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Microstructure and Mechanical Properties Investigation of Al-Fe Transition Joints Produced By Additive Manufacturing

Ramezani, Habibollah | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56391 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Movahedi, Mojtaba
  7. Abstract:
  8. Joining metal and alloy is a continuous and inevitable effort in oil and gas and automotive industry, and a considerable number of these joints are dissimilar joints. Steels and aluminum alloys are two of the most utilized engineering material and bi-metallic steel-aluminum parts have a lot of applications due to having the combined properties of both alloys (for example the high tensile strength and wear resistance of steels along with good thermal and electrical conductivity and corrosion resistance of aluminum alloys). However, fusion welding of aluminum to steel possesses great challenges due to the difference in melting point, coefficient of thermal expansion, thermal conductivity and formation of brittle intermetallic compounds. One way of overcoming these challenges is using bi-metal aluminum-steel transition joints which can convert a dissimilar joint into two similar, less challenging joints. But the methods of making aluminum-steel transition joints have many geometrical and practical drawbacks for industrial applications. Additive manufacturing is one of the most recently developed production methods which can eliminate some of the transition joint making drawbacks. The aim of this research was to investigate the effect of heat input and characteristics of the substrate on the microstructure and mechanical properties of bi-metal AA5183 aluminum-AISI316L steel transition joints made by Gas Metal Arc Welding (GMAW) based Wire Arc Additive Manufacturing (WAAM) process. The transition joints were made via two methods, 1- direct deposition of aluminum of steel substrate and 2- deposition of aluminum and steel on bi-metallic aluminum-steel substrate produced by Roll Bonding process. Process parameters were deposition heat input and the roll bonded substrates thickness as well as post rolling heat treatment. Microstructural transformations were studied using optical and scanning electron microscopes, while uniaxial tensile test and microhardness test were used to investigate the mechanical properties of the samples. Results showed that despite various attempts, direct deposition of aluminum on steel using WAAM process leads to formation of a thick layer of intermetallic compounds at the interface and formation of cracks and discontinuities upon cooling. On the other hand, using bi-metal aluminum-steel substrates enabled the possibility of controlling formation of intermetallic compounds, leading to a continuous bond between aluminum and steel at the interface. Results of the tensile test showed that using optimal parameters, tensile strength of aluminum-steel transition joints produced by WAAM with roll bonded substrates reached up to 42 MPa. Microhardness test also confirmed lack of intermetallic compound at the interface of the optimum sample. These results show that using optimal parameters and substrate, WAAM process can be a viable option to produce aluminum-steel transition joints
  9. Keywords:
  10. Wire and Arc Additive Manufacturing ; Microstructure ; Mechanical Properties ; Gas Metal Arc Welding (GMAW) ; Aluminum-Steel Joining ; Transition Joints

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