Extrusion welding of AlZnMg alloys encounters great technological difficulties in practice associated with high shaping forces and the low quality of longitudinal welds. Three different chemical ...compositions of 7021 aluminum alloy, differing in terms of Zn and Mg contents, were used in the first stage of the research. The laboratory device modelling the behavior of metal in welding chambers of the porthole die was applied to examine the ability of 7021 alloys to produce high-quality joints. The weldability tests were carried out for different welding temperatures—400, 450 and 500 °C—and for a fixed welding pressure of 300 MPa. The microstructural effects in pressure-welds were evaluated with the use of OM and SEM/EDS. The temperature–pressure parameters in the welding chambers were analyzed by using the FEM method for original porthole dies while extruding tubes with dimensions of Ø50 × 2 mm. Finally, the industrial extrusion trials were performed with examination of the structure and strength of the seam welds. It was found that it is possible to produce high-quality high-strength welds in tubes extruded from AlZnMg alloys in industrial conditions (the strength of welds in the range of 96–101% of the strength of the basic non-welded material) through properly matched alloy chemical composition of the alloy, construction of the porthole dies and temperature–speed conditions of deformation.
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The study presents the results of research on the influence of different contents of main alloying additions, such as Mg (2 ÷ 2.5 wt.%), Cu (1.2 ÷ 1.9 wt.%), and Zn (5.5 ÷ 8 wt.%), on the strength ...properties and plasticity of selected Al–Zn–Mg–Cu alloys extruded on a bridge die. The test material variants were based on the EN AW-7075 alloy. The research specimens, in the form of 100 mm extrusion billets obtained with the DC casting method, were homogenized and extrusion welded during direct extrusion on a 5 MN horizontal press. A 60 × 6 mm die cross-section was used, with one bridge arranged in a way to extrude a flat bar with a weld along its entire length. The obtained materials in the F and T6 tempers were characterized in terms of their strength properties, hardness, and microstructure, using EBSD and SEM. The extrusion welding process did not significantly affect the properties of the tested materials; the measured differences in the yield strength and tensile strength between the materials, with and without the welding seam, were up to ±5%, regardless of chemical composition. A decrease in plasticity was observed with an increase in the content of the alloying elements. The highest strength properties in the T6 temper were achieved for the alloy with the highest content of alloying elements (10.47 wt.%), both welded and solid. Significant differences in the microstructure between the welded and solid material in the T6 temper were observed.
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The extrusion of hollow profiles from hard-deformable AlZnMg alloys by using porthole dies encounters great technological difficulties in practice. High extrusion force accompanies the technological ...process, which is caused by high deformation resistance and high friction resistance in extrusion conditions. As a result of high thermo-mechanical loads affecting the die, a significant loss of dimensional accuracy of extruded profiles can be observed. The different projects of porthole dies for the extrusion of Ø50 × 2 mm tubes from the 7021 alloy were numerically calculated and then tested in industrial conditions by using a press of 25 MN capacity equipped with a container with a diameter of 7 inches (for 7021 alloy and 6082 alloy for comparison). New extrusion die 3 with modified bridge and mandrel geometry and a special radial-convex entry to the die opening was proposed. FEM was applied to analyse the metal flow during extrusion, geometrical stability of extruded tubes and the die deflection. The photogrammetric measuring method was used to evaluate dimensional accuracy of tubes extruded in different conditions and geometrical deviations in porthole dies elements, especially the bridges and the mandrels. Research revealed a high dimensional accuracy of tubes extruded from the 6082 alloy and from the 7021 alloy by using original extrusion die 3, while much higher dimensional deviations were noted for tubes extruded from the 7021 alloy by using extrusion dies 1 and 2, particularly in relation to the circularity, centricity and wall thickness.
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The MgCa0.7 alloy may be a promising material for biodegradable surgical wires. In this paper, the technology for producing surgical wires from this alloy has been developed, based both on finite ...element modelling and experimental study. In particular, the extrusion and hot-drawing effects on the mechanical properties, microstructures, in-vitro rates of biocorrosion, and cytotoxicity to human cancer cells (SaOS-2) and healthy (hPDL) ones, have been determined. An approximately 30–40% increase in corrosion rate due to increasing hot-drawing temperature was observed. An effect of hot-drawing temperature on cytotoxicity was also found. Notably, at various stages of the final wires’ production, the MgCa0.7 alloy became toxic to cancer cells. This cytotoxicity depended on the alloys’ processing parameters and was maximal for the as-extruded rod and for the wires immediately after hot drawing at 440 °C. Thus, the careful selection of processing parameters makes it possible to obtain a product that is not only a promising candidate for biodegradable surgical wires, but one which also has intrinsic bioactive properties that produce antitumor activity.
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Development of technological production process of biocompatible magnesium tubes for medical applications is the subject of the present paper. The technology consists of two stages—extrusion and ...dieless drawing process, respectively. Mg alloys for medical applications such as MgCa0.8 are characterized by low technological plasticity during deformation that is why optimization of production parameters is necessary to obtain good quality product. Thus, authors developed yield stress and ductility model for the investigated Mg alloy and then used the numerical simulations to evaluate proper manufacturing conditions. Grid Extrusion3d software developed by authors was used to determine optimum process parameters for extrusion—billet temperature 400 °C and extrusion velocity 1 mm/s. Based on those parameters the tube with external diameter 5 mm without defects was manufactured. Then, commercial Abaqus software was used for modeling dieless drawing. It was shown that the reduction in the area of 60% can be realized for MgCa0.8 magnesium alloy. Tubes with the final diameter of 3 mm were selected as a case study, to present capabilities of proposed processes.
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Designing new aluminium alloys always requires an assessment of the influence of modified contents of the main alloying additions on the required properties for a specific application. The aim of ...this study was to develop a new alloy with a higher tensile strength than the tensile strength obtained in typical 6xxx series alloys, with a satisfactory hot extrusion ductility. The article presents the results of studies on the influence of copper additions, in three variants, on the structure and mechanical properties of extruded aluminium profiles in various heat treatment states. The base reference for the presented studies was the following aluminium alloys: AlMgSi (EN AW-6063) and AlCuMgMn (EN AW-2017). On this basis, three alloy variants with Cu contents of 2.5, 3.5 and 4.5 weight % were selected. These alloys were cast by vertical semi-continuous casting in the form of ingots with a diameter of 100 mm. Hot deformation studies were carried out in the process of co-extrusion on a semi-industrial line consisting of a horizontal 5 MN press together with auxiliary devices. The extruded profiles were free from defects that could have resulted from the process, such as overheating, cracks and blisters. The materials in the form of extruded profiles, in the heat treatment states T1 and T4, were characterised in terms of structure and mechanical properties. The variants with Cu contents of 2.5 wt% and 3.5 wt% had comparable structure and grain size, and the variant with 4.5 wt% Cu had a finer microstructure. For the studied alloys after heat treatment, higher the strength, higher the Cu content in the alloy, ranging from 445 to 543 MPa. It has been found that it is possible to develop modified aluminium alloys based on the 6xxx series with an increased copper addition (but still below the content typical for Al alloys of the 2xxx series) that will have a strength above 400 MPa. The first variant of the new alloy with a Cu content of 2.5 wt% meets the set goal and meets the requirements set at the beginning of the studies.
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The paper presents a review of the literature and authors’ research on the current achievements in the field of extrusion of aluminium alloys, magnesium alloys, powders and aluminium-based composites ...in particular. The microstructure transformations taking place during homogenisation of billets from the medium- and high-strength heat-treatable aluminium alloys are still an object of interest of researchers. The recently published papers are related to dissolution of soluble phases formed during solidification and elimination of microsegregation, precipitation of the dispersoids, insoluble phases’ transformation as well as particles re-precipitation during cooling. The novelties in the extrusion of magnesium alloys and aluminium-based composites are shortly reported. Specifics of the extrusion dies design and their working conditions, which limit the products quality and working life of the tools, are extensively reported. The computer-aided designing (CAD) and finite-element method (FEM) and 3D optical scanning were used in analysis aimed at dimensional deviations of the dies and the extruded products. The surface engineering techniques such as welding techniques, diffusion layers and protective coatings such as produced by physical vapour deposition (PVD), plasma-enhanced physical vapour deposition (PAPVD), chemical vapour deposition (CVD) and plasma-enhanced chemical vapour deposition (PECVD) are described. Various original methods of extrusion including the severe plastic deformation processes (SPD), such as cyclic extrusion compression (CEC), equal-channel angular pressing (ECAP) and hydrostatic extrusion (HE) are discussed. The above techniques as well as the new KOBO extrusion process with oscillating die movement generate significant refining of the microstructure of metals and alloys and enable consolidation of the powdered materials. The application of the rapid solidification process connected with the hot extrusion permits production of beneficial microstructure and above-standard mechanical properties of the extruded products. Finally, the opportunities and directions of development of the extrusion process of metals and alloys are indicated.
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The paper is devoted to the study of the mechanical, microstructural, and bio-corrosive behavior of low-alloyed Zn–Mg biodegradable surgical wires for bone reconstructions. Three biodegradable alloys ...with different magnesium content have been studied, their production technology has been developed and the product properties have been determined. The technology includes casting, extrusion, hot and cold drawing of the wire, and the product surface finishing. The paper shows the most important stages of the process (i.e., extrusion and drawing) in detail. The technological parameters have been selected based on the results of the computer modeling. The flow stress–strain curves of extruded materials have been obtained at various strain rates and temperatures. Two drawing technologies have been compared. The first one is the room temperature conventional wire drawing. In the second one, the first few passes have been made at an elevated temperature and the rest at room temperature. This allowed avoiding the breaking of the wire during the first passes (a typical issue of the conventional technology for these alloys) and increasing the ductility of the final product. Mechanical properties, bio-corrosion, and crystallographic texture of the material were determined at different stages of the processing. A simultaneous increase in the wire strength, the number of repeated bending until the rupture of the wire, and in the bio-corrosion rate due to drawing has been registered. This phenomenon coincided with a change in the crystallographic texture. It has been shown that the product tensile strength of about 250–300 MPa can be reduced by about 30% due to surgical knots tied on it.
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High strength biodegradable surgical threads are in demand for surgical practice. Nowadays, such threads can be made of metallic materials such as magnesium, zinc or alloys based on these metals. In ...current paper, manufacturing technology of biodegradable surgical threads of Mg–Ca alloys and of pure Zn was developed and basic properties of the obtained product have been characterized. The influence of in vitro corrosion in bovine serum simulating environment in the mammal’s body on the surgical threads mechanical properties was determined. It was found that Zn and hot extruded alloys MgCa0.9 and MgCa1.2 can be recommended as a candidate for the future study in vivo. Properties of the room temperature drawn wires of the alloy MgCa0.7 are not sufficient for its application as surgical threads.
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