Journal of Vacuum Science & Technology A, Vol.20, No.4, 1416-1419, 2002
Surface and microstructural characterization of laser beam welds in an aluminum alloy
The weldability of aluminum alloys is one of the main requirements to be considered for their application in the automotive and aerospace industry. In this work, the weld joints of an AA7020 alloy obtained by laser process were characterized by scanning electron microscopy, energy-dispersive x-ray spectrometry, wavelength-dispersive x-ray spectrometry, and x-ray photoelectron spectroscopy. The laser process can be described as a high-speed solidification process. The solidification rate can be estimated from the correlation among several solidification rates and the corresponding dendritic/cellular spacings, and the value calculated for this rate was 3.0 X 10(3) K/s. The inclusions present in the base metal were identified as (Cr,Fe)(4)Si4Al13, which were not observed in the fused zone. The fused zone microstructure showed two distinct phases: an aluminum solid solution and fine precipitates of MgZn2. The transition from the base metal to the fused zone presented a narrow heat-affected zone. A strong depletion of Zn was observed, and this does not influence the hot tearing susceptibility since hot cracks were not observed in the weld zone.