered materials in engineering applications, such as in the automotive industry.

Boron nitride (BN) reinforced Al6061 aluminum-based composites are synthesized by conventional stir casting method followed by exposure to hot extrusion. The optical images confirmed the distribution of BN nanoparticles in the aluminum alloy matrix. The concentration of BN is varied from (0.5, 1.5, 3, 4.5, 6, 7.5, and 9 wt%) in the composites and its effect on the tensile strength was investigated. The results revealed that both extruded and heat-treated composites specimens showed enhanced toughness and tensile strength by increasing BN nanoparticle concentration. The heat-treated composite samples showed lower flexibility of up to 40%, and further, it exhibited 37% greater hardness and 32% enhancement in tensile strength over the extruded sample. The tensile properties of Al6061-BN composites were evaluated by temperature-dependent internal friction (TDIF) analysis and the results showed that the as-prepared composite's strength increased with temperature.

The present study aimed at investigating the effect of Ca (0–3 wt%) on the microstructure and tensile properties of as-cast and as-extruded Mg–Zn alloy, in which tensile tests, X-ray diffraction, SEM, EDX and texture analysis were used to evaluate these features. Based on the results obtained, it is shown that the average grain size decreased from 305 to 84 μm by adding 3 wt% Ca to the as-cast Mg–Zn alloy. XRD and SEM results reveal that the dominant second phase in the presence of Ca is Ca2Mg6Zn3 which is formed continuously between dendrite arms spacing. It has been observed that the addition of 0.1 wt% Ca, significantly enhanced both UTS and elongation of as-cast alloy. It is found that the size of DRXed grains decreases with the increase of Ca (4 μm with 3 wt% Ca addition) after hot-extrusion. Further, it has been observed that Ultimate tensile strength (UTS) and elongation values of extruded alloys containing Ca are enhanced and the best result is obtained for Mg–5Zn–0.1Ca sample. Ultimate tensile strength (UTS) of 351 MPa and elongation percentage of 24% are obtained for Mg–5Zn–0.1Ca extruded alloy. [ABSTRACT FROM AUTHOR]

Boron nitride (BN) reinforced Al6061 aluminum-based composites are synthesized by conventional stir casting method followed by exposure to hot extrusion. The optical images confirmed the distribution of BN nanoparticles in the aluminum alloy matrix. The concentration of BN is varied from (0.5, 1.5, 3, 4.5, 6, 7.5, and 9 wt%) in the composites and its effect on the tensile strength was investigated. The results revealed that both extruded and heat-treated composites specimens showed enhanced toughness an tensile strength by increasing BN nanoparticle concentration. The heat-treated composite samples showed lower flexibility of up to 40%, and further, it exhibited 37% greater hardness and 32% enhancement in tensile strength over the extruded sample. The tensile properties of Al6061-BN composites were evaluated by temperature-dependent internal friction (TDIF) analysis and the results showed that the as-prepared composite's strength increased with temperature.. [ABSTRACT FROM AUTHOR]

Bimodal carbon nanotube reinforced 7055Al (CNT/7055Al) composites containing coarse grain bands and ultra-fine grain zones were fabricated by high energy ball milling, vacuum hot pressing followed by hot extrusion. The effect of extrusion temperature varied from 320°C to 420°C on the microstructure evolution and tensile properties were investigated. Microstructure observation indicates that the elongated coarse grain bands aligned along the extrusion direction after extrusion. The width of the coarse grain bands increased, and the length of the coarse grain bands increased firstly and then decreased with the increase of extrusion temperature. The grain size of the ultra-fine grain zones changed little after hot extrusion, but the ultra-fine grains coarsened after subsequent heat treatment, especially for the composite extruded at low temperature of 320°C. By observing the CNT distribution, it was found that the higher temperature extrusion was beneficial to the CNT orientation along the extrusion direction. Furthermore, a precipitated free zone formed at the boundary between the coarse grain band and the ultra-fine grain zone as the composite extruded at high temperature of 420°C. As the result of the comprehensive influence of the above microstructure, the tensile strength of the composite extruded at moderate temperature of 370°C reached the highest of 826 MPa. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nanomaterials play an important role in metal matrix composites (MMC). In this study, 3.0 wt.%, 6.0 wt.%, and 9.0 wt.% nano-AlN-particles-reinforced AA6061 (nano-AlN/AA6061) composites were successfully prepared by pressure infiltration technique and then hot extruded (HE) at 500 °C. The microstructural characterization of the composites after HE show that the grain structure of the Al matrix is significantly refined, varying from 2 to 20 μm down to 1 to 3 μm. Nano-AlN particles in the composites are agglomerated around the matrix, and the distribution of nano-AlN is improved after HE. The interface between AA6061 and nano-AlN is clean and smooth, without interface reaction products. The 3.0 wt.% nano-AlN/AA6061 composite shows an uppermost yield and supreme tensile strength of 333 MPa and 445 MPa, respectively. The results show that the deformation procedure of the composite is beneficial to the further dispersion of nano-AlN particles and improves the strength of nano-AlN/AA6061 composite. At the same time, the strengthening mechanism active in the composites was discussed.

Aluminium matrix composites (AMC) are gaining wide popularity in various sectors due to their excellent properties which are synergic. Apart from strength, wear resistance of a material is also an essential criterion for the number of applications. Extensive studies are being carried out on the secondary processing of these materials to enhance the suitability of the AMC for engineering applications. In this study, initially, Al 2014 base alloy and their composites with 5, 10, and 15 wt.% SiCp fabricated by stir casting route were subjected to wear test. Based on the encouraging wear performance, the Al-10 wt.% SiC composite was further subjected to extrusion. Pin-on-disc sliding wear tests on the as-cast & extruded base alloy and the composite samples were carried out at a constant load of 20 N for a total sliding distance of 1000 m with a velocity of 2 m/s. Microhardness and porosity measurements were carried out besides the study of wear performance, such as coefficient of friction and wear by weight loss. The worn surfaces were analyzed both by optical and scanning electron microscopes. The effect of particle addition, extrusion, porosity, and microhardness on the wear performance of the samples was discussed. Among the samples studied, the Al-10 wt.% SiC composite extruded at a ratio of 8:1 is found to have the highest wear resistance. [ABSTRACT FROM AUTHOR]

The deformation behavior of Al–Cu–Mg sintered preforms has been investigated by extrusion in the temperature range of 450–550°C and strain rate range of 0.1–0.3 s−1, respectively. The aim of this study is to analyze the effect of initial preform relative density on the hot deformation behavior and to model and predict the flow stress of extruded samples using constitutive equations. The true stress–strain curves exhibit three stages of deformation, which represent work hardening, dynamic recovery, and dynamic recrystallization during deformation at different temperatures, strain rates, and initial preform relative densities of 70%, 80%, and 90%, respectively. The results show that the flow stress values are influenced by initial preform relative density, deformation temperature, and strain rate. Microstructural examination of extruded specimens has been performed by optical microscopy and scanning electron microscopy. Arrhenius-type constitutive equations are developed to predict the flow stress of hot-extruded powder metallurgy processed aluminum alloy (Al–4%Cu–0.5%Mg). Zener–Hollomon parameter is used to explain the relationship between peak flow stress, temperature, and strain rate in an exponential equation containing the deformation activation energy and material constants. Subsequently, the statistical indicators correlation coefficient (R) and the average absolute relative error are assessed to confirm the validity of constitutive equations. The results indicate the experimental and predicted peak flow stress values are in good agreement, which indicate the accuracy and reliability of the developed model for powder metallurgy processed Al–4%Cu–0.5%Mg preforms. [ABSTRACT FROM AUTHOR]

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Homogeneous dispersion of high-content graphene nano-platelet (GNP) in metals is challenging due to the serious aggregation tendency of graphene. Traditional secondary processing such as extrusion usually has too limited shear strains to reach a desirable GNP dispersion state. Our previous work demonstrated that 1.0 vol% GNP/Al composite was successfully produced via multiple wire-drawing at ambient temperature. However, the fabrication of 5.0 vol% GNP/Al composite was not successful because of the limited cumulative shear strains. Here we described fully dispersed state of 5.0 vol% GNP in Al by hot-drawing at an elevated temperature 400 °C. The evolution of the microstructures and mechanical properties were investigated in relation to the number of drawing passes. The ultra-fine grains with size 372 nm were obtained via dynamic recrystallization after drawing for six passes (cumulative strain 94%). In particular, stripping of the GNP into thin layers and their preferential alignment in the wire axis occurred during the shear deformation. As a result, 5.0 vol% GNP/Al composite produced by six-pass drawing possessed improved yield strength (σs, 449 MPa) and ultimate tensile strength (UTS, 461 MPa). The results demonstrated the feasibility of dispersing high-content GNP in aluminum alloys by extrusion followed by multi-pass hot drawing techniques.

The paper addresses issues of interest related to the uniform distribution of the reinforcement phase and the continuity of the metal matrix, for two ways of obtaining the powder composites, the hot extrusion and the spark plasma sintering (SPS) respectively. The reinforcement phase is the nickel aluminides obtained by mechanical alloying in ball mills, and the metal matrix is made of aluminum powders. Prior to extrusion, the mixture of aluminum powders and nickel aluminides was pressed and subsequently sintered in environments with high carbon potential, so that in the final product, nickel aluminides, carbide and aluminum oxides were found as reinforcement phases. The obtained results confirmed the hypothesis that, from a blank product with a random distribution of the reinforcement phase, a product with an ordered distribution of the reinforcement phase is obtained after extrusion and that for the same initial proportion of nickel aluminides as reinforcement phase, the composite hardness obtained by hot extrusion is higher compared to that obtained by SPS, the difference being determined by the increase of the proportion of the reinforcement phase by the appearance of aluminum carbide and aluminum oxides during the sintering operation in the high carbon environment.

In this paper, the Conditional Average Estimator artificial neural network (CAE ANN) was used to analyze the influence of chemical composition in conjunction with selected process parameters on the yield strength and elongation of an extruded 6082 aluminum alloy (AA6082) profile. Analysis focused on the optimization of mechanical properties as a function of casting temperature, casting speed, addition rate of alloy wire, ram speed, extrusion ratio, and number of extrusion strands on one side, and different contents of chemical elements, i.e., Si, Mn, Mg, and Fe, on the other side. The obtained results revealed very complex non-linear relationships between all of these parameters. Using the proposed approach, it was possible to identify the combinations of chemical composition and process parameters as well as their values for a simultaneous increase of yield strength and elongation of extruded profiles. These results are a contribution of the presented study in comparison with published research results of similar studies in this field. Application of the proposed approach, either in the research and/or in industrial aluminum production, suggests a further increase in the relevant mechanical properties.

The effect of different Ti contents on the microstructures and tensile mechanical properties of the hot-extruded Cu-15Ni-8Sn alloys was investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy and tensile test. The results show that both ultimate tensile strength and yield strength increase significantly with the increase of Ti content, while elongation decreases. The addition of 0.02% (mass fraction, the same below) Ti facilitates the precipitation of γ-(Cu, Ni)3Sn phase, and thereby leads to a significant refinement of recrystallization grain. When the content of Ti increases to 0.3%, a small quantity of needle-like Ni3Ti phase is formed, which abates the effect of γ precipitates on inhibition of recrystallized grains growth. With the addition of up to 0.5% Ti, a larger amount of Ni3Ti precipitates are formed, which enhance the effect of recrystallized grain refinement; however, a few Ni3Ti precipitates become large and deteriorate the elongation of the alloy. In this study when 0.3% Ti is added, the mechanical properties of the alloy are preferable, where the tensile strength, yield strength and elongation are 875, 713MPa and 24.1% respectively.

In the present paper, the trace B doped Ni3Al alloy was prepared by the thermal explosion and hot extrusion (TH/HE) technique. Its micro-structure characterization and mechanical properties were carried out by OM, XRD, TEM, compression and micro-hardness tests. Micro-structure examinations exhibit that the TH/HE technology has transformed the powders into Ni3Al alloy with less porosity. In the synthesized part, coarse and ultrafine Ni3Al grains comprise the dual-scale grain structure with segregated Al2O3 particles along grain boundary. TEM observations reveal that γ-Ni, Al2O3 and Ni3Al phases coexist in the synthesized part. Moreover, the Al2O3 particles in the synthesized part have α-Al2O3 and γ-Al2O3 two crystal structures. In addition, there is a transition region along the interface of Al2O3 and Ni3Al grain. The subsequent hot extrusion optimize the micro-structure of the extruded part by homogenizing the Ni3Al grain, uniformly distributing Al2O3 and generating massive substructures. The great deformation results in the pile-up of dislocations, intersected dislocations and substructures. Moreover, the movement of dislocation promotes the formation of micro-twinning in the Ni3Al grain, which is accompanied with the stacking faults and nano-structure. The mechanical properties exhibit that the micro-structure optimization caused by the TE/HE technology improves the compressive ductility and strength of the Ni3Al alloy obviously. DOI: http://dx.doi.org/10.5755/j01.ms.24.4.19460

In this paper, fabrication and characterization of Al-SiC nanocomposites is investigated. The Al matrix is reinforced with different amounts of SiC nano-particles using mechanical milling, cold pressing, and, hot extrusion techniques. To get the best quality of the samples, the extrusion process is optimized firstly. With this regard, hot extrusion parameters such as the rate of extrusion, temperature, the extrusion ratio, lubrication, and the die set dimensions are experimentally studied. Finally, the nanocomposites with relative density more than 99% could be successfully fabricated under extrusion ratio of 8.5:1. As-extruded billets were then used to prepare standard tensile test specimens based on ASTM-E8. Afterwards, relative density, tensile behaviour, and micro-hardness of the samples were determined. The results show about 50% improvement for both the tensile strength and micro-hardness and near 1% reduction of relative density as the content of SiC reinforcement increases to 3 vol%. Therefore, specimens with higher strength-to-weight ratio which is a key parameter in aerospace and automotive applications can be produced using current techniques.

With excellent radiation resistance and high temperature strength, the oxide dispersion strengthened (ODS) nickel-based superalloys are deemed as candidate materials for advanced fission and fusion reactor. Since conventional manufacturing processes are difficult to produce components with complex shapes, additive manufacturing becomes an alternative method. In this work, ODS nickel-based superalloy was manufactured by laser metal deposition (LMD) technology using mechanically alloyed powder. The microstructure and high temperature mechanical properties of the as-deposited alloy were analysed. The results indicated that the as-deposited alloys prepared by this method owned anisotropic structure and uniformly distributed high-density oxides, contributing to superior high-temperature performance, in comparison with the samples produced by LMD using pre-alloyed powder and traditional hot extrusion. [ABSTRACT FROM AUTHOR]

A combination of numerical simulations and experiments was used to study the influence of glass lubricant on the hot extrusion of Inconel 625 alloy. The results showed that the glass lubricant left a large amount of abrasive debris and furrows on alloy surface, which produced different friction states. The use of a lubricant changed the alloy microstructure, decreasing the grain size, the high-angle grain boundaries (HAGBs), and the dynamic recrystallization volume fraction of the sample with lubricant. The temperature increase due to deformation and friction heat significantly affected the stress, strain, and flow rate of the billet during extrusion. The uneven friction states generated excessive local frictional heat, making the billet prone to overheating and crack initiation. The frictional heat caused local grain size and stress differences in the billet, causing further expansion of cracks. [ABSTRACT FROM AUTHOR]

This paper focuses on studying the influence of texture on the deformation mechanism of oxide dispersion strengthened (ODS) 18Cr ferritic steel subjected to high-temperature tensile testing after consolidation by hot extrusion. The initial microstructure of the hot extruded steel showed preferential (1 1 0) planes alignment in perpendicular and parallel direction to extruded (ED) and transverse (TD), respectively. Two types of anisotropy have been highlighted: (1) A strong anisotropy of elongation properties with a transverse ductility is lower as compared to the axial ductility; (2) yield stress anisotropy (mechanical strength anisotropy) which is found to be temperature dependent. The material flow in 〈1 1 1〉 direction is observed during the application of load along extruded direction during the tensile test; however, (1 1 0) slip plane normal is parallel to the direction of loading for transverse direction and brings the Schmid factor to a lower level which makes slip activation unlikely. Deformation band is found to be aligned with the loading direction in the ED specimen and covering across a number of neighboring ferrite grains could be noticed irrespective of material flow. However, the areas near the grain boundaries in the microstructure are found to be the strain gradient regions. Further, it shows a preferential accommodation of strain in proximity to the boundary network for TD specimen. High temperature (973 K) tensile test in ED is found to promote grain-subdivision of elongated bands by dynamic recrystallization, and inverse pole figure distribution reveals a preferential increase in the intensity of clustering toward (1 1 1) plane parallel to the loading direction. [ABSTRACT FROM AUTHOR]

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