Hot Extrusion Process Research Articles

Review and analysis of extrusion technology in the production of feed additives based on probiotic microorganisms

Ensuring a well-organised and sustainable feed base is the main condition for the development of animal husbandry, increasing its productivity and product quality. To ensure active growth and high productivity, probiotic feed additives are added to the feed, which increase the immune response of the host organism to pathogenic microorganisms, increases the conversion of feed and live weight gain. One of the main processes of feed production is extrusion, which can be cold, warm and hot. The hot extrusion process takes place at a temperature above 130℃ and cannot be used in the production of compound feeds with probiotics that withstand temperatures up to 85℃. During cold extrusion, the temperature reaches no higher than 70℃, which allows the extrusion of mixed feed mass, which contains probiotic feed additives.

Comparative Study of Prior Particle Boundaries and Their Influence on Grain Growth during Solution Treatment in a Novel Nickel-Based Powder Metallurgy Superalloy with/without Hot Extrusion

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.

Effect of Varying Hot Extrusion Temperatures on the Properties of a Sinterless Turning Induced Deformation Processed Eco-Friendly Mg-Zn-Ca Alloy

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.

Processability of mesoporous materials in fused deposition modeling for drug delivery of a model thermolabile drug

The incorporation of drug-loaded mesoporous materials in dosage forms prepared with fused deposition modeling (FDM) has shown the potential to solve challenges relating to additive manufacturing techniques, such as the stability of poorly-soluble drugs in the amorphous state. However, the addition of these non-melting mesoporous materials significantly affects the mechanical properties of the filament used in FDM, which in turn affects the printability of the feedstock material. Therefore, in this study a full-factorial experimental design was utilized to investigate different processing parameters of the hot melt extrusion process, their effect on various mechanical properties and the potential correlation with the filaments' printability. The thermolabile, poorly-soluble drug ibuprofen was utilized as a model drug to assess the potential of two mesoporous materials, Mesoporous Magnesium Carbonate (MMC) and a silica-based material (MCM-41), to thermally protect the loaded drug. Factorial and principal components analysis displayed a correlation between non-printable MCM-41 filaments and their mechanical properties where printable filaments had a maximum stress >7.5 MPa and a Young's modulus >83 MPa. For MMC samples there was no clear correlation, which was in large part attributed to the filaments' inconsistencies and imperfections. Finally, both mesoporous materials displayed a thermal protective feature, as the decomposition due to the thermal degradation of a significant portion of the thermolabile drug was shifted to higher temperatures post-loading. This highlights the potential capability of such a system to be implemented for thermosensitive drugs in FDM applications.

Achieving ultra-high strength in Be/Al composites by self-exhaust pressure infiltration and hot extrusion process

Beryllium particle reinforced aluminum matrix (Be/Al) composite with exceptionally high strength was fabricated from Be debris by self-exhaust pressure infiltration and hot extrusion process. The microstructures characteristics and mechanical properties of the Be/Al composite at as-cast and as-extruded state were systematically investigated in the current study. It was found for the as-cast composite that uniform distribution of beryllium particles with average size of 2.2 μm were achieved, the microcracks in beryllium particles were repaired in situ by infiltrating liquid aluminum into these microcracks under external pressure. The Be phase and Al phase were well bonded despite the presence of nano BeO at the interface. After hot extrusion, the beryllium particle deformed and elongated along the extrusion direction. The average grain size of Al was refined from hundreds of microns to 450 nm, and the dislocation density increased significantly. The tensile strength and yield strength of Be/Al composite reached 595 MPa and 494 MPa by hot extrusion, respectively. The ultra-high strength was mainly related to grain boundaries strengthening, dislocation strengthening, precipitation strengthening and load transfer strengthening. Compared with the composites prepared by the investment casting and powder metallurgy methods, the Be/Al composite showed more than 100% increment in strengthening efficiency and 80% increment in yield strength. It indicated that the self-exhaust pressure infiltration technology combined with hot extrusion process was a feasible and successful method to prepare high performance Be/Al composites.

Pharmaceutical hot melt extrusion process development using QbD and digital twins

Pharmaceutical product development guided by Quality by Design (QbD) is based on a complete understanding of the critical process parameters (CPPs) that are important for achieving the desired product critical quality attributes (CQAs). The effect of process settings, such as the screw speed, the throughput, the barrel temperature, and the screw configuration, is a well-known factor in the setup of pharmaceutical hot melt extrusion (HME) processes. A CPP that has not yet been extensively researched is the type of cross-section geometry of the screw elements. Typically, pharmaceutical extruders have double-flighted screw cross-sections, with some elements having a single- or triple-flighted element section. The exception is a NANO16 extruder from Leistritz, with all screw elements having a triple-flighted screw geometry. We investigated the process setup and scale-up to a double-flighted extruder experimentally and in silico via a digital twin. Two formulations were processed on a NANO16 extruder and virtually transferred to a ZSE18 double-flighted co-rotating twin-screw extruder. Detailed smoothed particle hydrodynamics simulations of all screw elements available from both extruders were performed, and their efficiency in conveying, pressure build-up, and power consumption were studied. Reduced-order 1D HME simulations, which were carried out to investigate the process space and scalability of both extruders, were experimentally validated.

Preparation of Mg2Si/Al–Cu composite under a novel continuous squeeze casting-extrusion process assisted with ultrasonic treatment

In this study, in-situ 3 wt% Mg2Si/Al–Cu composites have been prepared by a novel continuous squeeze casting-extrusion (CSCE) process assisted with ultrasonic treatment (UT) for the first time. Different from the traditional semi-continuous hot extrusion process, the new method eliminates billet homogenization annealing and preheating. After UT + CSCE, the fine Al2Cu and eutectic Mg2Si phases in the UT + SC (squeeze casting) billet are further crushed to form a fibrous microstructure distributed along the extrusion direction (ED). Moreover, the α-Al grains are elongated along the extrusion direction, and the proportions of LAGBs (low-angle grain boundaries) and HAGBs (high-angle grain boundaries) are 72.3% and 27.7%, respectively. Meanwhile, fiber textures with orientations <111>//ED and <100>//ED are formed, and the ratios of the two textures are 60.9% and 30.5%, respectively. After UT + CSCE, the ultimate tensile strength (UTS), yield strength (YS) and elongation of the in-situ 3 wt% Mg2Si/Al–Cu composite are 330 MPa, 250 MPa and 11%, and its YS and elongation are 23.2% and 69.2% higher than those of the UT + SC billet, respectively. Compared with the Al–Cu alloy prepared by UT + CSCE, its UTS and YS are increased by 11.9% and 38.9%, respectively.

Analysis of wear of a nitrided AISI H13 hot work tool steel in an aluminium hot extrusion process

The present work present experimental results of hot wear testing of AISI H13 tool steel with the aim of replicating the wear mechanisms occurring during hot extrusion process. The hot wear tests were carried out at a temperature of 550 °C and a sliding speed of 0.5 m/s for sliding distances of 1800, 3600 and 5400 m. A pin-on-disk test fixture was designed and fabricated to investigate the sliding between nitrided AISI H13 steel pins and 6063 aluminium alloy disks in a "flat surface-flat surface" conformal contact mode. The different characterisation techniques used (SEM/EDS, XRD) helped to better explain the complex wear mechanisms leading to surface degradation in the tribological couple. Graphitisation phenomenon caused by the dissolution of metastable iron carbide Fe3C was observed to occur after a sliding distance of 3600 m. In addition, coarsening, coalescence and tearing of carbides in the ultimate lower valleys of the degraded surface were observed to occur after 5400 m sliding distance. Nano-indentation technique was used to evaluate the cross-sectional hardness evolution of the nitrided layer, and results showed that the maximum value of hardness of 12.01 ± 0.63 GPa was obtained at the nearest point of the surface. Volume and surface parameters were used to characterise the surfaces before and after wear damage as function of sliding distance. The progressive variation and evolution of the peak material volume parameter (Vmp), core material volume (Vmc), core void volume (Vvc) and dale void volume (Vvv) parameters reached higher values after wear testing at 3600 m sliding distance indicating a synergy between different and complex wear mechanisms.

Key technologies of cooling and lubrication for closed hot extrusion automatic production line

For the problems that the stability problem that affects the fully automated production of precision extrusion of cylindrical parts, the cooling and lubrication of the die under high temperature and high pressure is the key technology that affects the production stability. During the hot extrusion process, the punch die has a short life under high temperature and high pressure, and cannot be Achieving continuous production and maintaining the life of the punch is the key technology to realize high-efficiency unmanned production of hot extrusion automation. First, the temperature rising and cooling formula for die especially for punch was obtained by theoretical calculation. The convective heat transfer coefficient on the surface of the internal cooling pipe was calculated and punch cooling device was made based on the forced convection heat transfer of cooling water. The changing law of the temperature field after punch extrusion was obtained by the infrared temperature measuring device and the test results were consistent with the theoretical calculation results.

Adjusting the melting point of an Active Pharmaceutical Ingredient (API) via cocrystal formation enables processing of high melting drugs via combined hot melt and materials extrusion (HME and ME)

One of the biggest challenges for the application of materials extrusion (ME) technology in the pharmaceutical sector is the lack of ready-to-use polymeric materials (filaments) of pharmaceutical quality. To overcome this challenge materials extrusion can be combined with the Hot Melt Extrusion (HME) process enabling the production of filaments using pharmaceutically approved polymers with incorporated drugs. This manuscript presents a step by step approach for the formulation of additively manufactured tablets containing a high melting point API (hydrochlorothiazide, HCT, T m = 266-268 °C) with two pharmaceutically approved polymers (polyvinyl alcohol, PVA and hydroxypropyl methylcellulose acetate succinate, HPMCAS) of different technological and pharmaceutical properties via combined HME and ME processing. The thermal properties of a model drug were adapted to the processing window of both HME and ME by obtaining a hydrochlorothiazide: nicotinamide cocrystal (HCT:NIC) with a lower melting point (T m = 173.3 °C) than the starting material. Two plasticizers were used - triethyl citrate (TEC) for HPMCAS and sorbitol (SOR) for PVA. Blends containing 10-50 wt. % of plasticizer were prepared using the fusion method and thoroughly analysed using PXRD, DSC, and FTIR enabling the selection of formulations for further HME processing. Placebo filaments with 10-30 wt. % of plasticizer were obtained and their mechanical properties and ME processability were assessed to select a polymer blend with desirable process parameters. Finally, the filaments containing 20 wt. % of plasticizer with HCT or the HCT:NIC cocrystal were produced and processed using ME to form tablets. The phase of the drug (crystalline or amorphous), mechanical properties of filaments and tablets as well as the drug content in the obtained materials were assessed using PXRD, DSC, and FTIR followed by materials imaging with polarising microscopy and SEM. The cocrystal formation not only enabled to modify the melting point of the drug to match the temperature of both processes but also improved the mechanical properties of the filaments which is important for ME processing. In the case of PVA based formulations the cocrystal turned amorphous upon HME processing forming flexible and printable filaments. In contrast, the drug embedded in HPMCAS based filaments formed crystals that affected the mechanical properties of the extrudates. The mechanical properties of the obtained tablets and the release profile of the drug from the AM tablets were enhanced as compared to the materials obtained using conventional methods, i.e. tableting and encapsulation. • High melting drugs can be incorporated into pharmaceutically approved polymers in the form of cocrystals via combined HME and ME processing, • Modification of physicochemical properties of the API via cocrystal formation enables successful processing of high melting point APIs into elastic filaments, • Low miscibility of the drug with polymers and the presence of crystalline drug in the filaments may result in brittle materials difficult to process via ME, • Openwork 3D tablet structure and cocrystal formation substantially improve drug dissolution.

Hot melt extrusion: A single-step continuous manufacturing process for developing amorphous solid dispersions of poorly soluble drug substances

In today’s world with increasing patient population, the demand for pharmaceutical medications is increasing enormously. However, poor solubility of drug substances and underdeveloped manufacturing process are affecting the revenue of the pharmaceutical industries. Improving the solubility and establishing a robust manufacturing process is the primary prerequisite of the developmental scientists. Among various approaches amorphous solid dispersion has gained a tremendous response for improving the solubility of the drug substances. In addition, the process of hot melt extrusion has attracted the investigators from regulatory agencies and industries. The process of hot melt extrusion involves application of thermal and mechanical energy on to the processing material. The process requires no solvent and is referred as “green technique.” Various factors need to be taken into consideration for developing amorph amorphous solid dispersions. The miscibility of drug and polymer, solubility of drug in polymer, drug-polymer interactions, glass transition temperature, storage conditions majorly influence the stability of the amorphous solid dispersions systems. Though hot melt extrusion is most widely employed for developing amorphous solid dispersions still a lot of research is warranted for developing strategies to formulate high drug loading medications with improved stability. This review article mainly focuses on the instrumentation, and process for developing amorphous solid dispersions by hot melt extrusion with a small note on the various advantages and limitations.

Development of the Composition and Technology for Production a Solid Dispersion System by Hot Melt Extrusion to Increase the Bioavailability of the Active Substance

Introduction. The solubility of an active pharmaceutical ingredient plays a major role in drug absorption. Hot melt extrusion is a batch or continuous process that allows creating solid dispersion systems based on various carriers in order to increase solubility and bioavailability of active substances. Development of effective and safe analgesics is one of the most vital tasks of organic and medicinal chemistry. An innovative non-opioid analgesic with very low toxicity and low dosage, but practically insoluble in water, was used in this work. It was suggested to obtain a solid dispersion by hot melt extrusion in order to increase bioavailability.Aim. Development a hot melt extrusion technology for production of a solid dispersion system of PAV-0056 as an active substance and Plasdone™ S-630 as a polymeric carrier to increase the solubility.Materials and methods. PAV-0056 (methyl-2-(7-nitro-2-oxo-5-phenyl-3-propoxy-2,3-dihydro-1H-benzo[e][1,4]diazepin-1-yl)acetate) (JSC "Organica", Russia) Figure 1; Plasdone™ S-630 (Boai NKY Pharmaceuticals Ltd., China); PEG-1500 (Clariant, Switzerland); acetonitrile for chromatography (Thermo Fisher Scientific, Germany). Extrudates were obtained using a HAAKE™ MiniCTW co-rotating twin-screw laboratory extruder (Thermo Fisher Scientific, Germany). Extrudates were examined by optical microscopy and differential scanning calorimetry, and time of water solution stability was determined. The quantitative content of the active substance and related impurities in the 2.5 % solid dispersion of PAV-0056 was determined by HPLC-UV.Results and discussion. Hot melt extrusion process conditions were established for a mixture of 2.5 % PAV-0056 and Plasdone™ S-630. Stability of the extrudate solution in water was studied, the content of the active substance and impurities in the extrudates was determined. Based on the binary mixture, a composition containing 10 % of PEG-1500 was developed. The optimal conditions for the extrusion process were chosen for obtaining a solid dispersion system that meets the requirements of the regulatory documentation for the content of the active substance and impurities.Conclusion. The binary mixture proved to be unsuccessful for the creation of SDS by hot melt extrusion due to significant accumulation of impurities during the extrusion process. By adding PEG-1500 to the composition, it was possible to considerably lower the operating temperature of the process, reduce the impurity content in the extrudate, and maintain satisfactory stability of the PAV-0056 solution in water.

Tensile flow behavior of AA7075–Ag/C composites evaluated by the Hollomon and Voce equations

Annealed 7075 aluminum (AA7075) alloy swarf and carbon-coated silver nanoparticles were mechanically milled for 10 h to produce nanostructured composites. The obtained powders were compacted, sintered, and hot extruded for obtaining round bars. Silver nanoparticles acted as a process control agent, reducing the crystallite size and powder particle size. In addition, they kept their spherical form after hot extrusion process, and were seen homogeneously distributed into the aluminum matrix. From these bars, tension specimens were produced and tested. The flow curves generated were evaluated using the Hollomon and Voce equations. The different terms of such equations were employed to obtain mathematical expressions relating the amount of silver nanoparticles. Both equations generated a suitable mathematical fitting of the curve, finding that the Hollomon equation overestimated the stress at higher deformations, while the Voce equation produced a better fitting of the entire flow curve. Overestimation of the flow curve is undesirable in formability processes; therefore, the Voce equation should be used when it concerns such processes.

A Review of Various Manufacturing Approaches for Developing Amorphous Solid Dispersions

In recent years amorphous solid dispersions (ASD) has gained a tremendous response for improving the solubility of poorly water-soluble drug substances. Despite the stability challenges, various ASD commercial products have been successfully launched into the market over the last two decades. Among various manufacturing approaches, hot melt extrusion (HME) and spray drying techniques have attracted industries attributing to their simple manufacturing processes. In addition, KinetisolÒ, a solvent-free approach, is also being most widely investigated for developing ASDs since the thermal exposure time of the formulations is significantly less compared with the hot melt extrusion process. KinetisolÒ can be employed for developing ASDs of thermolabile drug substances. Another solvent-based technique, electrospinning, is also employed for developing nanofibers-based ASD. However, much research is warranted for the electrospinning process before implementing it in commercial manufacturing. Various critical factors such as drug-polymer solubility, the solubility of the drug in the polymer, drug-polymer interactions, type of manufacturing process, and storage conditions need to be considered for developing a stable and robust ASD formulation. This review mainly focuses on the most advanced manufacturing technologies of ASDs, namely HME, spray drying, KinetisolÒ, and electrospinning, along with a note on the various critical factors that affect the stability of ASD formulations.&#x0D; Keywords: amorphous solid dispersions; hot melt extrusion; spray drying; KinetisolÒ; electrospinning

Microstructural evolution of nanodiamond-reinforced aluminum matrix composites during the process of hot extrusion

Nanodiamond (ND) has been recently considered to be an excellent reinforcement for strengthening metal matrix composites. However, most of the previous studies focused on manufacturing process, final structure, and mechanical properties. Systematic exploration of the microstructural evolution, which is critical to understand the effect mechanism of ND particles, still lacks. Herein, we seek to understand the effect of ND particles on microstructural evolution via comparative investigation of microstructures in different test points on extrusion remnant specimens of pure aluminum, 0.5 wt% and 1.0 wt% ND-reinforced aluminum composites prepared by powder metallurgy and hot extrusion. Finite element simulations were used to analyze the relative stress–strain states and deformation modes in different test points. Electron backscatter diffraction and transmission electron microscopy studies reveal that the mean grain size of ND-reinforced aluminum composite declined rapidly after entering the extrusion deformation zone. Microstructures in simple shear, tensile pure shear, and compressive pure shear deformation modes were quite different. The dispersed ND particles effectively promoted grain refinement and improved dislocation driving force with the increase in plastic strain. The large localized high-content ND clusters were broken into small ones, and small ones acted as non-deformable particles to stimulate nucleation and recrystallization under high dislocation driving force. Test results show that the hardness of 0.5 wt% and 1.0 wt% ND-reinforced aluminum composites was 1.9 and 2.1 times that of pure aluminum, respectively. The 0.5 wt% ND-reinforced aluminum composites exhibited optimal comprehensive mechanical properties with a tensile strength of 205 MPa and elongation of 18%, which were 115% and 91% of pure aluminum, respectively.

Microstructures and mechanical properties of Mg–5Li–4Sn–2Al–1Zn alloy after hot extrusion

In this work, Mg–5Li–4Sn–2Al–1Zn deformed magnesium alloy was prepared and the effects of the extrusion process on its microstructure, texture evolution, and mechanical properties were investigated. The microstructures of as-homogeneous and as-extruded alloys were characterized by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results show that the alloy underwent dynamic recrystallization (DRX) after hot extrusion processes. Drastic refinement occurred in grain size, and the weakening of the basal fiber texture was obvious after the Forward-Parallel Channel Extrusion process, and the microstructure was more uniform. As a result, the mechanical properties of the alloy were superior after the Forward-Parallel Channel Extrusion process, and the best combination of strength and plasticity was obtained after the 105° FPE process. YS, UTS, and EL were 187 MPa, 275 MPa, and 15%, respectively. The increase in strength is mainly attributed to grain boundary strengthening and the pinning effect of shattered particles on the migration of dislocations and grain boundaries. The increase in plasticity can be explained by the activation of non-basal slip and the weakening of the basal fiber texture, the fine grains can coordinate the plastic deformation well and improve the plasticity of the alloy to some extent.

The solid-state combustion synthesis of in-situ hybrid (Al3Ni+Al2O3)/Al composites and evaluation of its mechanical properties

In-situ hybrid (Al3Ni+Al2O3)/Al composites with bimodal size particles distributions were fabricated via an Al-NiO solid-state combustion reaction and subsequent hot extrusion process. The reaction system between Al and NiO was investigated by differential thermal analysis (DTA). The presence of Al2O3 and Al3Ni in the matrix was verified by XRD/EDS analysis. The in-situ formed Al3Ni phase with varying morphologies and sizes such as particle, plate, strip and flake at different sintering temperatures were observed. And the exothermic reaction of Al-NiO can be reduced to below the melting point of Al, and the desirable sintering temperature was. 600 ℃. In hot-extruded samples, both nano Al2O3 and Al3Ni particles distributed homogeneously, and most of Al3Ni particles is smaller than 2 µm in size. When NiO content increases from 8% to 12%, Al matrix grains in composites can be refined from 1.7510 µm to 1.2050 µm. The mechanical properties of composites are enhanced significantly due to the introduction of Al3Ni and Al2O3 particles, and can be up a YS of 322 MPa and a UTS of 407 MPa in the 15% NiO-Al composite. In addition, when the content of NiO increases from 10% to 12%, the strength of composites enhances without obvious sacrifice of EI. The strengthening and toughening mechanisms also was discussed in detail.

STUDY ON THE CORROSION RESISTANCE CHARACTERISTICS OF N-TiO2/Al2O3 REINFORCED HYBRID Mg COMPOSITES

The Mg based composites with the element addition of 3Zn, 0.5Mn and the reinforcement of ceramic particles nanoTiO2 and Al2O3 are added to form an Mg- hybrid composites through powder metallurgy method. The examination is mainly concentrated on the effect of multi ceramic particles such as nanoTiO2 and Al2O3 inclusion in the composite matrix for the characteristics of hardness, tensile strength, wear and corrosion. Optical and scanning electron microscopy are used for the micro structural variation. X-ray diffraction is used to analysis the various phases available in the hybrid composites matrix. Many intermetallic phase are formed during heat treatment process which reduces the porosity and increases density and corrosion resistance of the composites. The hard ceramic particles inclusion, hot extrusion process and heat treatment or stress-relieving mechanism enhances the above said properties of the prepared hybrid composites.

The role of interfaces in governing processing and properties of stacked hot extrusion of multilayered Al composites with amorphous interlayers

In order to prepare high-strength lightweight components with aluminum alloys and Zr-based amorphous alloys and to avoid brittle fracture, the fabrication of 7075/Zr44Ti11Cu10Ni10Be25/7075 composites by stacked hot extrusion process is proposed in this study. In the supercooled liquid region (SLR) of Zr44Ti11Cu10Ni10Be25 (Vit1b), experiments were conducted with seven different temperature-velocity combinations, the effects of extrusion conditions on the connected interfaces of 7075/Vit1b/7075 composites and the thickness uniformity of Vit1b interlayers were systematically investigated. The results show that: too fast or slow extrusion speed and too high extrusion temperature can lead to crystallization or phase separation of amorphous alloys. The most uniform and continuous Vit1b interlayers can be obtained under the extrusion conditions of heating temperature 430 °C–440 °C and extrusion speed 2 mm/min-3 mm/min. The hardness of Vit1b interlayers increases with the increase of the extrusion temperature while it decreases as the extrusion speed increases. The holes at the interface between amorphous and aluminum alloys are gradually filled by element diffusion, forming discontinuous diffusion areas at the interface, allowing Vit1b and 7075 to be connected.

Manufacturing of (Al–10Zn) / TiB2 in-situ nanocomposites by reactive liquid metallurgy and hot-extrusion for enhanced interfacial bonding and mechanical properties

This work systematically deals with the development of an (Al–10Zn) die-casting alloy reinforced with in-situ synthesized hexagonal-shaped TiB2 nano-rods through casting and hot-extrusion processes. The cast specimens were extruded at 673 K with an extrusion ratio of 2:1 to orient the micro-texture, generate sub-grains within grains, reorder the reinforced in-situ TiB2 nanoparticles in the matrix, and engender strain fields to improve the mechanical properties. The nanoscale hexagonal TiB2 nano-rods (∼89 nm length and 14 nm edge) were synthesized by the chemical reaction of two halide salts (K2TiF6 and KBF4) with (Al–10Zn). The fabricated AMNCs were characterized using diffracted beams (XRD), scattered beams (FESEM and EBSD) and transmitted beams (TEM) received from the specimen. The diffracted beams from the X-rays reveal the formation of a TiB2 phase with a major α-Al phase and an individual Zn phase. The scattered beams from FESEM and EBSD revealed the homogenous distribution of TiB2 with less particle-free spacing, refinement of grains to an ultrafine level, and the absence of imperfections such as voids and interfacial de-bonding. The strain fields were observed through transmitted beams in the TEM analysis which were engendered by the thermal misfit between the matrix and TiB2 reinforcement. Among the fabricated AMNCs, (Al–10Zn) + 6 wt% TiB2 nanocomposite exhibited higher mechanical strength (160 MPa UTS) whereas (Al–10Zn) + 4.5 wt% TiB2 nanocomposite retained the ductility with improved strength (151.7 MPa UTS and 40% elongation). The strengthening mechanisms were computed using the (a) Zheng and Chen model and (b) Modified Cylne model to estimate the contribution of individual strengthening, and compared with the experimental results. The grain size strengthening contributed more to the total strength owing to the Zener pinning effect by in-situ TiB2 nano-rods.