Papers by Keyword: Hot Extrusion

Abstract: Many of our modern technologies require materials with unusual combinations of properties that cannot be met by the conventional metal alloys, ceramics and polymeric materials. This is especially true for materials that are needed for aerospace, underwater and transportation applications. An economical way of producing metal matrix composite (MMC) is the incorporation of the particles into the liquid metal and casting. The objective of this work is to reinforce Al 1100-Mg alloy with different wt% of MnO₂ (0, 3, 6, 9 and 12) was added by melt stirring method and Hot Extrusion is carried out. Microstructural Studies using Scanning Electron Microscopy (SEM) and Mechanical property like hardness and tensile properties have been investigated for extruded base alloy and composites.

Abstract: In this work, hot extrusion of light metal scraps as a new way of plastic consolidation will be presented. This kind of material recovering is a promising alternative for conventional recycling processes. Nowadays discards from machining of semi-finished products are being recycled throughout re-melting processes. However, due to its significant susceptibility to oxidation most of the chips and scraps are burnt during the melting process. It has been already recognized that aluminum losses connected with this operation can reach from 40% to 50%. A technology that has been presented in this work combines cold compaction and hot extrusion of 413.0 aluminum alloy scraps. It was found that quality of as-extruded rods depends strongly on extrusion conditions. Higher extrusion speed leads to higher quality of rods surface. Additionally brittle Si and Al-Fe-Si particles increases overall mechanical properties in comparison to its industrial counterpart.

Abstract: Metal extrusion is currently very beneficial for producing workpieces with long dimensions or when a uniform cross section area is required. Design of extrusion dies, which results to the shape, geometry and size of the workpiece, is the main factor for quality, productivity and durability of the products. Besides improving the bearing length, a die pocket is a good solution to effectively control the velocity of material flow into the die hole. Therefore, this study aimed to evaluate the structures of die pockets that influence the material flow in the extrusion process. Thus, the finite element method (FEM) was used to determine the parameters that affect the strength of the extrusion die due to the maximum stresses which occurred on the die and pocket. From this study, it was found that the circular shaped pocket with 31degrees pocket angle, 22 mm pocket die thickness and made of titanium alloy provided the maximum strengths and safety factors. This result from the simulations can sufficiently predict the risk of damages on the extrusion die and pocket for further extension of the tool’s life cycle.

Abstract: Metal matrix composites, in which crystalline Al was reinforced by particulates of the Al_87.5Ni₄Sm_8.5 amorphous alloy, were produced using cold pressing and hot extrusion processing. Controlled nanoprecipitation was used to improve the mechanical properties of the amorphous alloy. Amorphous melt-spun ribbons were produced by melt-spinning technique and then fragmented in fine powder by high-energy ball milling. Amorphous and pure aluminum powders were mixed in two different proportions: 85:15 and 70:30 (wt%) and homogenized by ball milling. Bulk samples were produced via cold pressing and hot extrusion. Controlled nanoprecipitation within the amorphous alloy was obtained by the correct choice of processing temperature. The composites were analyzed for reinforcement distribution, porosity content, microhardness and compression tests. The results showed that it was possible to control the precipitation by producing almost the same volume fraction of nanocrystals in each condition. Compression tests showed an improvement on the mechanical properties, which were correlated with the presence of the amorphous/nanocrystals reinforcement in the Al-matrix. The compression yield-strengths of the as-extruded composites were 192 and 310 MPa for 15% and 30% in volume of Al_87.5Ni₄Sm_8.5, respectively. These values are significantly higher than the typically found for the AA1100 wrought pure aluminum (180 MPa).

Abstract: Nowadays manufacturing technologies have to be evaluated not only for the technical features they can provide to products, but also considering the environmental perspective as well. As long as the technological feasibility of a given process is guaranteed, processes minimizing resources and energy consumption have to be selected for manufacturing. With respect to this topic, the research studies in the domain of metal processing technologies predominantly focus on conventional material removal processes as milling and turning. Despite some exceptions, many other non-machining technologies, such as metal forming processes, are still not well documented in terms of their energy and resource efficiency, and related environmental impact. In this paper, an environmental challenge between two traditional technologies is developed: the environmental performances of a partial hot extrusion process and of a turning processes are quantified and compared. A Life Cycle Assessment (LCA) approach is implemented to properly analyze the considered processes. The material production step and the manufacturing phase to obtain a simple axy-symmetric aluminum component is considered for the Life Cycle Inventory (LCI) data collection step. Besides, the material and consumables usage and the consumed electrical power are measured in order to quantify the energy consumption of the manufacturing phase. Further, the environmental impacts related to the manufacturing of the extrusion dies and of the turning process are included in the analysis. The paper presents an early step of a wider research project aiming at identifying the greenest technologies as functions of given product features.

Abstract: Oxides Dispersed Strengthened (ODS) stainless steels are foreseen for fuel cladding tubes in the coming generation of fission nuclear reactors. In spite of a bcc matrix, those steels present a convenient creep behavior thanks to very fine oxides dispersion. Those grades are currently obtained by Powder Metallurgy (PM). After mechanical alloying with the oxide, the powder is commonly consolidated as seamless tube. On CEA facilities, new ferritic ODS stainless steels are produced by Hot Extrusion (HE). The control of the microstructure after extrusion is a key issue for this grade regarding service conditions. In order to explain the microstructure induced by hot processing, the thermo-mechanical history applied to the material must be taken into account. In this study, the strain and thermal histories are obtained from Finite Element Method simulation. Thus, crystallographic texture development during hot extrusion of ODS ferritic steels is simulated using a Visco-Plastic Self-Consistent (VPSC) model. By comparing the texture predictions with the experimental observations, it is shown that self-consistent model reproduces the extrusion texture, α-fiber, very well in the case of monotonic loading. However, for complexes strain path observed during HE, VPSC results differ from the experimental deformation texture.

Abstract: The study investigates the influence of different fraction of Mg₂B₂O5 whiskers (5, 10, 15 and 20vol.% ) on the microstructure of the hot extruded composite as well as on the mechanical properties in the same condition. The results indicate that the process is available for producing the composite, image analysis shows the whisker tends to cluster together with increasing content of reinforcement. When the content of the reinforcement is 10%, the composites exhibit the best mechanical properties, meanwhile, it demonstrate cluster is unfavorable to the improvement of properties of materials. The ductile failure of 6061Al matrix, the reinforcement fracture and the whisker-matrix interface debonding acted as the main mechanism of fracture nucleation.

Abstract: The powder metallurgy (PM) nickel-base superalloy FGH96 was extruded at temperature from 1050°C to 1180°C,and the as-extruded samples in the extrusion temperature 1050°C were heat-treated at from 1000°C to 1100°C during 10min, 30min, 60min and 90min apart. The microstructure of recrystallization, γ' phase and growth behavior of grain were discussed. The results indicate that the extrusion temperature have a severely influence on the dynamic recrystallization and γ' phase behavior. The content and pattern of γ' phase is influenced by extrusion temperature and the big size of γ' phase in the grain boundary hinder effectively the growth of dynamic recrystallized grain. The degree of dynamic recrystallization is completed when the extrusion temperature increases. When the extrusion temperature reach 1100°C, the big size of γ' phase lie the grain boundary dissolves gradually and the grain grows obviously. As the heat temperature of as-extruded samples increases, the small size of γ' phase dissolves early and the degree of recrystallization is completed. When heat temperature reach 1080°C, the small size of γ' phase begin to dissolve and the recrystallization grain begins to grow, for the strain energy is given off and existence of interface energy. When heat temperature reach 1100°C, the recrystallization grain become uniform, for the pinning of big size of γ' phase. As the time of heat treatment elongate, the recrystallization grain size increase and the content of γ' phase decrease. When the heat temperature is 1080°C, the final microstructure is fine and uniform grain due to the pinning of big size of γ' phase. When the heat temperature is 1100°C, large of big size of γ' phase dissolve and the largest grain size reach 8μm. The nucleation and growth of recrystallization grain is influenced by small size of γ' phase and the fast growth of recrystallization grain is due to the big size of γ' phase in the grain boundary.

Abstract: Two different conditions were used to study the effect of homogenization on extrusion texture and microstructure evolution in AA3003. The first condition considered homogenization for 8 h at 500°C to obtain a high density of dispersoids and the other condition was homogenized for 24 h at 600°C to produce a sample with a very low density of dispersoids. After uniaxial extrusion at 400°C with a speed of 32 mm/s and an extrusion ratio of 70:1, the material with a high density of dispersoids formed <001> and <111> double fibre texture in the centre of extrusion rod and a smeared texture from <011> to <111> near the surface. For the material without dispersoids, only <001> texture fibre is observed in the centre of extrusion rod and a strong <011> fibre is observed near the surface.

Abstract: The effect of different thermomechanical processes (hot extrusion and Properzi continuous rolling) on the electrical and mechanical properties of the Al-Fe aluminum conductor alloys was investigated. The microstructural evolution of the supply rods was characterized by an optical microscope, a transmission electron microscope and the electron backscatter diffraction technique (EBSD). Tensile tests and electrical conductivity measurements were carried out at room temperature on the supply rods. Results showed that, at the same Fe content, the continuously rolled rods demonstrated higher tensile strength but lower elongation and electrical conductivity compared with those of the extruded rods. A partially recrystallized structure along with a big subgrain size appeared in the extruded rods while only a dynamic recovery with a small subgrain size was found in the continuously rolled rods. The precipitation of iron-rich dispersoids was observed in the extruded rods and is associated with a depletion of the iron concentration.