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Tensile behavior, microstructure, and substructure of the friction stir welded 70/30 brass joints: RSM, EBSD, and TEM study

100%

Heidarzadeh A.

Archives of Civil and Mechanical Engineering

2019

tom Vol. 19, no. 1

137--146

The effect of bead on plate friction stir welding parameters on the tensile properties of the 70/30 brass joints was investigated using response surface method. The microstructures of the joints were characterized using optical microscopy, electron backscattered diffraction (EBSD), and transmission electron microscopy (TEM). The tensile test was conducted to measure the ultimate tensile strength and elongation of the joints. In addition, the fracture surfaces of the tensile specimens were analyzed by scanning electron microscopy (SEM). The results showed that the most effective parameters on the strength and elongation of the joints were tool rotational speed and axial force, respectively. Optimizing the parameters revealed that the maximum strength and elongation of 318.5 MPa and 54.9% can be achieved at a rotational speed of 1000 rpm, a traverse speed of 58.4 mm/min, and an axial force of 3 kN. The strengthening mechanisms of grain boundary and dislocation density effects were responsible for the higher ultimate tensile strength of the joints welded at the lower heat input conditions. Furthermore, the effect of friction stir parameters on the ultimate tensile strength and elongation of the joints has been discussed, thoroughly.

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

51%

Heidarzadeh A. , Taghizadeh B. , Mohammadzadeh A.

Archives of Civil and Mechanical Engineering

2020

tom Vol. 20, no. 3

494--505

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.