Low power CO2 laser modified iron/nickel alloyed pure aluminum surface: Evaluation of structural and mechanical properties

Surface modification of metals is demanding for high strength industrial purposes. Weak mechanical properties of aluminum (Al) are disadvantageous for several applications and needs improvement. We modify the surface of pure Al substrate by alloying it with a thick layer of Fe-Ni, where a low power (27 watt) cw CO2 laser with varying exposure time (30, 40 and 50 s) is used. The exposure time dependent microstructure, surface morphology, and surface hardness of the achieved inter-metallic alloyed samples are determined. Microstructure analysis revealed the formation of different phases (Al0.9Ni1.1, AlNi3, Al6Fe, AlFe3, Al5Fe2 and Al76.8Fe14, Al5FeNi) with chemical heterogeneity. Alloyed sample displayed enhanced surface hardness (varied from 27 HV0.1 to 53.9 HV0.1) for extended laser radiation exposure time (from 30 to 50 s). A new inter-metallic compound aluminum-iron-nickel (Al-Fe-Ni) with considerably tougher surface is achieved. Our observations may contribute towards the development of laser assisted modification of metal surface alloying.