Inner surface alloying on pores of lotus-type porous copper through electroless plating with supersonic vibration and annealing treatment

• A new method was explored for inner surface alloying on pores of lotus-type porous copper.
• Supersonic vibration was employed for the help of depositing Zn coatings on the inner surface of pores.
• Alloy layers were distributed evenly along the pore axial direction.
• The influence of annealing temperature on the densification and phase constitution of alloy layers was studied.

A new method was explored for inner surface alloying on pores of lotus-type porous copper. Zinc was deposited on the inner surface of pores by electroless plating with thorough supersonic vibration. Then, the Cu substrate together with Zn coatings was transformed into a brass layer by annealing treatment. From images filmed by a digital single lens reflex camera and a field emission scanning electron microscopy, it can be observed that the appearance and microstructure of lotus-type porous copper surface and pore walls were changed after the sequential treatments. The statistical thickness of the alloy layer at the distance of 0.5 mm from pore openings increased with the electroless plating time increase, attaining a maximum of about 1.7 μm when the time exceeded 1.5 h. The alloy layer thickness at the sample height of 2.5 mm along the pore axial direction was determined as about 1.5 μm by the nano-indentation technique. Uniform coating and alloy layer can be achieved on the inner surface of 5 mm-long pores. The influence of annealing temperatures on phase compositions was studied by X-ray diffraction.