Papers by Keyword: Plastic Consolidation

Abstract: Method of scrap recovery by hot extrusion in a contrast to traditional aluminum recycling process distinguishes itself with a low energy consumption and high recovery efficiency. Additionally, this type of recycling allows to recover materials even from highly fragmented forms of metal like chips, foils or filings by omitting melting procedure. In the present study results of 413.0 aluminum chips plastic consolidation will be presented. Chips after machining process were used as a charge material for the entire recycling process. In order to determined the best emulsion elimination method, three separate processes such as centrifugation, annealing and pressing were carried out. In result dry, wet and cleaned chips in a form of cylindrical billets were hot extruded into longitudinal square cross-section profiles. Mechanical properties were examined by uniaxial tensile tests while microstructure observations were performed by means of scanning electron microscopy. It has been showed that emulsion elimination by annealing gives the best results while at the same time all extruded materials revealed no significant differences in mechanical properties.

Abstract: Mixed and preliminarily consolidated powders of aluminium and nickel (90 mass % Al and 10 mass % Ni) were hot extruded. As results the rod, 8 mm in diameter, was obtained. As-extruded material was subjected to the microstructural investigations using scanning electron microscopy (SEM/EDS) and X-ray analysis (XRD). The differential scanning calorimetry (DSC) and thermo-mechanical analysis (TMA) were also performed. The mechanical properties of as extruded material were determined by the tensile test and Vickers hardness measurements. In order to evaluate the thermal stability of PM alloy, samples were annealed at the temperature of 475 and 550 °C. After annealing Vickers hardness measurements and tensile tests were carried out. The plastic consolidation of powders during extrusion was found to be very effective, because no pores or voids were observed in the examined material. The detailed microstructural investigations and XRD analyses did not reveal the presence of the intermetallic phases in the as-extruded material. During annealing, the Al₃Ni intermetallic compound was formed as the result of chemical reaction between the alloy components. The hardness of the alloy after annealing at the temperature of 475°C was found to be comparable to the hardness in as-extruded state. Annealing of the material at the temperature of 550°C results in hardness decreasing by about 50%, as the consequence of porosity formation and Al₃Ni cracking.

Abstract: Rapid solidification (RS) combined with plastic consolidation by hot extrusion was used to produce Al alloys with additions of varied concentration of Mn. RS flakes were manufactured using an inert gas atomizing of the molten alloy and the spray deposition on the water-cooled cooper roll. Rods of 7mm in diameter were received using cold pressing of RS-flakes, vacuum degassing and hot extrusion procedures. Mechanical properties of as extruded materials were tested in hot compression at temperature range 293K - 773K. It was found that the flow stress was reduced monotonically with deformation temperature for all tested materials. RS alloys exhibit higher mechanical properties than those produced by conventional metallurgy methods. Higher mechanical properties of RS materials are ascribed to beneficial particles morphology obtained due to the rapid solidification. Development of fine Al₆Mn particles was observed in all tested RS-materials.

Abstract: Series of experiments on a series of Al-Fe-Mg alloys were performed to determine the effect of rapid solidification (RS) on the material strengthening, which result from the refining of thegrain size and intermetallic compound. Additionally, an enhancement of the material strengthening due to magnesium addition was also observed. Manufacture of RS Al-Fe-Mg alloys combined a spraydeposition of the molten alloy on the rotating water-cooled copper roll and plastic consolidation bymeans of powders pressing and hot extrusion methods. The results suggest that the rapid solidification provides an effective method of microstructure refinement and, in combination with solid solutionhardening due to Mg, leads to significant improvement of mechanical properties of Al-Fe-Mg based alloys.

Abstract: Ultra-fine grained metallic materials are characterized by higher mechanical properties comparing with their conventional equivalents. However increase in strength under static load is not always accompanied by improved fatigue behaviour. Previous investigations on submicrocrystalline RS442 aluminium alloy produced by plastic consolidation of rapidly solidified flakes in the extrusion process revealed increase in its high cycle fatigue bending strength caused by annealing at 450°C. The aim of present studies was to evaluate the influence of heat treatment – also precipitation hardening – on static mechanical properties (hardness, tensile and yield strength) and fatigue strength of the alloy determined in high cycle stress controlled bending tests. Correlation between microstructure, static mechanical properties and fatigue behaviour was analyzed too.

Abstract: Experiments on Al-1Fe-1Ni-5Mg alloy were performed to determine the effect of rapid solidification (RS) on the material strengthening, which result from the refining of the grain size and intermetallic compounds. Additionally, an enhancement of the material strengthening due to magnesium addition was also observed. RS procedure was performed using spray deposition of the molten alloy on the rotating water-cooled copper roll. As a result, highly refined structure of rapidly solidified flakes was obtained. Using common powder metallurgy (PM) techniques, i.e. cold pressing, vacuum degassing and hot extrusion, as received RS-flakes were consolidated to the bulk PM materials. For comparison purposes, the conventionally cast and hot extruded Al-1Fe-1Ni-5Mg alloy was studied as well. RS process combined with hot pressing and extrusion procedure was found to be very effective method for the manufacture of fine grained material and effective refinement of intermetallic compounds. However some inhomogenity of particles distribution was observed, which was ascribed to varied cooling rate dependent on the particular spray-drop size. Mechanical properties of as-extruded material were examined using compression test at 293K – 873K. High strength and ductility of as-extruded RS material with respect to conventionally produced alloy were observed. However, the effect of enhanced mechanical properties of RS material is observed only at low deformation temperatures. It was found that increasing deformation temperature above 400K results in negligible hardening of RS samples if compared to conventionally produced material.

Abstract: The present paper reports an experimental investigation of rapid solidification (RS) influence on the structure and mechanical properties of commercial AZ91 magnesium alloy. In order to obtain RS material melt spinning process was applied in protective atmosphere, resulting in formation of 50 to 100 μm thickness RS ribbons. Application of plastic consolidation (PC) by hot extrusion to the highly fragmented magnesium strips allowed to obtain high bulk strength material. It was found that yield strength (YS) and ultimate tensile strength (UTS) of RS+PC material with comparison to the cast and extruded samples were increased from 220 MPa to 303 MPa and from 287 MPa to 385 MPa, respectively, while plasticity of the RS material was slightly decreased. It was noticed that the grain size of both materials was at the same level of 2 μm, thus higher mechanical properties of RS material was ascribed to dispersion strengthening caused by the high amount of fine (below 50 nm in diameter) Mg₁₇Al₁₂ phases evenly distributed in the material structure.

Abstract: Rapid solidification (RS) of Al-2Fe-2Ni-5Mg alloy and following mechanical consolidation of powders by means of powder metallurgy (PM) methods was used with success to produce a bulk RS-material. RS powders were manufactured using an inert gas atomizing of the molten alloy and the spray deposition on the rotating water-cooled copper roll. Rods of 7 mm in diameter were received by means of the cold pressing of the flakes, vacuum degassing and hot extrusion method. For comparison purposes, the conventionally casted and hot extruded Al-2Fe-2Ni-5Mg alloy was tested as well. Mechanical properties of as-extruded materials were examined at 293 K – 873 K by compression tests performed at constant true strain rate of 5·10^-3[s^-1]. It was found that relatively high strength of as-extruded RS/PM material was accompanied by the high ductility of the samples deformed by hot compression tests. It was noticed that the most effective solution strengthening due to particles refining was observed at low deformation temperatures. Rising the test temperatures above ~ 420 K, was found to result in reduction of the flow stress to the values received for the industrial material (IM).The formation of coarse primary intermetallic compounds, which is typical for IM material, was effectively reduced for RS material. However some inhomogeneity of fine precipitates distribution in RS/PM material was observed. Nevertheless, it was considered that both solid solution hardening due to Mg addition and the dispersion strengthening due to refining of intermetallic compounds substantially increase the mechanical properties of the RS/PM material.

Abstract: The subject of the research was an alloy AlZnMg and AlCuMg with addition of Zr and Ag manufactured of powders by hot plastic consolidation in process of direct extrusion. Paper also presents results of research of structure evolution and mechanical properties for different tempers of precipitation strengthening and further plastic deformation, including hydrostatic extrusion. Obtained results R_m above 700MPa (for AlZnMg alloy) and above 500MPa (for AlCuMg alloy) shows significant possibilities of manufacturing from Al alloys powders products with ultrafine grain and nanometric structure which properties exceeding alloys manufactured with standard methods.

Abstract: Rapid solidification (RS) combined with following mechanical consolidation of RS powders is considered as a valuable commercial method for the production of a wide range of metallic materials having fine-grained structures. Reported research results for various alloys demonstrate better compositional homogeneity, smaller grain size and relatively fine precipitates distributed homogenously in RS alloys than that for the materials produced by conventional metallurgical processing. The effect of rapid solidification on the microstructure and mechanical properties of selected Al-Fe-Ni-Mg alloys have been investigated. The basic item of the research work was obtaining aluminum PM materials strengthened by highly-dispersed transition metal compounds and aluminum-magnesium solid solution. Rapid solidification (RS) of Al-4Fe-4Ni and Al-4Fe-4Ni-5Mg alloys was performed by means of gas atomizing of the molten alloy and the spray deposition on the rotating water-cooled copper roll. Using typical powder metallurgy (PM) methods, i.e. cold pressing, vacuum degassing and hot extrusion, the RS-flakes were consolidated to the bulk PMmaterials. For comparison purposes, the conventionally cast and hot extruded Al-4Fe-4Ni and Al-4Fe-4Ni-5Mg alloys were studied as well. Mechanical properties of as-extruded materials were examined by compression tests performed at 293 K – 873 K. It was found that relatively high strength of as-extruded PM materials was accompanied by high ductility of samples deformed by hot compression test. Structural observations confirmed beneficial influence of rapid solidification on effective refining of intermetallic compounds, although some inhomogeneity of fine precipitates distribution was observed. Nevertheless, it was considered that an effective increase of the microhardness and strength of tested RS materials mostly result from achieved dispersion of structural components and can be intensified by solid solution hardening due to Mg-addition.