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Laser beam welding of high-alloyed aluminium-zinc alloys
Citation Link: https://doi.org/10.15480/882.1405
Publikationstyp
Doctoral Thesis
Date Issued
2017
Sprache
English
Author(s)
Advisor
Referee
Title Granting Institution
Technische Universität Hamburg-Harburg
Place of Title Granting Institution
Hamburg
Examination Date
2016-11-09
TORE-DOI
The automotive industry is currently facing major challenges. In the course of the enacting of comprehensive environmental regulations for the fuel consumption and CO2 emission of passenger vehicles in Europe and the world, the weight of future vehicles need to be considerably reduced. A weight reduction for automotive structures can be achieved by the substitution of heavy materials by lighter and stronger materials, the implementation of new designs and manufacturing technologies or ideally by a combination of both.
High-alloyed Al-Zn alloys are promising candidates for the use as structural light-weight materials for the automotive industry. This is mainly due to their very high strength-todensity ratio in comparison to conventionally used steels and aluminium alloys. Laser beam welding is an efficient method for producing joints with high weld quality and is established in the industry since many years. However, it is well known that aluminium alloys with a high Zn content or, more precisely, with a high Zn+Mg+Cu content are hard to fusion weld or even unweldable due to the formation of severe weld discontinuities. And currently, there is a lack of approaches for solving these weldability problems, which finally results in a disregard of these alloys by the automotive industry.
The present thesis aims at solving the laser weldability problems of these high-alloyed Al-Zn alloys. For this purpose a deep understanding of the theoretical fundamentals of laser weldability in terms of material properties and processes during laser beam welding was mandatory. By this means, typical reasons for weldability problems were derived and crucial influencing factors were identified. Based on the knowledge obtained, it was possible to develop two approaches for improving the laser weldability of high-alloyed Al-Zn alloys. The first approach implies the use of an appropriate filler material - namely vanadium - additional to the conventional filler wire recommended for welding Al-Zn alloys. In this regard, vanadium enables the manipulation of the material properties of the weld metal. This first approach is feasible for different laser systems used for welding.
The second approach implies the use of a high-power fibre laser with a large beam diameter and a high beam quality. Here, the laser beam welding process itself is manipulated. This approach does not necessarily require a certain filler material.
The effectiveness of both developed approaches was verified by their application to diverse high-alloyed Al-Zn alloys. The assessment of the resulting weld properties finally also allowed assessing the capability of the approaches for industrial applications. Here, the second approach excels in its versatility and capability for large-scale productions.
High-alloyed Al-Zn alloys are promising candidates for the use as structural light-weight materials for the automotive industry. This is mainly due to their very high strength-todensity ratio in comparison to conventionally used steels and aluminium alloys. Laser beam welding is an efficient method for producing joints with high weld quality and is established in the industry since many years. However, it is well known that aluminium alloys with a high Zn content or, more precisely, with a high Zn+Mg+Cu content are hard to fusion weld or even unweldable due to the formation of severe weld discontinuities. And currently, there is a lack of approaches for solving these weldability problems, which finally results in a disregard of these alloys by the automotive industry.
The present thesis aims at solving the laser weldability problems of these high-alloyed Al-Zn alloys. For this purpose a deep understanding of the theoretical fundamentals of laser weldability in terms of material properties and processes during laser beam welding was mandatory. By this means, typical reasons for weldability problems were derived and crucial influencing factors were identified. Based on the knowledge obtained, it was possible to develop two approaches for improving the laser weldability of high-alloyed Al-Zn alloys. The first approach implies the use of an appropriate filler material - namely vanadium - additional to the conventional filler wire recommended for welding Al-Zn alloys. In this regard, vanadium enables the manipulation of the material properties of the weld metal. This first approach is feasible for different laser systems used for welding.
The second approach implies the use of a high-power fibre laser with a large beam diameter and a high beam quality. Here, the laser beam welding process itself is manipulated. This approach does not necessarily require a certain filler material.
The effectiveness of both developed approaches was verified by their application to diverse high-alloyed Al-Zn alloys. The assessment of the resulting weld properties finally also allowed assessing the capability of the approaches for industrial applications. Here, the second approach excels in its versatility and capability for large-scale productions.
Subjects
Laser beam welding
High-alloyed Al-Zn alloy
Al-Zn-Mg-Cu
Weldability
Non-destructive testing
Microstructural analysis
Mechanical testing
High-strength Al alloy
Corrosion testing
DDC Class
620: Ingenieurwissenschaften
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Name
PhD-Thesis-Enz.pdf
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25.49 MB
Format
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