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Mechanical Properties of TLP Bonding of AISI 304 Stainless Steel with a Ni-based Interlayer at High Temperature

Jamshidi Lemjiri, Rasoul | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48785 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ekrami, Ali Akbar
  7. Abstract:
  8. Stainless steels have many applications in different industries. Therefore, it was always a main concern to find an appropriate joining method for using these materials in complex structures. In the present investigation, AISI 304 stainless steel was successfully joined by transient liquid phase (TLP) bonding, using a MBF-30 interlayer. The joining process was carried out at 1150 ℃ temperature and for different bonding times. Also joints with complete isothermal solidification were homogenized at 950 ℃ for different holding times. Microstructure and compositional changes of the joints were studied using optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Microhardness and shear strength tests were performed to characterize mechanical properties of the bonded specimens. Results showed that complete isothermal solidification occurred at the bonding temperature within 20 min. In addition, acicular intermetallic compounds (IMCs) were formed in diffusion affected zone (DAZ) of the samples. It was concluded that these intermetallic compound are Fe-Cr borides, According to EDS results and Fe-B and Cr-B phase diagrams. Also it was found that by increasing the homogenization time, more diffusion occurred across the joint and the amount of IMCs in the DAZ of the samples were reduced. Breaking and dissolving of the borides and therefore reducing the amount of them in the DAZ resulted to decreasing hardness of this zone. Also 3h homogenization time led to a good balance between hardness and alloying elements distribution. Finally, shear test results showed that the shear strength of 20 min bonded samples and homogenized samples are 532 MPa and 552 MPa, respectively. Furthermore, fracture analysis of the shear test samples indicated that part of the crack propagation path is within the base metal and away from the joint
  9. Keywords:
  10. Shear Strength ; Homogenization ; 304 Austenitic Stainless Steel ; Transient Liquid Phase Boneling (TLPB) ; Nickel Based Interlayer

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