Low Extrusion Research Articles

Effects of Extrusion Parameters by KoBo Method on the Mechanical Properties and Microstructure of Aluminum

Abstract Commercial purity aluminum was extruded by means of KoBo method at varied processing parameters. Received extrudates, with different mechanical and electrical properties and work hardening behavior, were obtained. It was found, that some conditions of KoBo extrusion process such as low initial billet temperature, low extrusion rate and low frequency of oscillating die lead to extremely high strength and high electrical resistivity of the material. The absence of work hardening (up to 40% strain) during subsequent groove rolling is also a specific feature of received materials. It was suggested that mentioned features are related to the development of overbalance concentration of point defects (clusters) generated during the extrusion process. During following cold rolling of the extrudate, mentioned defects annihilate at gliding dislocations and make the dislocation climbing and their rearrangement easier. Therefore, until the exhaustion of this mechanism, the hardening of material during cold rolling is very limited. Following increase of the material strengthening at higher rolling strains point to the return of the material to its typical behavior observed for cold deformed aluminum produced by conventional hot extrusion.

Extrusion of flavored corn grits: Structural characteristics, volatile compounds retention and sensory acceptability

The effects of the moisture content of the raw material, extrusion temperature and screw speed on flavor retention, sensory acceptability and structure of corn grits extrudates flavored with isovaleraldehyde, ethyl butyrate and butyric acid were investigated. Higher temperature resulted in more expanded extrudates with lower density and cutting force, while higher moisture content increased ethyl butyrate retention. The most acceptable extrudates were those obtained with low moisture content, under conditions of high extrusion temperature and high screw speed, or low screw speed and low extrusion temperature, whereas the aroma intensity closest to the ideal was observed under conditions of low extrusion temperature and low moisture content of the raw material.

Morphology of oxide and interface structure in AZ31B magnesium alloy prepared by solid state recycling

Ultrathin AZ31B magnesium alloy chips were recycled by solid state recycling process at different extrusion ratios. The morphology and distribution of the oxide in recycled magnesium alloy were characterised, and the interface structure between the oxide and magnesium alloy matrix was investigated by means of high resolution transmission electron microscopy. The results indicate that the oxide film introduced from the surface of the chip was broken up in the process of extrusion. MgO shows a nanoscale spherical particle and homogeneously distributes in some tiny areas in the magnesium alloy matrix. In the investigated extrusion ratio range, the diameter of the MgO particle differs little. However, the oxide film was not broken up completely in the recycled alloy with low extrusion ratio. The oxide particle exhibits good bonding with the magnesium matrix. The dispersion strengthening of MgO particle will contribute to the higher strength of recycled magnesium alloy, whereas the good bonding of MgO and magnesium matrix is the prerequisite.

Structure memory effects of polyethylene blends in temperature window

Temperature window effect has been used to extrude polyethylene blends 5000s/TR-571 and bimodal polyethylene GC100s with low extrusion temperatures and pressures. Rheological results indicate that the temperature window effect occurs during the extrusions of the GC100s and blends 5000s/TR-571. For the blends 5000s/TR-571, both the temperature window and the minimum extrusion pressure dramatically decreases with increasing content of 5000s. For bimodal polyethylene GC100s, successive self-nucleation and annealing (SSA) fractionation results suggest that the pick at high temperature on the SSA curve of the extrudates obtained inside the temperature window is remarkably lower than those of the extrudates obtained outside the temperature window. This indicates that the lamellae of the extrudates obtained in the window are thinner than those obtained outside the window, which is attributed to the fact that the well-aligned chains as the result of structure memory effect can act as nucleating agent in the crystallization process. POLYM. ENG. SCI., 54:303–309, 2014. © 2013 Society of Plastics Engineers

Development and characterization of novel alginate-based hydrogels as vehicles for bone substitutes

In this work three different hydrogels were developed to associate, as vehicles, with the synthetic bone substitute GR-HAP. One based on an alginate matrix (Alg); a second on a mixture of alginate and chitosan (Alg/Ch); and a third on alginate and hyaluronate (Alg/HA), using Ca2+ ions as cross-linking agents. The hydrogels, as well as the respective injectable bone substitutes (IBSs), were fully characterized from the physical–chemical point of view. Weight change studies proved that all hydrogels were able to swell and degrade within 72h at pH 7.4 and 4.0, being Alg/HA the hydrogel with the highest degradation rate (80%). Rheology studies demonstrated that all hydrogels are non-Newtonian viscoelastic fluids, and injectability tests showed that IBSs presented low maximum extrusion forces, as well as quite stable average forces. In conclusion, the studied hydrogels present the necessary features to be successfully used as vehicles of GR-HAP, particularly the hydrogel Alg/HA.

Effect of lubrication and green-compact shape on mechanical properties of mechanically alloyed Zn-22wt%Al powders during hot extrusion of spur gears

We investigated the extrusion behavior of mechanically alloyed Zn-22wt%Al powders with different lubricants and green-compact shapes. The mechanical alloying of powder particles was performed by planetary ball milling for 4 h, 8 h, 16 h, 32 h, and 64 h. The mechanical properties of these powders, as compacted and sintered cylindrical preforms, were estimated by uniaxial compression tests. The alloyed powder with an average particle size of 10 μm obtained after milling for 32 h had the highest compressive strength (288 MPa). Extrusions of miniature spur gears with pitch circles of 1.8 mm using the alloyed powder were carried out at different extrusion temperatures. An extrusion temperature of 310°C resulted in the highest Vickers hardness without surface defects when alloyed powder milled for 32 h was used. To investigate the effect of green-compact shape and lubricant on the dimensional accuracy and cracking regions during the first stage of hot extrusion, extrusion experiments with conical- or cylinder-type green compact shapes and BN spray or a graphite lubricant were performed at an extrusion temperature of 310°C. The results showed that the extrusion of spur gears by using the conical-shaped billet and graphite lubricant resulted in a low extrusion load, good surface roughness, a short cracking region during the first stage, and high dimensional accuracy.

Experimental, Analytical, and Numerical Studies on the Forward Extrusion Process

This article in concerned with studying the effect of die profile on the load and energy necessary for plane-strain forward extrusion. With this regard, the geometries of the second-order polynomial and exponential die profiles were optimized in order to minimize the required extrusion pressure calculated based on the slab method. These optimal extrusion dies and the relevant linear one were manufactured for three extrusion ratios. After performing the extrusion experiments, the corresponding finite-element simulations were carried out under the same test conditions. All the analytical, experimental, and numerical findings, which were in good agreement with each other, showed that for all the extrusion ratios, the optimized polynomial and exponential die profiles involved the minimum and maximum force and energy requirements for the process, respectively. Moreover, the influence of the die geometry was more apparent at lower extrusion ratios. When the experimental results were analyzed based on the Taguchi method, it was also found that the effect of the die profile on the maximum extrusion load was more than one third that of the extrusion ratio.

The microstructures of extrusion cast biodegradable poly(butylene succinate) films investigated by X-ray diffraction

Cast films of poly(butylene succinate) (PBS) were prepared by extrusion followed by stretching using a chill roll. The effects of extrusion temperature and take-up speed on the microstructures of the PBS cast films were investigated by two-dimensional wide angle X-ray diffraction (2D-WAXD) and small angle X-ray scattering (2D-SAXS) techniques. It was found that the processing conditions had almost no influence on the degree of crystallinity and the long period of the lamellae of the films, whereas the orientations at both crystal and lamellar levels increased with increasing take-up speed and decreasing extrusion temperature. In addition, the 2D-SAXS patterns revealed the formation of the shish-kebab structure at a lower extrusion temperature and higher take-up speed.

Dependence of microstructure and mechanical properties on hot-extrusion temperatures of the developed high-strength Cu40Zn–CrFeTiSn brass by powder metallurgy

Effect of extrusion temperature on the microstructure and mechanical properties of the powder metallurgy Cu40Zn–CrFeTiSn alloy were investigated, through analysis on the solid solution of alloying elements, phase transformation and precipitation behavior. The extrusion was carried out between 500°C and 650°C using an extrusion ratio of 37:1. After extrusion, the microstructure was found consisting of the dual α+β phase structure and precipitates dispersing uniformly in the matrix. The tensile strength gradually decreased when the extrusion preheating temperature was increased. Solid solubility of Ti and Cr decreased steadily and grain coarsening occurred with increase in the extrusion temperature. Consequently, the lower extrusion preheating temperature was necessary to obtain excellent final mechanical properties, thus the extrusion temperature of 500°C was enough to produce good ductility while maintaining the promising values of mechanical properties after extrusion.

Finite element analysis of strain distribution in ZK60 Mg alloy during cyclic extrusion and compression

Finite element method was used to study the strain distribution in ZK60 Mg alloy during multi-pass cyclic extrusion and compression (CEC). In order to optimize the CEC processing, the effects of friction condition and die geometry on the distribution of total equivalent plastic strain were investigated. The results show that the strain distributions in the workpieces are inhomogeneous after CEC deformation. The strains of the both ends of the workpieces are lower than that of the center region. The process parameters have significant effects on the strain distribution. The friction between die and workpiece is detrimental to strain homogeneity, thus the friction should be decreased. In order to improve the strain homogeneity, a large corner radius and a low extrusion angle should be used.

Microstructure, mechanical properties, biocorrosion behavior, and cytotoxicity of as-extruded Mg–Nd–Zn–Zr alloy with different extrusion ratios

Recently, commercial magnesium (Mg) alloys containing Al (such as AZ31 and AZ91) or Y (such as WE43) have been studied extensively for biomedical applications. However, these Mg alloys were developed as structural materials, not as biomaterials. In this study, a patented Mg–Nd–Zn–Zr (denoted as JDBM) alloy was investigated as a biomedical material. The microstructure, mechanical properties, biocorrosion behavior, and cytotoxicity of the alloy extruded at 320 °C with extrusion ratios of 8 and 25 were studied. The results show that the lower extrusion ratio results in finer grains and higher strength, but lower elongation, while the higher extrusion ratio results in coarser grains and lower strength, but higher elongation. The biocorrosion behavior of the alloy was investigated by hydrogen evolution and mass loss tests in simulated body fluid (SBF). The results show that the alloy extruded with lower extrusion ratio exhibits better corrosion resistance. The corrosion mode of the alloy is uniform corrosion, which is favorable for biomedical applications. Aging treatment on the as-extruded alloy improves the strength and decreases the elongation at room temperature, and has a small positive influence on the corrosion resistance in SBF. The cytotoxicity test indicates that the as-extruded JDBM alloy meets the requirement of cell toxicity.

Texture Modification During Extrusion of Some Mg Alloys

The effects of extrusion ratio and alloying addition on the microstructure of Mg-0.2 wt pct Ce alloys are investigated by electron backscatter diffraction. The results show that in this alloy, texture randomization does not occur at high or low extrusion ratios but at a ratio of 25:1 at 400 °C. When extruded at the same temperature and extrusion ratio, Ca addition to Mg results in a weak nonbasal texture. In contrast, Mg-Al and Mg-3 wt pct Al-0.2 wt pct Ce alloys do not exhibit texture modification in single-pass extrusion. In the Mg-Al-Ce alloy, Ce and Al form Al11Ce3 particles, leaving little Ce solute in the matrix. The texture modifications in Mg-Ce or Mg-Ca alloys are related to the nature of the solid solution and consistent with dynamic strain aging during extrusion.

Processing and Characterization of Poly(Lactic Acid) Screw

Usage of the conventional bioabsorbable plastic bone fixation devices have been limited, because the mechanical characteristics of them are lower. In this study, poly-L-lactide ( PLA ) which is one of the bioabsorbable plastic was molded into the screw shape and the mechanical characteristics of the PLA screw was investigated. In order to strengthen by orientation of molecular chain, a PLA screw was prepared by extruding a rectangular PLA block followed by forging. The molding conditions were varied to evaluate the formability of PLA. The mechanical properties, such as pulled out strength, shearing strength and the twist strength were measured. The cross-sectional surface of the thread was observed and the crystallinity was measured. Decrease in void in the thread for the screw extruded using lubricants were observed. This results suggested void formation in the thread was caused at higher extrusion ratio. Decrease in shear strength and increase in twist strength were observed for the screw extruded using lubricants, which is due to lower extrusion ratio. Same tendency is observed for the screws molded at higher temperature. These results suggested the lubrication and higher molding temperature have similar effects. Decrease in twist strength at molding temperature of 120°C was obtained, which was caused by embrittlement due to crystallization.

Optimisation of the melt-spinning of anthracene oil-based pitch for isotropic carbon fibre preparation

This paper demonstrates the suitability of a new environmentally friendly pitch, obtained from anthracene oil, for the preparation of isotropic carbon fibres. The pitch exhibits an adequate thermal behaviour and it is free of solid particles. Green carbon fibres were prepared by means of a melt-spinning process with no filtering step, and subsequent stabilisation and carbonisation. For the optimisation of the melt-spinning process, the influence of the spinning temperature, extrusion pressure, spinneret hole size, winding speed and the interrelationship of these factors upon the microstructure and diameter of the fibres was studied. High winding speeds (250 cm s −1), in combination with a large spinneret hole size (500 μm) and low extrusion pressures (1 bar), led to high quality isotropic carbon fibres with diameters as low as ~ 15 μm and a tensile strength of > 1100 MPa which fulfil the requirements for their application as standard isotropic carbon fibres.

Rheo-Extrusion of Hypereutectic Al-14.8Si-4.5Cu-1.1Mg Alloy

Rheo-extrusion of hypereutectic Al-14.8%Si-4.5%Cu-1.1%Mg (in mass%) alloy which is considerably difficult to hot-extrude was tried using semi-solid slurry with fine solid granules and almost finely dispersed primary Si particles, made by a newly developed rotor process. Trials of rheo-extrusion at the constant extrusion ratio of 36 using this semi-solid slurry were carried out at the different conditions of the extrusion temperature and the ram speeds ranging from 520 to 560oC and from 5 to 20mm/s, respectively. Under the all rheo-extrusion conditions, this semi-solid slurry could easily be rheo-extruded to the round bars of 6mm diameter with sound surface at much lower extrusion force than that of hot-extrusion at very low extrusion ratio. In addition, the characteristic age-hardening behavior which is thought to be essential for the rheo-extrusion process has been found out, namely the peak hardness values of aged bars rheo-extruded at 520 and 540oC were considerably higher, 30HV at maximum, than that of a gravity casting.

Low temperature extrusion of 6061 aluminum matrix composite reinforced with SnO 2-coated Al 18B 4O 33 whisker

The 6061 aluminum matrix composite reinforced with SnO 2-coated Al 18B 4O 33 whisker was fabricated by squeeze casting and following by extrusion extruded at elevated temperatures from 300 °C to 400 °C. Optimization of the extruding process, microstructure, texture and mechanical properties of the extruded composites were investigated. The lowest extrusion temperature at which a composite rod with high surface quality was successfully produced was 300 °C. The yield strength of composites is much improved after extrusion, and especially their elongation is increased by 300%. Such big improvements depend on a fact that SnO 2 coating can introduce low-melting-point Sn phase into the interface through an interfacial reaction. The melting of interphase and their surrounding areas is the main reason for the excellent extrusion ability of the composite. Besides, detailed X-ray diffraction analysis of the extruded composite textures reveals the significant effects of extrusion temperatures on their features.

The Influence of the Extrusion Temperature on the Mechanical Properties of MMT Filled PA 6 Composite

Effects of varying extrusion temperatures on the mechanical properties of polyamide 6 (PA 6) matrix montmorillonite (MMT) filled composites were investigated in this paper. Five different temperature programs were used for producing composites with 1 wt.% nanoparticles content. The mechanical properties were evaluated by tensile and flexural tests and SEM pictures were taken from the fracture surfaces. X-ray diffraction patterns were also measured to obtain some information about the structures of the materials. The results showed that the lower extrusion temperatures resulted in better mechanical properties of the composite.

Solute segregation and texture modification in an extruded magnesium alloy containing gadolinium

The alloy Mg–1.5Gd has been extruded at different temperatures to produce two significantly different textures. At lower extrusion temperatures there was significant solute clustering in the matrix, coupled with segregation of solute to the grain boundaries. At higher temperatures these two phenomena were both less pronounced. It is suggested here that segregation of solute to the grain boundaries plays a significant role in the texture modification effect that rare earth elements have in magnesium alloys.

Influence of Initial Microstructure on Rheology of Al-Zn-Mg-Cu Alloy during Thermal Compression

The rheological behavior of two kinds Al-Zn-Mg-Cu aluminum alloy with different extrusion ratio was studied by thermal compression in 300°C~450°C and in strain rate range of 0.01 s-1~10s-1 on Gleeble1500D simulator. The results show that: (1)the flow stress increases with deSuperscript textcreasing deformation temperature and increasing strain rate, and the initial microstructure influence the rheological behavior, the flow stress with fine grain is higher than that with coarse one except in strain rate 0.01s-1 and 0.1s-1 in 450°C owing to deformation easily with more grain boundary sliding in high temperature and low strain rate.(2)The flow stress of Al-Zn-Mg-Cu aluminum alloy during hot compression can be expressed as hyperbolic sine constitutive equation with Arrhenius parameter, the apparent steady state activation energy for hot compression with coarse grain is of 181.51kJ/mol, while that with fine grain is of 203.02kJ/mol.(3) The apparent steady state activation energy decreases with increasing temperature and strain rate, and the value of fine initial microstructure is higher than the low extrusion ratio rod commonly.

Investigation of metal extrusion forming through steadily rotating container

To deal with the problems of high energy consumption and low material utilization in low plastic alloy extrusion, a new forming technology – container rotation extrusion – is proposed, and the die structure is also designed. Compared with the die rotation extrusion, which is only suitable for circular section parts, container rotation extrusion can solve the problem of axial ‘cut off’ caused by odd-shaped section product extrusion. The study results show that, in comparison to conventional extrusion, plastic zone expands obviously during forming process and the forming load decreases by 42.1%. What is more, during container rotation extrusion, ‘dead zone’ is disappeared. Consequently, this technology can form both complex cross-section and low plastic material products to achieve ‘small equipment does large workpiece’.