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Development of mechanical properties and microstructure for Al-Zn-Mg-Cu alloys through ECAP after optimizing the outer corner angles through FE modeling

Ghosh Abhishek, Das Kalyan, Eivani Ali Reza, Mohammadi Hossein, Vafaeenezhad Hossein, Murmu Uttam Kumar, Jafarian Hamid Reza, Ghosh Manojit

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e78, 2023

EN

Equal channel angular pressing (ECAP) is an efficient metal forming tool, generally used to improve the mechanical properties by refining the grain structure in metals and alloys. In the present work, both experimental and simulation approaches have been utilized to investigate the deformation behavior of EN AW 7075 alloy during ECAP. The formation and homogeneity of the Von-Mises stress and plastic strain of the samples during ECAP with different outer corner angles (OCAs) have been investigated by the finite element method (FEM). The results revealed that the effective strain was higher and uniform for 10°, 20°, and 30° OCAs die compared to other OCAs. Beyond 30°, the magnitude of strain was found lower with a less homogenous distribution of strain. A sharp plastic deformation zone (PDZ) was noticed for 10° and 20° OCAs, although broadened gradually over an OCA value of 20°. Moreover, lower and uniform Von-Mises stress was generated along the diameter of the sample for the OCA of 20° compared to other OCAs. A gradual reduction of plastic strain has been documented with the enhancement of OCAs along with the sample diameter. The sharpest damage, however, was noticed for the OCA of 90° due to the higher gap between the sample and both die surfaces. Interestingly, the most uniform severe plastic deformation and highest strain homogeneity in terms of inhomogeneity index and coefficient of variance were achieved for 20° and 30° OCAs. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analysis illustrated the formation of ultra-fine grain structures containing very fine η´ and η precipitates during the post-ECAP process. An improvement in the hardness, yield strength, and ultimate strength by 22%, 18%, and 14%, respectively, after ECAP has been recorded in comparison to the initial artificially aged condition. The improvements in mechanical properties were improvised primarily due to grain refinement combined with precipitate hardening.

2

Comparative Studies on a Chamfer Technology and a Convex Roll Technology During the Soft Reduction Process

Zong Nanfu, Jing Tao, Liu Yang

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 3

819--829

EN

To comprehensively investigate the diversity of a chamfer technology and a convex roll technology under the same soft reduction process (i.e., section size, reduction amount, casting speed and solid fraction), a three-dimensional mechanical model was developed to investigate the effect of the chamfer profile and roll surface profile on the deformation behavior, cracking risk, stress concentration and reduction force of as-cast bloom during the soft reduction process. It was found that a chamfer bloom and a convex roll can both avoid the thicker corner of the as-cast bloom solidified shell, and significantly reduce reduction force of the withdrawal and straightening units. The convex profile of roll limits lateral spread along bloom width direction, therefore it forms a greater deformation to the mushy zone of as-cast bloom along the casting direction, the tensile strain in the brittleness temperature range (BTR) can obviously increase to form internal cracks. The chamfer bloom is much more effective in compensating the solidification shrinkage of mushy zone. In addition, chamfer bloom has a significant decrease of tensile strain in the brittleness temperature range (BTR) areas, which is expected to greatly reduce the risk of internal cracks.

3

Close to reality methods for the structural design of towers. The basics of the relevant standards for industrial chimneys

Noakowski P.

Architecture Civil Engineering Environment

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2010

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Vol. 3, no. 3

79-84

EN

Numerous large concrete chimneys were built in many different countries in the seventies and eighties last century. Unfortunately, the professional scene had to realize that those structures were very different in their forms, wall thicknesses and reinforcements. In addition to this many of them had been impaired by wide vertical through cracks decreasing their durability and wind bearing capacity. Both findings revealed dissatisfying situation that the existing chimney standards were mostly over safe and in some cases unsafe. Due to this, efforts were undertaken to develop modern, close to reality methods for the structural design of chimneys. These new design methods became popular and as such entered the most relevant European standards on chimneys.

4

Homogeneity of the crystallographic texture and deformation behavior in Cu and Ti under severe plastic deformation

Alexandrov I. V., Bonarski J., Korshunov A. I., Tarkowski L., Sitdikov V. D.

Archives of Metallurgy and Materials

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2008

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Vol. 53, iss. 1

237-241

EN

The paper presents the results of experimental studies of the evolution of the homogeneity of the crystallographic texture and deformation behavior in bulk Cu and Ti billets subjected to the different numbers of equal-channel angular pressing (ECAP). It is found that the 1st pass during ECAP of pure Cu and Ti results in the formation of the pronounced preferred orientation of crystallites. Increase of the number of ECAP passes is accompanied by the formation of pronounced texture maxima which are orderly arranged in the pole figure. The intensity of texture maxima corresponding to the central part of the billet is the highest. The heterogeneity of the deformation behavior grows significantly after the 1 st ECAP pass as compared to the initial state, but it reduces with the increasing number of ECAP passes.

PL

Artykuł przedstawia wyniki badań eksperymentalnych nad rozwojem jednorodności tekstury krystalograficznej I postępu deformacji w prętach Cu I Ti poddanych cyklicznemu odkształceniu metodą przeciskania przez kanał równo-kątowy (ECAP). Stwierdzono, że w czystej Cu i Ti podczas pierwszego przepustu ECAP formuje się wyraźna uprzywilejowana orientacja krystalitów. Wraz ze wzrostem liczby przepustów ksztaltują się składowe tekstury, które są coraz bardziej stają się wyraźniejsze w postaci maksimów na figurze biegunowej. Największa intensywność tekstury występuje w obszarach zlokalizowanych w centralnej części przekroju poprzecznego odkształcanego pręta. Jednorodność postepującej deformacji po 1-wszym przepuście ECAP zwiększa się znacząco w porównaniu ze stanem wyściowym z tym, że po każdym następnym przepuście zostaje osłabiana (szczególnie w Ti).