EFFECT OF ECAP DIE ON STRUCTURE AND PROPERTIES OF AlMg ALLOY (original) (raw)
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Microstructural evolution of AA7050 al alloy processed by ECAP
Matéria (Rio de Janeiro), 2010
This work aimed to study the microstructural evolution of commercial aluminum alloy AA7050 in the solution treated condition (W) processed by equal channel angular pressing -ECAP. The analyses were made considering the effects of process parameters as temperature (T amb and 150°C), processing route (A and B C ) and number of passes. Optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for microstructural characterization, and hardness tests for a preliminary assessment of mechanical properties. The results show that the refining of the microstructure by ECAP occurred by the formation of deformation bands, with the formation of dislocations cells and subgrains within these bands. The increase of the ECAP temperature led to the formation of more defined subgrains contours and intense precipitation of η phase in the form of spherical particles. The samples processed by Route B C present a more refined microstructure.
Effect of Processing Temperature on Microstructure Development during ECAP of Al-Mg-Sc Alloy
Materials Science Forum, 2008
Microstructural evolution taking place during equal channel angular pressing (ECAP) was studied in a commercial coarse-grained Al-6%Mg-0.4%Mn-0.3%Sc alloy in a temperature interval 200-450 o C (~0.5-0.8 T m ). Samples were pressed using route A to a total strain of 12 and quenched in water after each ECAP pass. Uniform fine-grained microstructures with the average grain sizes of 0.7 and 2.5 µm, are almost fully evolved at high ECAP strains at 250 o C and 450 o C, respectively, while ECAP at 300 o C (~0.6 T m ) leads to the formation of bimodal grain structure with fine grains of around 1 µm and relatively coarse grains of around 8 µm. The latter are developed due to the occurrence of static recrystallization during "keeping" time in the ECAP channel and/or reheating between ECAP passes. The microstructural development under warm-to-hot ECAP conditions is discussed in terms of the large potential for grain boundary migration resulted from an overlapping of accelerated grain boundary mobility at high pressing temperatures and enhanced driving force for recrystallization, which is caused by a strong inhibition of dynamic recovery in a heavily-alloyed Al alloy.
Microstructure behavior of Al–Mg–Sc alloy processed by ECAP at elevated temperature
Acta Materialia, 2008
Microstructural evolution taking place during equal channel angular pressing (ECAP) was studied in a coarse-grained Al-6% Mg-0.4% Mn-0.3% Sc alloy at 300°C ($0.6T m ). Samples were pressed to strain 12 and quenched in water after each pass. ECAP at moderate-to-high strains leads to formation of a bimodal grain structure, with grain sizes of about 1 and 8 lm and volume fractions of 0.3 and 0.6, respectively. The development of new-grained regions has been shown to result from the concurrent operation of the continuous dynamic recrystallization that occurs during deformation and the static recrystallization that occurs by the exposure of the as-deformed material in the die kept at 300°C and/or reheating between pressings. The microstructural development is discussed in terms of the enhanced driving force for recrystallization, resulting from the evolution of high-density dislocation substructures due to localization of plastic flow and inhibition of recovery in the present alloy.
Mechanical and Structural Properties of High Purity Al Processed by ECAP
Acta Physica Polonica A, 2012
The mechanical properties and substructure formation of high purity aluminium (99.999%) processed by severe plastic deformation method (equal channel angular pressing) were studied. The equal channel angular pressing process was carried out at room temperature by route C (sample rotation around the axis about 180 • after each pass) in a die with two channels intersecting at an angle of Φ = 90. The softening mechanism through dynamic recovery was recognized up to 6th equal channel angular pressing pass, however, after that the mechanical strengthening was revealed. The samples after equal channel angular pressing processing were annealed in dierent temperature and time conditions. The inuence of annealing temperature and time on microhardness as well as diameter of grain size were investigated in samples processed by the 4th equal channel angular pressing pass.
Investigation of Microstructural and Hardness Changes of AA7075 Alloy Processed by Ecap
Mühendislik bilimleri ve tasarım dergisi, 2021
This study aims to examine the change in microstructural and hardness values AA7075 aluminum alloy, which is frequently preferred in the aviation industry by applying the Equal Channel Angular Pressing (ECAP) method. ECAP method, one of the plastic deformation methods, has been successfully carried out by applying 0.025mm/sec pressing speed and 200°C temperature for a different route (A, Bc, C) and the different number of passes (2, 4, 8). The characterization of the aluminum alloy obtained by applying ECAP process was carried out by optical microscope (OM), X-ray diffraction (XRD), and scanning electron microscope (SEM) analysis. Hardness tests have been applied to examine the mechanical properties of the material. The microstructures of the materials obtained as a result of the application were examined. It was observed that precipitation occurred in the AA7075 alloy depending on the applied temperature, pressing, and grain breakage. Moreover, it is seen that the grain size of the materials produced by the ECAP method has been reduced, and consequently the strength of the material increases. As a result of the ECAP process, it was seen that the existing phases were α-Al, -MgZn2, S-Al2CuMg, and Al7Cu2Fe. The grain size of 288.4 nm obtained after 8 repeated passes using the Bc route was the smallest grain size obtained.
IOP conference series, 2019
In this study, the effect of die angle on the microstructure and mechanical properties of industrial aluminium alloy AA6061 produced by severe plastic deformation (SPD) through equal channel angular pressing (ECAP) is examined. The objectives of the present investigation are to evaluate the effect of ECAP die angle on the microstructure and mechanical properties of ECAP-ed AA6061. Heat treated AA6061 were divided to three conditions which is non-ECAP, ECAP-ed by 126º channel angle and ECAP-ed by 120º channel angle. The hardness evaluation and microstructural analysis were done on the samples after ECAP. The grain size of all materials was compared by applying the technique of grain size analysis while the hardness of the materials was compared by performing Vickers hardness calculation. From the hardness test, it found that 120º channel angle gives out an increment of hardness by 43.64% while for 126º channel angle the increment hardness is 40.14% compared to non-ECAP AA6061. Microstructural analysis reveals both ECAP-ed samples have elongated and refined grain size with smaller precipitate particulate compared to non-ECAP sample however no significant difference between the angles were observed. High strain induced during ECAP process increase dislocation in AA6061 and breaking the precipitate thus causing high hardness due to grain refinement. Varying the ECAP die angle may lower the pressure used during pressing without compromising the benefit of ECAP process in producing materials with improved mechanical properties.
Advances in Applied Mechanical Engineering, 2020
The formation of the dead metal zone (DMZ) in equal channel angular extrusion (ECAE) process significantly affects the deformation uniformity and mechanical properties of work material. The aim of the present study is to investigate the effect of the dead metal zone on structural homogeneity and hardness of Al 5083 alloy processed by ECAE and suggest the way to minimize that adverse effect. In this work, the rectangular billets with 1-mm-thick copper casing on two longitudinal faces and square billets with no casing are processed by ECAE up to four passes in route A. It was observed that the soft and ductile nature of the copper casing allows smooth flow of the work material at low pressing loads as compared to the alloy ECAE'd without a casing. Field emission scanning electron microscope (FESEM) images of the processed material with casing show the noteworthy improvement in structural homogeneity and grain refinement than another set of billets. The obtained structural homogeneity indicates the uniform strain distribution in the processed material is achieved by minimizing the formation of the dead metal zone at the intersection of ECAE die channels. The higher hardness and tensile strength measurements of the processed materials indicate the significance of grain refinement and uniform strain distribution. The variations in the test results confirm the non-homogeneous strain distribution caused by the dead metal zone is high for the billets processed with no copper casing.
Journal of Alloys and Compounds, 2003
The 6061 (Al-1.01 wt% Mg-1.07 wt% Si) Al alloy was fabricated by powder metallurgy, and then subjected to equal channel angular pressing. The microstructure and mechanical properties such as microhardness and tensile properties of the equal channel angular pressed P/ M 6061 Al alloy were investigated. The P/ M 6061 Al alloy had an initial grain size of approximately 20 mm. After two pressings at 373 K using route A, the sample revealed microstructure of subgrain bands with a length of |0.8 mm and a width of |0.3 mm. The subgrain bands became larger above 1 mm in length and width after two pressings at 573 K. An equiaxed ultra-fine grained structure with the mean grain size of |0.5 mm was obtained after four repetitive equal channel angular pressings at 473 K using route A and C. The microhardness of P/ M 6061 Al alloys was drastically increased from about 40 to 80 Hv by two repetitive pressings at 373 K. However, the microhardness decreased with increasing the pressing temperature. The tensile strength of 6061Al alloy before the equal channel angular pressing was 95 MPa, whereas it increased to both 248 MPa after two pressings at 373 K and 130 MPa after four pressings at 473 K, which was superior to that of a commercial 6061-O Al alloy.
Transactions of Nonferrous Metals Society of China, 2016
The combined effects of equal channel angular pressing (ECAP) and subsequent heating to a semi-solid temperature on the microstructural characteristics of the 7075 aluminum alloy were investigated. The microstructure is influenced by several parameters including the number of ECAP passes, ECAP route, consequent heating temperature, and holding time. The effects of these parameters on the microstructural characteristics including grain size and shape factor of the 7075 aluminum alloy were studied using experimental tests and Taguchi method. The results indicate that five-pass ECAP in route B A and subsequent isothermal holding at 630 °C for 15 min are more appropriate for achieving a semi-solid microstructure. The processing route and holding time have the highest impact on the grain size while the number of ECAP passes and heating temperature have the least impact on the grain size. Meanwhile, the shape factor is significantly influenced by the processing route, holding time and heating temperature while it is less influenced by the number of ECAP passes.
Journal of Materials Science, 2018
This study investigates the influence of the initial state of the commercial AX41 magnesium alloy on the microstructure evolution and mechanical properties after equal-channel angular pressing. Two initial conditions, an as-cast one with a grain size of 200 lm and a random crystallographic texture, and an extruded one having a grain size of 10 lm and a strong fibre texture, are compared. ECAP processing was performed at the temperature of 220°C up to 8 passes via route B C. A much smaller grain size was obtained in the ECAP-processed as-cast material compared to the extruded one. This difference was attributed to the different evolution of the dislocation density and its fractions in different slip systems. Consequently, different refinement mechanisms were dominant in the later stage of ECAP processing. It was shown that ECAP processing leads to the formation of similar crystallographic textures for both initial states, having dominant basal texture component. The mechanical properties investigation showed improvement in the microhardness, tensile strength and elongation in both ECAP-processed samples.