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Microstructure and mechanical properties of CuZn-Al2O3 nanocomposites produced by friction stir processing

Heidarzadeh Akbar, Taghizadeh Babak, Mohammadzadeh Ahad

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

494--505

EN

For the first time, ceramic nano particles were incorporated into the brass alloy to produce surface nano composites by friction stir processing. For this aim, Al2O3 particles with an average diameter of 30 nm were inserted into a Cu-37Zn alloy at different tool rotational speeds of 450, 710, and 1120 rpm, multi passes, and a constant traverse speed of 100 mm/min. The microstructures of the processed materials were analyzed using optical and scanning electron microscopes equipped with an energy dispersive spectroscopy. In addition, tensile test was employed to evaluate the mechanical properties. The results showed that the optimum rotational speed was 710 rpm. At lower rotational speeds, Al2O3 particles were agglomerated. On the other hand, at higher rotational speeds, tool was damaged by severe wear. The effect of multi passes showed that one and two passes could not distribute the Al2O3 particles, uniformly. However, three passes resulted in a uniform distribution of the Al2O3 particles inside a bimodal grain structure composed of both 3–5 μm grains and ultra-fine grains (< 1 μm). By using multi-pass friction stir processing, a synergic increase in ultimate tensile strength and elongation was obtained. Moreover, three passes caused superior mechanical properties i.e. ultimate tensile strength of 430 MPa and elongation of 39%. The fracture behavior and strengthening mechanisms are also discussed in details.

2

Mechanical properties enhancement of cast Al-8.5Fe-1.3V-1.7Si (FVS0812) alloy by friction stir processing

Nouri Z., Taghiabadi R., Moazami‑Goudarzi M.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

35--46

EN

This study was conducted to investigate the capability of multi-pass friction stir processing (FSP) on microstructure modification and mechanical properties improvement of FVS0812 alloy. FSP was performed at different rotation speeds (1250, 1600, 2000, and 2500 rpm) and traverse speeds (8, 12, and 25 mm/min) for one, two, and four passes. According to the results, applying single-pass FSP at optimized conditions (i.e. 1600 rpm and 12 mm/min) enhanced the tensile strength, fracture strain, and microhardness of the alloy by about 1020, 1050, and 60%, respectively. This improvement can be mainly attributed to the intense breakage and uniform distribution of θ-Al13Fe4 and α-Al12(Fe,V)3Si intermetallics within the matrix, formation of ultrafine recrystallized grains, and elimination of casting defects. Increasing the number of FSP passes up to four slightly decreased the average size of intermetallic particles, but significantly improved their distribution within the matrix which led to 18 and 200% improvement of tensile strength and fracture strain of one-pass FSPed sample, respectively. The fractography results also revealed that multi-pass FSP has changed the fracture mode of Al-8.5Fe-1.3V-1.7Si alloy from low-energy brittle to a more ductile-dimple fracture.

3

Fabrication and effect of Mg–Zn solid solution via Zn foil interlayer alloying in FSW process of magnesium alloy

Sahu Prakash Kumar, Pal Sukhomay, Das Bipul, Shi Qingyu

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

589--603

EN

The present study demonstrates the friction stir welding (FSW) process can be used as a mechanical alloying tool to fabricate a solid solution. An attempt has been taken for alloying the AM20 Mg base matrix using Zn at the weld zone during friction stir welding. Successful joints with sound mechanical properties and enhanced quality attributes are observed in the welds. Use of Zn alloying element at the nugget zone, the joint efficiency reached 90% to that of the base material and also which is about 25% more than the strength obtained in the case of without alloying element set of experiments. The addition of Zn alloy to Mg substrate forms Mg–Zn binary solid solution reinforcing intermetallic compounds, namely MgZn and Mg7Zn3 resulting in improved joint properties. This research work also reports the investigative outcomes, namely flow in the joint area, metallurgical deviation, microstructural modification, and diffusion of the constituent alloying element during the welding process. The targeted objective was effectively accomplished and the Zn alloyed stir area can fulfil the required application. The findings from the selective alloying process may be relevant for the implementation of industrial users over Mg alloys using a FSW process with better weldability and improved strength.

4

Development of a repair process for manmade structures in space by using aluminium brazing and friction stir spot welding

Koehler Tobias, Yu Cheng-Nien, Schmidt Kiril, Graetzel Michael, Wu Yangyang, Bergmann Jean Pierre, Sekulic Dusan P.

Welding Technology Review

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2019

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R. 91, nr 9

39--49

EN

Small-sized parts and micrometeoroids’ impacts represent an increasing threat to artificial components/structures. The damages caused by them can be fixed using e.g., mechanical fixture with epoxy adhesive. However, the repair process is costly and only intended for a temporary fixing the penetration. In order to increase the life time of the repair, an approach for a more reliable process using similar materials is needed. The objective of this work is to develop a process for repairing manmade structures in space by generating joint properties similar to the base material. In this work, two approaches for repairing complex structures were considered. The first approach aims to fill a hole using liquid aluminium phases by brazing, and the second approach aims to fill the holes by a solid-state process (friction stir spot welding). In this study, different binding mechanisms of these two approaches were analyzed preliminarily by means of mechanical and/or metallographic characterization under terrestrial, controlled atmosphere conditions. Both concepts are proven feasible under these conditions. It has been shown that it is possible to realize a good filling of the hole with the investigated materials and under selected process conditions with both presented concepts.

PL

Uderzenia małych części i mikrometeorytów stanowią rosnące zagrożenie dla sztucznych komponentów/struktur. Uszkodzenia przez nie spowodowane można naprawić np. za pomocą mechanicznego osprzętu z klejem epoksydowym. Proces naprawy jest jednak kosztowny i służy jedynie do tymczasowego zatrzymania penetracji. W celu zwiększenia żywotności naprawy potrzebne jest podejście do bardziej niezawodnego procesu z wykorzystaniem podobnych materiałów. Celem tej pracy jest opracowanie procesu naprawy sztucznych konstrukcji w przestrzeni kosmicznej poprzez generowanie właściwości połączeń podobnych do materiału podstawowego. W pracy tej rozważono dwa podejścia do naprawy złożonych konstrukcji. Pierwsze podejście ma na celu wypełnienie otworu za pomocą faz ciekłego aluminium przez lutowanie, a drugie podejście ma na celu wypełnienie otworów metodą półprzewodnikową (zgrzewanie tarciowe punktowe z przemieszaniem). W tym badaniu wstępnie przeanalizowano różne mechanizmy wiązania tych dwóch podejść za pomocą mechanicznej i/lub metalograficznej charakterystyki w warunkach kontrolowanej atmosfery ziemskiej. Obie koncepcje okazały się wykonalne w tych warunkach. Wykazano, że możliwe jest prawidłowe wypełnienie otworu badanymi materiałami oraz w wybranych warunkach procesu przy obu przedstawionych koncepcjach.