MECHANICAL AND CORROSION BEHAVIOUR OF AA5059 H116 AFTER FRICTION STIR WELDING AND MIG WELDING

Abstract

Mechanical and corrosion behavior of friction stir welded (FSW) specimen, metal inert gas welded (MIG) specimen and base material of AA5059 H116 are studied. Cyclic polarization test, Tafel test, Electrochemical impedance spectroscopy(EIS) test and immersion test With Nitric acid mass loss (NAMLT) test are performed on the base material, MIGed zone and FSWed zone. Hardness and tensile tests are performed on FSWed joint specimen, MIGed joint specimen, and base material in order to determine their mechanical behavior. The fracture occurred at the interface region of HAZ and TMAZ in FSWed zone specimen and Fracture occurred at the interface region of HAZ and welded zone in MIGed specimen. Cyclic polarization test, the Tafel tests, electrochemical impedance spectroscopy (EIS) tests are performed in simulating sea water (3.5 wt% NaCl solution). Slow strain rate(SSRT) corrosion test with 1.5x10−6 s−1, 6.5x10−6 s−1and 1.15x10−5 s−1 performed on AA5059 H116, FSWed zone specimen and MIGed zone specimen.SSRT results suggested that FSWed zone specimen has less SCC susceptibility than base material and MIGed zone specimen. The higher corrosion rate is observed in MIGed zone as compared to FSWed zone. For characterization, optical microscopy, and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), High-resolution transmission electron microscopy(HR-TEM) is performed to study the fracture characteristics and precipitates formations with SAED pattern and EDS.