摘要

The coupled heat transfer and fluid flow behaviours during deep penetration laser welding of titanium alloy sheet were investigated with a coupled three-dimensional transient keyhole welding model and a high speed in situ CCD camera-based imaging system. An unusual small scale heat transfer phenomenon of the weld pool that the shape of some high temperature isothermal lines in the central part of top weld pool surface could be regularly concave towards to welding direction, was found by the theoretical modelling and high speed imaging experiments. It was shown that the occurrence of this phenomenon closely relates to the vigorously convective heat transfer of the weld pool.

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