National Projects
Analysis of microstructural changes occurring during friction welding with material mixing (FSW) of magnesium alloys and magnesium alloys with aluminium alloys and their impact on the mechanical properties of joints
Title:
Analysis of microstructural changes occurring during friction welding with material mixing (FSW) of magnesium alloys and magnesium alloys with aluminium alloys and their impact on the mechanical properties of joints
Programme Name: OPUS
Financing Institution: National Science Centre
Co-financing for Łukasiewicz – GIT: PLN 151,300.00
Total value of the project: PLN 875,000.00
Start: 24.07.2019 / End 23.07.2023
Consortium:
- Stanisław Staszic AGH University of Science [Leader],
- Łukasiewicz Research Network – Upper Silesian Institute of Technology,
- University of the National Education Commission, Kraków.
Project Manager:
Aleksandra Węglowska, BEng, PhD
Tel.: 32 33 58 329
E-mail: aleksandra.weglowska@git.lukasiewicz.gov.pl
Objective:
The project concerns the analysis of phenomena occurring during solid agitation of aluminium and magnesium alloys. Such mixing takes place when joining metal alloys using the FSW method – welding with mixing of weld materials.
The principle of the FSW process is that a rotating tool with a specially designed tip (mandrel) is inserted between the contacting edges of the joined plates (pressed against each other with great force) and moved along the contact line. The tool performs two basic functions: friction heating of the joined materials and mixing the material during the formation of the joint. Due to the nature of the material flow around the mandrel, the process is not symmetrical. On one side of the weld, the flow of material is consistent with the direction of movement of the tool, while on the other side, the direction is opposite. Distinguishing these zones is very important because they differ in the size of deformations and eigenstresses, which in turn affect the microstructure and mechanical properties of the connection. The welding process takes place in a solid state without melting the bonded materials. The flow of material around the mandrel is a very complex and not fully understood phenomenon. During this process, the material is subjected to mechanical mixing and intense plastic deformation at an elevated temperature, which also extends beyond the mixing zone (thermal-plastic zone). In addition, there is a significant temperature gradient extending beyond the thermal-plastic zone (heat-affected zone) on the weld cross-section. The result of these factors is the formation of a very complex microstructure in the weld, directly affecting the mechanical properties of the joint.
Microstructure changes are associated with deformation, recovery, and recrystallisation processes, as well as with phase transformations of microstructure components, e.g. with the secretion or dissolution of intermetallic phases. While the phenomena occurring during friction welding with material mixing in relation to alloys of the same type are already sufficiently known, for this method to be used in practice, the process of solid mixing of heteronymous materials, in this case aluminium alloys and magnesium alloys, is far from being fully understood. This is due to the different properties of the mixed materials, such as melting point, viscosity, mechanical and physical properties.
In-depth knowledge and characteristics of the mixing process of different materials require research at different scales – from the macro scale to the nano scale. Therefore, the research will be carried out using both routine metallographic techniques and state-of-the-art transmission and scanning electron microscopes. Phase transformations, deformation and recrystallisation processes, and other microstructure changes caused by the mixing tool will be analysed. Mechanical properties will also be tested by analysing changes in hardness on the cross-sections of joints and analysing the results of tensile tests. Tensile tests will also be carried out on microsamples cut from individual connection zones. The results of the experiments will enable the development and verification of numerical models of the observed phenomena.
The planned research will provide new knowledge about the phenomena occurring in the area of mixing various materials at a temperature lower than the melting point of the tested alloys.
