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| 1 | Designing of ECAP parameters based on strain distribution uniformity | F.Djavanroodi B.Omranpour M.Ebrahimi M.Sedighi | 2012 | Progress in Natural Science:Materials International2012，22，5： | 8 |
| 2 | Effect of ECAP temperature on microstructure and mechanical properties of Al–Zn–Mg–Cu alloy显示文摘The effect of equal channel angular pressing(ECAP) at different temperatures(room temperature, 120,150 and 180 °C) on microstructure and mechanical properties of Al-7075 solid solution alloy was investigated. Microstructure of the specimens was examined using orientation imaging microscopy,transmission electron microscopy as well as X-ray diffractometer, and mechanical properties were measured by Vickers microhardness and tensile tests. Microstructural investigations showed that after3 or 4 passes of ECAP, fi ne grains with average grain sizes in range of 300–1000 nm could be obtained at different ECAP temperatures. Increasing ECAP temperature from 120 to 180 °C caused a decrease in mechanical properties as a result of increasing grains and precipitates sizes, decreasing fraction of high angle boundaries and also transformation of η′ into η phase, while increasing ECAP temperature from RT to 120 °C leads to an increase in mechanical properties due to the formation of small η′ precipitates. So it can be concluded that ECAP process at 120 °C is the optimum process for attaining maximum mechanical properties. Quantitative estimates of various strengthening mechanisms revealed that the improvement of mechanical properties was mainly attributed to grain re fi nement strengthening, precipitation strengthening and dislocation strengthening. | M.H.Shaeri M.Shaeri M.Ebrahimi M.T.Salehi S.H Seyyedein | 2016 | Progress in Natural Science:Materials International2016，26，2： | 7 |
| 3 | Experimental and numerical analyses of pure copper during ECFE process as a novel severe plastic deformation method显示文摘In this paper,a new severe plastic deformation method called equal channel forward extrusion(ECFE) process has been proposed and investigated by experimental and numerical approaches on the commercial pure copper billets. The experimental results indicated that the magnitudes of yield strength,ultimate tensile strength and Vickers micro-hardness have been markedly improved from 114 MPa,204 MPa and68 HV as the annealed condition to 269 MPa,285 MPa and 126 HV after the fourth pass of ECFE process,respectively. In addition,scanning electron microscopy observation of the samples showed that the average grain size of the as-received state which is about 22 μm has been reduced to 1.4 μm after the final pass. The numerical investigation suggested that although one pass ECFE process fabricates material with the mean effective strain magnitude of about 1,the level of imposed effective plastic strain gradually diminishes from the circumference to the center of the deformed billet. | M.Ebrahimi F.Djavanroodi | 2014 | Progress in Natural Science:Materials International2014，24，1： | 4 |
| 4 | Damage prediction of 7025 aluminum alloy during equal-channel angular pressing显示文摘Equal-channel angular pressing(ECAP) is a prominent technique that imposes severe plastic deformation into materials to enhance their mechanical properties. In this research, experimental and numerical approaches were utilized to investigate the mechanical properties, strain behavior, and damage prediction of ECAPed 7025 aluminum alloy in various conditions, such as die channel angle, outer corner angle, and friction coefficient. Experimental results indicate that, after the first pass, the yield strength, ultimate tensile strength, and hardness magnitude are improved by approximately 95%, 28%, and 48.5%, respectively, compared with the annealed state, mainly due to grain refinement during the deformation. Finite element analysis shows that the influence of die channel angle is more important than that of outer corner angle or friction coefficient on both the strain behavior and the damage prediction. Also, surface cracks are the main cause of damage during the ECAP process for every die channel angle except for 90°; however, the cracks initiated from the neighborhood of the central regions are the possible cause of damage in the ECAPed sample with the die channel angle of 90°. | M.Ebrahimi Sh.Attarilar C.Gode F.Djavanroodi | 2014 | International Journal of Minerals,Metallurgy and Materials2014，21，10： | 1 |
| 5 | Equal Channel Angular Pressing of Tubular Samples显示文摘A new technique to equal channel angular pressing of tubular samples has been proposed and investigated through experiments and simulations.Deformation behavior of copper tube sample was numerically analyzed during the first pass of tubular ECAP process.The investigation included the efect of various tube wall thicknesses on the efective strain magnitude and strain distribution uniformity.It is shown that tube wall thickness of 3.5 mm gives the optimum value for strain behavior.In addition,copper tube specimens with3.5 mm wall thickness have been successfully ECAPed up to four passes with the die channel angle of 90° using flexible polyurethane rubber pad.Micro-hardness measurements on both annealed and ECAPed tubes show that 33%and 57%increases in hardness value and also,50%and 70%reductions in the grain size were achieved after the first and fourth passes respectively.Furthermore,tube wall thickness measurements show that the process does not change the dimension of deformed specimens. | F.Djavanroodi A.A.Zolfaghari M.Ebrahimi K.M.Nikbin | 2013 | Acta Metallurgica Sinica(English Letters)2013，26，5： | 0 |
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