Rapidly Solidified Microstructure in Laser Alloyed Ni-Al Layer by TEM, STEM z-contrast and HRTEM Techniques

In the present study, laser alloying of electroless Ni–P coating on aluminum substrate was conducted using Nd:YAG pulsed laser under the condition of 5.36 × 10 9  W/m 2 in power density and 3.0 mm/s in scanning speed. The rapidly solidified microstructure in the alloyed layer was studied. The results showed that the alloying element distributed in the alloyed layer is inhomogeneous. The dendrite containing relatively high Ni was identified as Al 3 Ni phase and the areas between the dendrites are rich in Al content. Featureless with cell structure in Al-rich areas was firstly displayed by z-contrast image. Amorphous structure was revealed to exist in Al-rich areas.