A6

Working Group A | Metallurgical joint

 
 
a6_spp1640

Mechanisms in Joining of Dissimilar Materials using Friction Stir Welding

Prof. Dr.-Ing. Michael F. Zäh, TU München
Prof. Dr. rer. nat. Ferdinand Haider, Universität Augsburg

 
 

Initial Situation:

Modern lightweight structures play a key role in the automotive and the aeronautics industry to enable the efficient use of resources and energy. One promising approach is the load-adapted application of materials. This often requires the joining of dissimilar materials, which imposes a challenge to traditional fusion welding technologies. Hence, innovative welding technologies, such as FSW, are used to join dissimilar materials, since the materials remain in the solid state during the process.

 
 

Objectives:

The research project aims to gain fundamental understanding of the metallographical processes at the interface layer of FSW joints of dissimilar materials. Therefore, cause-effect relations have to be identified and used to create models, which allow a prediction and adaptation of the joining mechanisms of friction stir welded dissimilar material joints. Thus, a method will be provided that allows a stress-related design of the weld seam.

 
 

Approach:

In the first phase of the project, an analysis of the joining mechanisms of aluminum-titanium joints was performed. These joints were welded in an overlap- and a butt-joint configuration with varying welding parameters. Extensive process data of the FSW process was collected and analyzed. Furthermore, the material was examined prior and after welding and analyses of the structures at the interface, which result from welding, were carried out to nanometer scale. The joining mechanisms could then be identified.

The previous data was enhanced by overlap welded aluminum-copper joints in the second project phase. This guaranteed a fundamental knowledge of the joining mechanisms of friction stir welded dissimilar materials. The research was focused on the cause-effect relations between the welding parameters, the material combination, the process parameters, the type, and development of each joining mechanism, as well as the strength of the joints.

This is the basis to model the (joining-) processes at the interface, which should allow the prediction and adaptation of the joining mechanisms and provide a method for a stress-related design of the weld seam. The effective joining mechanisms as well as the joint properties should now be made predictable using the gathered knowledge. By implementing a temperature control for the FSW of dissimilar joints, a stationary process behavior can be maintained. Hereby, the limits for a robust FSW process for dissimilar materials can be defined.

 
Schematische Darstellung FSW-Prozess
Schematic of the FSW Process
 
 

Results of the first project phase:

One essential result of the first project phase is that a metallic layer in nanometer scale exists at the interface of the joining partners. This was observed using transmission electron microscopy (TEM). Hence, the dominating joining mechanism seems to be a substance-to-substance bond. This was the basis to model and predict the cause-effect relations during FSW of dissimilar metal joints.

 
(a) TEM image of the intermetallic layer. (b) HRETM of the semi-coherent Al-AlCu boundary; Marstatt et al.; In: IOP Conference Series: Materials Science and Engineering. IOP Publishing, 2017. S. 012002.
(a) TEM image of the intermetallic layer. (b) HRETM of the semi-coherent Al-AlCu boundary; Marstatt et al.; In: IOP Conference Series: Materials Science and Engineering. IOP Publishing, 2017. S. 012002.
 
 

Results of the second project phase:

In the second phase, a layer consisting of several hundred nanometers of intermetallic phases could also be found in copper-aluminum joints. In addition to this joining mechanism, an increase in the joint strength could be attained when a minimal amount of deformation occurred along the boundary layer, thus creating an additional (macroscopic) form fit. Based on the results of the previous project phases, various modelling approaches were explored in order to describe the cause-and-effect relationships which occur during FSW of metal mixed-material joints. These could then be applied to the understanding and consequently the prediction of the joining process.

Set up of the temperature-control system; Krutzlinger et al.; In: Key Engineering Materials. Trans Tech Publications, 2018. S. 360-368.
Set up of the temperature-control system; Krutzlinger et al.; In: Key Engineering Materials. Trans Tech Publications, 2018. S. 360-368.
 
 

Overview of the third project phase:

The third project phase revolves around the realization of a reliable FSW process and consequently an improvement in the reproducibility of the joint properties. The first step in this process is to establish a temperature-controlled FSW process. The thickness of the intermetallic layers formed in this process were assessed using electron microscopy. The relationship between the process temperature and the intermetallic layer thickness caused by interdiffusion could be quantitatively described. In the remaining project phase, the various modelling approaches will be improved and adjusted to be suitable for temperature-controlled FSW. This will lead to an improved predictive accuracy of the models.

Arrhenius plot of the process temperature vs. IM-layer thickness; Marstatt et al. In: IOP Conference Series: Materials Science and Engineering. IOP Publishing, 2018. S. 012017.
Arrhenius plot of the process temperature vs. IM-layer thickness; Marstatt et al. In: IOP Conference Series: Materials Science and Engineering. IOP Publishing, 2018. S. 012017.
 

Publications:

2019   
  Friction Stir Welding of Dissimilar Metal Joints Zens, A.; Marstatt, R.; Haider, F.; Zaeh M.F.
In: Material Science and Engineering Technology 2019 (accepted)
  Application of temperature-controlled friction stir welding process to Al-Cu joints with complex geometries Grabmann, S.; Zens, A.; Marstatt, R.; Haider, F.; Zaeh M.F.
AIP Conference Proceedings 2019 (accepted)
  Gaussian process regression to predict the morphology of friction-stir-welded aluminum/copper lap joints Krutzlinger, M., Meltzer, E., Muehlegg, M., & Zaeh, M. F.
In: The International Journal of Advanced Manufacturing Technology, 1-14. 2019
2018   
  Tailoring the thickness of interme-tallic interfacial nanolayers by tem-perature control of FSW in Al-Cu lap joints Marstatt, R.; Krutzlinger, M.; Luder-schmid, J.; Haider, F.; Zäh, M. F.
In: Materials Science and Engineering Congress, Darmstadt, P07.1
  Intermetallic layers in temperature controlled Friction Stir Welding of dissimilar Al-Cu-joints Marstatt, R.; Krutzlinger, M.; Luderschmid, J.; Constanzi, G.; Mueller, J. F. J.; Haider, F.; Zaeh, M. F.
In: IOP Conf. Ser.: Mater. Sci. Eng. 373, S. 12017. DOI: 10.1088/1757-899X/373/1/012017.
  Temperature Control for Friction Stir Welding of Dissimilar Metal Joints and Influence on the Joint Properties Krutzlinger, M.; Marstatt, R.; Costanzi, G.; Bachmann, A.; Haider, F.; Zaeh, M. F.
In: Key Engineering Materials 767, 2018, 360-368
  Intermetallic layers in Temperature Controlled Friction Stir Welding of dissimilar Al-Cu-joints Marstatt, R.; Krutzlinger, M.; Luderschmid, J.; Constanzi, G.; Mueller, J. F. J.; Haider, F.; Zaeh, M. F.
20. Werkstofftechnisches Kolloquium, Chemnitz
  Tailoring the thickness of intermetallic interfacial nanolayers by temperature control of FSW in Al-Cu lap joints Marstatt, R.; Krutzlinger, M.; Luderschmid, J.; Haider, F.; Zäh, M. F.
In: DPG Spring Meeting of the Condensed Matter Section, Berlin MM 30.1
2017   
  Formation of a diffusion-based intermetallic interface layer in friction stir welded dissimilar Al-Cu lap joints Marstatt, R.; Krutzlinger, M.; Luderschmid, J.; Zaeh, M. F.; Haider, F.
In: IOP Conf. Ser.: Mater. Sci. Eng. 181, S. 12002. DOI: 10.1088/1757-899X/181/1/012002.
  Interface Nanolayer Analysis in Al-Cu FSW Lap Joints Marstatt, R.; Krutzlinger, M.; Luderschmid, J.; Haider, F.; Zäh, M. F.
In: DPG Spring Meeting of the Condensed Matter Section, Dresden MM 18.3
  Formation of a diffusion-based intermetallic interface layer in friction stir welded dissimilar Al-Cu lap joints Marstatt, R.; Krutzlinger, M.; Luderschmid, J. ; Zäh, M. F.; Haider, F.
19. Werkstofftechnisches Kolloquium, Chemnitz
2016   
  Towards an understanding of joining mechanism of dissimilar Friction Stir Welds Krutzlinger, M.; Marstatt, R.; Butzhammer, A.; Haider, F.; Zäh, M. F.
In: Proceedings of the 11th International Friction Stir Welding Symposium,
17.–19.05.2016, Cambridge (UK), 2016
  Formation of interface layers in dissimilar Al-Cu FSW-Joints Marstatt, R.; Krutzlinger, M.; Luderschmid, J.; Haider, F.; Zäh, M. F.
In: DPG Spring Meeting of the Condensed Matter Section, Regensburg, MM 60.5, 2016
  Vorhersage und Steuerung der Verbindungsfestigkeit von rührreibgeschweißten Metall-Mischverbindungen – ein möglicher Ansatz Krutzlinger, M.; Marstatt, R.; Haider, F.; Zäh, M. F.
In: Proceedings zum 7. FSW-Workshop Rührreibschweißen und verwandte Verfahren, 2016
2015   
  Analysis of interface layers in dissimilar Al-Ti FSW-Joints Marstatt, R.; Krutzlinger, M.; Luderschmid, J.; Bartel R.; Zäh, M. F.; Haider, F.
In: DPG Spring Meeting of the Condensed Matter Section, Berlin, MM 34.3, 2015
  Bindemechanismen beim Rührreibschweißen von Aluminium-Titan-Mischverbindungen Krutzlinger, M.; Marstatt, R.; Haider, F.; Zäh, M. F.
In: 21. Erfahrungsaustausch Reibschweißen, 10.03.2015, München, 2015
2014   
  Formation of Joining Mechanisms in Friction Stir Welded Dissimilar Al-Ti Lap Joints Krutzlinger, M.; Marstatt, R.; Suenger, S.; Luderschmid, J.; Zäh, M. F.; Haider, F.
In: Advanced Materials Research, 966–967, pp. 510–520, 2014
  Structural analysis of dissimilar Al-Ti FSW joints Marstatt, R.; Krutzlinger, M.; Gnedel, M.; Haider, F.; Zäh, M. F.
In: DPG Spring Meeting of the Condensed Matter Section, Dresden, MM 38.6, 2014
 
 

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