Open AccessX-ray phase contrast observation of solidification and hot crack propagation in laser spot welding of aluminum alloy
Author(s) -
Masanori Miyagi,
Yousuke Kawahito,
Hongze Wang,
Hiroshi Kawakami,
Takahisa Shoubu,
Masahiro Tsukamoto
Publication year - 2018
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.26.022626
Subject(s) - materials science , welding , keyhole , spot welding , heat affected zone , laser beam welding , laser , metallurgy , alloy , aluminium , composite material , thermal conductivity , phase (matter) , fracture mechanics , optics , chemistry , physics , organic chemistry
The inner characteristics of solidification and crack propagation in laser spot welding of four representative aluminum alloys, A1050, A2024, A5083 and A6061, were firstly observed with the X-ray phase contrast method. Keyhole disappeared within 1 ms after the laser was shut down. The solidification process finished in 2 ms for A1050, 3 ms for A2024, 5 ms for A5083, and 3 ms for A6061, respectively. Longitudinal view area of the molten pool decreased as the thermal conductivity increased, while the average solidification rate increased with increase of the thermal conductivity. Hot crack was observed to propagate from the bottom to the upper surface in the center of spot weld of A2024, A5083, and A6061, which was also the first in situ observation of crack during the welding process. Both the SEM, EBSD and Micro-X-ray computed tomography (CT) results validated that there was a crack propagation in the spot weld, and the mechanism for this crack formation was discussed. This paper provides a better understanding of solidification and crack formation in laser manufacturing.