Friction Stir Welded Butt Joints Research Articles

Mechanical and metallurgical characterization of friction stir welding joints of AA6061-T6 with AA6082-T6

A mechanical and metallurgical characterization of friction stir welded butt joints of aluminium alloy 6061-T6 with 6082-T6 was carried out. For comparison, similar material joints made from each one of the two alloys were used. The work included microstructure examination, microhardness, tensile and bending tests of all joints. An approximate finite element model of the joint, taking into account the spatial dependence of the tensile strength properties, was made, modelling a bending test of the weldments. This study shows that the friction stir welded dissimilar joint present intermediate mechanical properties when compared with each base material. In tensile tests the dissimilar joint displayed intermediate properties. For instance in the hardness profile the lowest values were obtained in the AA6082-T6 alloy plate side where rupture occurred, and in the nugget all type of joints present similar values.

Fatigue Crack Propagation in Friction Stir Welded Joints of Particulate Metal-Matrix Composite

In this work the fatigue crack growth properties of friction stir welded butt joints are evaluated. Fatigue Crack Growth (FCG) tests have been carried out on two particle-reinforced aluminium alloys (AA6061/Al2O3/20p and AA7005/Al2O3/10p). FCG properties have been evaluated at the centre and at the side of the weld, respectively. The results are compared with FCG properties of base materials. The role of alumina in particles inside the matrix is evident in the threshold region: this can be explained in terms of Roughness Induced Crack Closure.

Local Mechanical and Morphological Characterization of Friction Stir-Welded Butt Joints

In this paper the results of an experimental investigation into the local mechanical and morphological characterization of AA6082-T6 friction stir-welded (FSW) butt joints are illustrated. The softening effects of the welding process are highlighted through the use of micro-indentation tests on the top surface of the specimens. The effect of post-welding heat treatments was investigated, also.

An analysis of through-thickness residual stresses in aluminium FSW butt joints

In the paper, the results of a wide experimental campaign on friction stir welding (FSW) of aluminum alloys are reported. The attention was focused on the through-thickness residual stresses that occur on aluminum joints, after the welding process. In detail, using the hole-drilling method the residual stresses distribution in the zone close to the tool shoulder border of the joint advancing side, has been investigated; four different aluminum alloys and three different process conditions have been considered. The experimental analysis has shown that unlike traditional welding processes, the residual stresses are negative in the surface of the examined zone, and increase with depth until values of about 100–150 MPa that occur at a depth of about 0.5–1.0 mm. As expected, the maximum value of the residual stresses induced by the FSW process influences the mechanical behavior of the joint significantly, as it has been observed for the AA6082-T6 aluminum alloy by considering its static and fatigue resistance. Such results corroborate that the hole-drilling method, widely employed in the industrial field due to its simplicity and low cost, can be used for an accurate estimation of the maximum residual stresses that occur in an aluminum butt joint obtained by friction stir welding.

Thermal Characterization of Friction Stir Welded Butt Joints

In the paper the thermal characterization of friction stir welding processes (FSW) of aluminium alloys is presented. In particular both embedded thermocouples and a thermography analysis were utilized in order to acquire the temperature vs. time curves in point of interests of the joints and the temperature distributions, respectively. Such kind of results are very important in order to investigate the material conditions during the FSW process.

TEM analysis of a friction stir-welded butt joint of Al–Si–Mg alloys

The microstructure evolution of a joint of Al–Si–Mg alloys A6056-T4 and A6056-T6 has been characterized by transmission electron microscopy (TEM). Metallurgical investigations, hardness and mechanical tests were also performed to correlate the TEM investigations to the mechanical properties of the produced friction stir-welded butt joint. After friction stir-welding thermal treatment has been carried out at 530°C followed by ageing at 160°C (T6). The base material (T4) and the heat-treated one (T6) were put in comparison showing a remarkable ductility reduction of the joint after T6 treatment.