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Effects of HE and ECAP processes on changes in microstructure and mechanical properties in copper, iron and zinc

Kulczyk Mariusz, Skorupska Monika, Skiba Jacek, Przybysz Sylwia, Smalc-Koziorowska Julita

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 3

art. no. e145563

EN

The research presented in this paper concerns the influence of the rate of plastic deformation generated directly in the processes of severe plastic deformations on the microstructure and properties of three metals: copper, iron and zinc. The equal channel angular pressing (ECAP) method was used, and it was performed at a low plastic deformation rate of ∼ 0.04 s−1. The high plastic strain rate was obtained using the hydrostatic extrusion (HE) method with the deformation rate at the level of ∼ 170 s−1. For all three tested materials different characteristic effects were demonstrated at the applied deformation rates. The smallest differences in the mechanical properties were observed in copper, despite the dynamic recrystallization processes that occurred in the HE process. In Armco iron samples, dynamic recovery processes in the range of high plastic deformation rates resulted in lower mechanical properties. The most significant effects were obtained for pure zinc, where, regardless of the method used, the microstructure was clearly transformed into bimodal after the ECAP process, and homogenized and refined after the HE process. After the HE process, the material was transformed from a brittle state to a plastic state and the highest mechanical properties were obtained.

2

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.

3

Effects of equal channel angular pressing and heat treatments on the microstructures and mechanical properties of selective laser melted and cast AlSi10Mg alloys

Snopiński Przemysław, Król Mariusz, Pagáč Marek, Petrů Jana, Hajnyš Jiří, Mikuszewski Tomasz, Tański Tomasz

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

77--94

EN

This study investigated the impact of the equal channel angular pressing (ECAP) combined with heat treatments on the microstructure and mechanical properties of AlSi10Mg alloys fabricated via selective laser melting (SLM) and gravity casting. Special attention was directed towards determining the effect of post-fabrication heat treatments on the microstructural evolution of AlSi10Mg alloy fabricated using two different routes. Three initial alloy conditions were considered prior to ECAP deformation: (1) as-cast in solution treated (T4) condition, (2) SLM in T4 condition, (3) SLM subjected to low-temperature annealing. Light microscopy, transmission electron microscopy, X-ray diffraction line broadening analysis, and electron backscattered diffraction analysis were used to characterize the microstructures before and after ECAP. The results indicated that SLM followed by low-temperature annealing led to superior mechanical properties, relative to the two other conditions. Microscopic analyses revealed that the partial-cellular structure contributed to strong work hardening. This behavior enhanced the material’s strength because of the enhanced accumulation of geometrically necessary dislocations during ECAP deformation.

4

Development of ultrafine grained Al–Zn–Mg–Cu alloy by equal channel angular pressing: microstructure, texture and mechanical properties

Ghosh Abhishek, Ghosh Manojit, Gudimetla Kondaiah, Kalsar Rajib, Kestens Leo A. I., Kondaveeti Chandra Sekhar, Pugazhendhi Bhagat Singh, Ravisankar Balasubramanian

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 1

82--98

EN

In this article, an effort has been made to investigate the evolution of microstructure, texture and mechanical properties of AA 7075 alloy during equal channel angular pressing (ECAP) by route BC at room temperature at a pressing speed of 1 mm/min. Transmission electron microscopy (TEM) revealed the presence of rod-like (MgZn2) precipitates in annealed conditions which were broken after two ECAP passes along with remarkable grain refinement due to high imposed strain after the second pass. After two consecutive ECAP passes, hardness, yield strength, and tensile strength of the alloy increased significantly in comparison to initial annealed condition. The fraction of high angle boundaries (HABs) and grain misorientation angle significantly increased after ECAP passes compared to the initial condition. Texture measurements were performed by X-ray diffractometer (XRD), on TD plane (parallel to extrusion direction). Texture results revealed the dominance of Cθ and A∗2θ components after the first pass and the presence of strong Bθ, B¯θ and A¯θ components along with weaker A∗2θ,Cθ components after the second pass. Scanning electron microscopy (SEM) revealed that the average dimple size was gradually reduced with increasing the ECAP passes.

5

A comparison of axial fatigue strength of coarse and ultrafine grain commercially pure titanium produced by ECAP

Naseri R., Hiradfar H., Shariati M., Kadkhodayan M.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 3

755--767

EN

Commercially pure titanium (CP-Ti) has been recently used as metallic biomaterials due to excellent biocompatibility and specific strength. CP-Ti has less static and dynamic strength as compared to other metallic biomaterials. Processing by the equal channel angular pressing (ECAP) as one of the most effective severe plastic deformation (SPD) method could lead to an increase in the mechanical strength of materials, significantly. In this study, Grade 2 CP-Ti billet is inserted into Al-7075 casing, and is then deformed by ECAP, with the channel angle of 135°, through 3 passes at route BC and room temperature. The purpose of using casing is to attain higher deformation homogeneity and more material ductility in the billet. The microstructural analysis shows that the coarse grain (CG) CP-Ti is developed to ultra-fine grain (UFG) structures after ECAP. In order to investigate the static and dynamic strength of CG and UFG CP-Ti, the tensile and axial fatigue tests are conducted. The results represent that UFG CP-Ti has much more tensile and fatigue strength than CG CP-Ti, and it could be utilized as biomaterials for production of implants. Surface features of fatigue fracture are also investigated. It should be noted that the investigation of fatigue strength of UFG CP-Ti produced by ECAP at RT utilizing casing, has not been conducted so far.

6

Microstructure and mechanical properties of the annealed 6060 aluminium alloy processed by ECAP method

Karoń M., Kopyść A., Adamiak M., Konieczny J.

Archives of Materials Science and Engineering

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2016

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Vol. 80, nr 1

31--36

EN

Purpose: The main goal of this paper is to present the investigation results of microstructural evolution and mechanical properties changes in commercial EN AW 6060) aluminium alloy after intensive plastic deformation, obtained by equal channel angular pressing (ECAP) techniques in an annealed state. Design/methodology/approach: Annealing heat treatment was used to remove various types of internal stress in a commercially available alloy in order to increase workability of the material. The evolution of its properties and material behaviour was evaluated after 2,4,6,and 8 passes of the ECAP process. Findings: It was found that the mechanical properties and microstructure during intensive plastic deformation, such as that during the ECAP process, were changed. Plastic deformation refined grains in the aluminium alloy and increased its mechanical properties. Research limitations/implications: The presented study shows results of the investigated material in an annealed state. Practical implications: The applied processing route allows development of materials characterized by high strength and ultrafine grain microstructure compared to un-deformed annealed aluminium alloy. Originality/value: The work presents data about the influence of intensive plastic deformation on the microstructure and mechanical properties of 6060 aluminium alloy after annealing.

7

Effect of severe plastic deformation by ECAP on corrosion behaviour of aluminium alloy AA 7075

Ilieva M., Radev R

Archives of Materials Science and Engineering

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2016

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Vol. 81, nr 2

55--61

EN

Purpose: The present study compares the corrosion behaviour of overaged AA 7075 before and after equal channel angular pressing ECAP in two media, containing chlorides, in order to answer the question how grain refinement of aluminium alloys influences their corrosion properties. Design/methodology/approach: The effect of equal channel angular pressing ECAP on corrosion behaviour of aluminium alloy AA 7075 was studied in two water solutions, containing chloride ions: 1) 0.01 M Na2SO4 with addition of 0.01%Cl-, and 2) 3g/l H2O2 and 57g/l NaCl. The changes in electrochemical characteristics, provoked by grain size refinement after equal channel angular pressing ECAP, were found using potentiodynamic polarisation. Steady state potential, corrosion potential, corrosion current density; breakdown (pitting) potential of overaged and deformed by equal channel angular pressing ECAP aluminium alloy AA 7075 were measured. Findings: In the environment with lower chloride concentration equal channel angular pressing ECAP process led to increase in pitting corrosion resistance and in the medium with higher chloride concentration - to decrease in pitting corrosion resistance. That way grain refinement does not demonstrate a uni-directional influence on corrosion resistance of AA 70775. Research limitations/implications: The results suggest the possibility for development of materials having the same chemical composition but with different corrosion resistance to different environments. Originality/value: The paper presents the corrosion behaviour of ultrafine-grained aluminium alloy AA 7075 and the influence of the chloride ions concentration in the corrosion medium on this behaviour.

8

Experimental investigation of ultrasonic assisted equal channel angular pressing process

Djavanroodi F., Ahmadian H., Naseri R., Koohkan K., Ebrahimi M.

Archives of Civil and Mechanical Engineering

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2016

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Vol. 16, no. 3

249--255

EN

Improvement of equal channel angular pressing (ECAP) efficiency is an important challenge for industrialization of this technique. The reduction of pressing load and improvement of material mechanical properties are among the most challengeable subjects during this process. In this research, commercial pure aluminum has been ECAPed at room temperature using conventional and ultrasonic vibration techniques to investigate the influence of ultrasonic wave on the pressing load and mechanical characteristics of deformed samples. The results showed that the superimposing ultrasonic vibration on the ECAP process not only decreases the required punch load, but also improves the mechanical properties of the material as compared to the conventional condition. Interestingly, the ultrasonic vibration assisted process leads to about 16%, 10% and 12% increments at the yield strength, ultimate tensile strength and hardness value respectively and also, 9% reduction at the punch load. Furthermore, the dislocation density of the sample produced by ultrasonic assisted ECAP is about 35% more than the achieved conventional sample.

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Aparatura wysokociśnieniowa do przeróbki plastycznej materiałów z dużymi odkształceniami na zimno

Pachla W., Skiba J., Kulczyk M., Przybysz M.

Obróbka Plastyczna Metali

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2015

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T. 26, nr 4

283--306

PL

Obróbka plastyczna z dużymi odkształceniami powoduje rozdrobnienie mikrostruktury materiałów co skutkuje wzrostem własności mechanicznych. Aby powstrzymać utratę spójności materiału podczas odkształcania należy zachować duże naprężenia ściskające w strefie odkształcenia. W pracy przedstawiono korzystny wpływ wysokiego ciśnienia na wzrost plastyczności i powstrzymanie pękania poprzez zastosowanie metody przeciskania przez równoosiowy kanał kątowy ECAP i wyciskania hydrostatycznego HE. Opisano konstrukcje pras, ich podstawowe osiągi i parametry procesów. Scharakteryzowano prasę do HE o średnicy 22mm do 2 GPa i stanowisko do procesu ECAP o przekroju 30mm i nacisku do 2.3 GPa, uwzględniając optymalizowanie konstrukcji z wykorzystaniem metod analitycznych opartych o teorię sprężystości i plastyczności Lame’a, oraz metodą elementów skończonych MES. Analizie poddano materiały komór roboczych i podstawowe parametry procesu. Zredukowane naprężenia węzłowe komory ECAP ze stali S600 i komory HE ze stali 45HNMFA wykazały, że wytrzymałości dla maksymalnych obciążeń nie są przekroczone. Dla stopu aluminium 6060 optymalny kąt naroża kwadratowego kanału ECAP wynosi 16º. Przedstawiono, określone metodą MES, niejednorodność odkształcenia plastycznego przy wyciskaniu hydrostatycznym kwadratowego profilu miedzi oraz obszary lokalizacji umocnienia podczas wyciskania złożonego profilu z tytanu. Opisano łatwość łączenia ze sobą obu technik SPD i jego wykorzystania w celu wzmacniania efektu rozdrabniania ziaren do rozmiarów nanometrycznych. Wykazano, ze rozdrabnianie mikrostruktury metodami deformacji pod wysokim ciśnieniem prowadzi do wzrostu wytrzymałości o ponad 70% (miedź i stop tytanu Ti grade 5) oraz granicy plastyczności powyżej 100% (stop niklu C65500 i aluminium 5483). Przedstawiono obszary możliwych zastosowań przetworzonych materiałów jak instrumentarium i implanty medyczne, elementy złączne, oprzyrządowanie spawalnicze czy rury i profile złożone.

EN

Severe plastic deformation working results in refinement of the microstructure of materials, improving their mechanical properties. To prevent loss of the material's cohesion during deformation, high compressive stresses must be maintained in the deformation zone. This article presents the beneficial use of high pressure to increase plasticity and prevent cracking, by applying the equal channel angular pressing(ECAP) and hydrostatic extrusion (HE) methods. Basic press designs, performances, and process parameters are described. The HE press, with a diameter of 22mm, up to 2 GPa and an ECAP station with a cross-section of 30mm and pressing force up to 2.3 GPa are characterized, with design optimization by means of analytical methods based on Lame's theory of elasticity and plasticity and the finite-element method (FEM). The materials of working chambers and basic process parameters are analyzed. Reduced node stresses of the ECAP chamber, made of S600 steel, and the HE chamber, made of 45HNMFA steel, show that the materials' strength is not overcome at their respective maximum loads. For the 6000 aluminum alloy, the optimal angle of the square corner of the ECAP channel is 16º. Non-uniformity of plastic deformation during hydrostatic extrusion of a square copper section and hardening areas during extrusion of titanium sections determined using FEM are presented. The ease of combining both of these SPD techniques and using them to amplify the grain refinement effect to nanometric dimensions are described. It is shown that refinement of the microstructure by highpressure deformation leads to improvement of strength by over 70% (copper and grade 5 Ti alloy) and yield point above 100% (C65500 nickel and 5483 aluminum alloys). Possible areas of application for worked materials are presented, such as surgical instruments and medical implants, fixing elements, welding tools, pipes and complex sections.

10

Characterization Of An Equal Channel Angular Pressed Al-Zn-In Alloy

Banjongprasert C., Jak-Ra A., Domrong C., Patakham U., Pongsaksawad W., Chairuangsri T.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2A

887--890

EN

Equal channel angular pressing (ECAP) is a technique that creates a high accumulated strain in metals and results in ultrafine-grained structure. In this study, Al-5Zn-0.02In was processed by ECAP at a room temperature using route Bc through an ECAP die (press angle of Φ = 100° and Ψ = 20°). The samples were subjected to ECAP with 1, 2, 3 and 4 passes. The processed specimens were characterized using electron backscatter diffraction (EBSD). The results confirmed the grain refinement of the alloy after ECAP to an average grain size less than 5 μm after 4-pass ECAP. The microhardness test shows that the hardness increased with the number of passes. The hardness of the cross-sectional area of the sample was similar to that tested along the pressing direction.

PL

Metoda przeciskania w kanale kątowym (ang. Equal channel angular pressing; ECAP) prowadzi do powstania bardzo wysokich naprężeń, w wyniku czego otrzymuje się ziarna o bardzo drobnej strukturze. W niniejszej pracy, stop Al-5Zn-0,02In wytwarzano metodą ECAP w temperaturze pokojowej, wykorzystując ścieżkę Bc przez matrycę ECAP (kąty krzywizny: Φ = 100° i Ψ = 20°). Próbki poddano ECAP z 1, 2, 3 i 4 przejściami. Otrzymane próbki badano metodą dyfrakcji elektronów wstecznie rozproszonych (ang. electron back scatter diffraction; EBSD). W stopie otrzymanym metodą ECAP z 4 przejściami, średnia wielkość ziaren wynosiła mniej niż 5 μm. Badania mikrotwardości wykazały, że twardość zwiększała się wraz z liczbą przejść. Twardość zmierzona w poprzek próbki byłą porównywalna do tej mierzonej wzdłuż osi nacisku.

11

Combination of equal channel angular pressing and hydrostatic extrusion as a method for effective grain refinement of Cu and a Cu-alloy

Kulczyk M., Bazarnik P., Pachla W., Skiba J., Lewandowska M., Kurzydłowski K. J.

Inżynieria Materiałowa

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2013

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Vol. 34, nr 4

314--316

EN

In this work pure copper and copper alloy CuCrZr were processed by severe plastic defonnation (SPD) using the combination of equal channel angular pressing (ECAP) and hydrostatic extrusion (HE). Transmission electron microscopy revealed ultra-ﬁne grained (UFG) microstructure in both materials. It has been also proved that small addition of Cr and Zr signiﬁcantly increased grain reﬁnement level of ECAP + HE processed CuCrZr alloy. Microstructure changes resulted in a great increase in mechanical strength comparing with coarse grained materials. In the case of CuCrZr alloy, the yield strength (YS) increased by 1350%, whereas ultimate tensile strength (UTS) by 300%. The UFG samples possess reduced ductility compared to coarse grained ones, however the absolute values of their elongation are relatively high (over 10%).

PL

W pracy czysta miedź i stop miedzi CuCrZr były poddane dużemu odkształceniu plastycznemu przez połączenie metod przeciskania przez kanał kątowy (ECAP) i wyciskania hydrostatycznego (HE). Transmisyjna mikroskopia elektronowa ujawniła, że w obu materiałach otrzymano ultra drobnoziarnistą (UFG) strukturę. Ponadto pokazano, że niewielki dodatek Cr i Zr znacząco zwiększa stopień rozdrobnienia w próbce poddanej procesowi ECAP + HE. Porównując właściwości mechaniczne obrobio- nych materiałów z tymi dla materiałów wyjściowych, można powiedzieć, że rozdrobnienie struktury spowodowało znaczący wzrost właściwości mechanicznych badanych próbek. W przypadku stopu CuCrZr odnotowano 1350% wzrost wytrzymałości i 300% wzrost granicy plastyczności. Poprawa właściwości wytrzymałościowych odbyła się kosztem plastyczności, ale i tak wydłużenie do zerwania w obu materiałach przekracza 10%.

12

Methods of fabricating metals for nano-technology

Olejnik L., Rosochowski A.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2005

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Vol. 53, nr 4

413-423

EN

The paper gives an introduction to nanostructuring techniques used for industrial fabrication of hulk nanocrystalline metal s - basic materials utilized in shaping nanoscale structures. Nanostructured metals, called nanometals, can be produced by severe plastic deformation (SPD). We give an expert coverage of current achievements in all important SPD methods and present future industry developments and research directions including both batch and continuous processes. In the laboratories of both WUT and DOS we have developed industry standard equipment and machinery for nanometals processing. Utilizing the latest examples from our research, we provide a concise introduction to the field of mass production of nanometals for nanotechnology. Key words: ultra-fine grain structure, severe plastic deformation, ECAP (equal channel angular pressing), grain refinement, aluminium alloys.