Welding Metallurgy of

Hybrid Metal Extrusion and Bonding (HYB) is a novel solid-state welding method for metals and alloys that utilises continuous extrusion as a technique to enable aluminium filler metal additions. In the present study, a new semi-analytical model for the heat generation during aluminium butt welding is presented. As a starting point, the classical Rosenthal thin plate solution for the pseudo-steady-state temperature distribution around a fully penetrating line source is invoked. Then, the associated heat generation is calculated by considering the individual contributions from the tip of the rotating pin, the pin shoulder, and the filler metal additions on the net power input. In a calibrated form, the model yields thermal efficiency factors that are in close agreement with those obtained from more sophisticated finite element analyses but with considerably less computational effort.

https://www.mdpi.com/1996-1944/14/1/170/pdf

A Semi-Analytical Model for the Heat Generation during Hybrid Metal Extrusion and Bonding (HYB).

Failure competition behavior was found after low cycle fatigue (LCF) tests for the dissimilar welded joint between modified 9Cr steel and nickel-based alloy 617 at 600°C. The failure location shifted from base metal (BM) and fine grain heat affected zone (FGHAZ) on the 9Cr steel side to steel/Ni interface with the increase of the strain amplitude. At higher strain amplitude, strain concentration at the steel-Ni interface resulted in steel-Ni interface failure due to the differences in deformability. With the decreasing of the strain amplitude, the lower degree of transformation from lath to cell structure in coarse grain heat affected zone (CGHAZ) caused the competition between interface and FGHAZ failure. FGHAZ failure was governed by higher fraction of dynamic recrystallization (DRX) and formation of cell structure in FGHAZ. DRX was found promoting the formation of cell structure in FGHAZ, thus contributing to its lowest microhardness after LCF tests. As the strain amplitude further decreased, the reduction of DRX fraction made the formation of cell structure dominate the failure. The competing behavior between FGHAZ and BM led to the presence of case for BM failure.

Failure competition behavior of 9Cr/617 dissimilar welded joint during LCF test at elevated temperature

One of the most important negative consequence in the fusion welding processes is the generation of tensile residual stresses in welded joints. The main goals of this work are to determine the optimal combination of welding parameters to minimize the residual stress level and the influence of each welding parameter in that feature to weld 6082-T6 aluminum alloy plates using the GMAW welding process. To achieve these goals was implemented the Taguchi orthogonal array (L27) to define the design of numerical and experimental tests. All combinations were simulated in the Simufactwelding 6.0 software, from which it was possible to obtain the values of maximum residual stresses. The data treatment was carried out, reaching the combination of levels for each parameter. With ANOVA analysis was found that the parameter with the greatest influence in the residual stress generation was the welding speed, while the parameter with the least influence was the torch angle. Also, to minimize the residual stresses it was observed that the optimal combination of welding parameters is welding current intensity of 202 A, welding speed of 10 mm/s, and 30° of inclination of the angular torch. The two simulations that resulted in the highest and lowest residual stresses were validated experimentally by the hole drilling method to measure the residual stresses.

Experimental and numerical study to minimize the residual stresses in welding of 6082-T6 aluminum alloy

Hybrid metal extrusion & bonding (HYB) is a new solid-state joining method for metals and alloys that utilizes continuous extrusion as a technique to enable aluminium filler metal additions. In the HYB case, heat is generated by friction between the rotating tool and the workpiece and by plastic deformation of the base and filler materials. To get further insight into how the PinPoint extruder behaves during aluminium butt welding, a finite element (FE) model for the HYB process has been developed by exploiting the framework provided by the numerical code WELDSIM. The model allows the thermal and microstructure fields along with the resulting HAZ hardness profile to be calculated from knowledge of the net power input. In the present investigation the FE model is used to determine the energy efficiency of the HYB process following calibration against thermal data being obtained from dedicated in-situ thermocouple measurements. In the future the FE element model will be extended to enable predictions of both residual stresses and global distortions by taking full advantage of the opportunities that the numerical code WELDSIM offers.

A First Approach on Modelling the Thermal and Microstructure Fields During Aluminium Butt Welding Using the HYB PinPoint Extruder

A series of experiments have been conducted to determine the mechanical properties of AA6082-T6 plates which have been joined by means of the Gas Metal Arc technique. Hardness Vickers tests, bending tests, tensile tests, fatigue tests and Charpy V-notch tests have been carried out to characterize the joints. In addition, an accurate microstructure analysis of selected fracture surfaces has been done. From the tests it is concluded that HAZ softening brings to a reduction in strength with respect to the parent material. It has been noticed that there is a minimum value of hardness in the heat affected zone, that corresponds to the weakest part of the component. From the Charpy V-notch impact tests it has been observed that the material in the HAZ has the highest energy absorption capacity.

Lise Sandness

Papers

Mechanical behavior of gas metal arc AA6082-T6 weldments