Solid State Joining Processes
Solid phase joining processes, Photo: HZG
Solid state joining and processing technologies are becoming the centre of attention of scientists and engineers involved with advanced lightweight structures. The main reason for that is the nature of such processes: since bonding and processing take place in the solid state all metallurgical reactions involved in melting and solidification are avoided, resulting in defect free joints with superior properties.
Core competences Friction Stir Processes und Friction Surfacing Processes
Friction Stir Processes and Friction Surfacing Processes represent one of the core competences where HZG has taken an international leading position. Such processes allow to a very high degree of freedom to modify, coat, or weld similar and dissimilar materials, which can not be treated by any other method.
Most of the equipment has been developed in-house. The optimising of the processes for industrial light-weight applications, heavily relies on new and improved equipment with high-precision hardware and state of the art control software. The department Solid State Joining Processes gladly accepts these challenges.
Profile
ICJ, Photo:HZG/Christian Schmid
The department Solid State Joining Processes is part of the Institute of Materials Research and works on basic- and application oriented research topics in the area of friction welding for joining and coating. The research activities in this area comprise the following processes:
- Friction Stir Welding (FSW)
- Friction Stir Spot Welding (FSSW)
- Friction Spot Welding (FSpW)
- Friction Hydro Pillar Processing (FHPP)
- Friction Surfacing
- Hybrid Friction Diffusion Bonding (HFDB)
- Rotational Friction Welding
- Friction Riveting
- Injection Clinching Joining
With the formulation of technological solutions and concepts for joining challenges for the national and European industry, a significant contribution is made in the programme topic "Mechanics and Joining of Light-Weight Materials" of the programme "Advanced Engineering Materials” within Helmholtz-Research-Area "Key-Technologies".
History of the Department
Since the beginning of the 90’s, the department Solid State Joining Processes works on friction based processes. In this context, at first radial friction welded Ti and Steel materials (especially for the welding of pipelines) were investigated.
In the middle of the 90’s, the group took up Friction Hydro Pillar Processing (FHPP) and stud welding, with emphasis on Ti- and steel materials. At the same time, the first investigations were initiated on Friction Surfacing, which comprises a wider selection of materials (Ti-, Ni- und Al-alloys, NiAl-bronze und corrosion resistant steels).
In 1996 the R&D activities on the Friction Stir Welding (FSW) process started.
Then, in 1999, the Friction Stir Spot Welding (FSSW) and the Friction Spot Welding (FSP) patents were filed.
In the last years, three new processes were developed, which have been successfully investigated in the context of two doctoral theses: Hybrid Friction-Diffusion Bonding (HFDB), FricRiveting and Injection Clinching Joining (ICJ).
For FSW and associated processes, foremost Al- und Mg-alloys as well as high strength steels are joined. The afore mentioned materials together with Ti- alloys and corrosion resistant steels (for HFDB) and Polymers (for FricRiveting und ICJ) act as joining partners.
With the exception of the ICJ-process, all above mentioned joining processes are based on similar physical and metallurgical processes. This singularity allows a simple depiction of the relevant scientific topics. (Please refer to Tabelle 1).
Scientific Topics
Scientific topics in the areas of materials, processes, and properties for the group Solid State Joining Processes (Table 1)
| Metallurgy | Processes | Properties |
|---|
| High Temperature Plasticity | Plasticity Understanding Bonding Processes | Determination of Properties |
| Recovery and Re-Crystallisation | Energy Balance for
Solid State Joining Processes | Failure Mechanisms of Welds |
| Non Plasticity | | Residual Stress and Distortion |
| Exclusion Processes | | |
| Phase Change | | |
| Diffusion Processes | | |
Interfaces and
Surface Processes | | |
Technological Topics
The technological topics are tightly connected to the scientific topics and are normally investigated together with industrial partners (Table 2)
| Technological Topics | |
|---|
| FSW: | *Investigations on weldability of hybrids: Steel/Mg-alloys, Steell/Al-alloys
*Failure development mechanisms for FSW of Al-alloys
*Repair of FSW-welds
*Development of Bobbin-Tool-Technology for Al-alloys
*Plastic deformation of FSW-welds
*Productivity increases for FSW (High Speed FSW)
*Investigation of the weldability of modern steels with FSW |
| Friction Stir Processing: | Functionalisation of surfaces |
| Polymer Metal Joints: | Process technology and parameters of the welds |
| FHPP of light weight metals: | Process technology and parameters of the welds |
| Friction Surfacing: | Development of laminate materials and relevant process technology |
| Hybrid Friction-Diffusion Bonding (HFDB): | Process technology and parameters of the welds |
| Friction Spot Welding: | Process technology and parameter of the welds |
