The effect of laser remelting in the formation of tunable nanoporous Mn structures on mild steel substrates

Abstract

Nanoporous manganese was fabricated by a three-step process involving high power laser cladding of a homogeneous Cu40Mn60 alloy coatings onto a mild steel substrate, laser remelting for tuning the grain size and the composition homogeneity followed by selectively electrochemical de-alloying for removal of Cu element and formation of nanoporous Mn. The microstructure and homogeneity of the precursor Cu40Mn60 alloys have a significant influence on the evolution of nanopores during selectively electrochemical de-alloying. Laser remelting can significantly refine the microstructure. The second dendrite arm spacing decreases with increasing of laser remelting scanning speed. A SDAS of 1.17μm was obtained at the laser scanning speed of 133mm/s. When the remelting scanning speed reaches 100mm/s, a nanoporous structure with average pore size less than 100nm was achieved under optimized dealloying electrode current density about 2mA/cm2. Nanoporous Mn with nanopore sizes ranging from 80 to 130nm was fabricated by this method. Surface-enhanced Raman scattering characteristics of the nanoporous materials have been investigated. It is found that smaller nanoporosity leads to significant improvements in surface-enhanced Raman scattering.