Improvemant of Mechanical Properties of FCC and HCP structured materials Processed by Equal Channel Angular Pressing (original) (raw)
Related papers
Equal Channel Angular Pressing (ECAP) is one of the most applicable Sever Plastic Deformation (SPD) processes which leads to strength and ductility improvement through the grain refining and development of a suitable texture. In this study, after designing and manufacturing a suitable die, 4 pass ECAP process at route C is done on strip shaped specimens of AZ31 magnesium alloy in order to achieve desirable microstructural and mechanical properties. Microstructure then got studied through the optical microscopy. Results show that mean grain size is decreased and grain size distribution got close to normal distribution state by increasing the pass number. However, the grain size is reduced by increasing of ECAP temperature.
Non-equal channel angular pressing of aluminum alloy
Scripta Materialia, 2009
Strain history, microstructure and texture were studied in an aluminum alloy processed by the recently proposed process of non-equal channel angular pressing (NECAP). Comparison with alloy processed by equal channel angular pressing (ECAP) has been performed. A much finer microstructure was obtained in NECAP, showing that in this modified ECAP test the grainrefinement process was more efficient. The results indicate that the NECAP test has some interesting features that may be of interest for further research.
Grain refinement of Al–Zn–Mg alloy during equal channel angular pressing (ECAP)
Results in Engineering
Locally produced Al-Zn-Mg alloy was subjected to severe plastic deformation through Equal Channel Angular Pressing (ECAP) technique at temperatures of 150 • C and 200 • C. Rectangular thick-walled medium carbon steel die (σ c = 450Mpa, σ y = 176Mpa) with an L-shaped channel of uniform configuration to provide the pressing chamber was used. Four ECAP passes were imposed consecutively on set of samples for 150 • C and 200 • C temperatures, and characterized with optical microscopy, scanning electron microscopy (SEM) and x-ray diffraction (XRD). The phases were identified by X-ray diffraction (XRD) using monochromatic Cu Kα radiation, while vickers' microhardness and tensile tests were performed for mechanical properties examination. Optical micrographs showed no tangible precipitation in the as cast samples with reduced grain width and deformation bands but at high temperatures of 150 • C and 200 • C, precipitation was promoted as a result of slipping systems activation. SEM images of the as-cast alloy exhibits dendrites of 250 ± 20 μm in size with η ′ phase (MgZn 2) precipitates in the inter-dendritic regions. For 150 • C ECAP temperature, a significant refinement was achieved as the passes increased with sub-grain development within the boundary and the precipitate observed has a grain size of 35 ± 15 μm, 25 ± 10 μm, 15 ± 8 μm and 8 ± 6 μm for first, second, third and fourth passes respectively. However, grain sizes of 85 ± 15 μm, 50 ± 10 μm, 30 ± 8 μm and 10 ± 5 μm for first, second, third and fourth passes were observed for 200 • C ECAP temperature. XRD results showed peaks for aluminum and other phases in as-cast condition with precipitates growth in the alloy after the first pass, identified as metastable η ′ phase. As the number of ECAP passes increases, η ′ peaks moved towards the equilibrium η phase confirming the transformation of η ′ phase to stable η phase. The microhardness, Ultimate tensile strength (UTS) and the yield strength of Al-Zn-Mg alloy in different conditions of 150 • C and 200 • C respectively also increased with increase in the number of ECAP passes. This is due to increase in dislocation density, work hardening and grain refinement during ECAP process.
2011
Four important commercial aluminum alloys, namely 1050, 5083, 6082 and 7010AA are processed through a single pass via two equal channel angular pressing (ECAP) dies with different geometries (die angles of 90°and 120°). Electron back scattered diffraction (EBSD) is applied on the flow plane of the processed samples. Large scans with a step size of 7 lm for grain size distribution and texture measurements, as well as small scans with a step size of 0.1 lm for determination of cell size distribution, were performed. Hardness and simple compression are employed to evaluate the mechanical properties of the ECAP processed samples. Shear bands in the ECAP processed 7010AA was a major feature that led to failure in all samples subjected to further simple compression. The hardness as well as the stressstrain behavior was similar in the ECAP processed 6082 and 5083AA. The die geometry and the strain involved in the single pass influenced the overall texture intensity developed in the wrought alloys (1050 and 5083AA) and had minimal influence on the texture intensity of the heat treatable alloys (6082 and 7010AA). Low angle grain boundaries dominated the microstructure of all alloys for all testing conditions.
Journal of Materials Engineering and Performance, 2020
In the present study, Al 1070 alloy pins were processed via micro/meso-scale equal channel angular pressing (channel diameter 1.5 mm, the smallest channel diameter has ever been achieved in mesoscale), up to four passes at room temperature. The microstructure characteristics, i.e., grain size, and misorientation angle distributions were analyzed by high-resolution electron backscatter diffraction on the transverse plane for the ECAPed samples. Tensile properties for such small processed pins were measured by constructed micro/ meso-scale tensile machine. The gauge length and the gauge diameter were 2 mm and 1.5 mm, respectively. After the fourth ECAP pass, the results revealed that the microstructure was refined remarkably from 15.5 lm (the initial undeformed sample) to nearly 1.9 lm due to the gradual transformation of the lowangle grain boundaries into high-angle grain boundaries as a result of the occurrence of grain subdivision. Micro/meso-scale ECAP does a significant enhancement in the ultimate tensile strength by 63%, whereas the ductility decreased after the fourth ECAP pass by 47.3% and this is supposed to be ascribed to the continuous decrease in subgrain size. The above results prove that the ECAP process has the potential for obtaining fine grains and improving material tensile properties even in micro/meso-scale.
Powder Technology, 2012
In the present study, commercial pure aluminum powders were successfully consolidated to nearly full density by a combination of equal channel angular pressing (ECAP) and torsional deformation at room temperature. This new modification of ECAP is named as torsional-equal channel angular pressing (T-ECAP). A mechanism has been suggested to demonstrate the changes in porosities' shape, which leads to the porosities elimination during the T-ECAP process. Metallographic investigations have shown that the shape of the porosities have been changed from an elongated orientation in the ECAP process into near spherical shape in the T-ECAP process. Due to the subsequent torsional strains during the T-ECAP process, pores eliminated more effectively. Density and micro-hardness tests have shown superior values for the samples produced by the T-ECAP process than that of the samples produced using ECAP process, which can be improved by increasing the number of passes. Due to the existence of a variation in porosity from edge to center of the samples produced by both ECAP and T-ECAP processes, a variation in micro hardness in a same trend is also detected. Examination of the mechanical properties of the T-ECAP samples shows some moderate plastic deformation during the compression tests and exhibits high magnitude of ductility with respect to the ECAP samples.
Metallurgical and Materials Transactions A, 2012
A commercial Al-Zn-Mg-Cu alloy, Al 7075, was overaged at 280 ºC during 5 h, and processed by equal-channel angular pressing (ECAP) using route B C. Different temperatures and number of passes, which determine the processing severity, were considered. The processing severity has been estimated by the maximum stress (σ Proc) recorded during each ECAP pass. The higher is the number of passes or lower is the processing temperature, i.e. the higher is the processing severity, the finer is the (sub)grain size obtained. A minimum ultrafine (sub)grain size of approximately 150 nm after 3 passes at 80 ºC or 8 passes at 130 ºC was obtained. The microhardness exhibited an instant increase from 76 HV for the overaged initial state to 115 HV after only the first pass. The coarsened precipitates in the overaged alloy lead to larger structural refinement than in pure aluminum.
Equal channel angular pressing processing of wrought AZ31 alloy
Equal channel angular pressing (ECAP) technique has been used to deform the material to refine the grain size of the AZ31 alloy. The main aim of present study is to evaluate the microstructure characterization and mechanical properties of alloy using ECAP die angle of 1200. Homogenized AZ31 alloy was pressed through ECAP channel up to two passes using route Bc at a temperature of 573K. Average grain size of the commercially available AZ31 alloy was found to be 22.5μm, which has been reduced to 13.3μm after two passes. Mechanical properties were experimentally evaluated at room temperature to improve the quality of AZ31 alloy. Yield strength of the material was decreased with respect to increased percentage of elongation after ECAP process. Hardness of the material was evidently increased with increasing number of passes at a room temperature.