Modifications in morphological, structural, electrical and mechanical properties of Fe-1.0 wt.% Cu alloy on irradiation with 532 nm-6 ns Nd:YAG laser shots

The role of laser irradiation in tailoring the mechanical and electrical properties of Fe-1.0 wt.% Cu alloy has been explored, and compared with that of energetic particle irradiation. Mechanically polished/annealed Fe-1.0 wt.% Cu alloy specimens were irradiated in a vacuum similar to 10(-3) Torr with 1-2500 laser shots. The laser fluence and laser intensity at the laser spot on the target surface were 86.54 J cm(-2) and 14.4 x 10(9) W cm(-2), respectively. Different surface morphological features, e.g. dips, ripples, ridges, nanohillocks, microcones, micropillars, cavities, grooves, nano- and micro-size droplets, as well as tadpole-like structures, etc, were observed by SEM. Surface roughness was maximum for 1 laser shot, decreased by 40% for 250 laser shots, and then reduced by 70% in the range 500-2500. Crystallite size D and lattice strain epsilon were determined by Williamson-Hall analysis of x-ray diffractographs. An increasing linear relationship between electrical resistivity and Vickers hardness was found. In a plot of hardness versus D-1/2, crossover from Hall-Petch to Inverse Hall-Petch relation was observed at a critical value of D approximate to 11 nm. This behaviour was also followed by electrical resistivity. It is established that the nature of microstructural changes produced in the alloy on laser irradiation and on energetic particle irradiation is different.