Mostafa Akbari

Mechanical Properties, Corrosion Resistance, and Microstructural Changes during Friction Stir Processing of 5083 Aluminum Rolled Plates

Friction stir processing is a solid-state process to modify microstructure and mechanical properties of sheet metals and as-cast materials. In this process, stirring action of the tool causes the material to intense plastic deformation that yields a dynamic recrystallization. In this study, the effect of friction stir processing (FSP) and process parameters on microstructure, mechanical properties, wear resistance, and corrosion behavior of AA5083-O has been investigated. Results show that FSP leads to finer and homogenized grain structure, as well as changes in hardness, corrosion resistance, and wear resistance of the material.

Effect of materials position on friction stir lap welding of Al to Cu

Abstract Friction stir welding has been successfully used to weld the dissimilar metals. A few investigations have been carried out on the friction stir lap welding of Al to Cu, but the basic issue of how the position of the metals would affect the joint strength is still not resolved. In the present study, the 7070 Al and the commercially pure copper are lap joined using friction stir lap welding technology. Two test cases are considered. The distinction refers to the position of Al with respect to Cu. Microstructural analyses are carried out to gain intermetallic compounds and some microcracks. The effect of position of materials on the heat generation is investigated and justified through the temperature measurements. Mechanical properties of each sample are characterized using both shear and hardness tests. The results reveal that the maximum fracture load of the joint is obtained when Al is placed on the top of Cu.

Sensitivity Analysis of the Artificial Neural Network Outputs in Friction Stir Lap Joining of Aluminum to Brass

Al-Mg and CuZn34 alloys were lap joined using friction stir welding while the aluminum alloy sheet was placed on the CuZn34. In addition, the mechanical properties of each sample were characterized using shear tests. Scanning electron microscopy (SEM) and X-ray diffraction analysis were used to probe chemical compositions. An artificial neural network model was developed to simulate the correlation between the Friction Stir Lap Welding (FSLW) parameters and mechanical properties. Subsequently, a sensitivity analysis was performed to investigate the effect of each input parameter on the output in terms of magnitude and direction. Four methods, namely, the “PaD” method, the “Weights” method, the “Profile” method, and the “backward stepwise” method, which can give the relative contribution and/or the contribution profile of the input factors, were compared. The PaD method, giving the most complete results, was found to be the most useful, followed by the Profile method that gave the contribution profile of the input variables.

Characterization of the Influence of Tool Pin Profile on Microstructural and Mechanical Properties of Friction Stir Welding

In this study, the effect of tool pin profile on mechanical properties, microstructural, material flow, thermal and strain distributions of friction stir welding of AA5083 was investigated. Two different tools with cylindrical and square pin profiles were employed to produce the welds. A numerical model is developed for investigating the effect of tool pin profiles on material flow, thermal and strain distributions based on thermo-mechanically coupled rigid-viscoplastic 3D FEM. Then, optical microscopy was employed to characterize the microstructures features of the weld. Finally, tensile test was carried out to characterize the mechanical properties of the weld. Obtained results showed that square pin profile produced finer grain structure and higher ultimate strength relative to cylindrical one. These results may be related to higher eccentricity, larger stirred zone, and higher temperature in the weld zone of the square pin profile.

Dissimilar Friction-Stir Lap Joining of 5083 Aluminum Alloy to CuZn34 Brass

In this research, lap joining of Al-Mg aluminum alloy and CuZn34 brass was produced by friction-stir welding during which the aluminum alloy sheet was placed on the CuZn34. Optical microscopy, scanning electron microscopy (SEM), X-ray diffraction analysis, and energy-dispersive X-ray spectroscopy (EDS) analysis were used to probe the microstructures and chemical compositions. In addition, the mechanical properties of each sample are characterized using both shear and hardness tests. The optimum parameters resulted in no visible welding cracks and defects. A dark area in the Al/CuZn34 interface contained intermetallic compounds Al2Cu, Al4Cu9, and CuZn. In addition, the results show that using high rotational speeds or low traverse speeds causes the growth of the interfacial intermetallic area.

Enhancing metallurgical and mechanical properties of friction stir lap welding of Al–Cu using intermediate layer

Abstract In this paper, the material behaviour and mechanical characteristics of lap joint friction stir welding (FSW) between dissimilar alloys, namely, Cu and Al, is investigated. In order to produce welds of a higher quality, a layer of Cu is anodised on the aluminium alloy. The mechanical and the microstructural characterisations are performed on the welds, which are produced using various welding parameters. Scanning electron microscope with energy dispersive X-ray spectroscopy is used to identify the elemental compositions of phases that are formed. The results reveal that the use of the copper anodised layer prevented formation of brittle intermetallic compounds due to the direct FSW of 6061 aluminium alloy to copper and, as a result, enhanced the weld metallurgical and mechanical properties.

Investigation of friction stir welding tool parameters using FEM and neural network

The welding tool geometry plays a critical role in acquiring desired microstructures and the heat-affected zones, and consequently improving the strength of the joint in friction stir welding. In this study, a friction stir welding process with different tool pin and shoulder diameter was numerically modeled. A thermomechanically coupled, 3D FEM analysis was used to investigate the effect of tool pin and shoulder diameter on welding force, material flow, thermal, and strain distributions in AA5083 aluminum alloy. Then, an artificial neural network model was employed to model the correlation between the tool parameters (pin and shoulder diameter) and heat-affected zone, thermal, and strain value in the weld zone.

Effect of tool pin profile on distribution of reinforcement particles during friction stir processing of B4C/aluminum composites

Boron carbide /aluminum composites have been produced on an aluminum–silicon cast alloy using friction stir processing. Effect of pin profile on the distribution of boron carbide in the stir zone of the friction stir processed specimens was investigated experimentally and numerically. The material flow generated by the threaded and circular tool pin profiles, being the main reason for the distribution of particles in the metal matrix, was numerically modeled using a thermomechanically coupled three-dimensional finite element model. Numerical and experimental results show that threaded pin profile produces a more uniform distribution of B4Cp than other pin profiles. Hardness tests were performed in order to investigate mechanical properties of the composites. Wear resistance of the composite was evaluated and obtained results showed that the hardness and wear resistance of the composite significantly improved.

The effect of in-process cooling conditions on temperature, force, wear resistance, microstructural, and mechanical properties of friction stir processed A356:

This paper focused on the effect of in-process cooling conditions (coolants and flow rate) on the temperature history, the tool applied forces, wear resistance, mechanical, and microstructural properties of friction stir processing (FSP) of Al–Si aluminum alloy. FSP was carried out using different compressed air and water coolants with different flow rates. The FSP tool force was measured experimentally using an especially designed load measuring system. Optical microscopy was used to probe the microstructures of the FSPed samples. The results showed that the Si particles size significantly decreases with increasing in-process cooling rate. Mechanical properties of each FSPed sample were also determined using hardness tests. Finally wear tests were conducted using a pin-on-disk tribometer.

A cellular automaton model for microstructural simulation of friction stir welded AZ91 magnesium alloy

To predict the grain size and microstructure evolution during friction stir welding (FSW) of AZ91 magnesium alloy, a finite element model (FEM) is developed based on the combination of a cellular automaton model and the Kocks − Mecking and Laasraoui–Jonas models. First, according to the flow stress curves and using the Kocks − Mecking model, the hardening and recovery parameters and the strain rate sensitivity were calculated. Next, an FEM model was established in Deform-3D software to simulate the FSW of AZ91 magnesium alloy. The results of the FEM model are used in microstructure evolution models to predict the grain size and microstructure of the weld zone. There is a good agreement between the simulated and experimental microstructures, and the proposed model can simulate the dynamic recrystallization (DRX) process during FSW of AZ91 alloy. Moreover, microstructural properties of different points in the SZ as well as the effect of the w/v parameter on the grain size and microstructure are considered.