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Effect of shoulder features during friction spot extrusion welding of 2024-T3 to 6061-T6 aluminium alloys

Han Jinzhen, Paidar M., Vignesh R. Vaira, Mehta Kush P., Heidarzadeh A., Ojo O. O.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

292--308

EN

Friction spot extrusion welding process is successfully performed on dissimilar aluminum alloys of AA2024-T3 and AA6061-T6 under the influence of shoulder features. The joints were analysed by microstructural features and mechanical properties using conventional and advanced tools of visual inspection, optical microscopy, scanning electron microscopy, transmission electron microscopy, electron back scattered diffractions, tensile testing and hardness testing. The results revealed that the joining was obtained by combination of mechanical locking from extruded material of top surface to predrilled bottom surface and diffusion in solid state. The stir zone and plastically deformed metal flow zone were influenced by scroll shoulder and smooth shoulder features. The tensile specimen of scroll shoulder was resulted to higher fracture load of 6381 N whereas the same was 4916 N in case of smooth shoulder. The interface of between plastically deformed metal flow zone and base material of AA6061-T6 can be considered as critical/weakest zone in case of friction spot extrusion. The variations of hardness were observed in stir zone, plastically deformed metal flow zone and thermo-mechanically affected zone in case of friction spot extrusion welding process.

2

Application of nanoindentation to evaluate the hardness and yield strength of brass joints produced by FSW: microstructural and strengthening mechanisms

Heidarzadeh A., Paidar M., Güleryüz G., Barenji R. Vatankhah

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 2

158--166

EN

Nanoindentation test was employed to measure the actual hardness and yield strength of the stir zone in the friction stir-welded single-phase brass joints. For this aim, different joints were prepared according to an experimental matrix based on the central composite rotatable design. In this design matrix, the tool rotational speed, tool traverse speed, and tool axial force were the input parameters. The outputs were the hardness and yield strength of the joints. To measure the hardness and tensile strength of the joints, the nanoindentation test was employed. Moreover, electron back scattered diffraction and transmission electron microscopy techniques were used to study the microstructural features. The results showed that by decreasing rotational speed and axial force, and by increasing the traverse speed, the hardness and yield strength of the joints were increased. In other words, lower heat inputs caused higher strength in the joints. Finer grain sizes, larger grain average misorientation amounts, i.e., existence of more dislocations, and greater Taylor factors in the lower heat input joints revealed that the influence of grain boundaries, dislocations, and texture were the origins of better mechanical properties.

3

Study on the post-rolling direction of severely plastic deformed Aluminum-Manganese-Silicon alloy

Jandaghi M. R., Pouraliakbar H., Khalaj G., Khalaj M. J., Heidarzadeh A.

Archives of Civil and Mechanical Engineering

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2016

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Vol. 16, no. 4

876--887

EN

Constrained groove pressing (CGP) as a severe plastic deformation (SPD) technique was applied on Al-Mn-Si sheets. In the following, direct- and cross-rolling were employed as supplementary processing in order to investigate the rolling-direction effect on CGPed sheets. The in-depth characterization of microstructural evolutions were employed using polarized light microscope and scanning electron microscope. Williamson–Hall analysis method was applied on X-ray diffraction (XRD) patterns of specimens. Analysis of XRD results revealed that post-rolling of CGPed sheets induced dynamic recrystallization (DRX) due to massive dislocations’ accumulation which follows by crystallite growth. The largest crystallite size which was 619 nm achieved after direct-rolling through the rolling strain of 1.27. Maximum acquired peak intensity ratio for rolled sheets was for (220) crystallographic plane similar to annealed one. Also, post-rolling had altered the distinguished plane from (111) for CGPed sheets into (220). Mechanical characteristics of specimens were examined using hardness and tension tests. Based on the obtained results, direct-rolling of CGPed samples was more susceptible for strength enhancement compared to cross-rolling. Optimum achieved values for yield and ultimate tensile strength were 155 and 197 MPa, respectively. Rolling in the both longitudinal and cross directions had almost similar effect on the final attained hardness.