Microstructure in hot cracking mechanism of welded aluminium alloys

Abstract

Microstructure in the hot cracking mechanism was investigated via the Spot-Varestraint test to assess the sensitivity of hot cracking for three aluminium alloys, i.e. A2024-T351, A2219-T87 and A7050-T6, after gas tungsten arc welding. A stereomicroscope, an optical microscope and a scanning electron microscope were adapted to observe the microstructure of hot cracking mechanisms in the weld metal fusion zone (WMFZ), the weld metal heat affected zone (WMHAZ) and the partially melted zone (PMZ). The results indicate that the hot cracking structures differ: solidification cracking in the WMFZ and liquefaction cracking in the WMHAZ. An energy dispersive spectrometer was used to analyse the PMZ of WMHAZ to confirm the segregation of elemental Cu in the liquefaction cracking mechanism at grain boundaries.

Keywords:

• Varestraint
• Hot cracking mechanism
• Aluminium alloy