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It is ideal to observe the vapor plume to have a better understanding of the keyhole dynamics in dissimilar laser welding. This work is dedicated to the high-speed imaging and spectroscopic analysis of the vapor plume and postmortem analysis of melted zone produced from the interaction of a 6 ms Yb:YAG laser pulse with the aluminum A5754 - titanium T40 interface. These experiments are performed for different offsets of the laser spot from the joint line. The high-speed imaging is performed at two different wavelength (infrared 810 nm and ultraviolet 394 nm) regions. Morphological characteristics such as dimensions and orientation of the plume are studied and compared. The laser spot position affects the angle of inclination. It is observed that the plume inclines towards the aluminum side. The observation of inclination varies with the recording wavelength. The interrelationship between the inclination of the vapor plume and the laser spot position for a chosen observation wavelength is not self-explanatory. postmortem observation and EDX analysis of the melted zone, are correlated with the results from high-speed imaging. Spectroscopic analysis of the vapor plume associated with the Boltzmann linearization for temperature calculation, provides confirmation on the existing correlations between results from high-speed imaging and postmortem analysis.