Synergistic strengthening is increasingly explored for developing high-performance copper matrix composite. In this work, the hybrid copper matrix composites reinforced with carbon nanotubes (CNTs) and micro- TiB2 particles（（CNTs-TiB2）/Cu composites）were prepared by electroless copper plating, powder metallurgy and hot extrusion. The arc erosion resistance of the hybrid copper matrix composites was studied in JF04C electrical contact testing system. And the synergistic effect of CNTs and TiB2 particles in different content ratios on the arc erosion resistance of composites was analyzed emphatically. The action mechanism of CNTs and TiB2 particles in arc erosion process is discussed in detail. Results show that the arc duration and arc energy of the hybrid copper matrix composites are lower than that of copper matrix composites single reinforced with CNTs or TiB2 particles. When the volume fraction of CNTs is 4.2% (The content of TiB2 particles is 1.6%), the arc erosion resistance of the hybrid copper matrix composites is optimal. In arc erosion process, CNTs can form a network structure parallel to the extrusion direction in copper matrix, and the continuous CNTs network structure can effectively disperse cathode arc, promote arc movement, increase work function of copper matrix composites, inhibit electron emission and reduce total emission current density. And the micro- TiB2 particles are helpful to improve the viscosity of molten pool, which can reduce the material mass loss and erosion pit on the surface of composites. Under the combined actions of CNTs and TiB2 particles (4.2CNTs-1.6TiB2)/Cu composite presents better arc erosion resistance stability, lower arc duration and energy.

Arc erosion resistance of hybrid copper matrix composites reinforced with CNTs and micro-TiB2 particles

The Hybrid Metal Extrusion & Bonding (HYB) process is a patented solid state joining method for metals which utilizes filler material additions to consolidate the weld. In the present investigation the interface microstructure and tensile properties of a 4 mm thick joint, belonging to the third generation Al-steel HYB butt welds, are characterized. The mechanical testing shows that the HYB weld exhibits excellent tensile properties, displaying ultimate tensile strength values in the range from 238 to 266 MPa. Moreover, supplementary digital image correlation analysis of the strain evolution occurring during tensile testing reveals that all plastic deformation is localized to the soft heat-affected zone on the aluminium side of the joint, leading to necking and final fracture in the aluminium. Scanning and transmission electron microscopy examinations of the Al-steel interface show that bonding occurs by a combination of microscale mechanical interlocking and intermetallic compound formation. The intermetallic layer has a thickness varying between 0.1 and 1 μm and is composed of Al–Fe–Si crystals. This makes the butt joint highly resistant against interfacial cracking. The subsequent benchmarking against commercial fusion and solid state welding methods reveals that the tensile properties of the Al-steel HYB weld even surpass those reported for comparable friction stir welds. At the same time, the HYB process allows butt welding to be performed at much higher speeds compared to friction stir welding, without compromising the mechanical integrity of the weldment.

Interface microstructure and tensile properties of a third generation aluminium-steel butt weld produced using the Hybrid Metal Extrusion & Bonding (HYB) process

HYB is a new solid-state joining method for metals and alloys that utilises continuous extrusion as a technique to enable aluminium filler metal additions. In the present paper a finite element (FE) model for the filler wire feeding inside the HYB PinPoint extruder has been developed and implemented within the commercial software package Deform 3D ™. Based on a comparison with experimental data for the extruder housing temperature, the drive spindle torque and the wire feed rate, it is concluded that the FE model is sufficiently relevant and comprehensive to be used in future developments of the HYB process. In addition to improved wire feeding control, a model-based approach will make it possible to reduce the engineering time and costs involved in case a modification of the design is needed to optimise the extruder performance in a real joining situation.

Finite Element Modelling of the Filler Wire Feeding in the Hybrid Metal Extrusion & Bonding (HYB) Process

The present investigation is concerned with solid state butt welding of 2 mm thin AA6060-T6 profiles at room temperature (RT), using the HYB process and AA6082-T4 as filler material (FM). In Part II of this investigation the tensile properties of the butt weld have been evaluated as a follow-up of the three-point bend testing done in Part I. In the HYB case the weld can be sub-divided into two distinct zones, i.e. the Extrusion Zone (EZ) and the Heat-Affected Zone (HAZ). The EZ, which is a composite material consisting of a mix of a strong FM and a soft HAZ material, displays superior tensile properties compared to the HAZ. By allowing for this in the subsequent finite element (FE) simulations of the load-bearing capacity of the joint, the observed stress-strain response of the HYB weld has been fully reproduced and rationalized. These results show that the tensile properties are comparable with those reported for FSW of 2 mm AA6082-T6 profiles and surpass those reported for FSW of 2 mm 6061-T6 profiles as far as the yield strength is concerned.

Assessment of the Mechanical Integrity of a 2 mm AA6060-T6 Butt Weld Produced Using the Hybrid Metal Extrusion & Bonding (HYB) Process – Part II: Tensile Test Results

Correspondence Lise Sandnes, Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands vei 2b, 7491 Trondheim, Norway. Email: lise.sandnes@ntnu.no Abstract The present investigation is concerned with high-cycle axial fatigue testing of a 2-mm AA6060-T6 hybrid metal extrusion & bonding (HYB) butt weld produced in the solid state using AA6082 filler metal addition. The results complement the three-point bend testing and the tensile testing done in two previous studies. In this study, optical microscope and scanning electron microscope examinations have been carried out to reveal the joint macro/microstructure and document possible surface and root defects deemed to affect fatigue life. In the as-welded condition, the HYB weld suffers from surface irregularities at the weld face and ‘kissing’ bond formation in the root region. Despite of this, the subsequent testing shows that the fatigue properties exceed those reported for comparable AA6082-T6 gas metal arc butt welds and matching those reported for corresponding high-strength laser beam and friction stir weldments.

Fatigue properties of AA6060‐T6 butt welds made by hybrid metal extrusion & bonding

Assessment of the Mechanical Integrity of a 2 mm AA6060-T6 Butt Weld Produced Using the Hybrid Metal Extrusion & Bonding (HYB) Process – Part I: Bend Test Results

Luca Romere

Papers

Assessment of the Mechanical Integrity of a 2 mm AA6060-T6 Butt Weld Produced Using the Hybrid Metal Extrusion & Bonding (HYB) Process – Part II: Tensile Test Results

Assessment of the Mechanical Integrity of a 2 mm AA6060-T6 Butt Weld Produced Using the Hybrid Metal Extrusion & Bonding (HYB) Process – Part I: Bend Test Results