Grain Refinement and Strengthening of an Aluminum Alloy Subjected to Severe Plastic Deformation through Equal-Channel Angular Pressing (original) (raw)
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Materials Science Forum, 2009
The influence of severe plastic deformation induced by ECAP on microstructure modification and aging effect was studied in two modified Al-Mg-Si aluminium alloys. The microstructure of both alloys in different heat treated and deformed state was characterised by X-Rays diffraction and polarised light microscopy. The effect of artificial aging was investigated after ECAP performed on samples in the as extruded condition. The aging effect was followed by hardness and electrical conductivity measurements. At higher aging temperature (170°C) the alloys showed an increasing softening with time due to recovery or/and grain coarsening effect. At the lower aging temperature, the hardness remains almost constant due to enhanced precipitation hardening effect.
Acta Materialia, 2010
The present paper analyzes the effect of the equal channel angular pressing (ECAP) routes A and Bc on the recrystallization conditions and mechanical properties of Al-5086 alloy. The specimens were processed up to 10 passes at 150 º C in a die with 120 º inner angle. The recrystallized grains developed after the tenth pass in the route A. By increasing the number of passes the grains became finer and after the tenth pass, the average grain size became finer than 2 m. The tensile and hardness tests results showed that in all passes, the route Bc had a stronger effect on the simultaneous improvement of strength and ductility. The fracture surfaces analyses showed that the local ductile behavior improves as increasing the number of passes. The textures analyses showed that the dominant component was altered from (111) to (200) and (220) plane by increasing the number of passes through both routes. Also, the dislocation density increased by increasing the number of passes.
This study aims to characterize the microstructure and the evolution of the mechanical behavior after annealing of the AA1070 aluminum alloy cold pressed equal angular channels. The deformation was conducted via route A in five consecutive passes and the accumulated deformation was 5.95. The annealing was carried out at 200 ° C and 250 ° C for 5, 10, 15, 20, 25, 30, 45, 60 minutes. The starting material was derived from a slab of 610 mm thick chopped in multiple passes through hot rolling to final thickness of 32 mm. The microstructure of the material was characterized with the aid of scanning electron microscopy (SEM) in the secondary electron mode. Vickers hardness tests were conducted in order to evaluate the mechanical behavior of the material after pressing and along the heat treatment. The final gran sizes were 1.91µm and 2.07µm ate 200ºC and 250ºC, respectively. The microstructure morphology evolved to near equiaxial. After five consecutive passes of ECAP deformation the average hardness measured was 48.2. The final hardness values after annealing at 200 ° C and 250 ° C were 44.7 Vickers and 40.1Vickers. The reduction at the end of the heat treatment was 7% for the temperature of 200 ° C and 14% for the temperature of 250 ° C. The softening throughout the heat treatment times was due to the activation of the recovery and recrystallization mechanisms that led to changes in the microstructure in order to form a lower energy configuration. The analysis of hardness maps constructed from the data of the mechanical tests allowed concluding that the thermal treatment lead to a development of
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2005
In the present study, ultrafine-grained microstructures of a conventional 5083 aluminum alloy were fabricated by equal-channel angular pressing, and their dynamic deformation and fracture behavior were investigated. Dynamic torsional tests were conducted on four aluminum alloy specimens using a torsional Kolsky bar, and then the test data were analyzed in relation to microstructures, tensile properties, and adiabatic shear-banding behavior. The equal-channel angular-pressed (ECAP) specimens consisted of ultrafine grains and contained a considerable amount of second-phase particles, which were refined and distributed homogeneously in the matrix as the equal-channel angular pressing pass number increased. The dynamic torsional test results indicated that the maximum shear stress increased, while the fracture shear strain remained constant, with increasing equal-channel angular pressing pass number. Observation of the deformed area beneath the dynamically fractured surface showed that a number of voids initiated mainly at second-phase particle/matrix interfaces and that the number of voids increased with increasing pass number. Adiabatic shear bands of 200 to µm in width were formed in the as-extruded and 1-pass ECAP specimens having coarser particles, whereas they were hardly formed in the four-pass and eight-pass ECAP specimens having finer particles. The possibility of adiabatic shear-band formation was explained by concepts of absorbed deformation energy and void initiation.
Thermo-mechanical responses of an aluminum alloy processed by equal channel angular pressing
A comprehensive study on the large deformation responses of Equal Channel Angular Pressing (ECAP) processed AA6082 over wide ranges of strain rates ð10 À4 _ e 5 Â 10 3 s À1 Þ and temperatures (294 6 T 6 473 K) are presented. The circular billets of as-received AA6082 was solution treated prior to over aging. The over aged billets were then ECAP processed at room temperature to 4 and 6 passes using route C. The Vickers micro hardness measurements indicated a gradual increase in the hardness values with number of ECAP passes. A significant increase in the yield strength with number of passes has also been observed. The observed compression experimental responses were modeled using the modified form of Johnson–Cook (JC) constitutive model. The correlations and predictions from the model are close to the observed experimental responses.
Thermal Stability of AA1050 Aluminum Alloy after Equal Channel Angular Pressing
Archives of Metallurgy and Materials, 2017
The annealing behavior of AA1050 aluminum alloy deformed by equal-channel angular pressing (ECAP) was studied experimentally. The material was subjected to extrusion through die with channels intersecting at an 90° angle. Samples were pressed for up to 8 passes using route BC, then cut into slices and subsequently annealed for 1 hour at temperatures from 100°C to 350°C. Hardness measurements were performed on each slice. Microstructure of material was analyzed in the longitudinal section by means of Electron Backscatter Diffraction system in a scanning electron microscope (EBSD/SEM). From the obtained sets of Kikuchi diffraction patterns orientation maps and Image Quality maps were determined. Grain size, disorientation distributions and crystallographic texture were also estimated. ECAP caused significant improvement of hardness, with stabilization after 4 passes. Refinement of microstructure was obtained with the increasing amount of passes. Material properties were stable during ...
Crystal Research and Technology, 2009
In the present work, investigations on the microstructure of a commercial purity 1100 aluminum that had been subjected to moderate to strong deformation (strains of 1 to 4) by equal channel angular pressing (ECAP) were carried out using X-ray diffraction (XRD) and scanning electron microcopy (SEM). A significant grain refinement and development of heterogeneous microstructure after ECAP were observed. High precision XRD and SEM investigations provided useful results on the dissolution of coherent iron rich precipitates, previously formed in the aluminium matrix, by ECAP deformation process.
Materials Science and Engineering: A, 2008
Deformation structures of a commercial Al-Mg-Si alloy (6082) processed by equal-channel angular pressing at room temperature were characterized by transmission electron microscopy. Deformation twins, which have never been observed in coarse-grained aluminium, were experimentally confirmed together with numerous other features. The possible roles of twinning and different grain boundary structures on the severe plastic deformation (SPD) mechanisms, including grain refinement, were discussed.
Materials Letters, 2015
A combination of severe plastic deformation by equal channel angular pressing (ECAP) and bake hardening (BH) was used to produce high strength ultrafine-grained AA6061 aluminum alloy. 2, 4 and 8 passes of ECAP were performed, and the bake hardenability of samples was tested by 6% pre-straining followed by baking at 200 1C for 20 min. The microstructures obtained for various passes of ECAP were characterized by XRD, EBSD, and TEM techniques. The microstructures were refined from an average grain size of 20 mm to 212 nm after 8 passes of ECAP. Maximum bake hardenability of 110 MPa, and final yield stress of 330 MPa were obtained in the specimens processed by 8 passes of ECAP.