The microstructure and dealloying kinetics of a Cu-Mn alloy
- PDF / 7,149,553 Bytes
- 6 Pages / 576 x 792 pts Page_size
- 101 Downloads / 195 Views
Porous copper was produced by electrolytic dealloying of a Cu-Mn alloy (Incramute: Cu, 40-48 wt. % Mn, 1.4-2.3 wt. % Al) conducted in a 0.3 N-NaCl solution at a potential of -0.2 V (SCE). The dealloying time needed for the as-received cold-rolled specimen (50 h) is shorter than that of the annealed specimen (850 °C for 2 h). The pore size, about 1 /mm, of the dealloyed cold-rolled specimen is bigger than that, about 0.1 yu-m, of the dealloyed specimen after annealing. This is probably because annealing reduced the phase inhomogeneity and removed the rolling effects.
I. INTRODUCTION Electrolytic dealloying is a corrosion process in which one constituent of an alloy is preferentially removed, leaving an altered residual structure.1 In order to achieve dealloying or selective dissolution, two criteria about the chemical potential difference and composition limit must be satisfied. One element of the alloy should be more reactive, such as Mg, Al, Mn, and Zn, and the other should be more noble, such as Au, Ag, Cu, and Ni. The electric potential is controlled to dissolve only the reactive element and not the noble one. For the composition limit of the alloy, the dealloying threshold is defined as the lowest atomic fraction of the reactive element below which the reactive element cannot be continuously dissolved.2 Because the selectivity of Cu-Mn is higher than those of Cu-Al and Cu-Zn alloys,3 Cu-Mn alloy was chosen as the base material. Incramute (Cu, 40 to 48 wt. % Mn, 1.4 to 2.3 wt. % Al) was chosen on the basis of its chemical potential difference and dealloying threshold. Keir and Pryor4 studied the dealloying behavior of Cu-Mn alloys. Their method to prepare porous copper was adopted in this research. Dealloying can make a porous network of ligaments on the atomic scale, but these pores may be enlarged by the coarsening of the skeletal structure.5 Pickering6 reported that pore-to-pore spacing for the dealloyed structure is about 50 nm in a potential-dependent increasing current region at 25 °C. Dealloying kinetics and the pore size are dependent on the microstructure of the original alloy. The effect of cold working on dealloying has been studied in terms of the dealloying rate and dezincification factor.37"10 Dezincification factor was defined as the zinc to copper ratio in the corrosion product versus that in the alloy itself. Dealloying rate was increased by prior cold working. 79 Cold working either lowered the dezincification factor9 or had no significant effect.3'10 2878 http://journals.cambridge.org
J. Mater. Res., Vol. 9, No. 11, Nov 1994
Downloaded: 02 Apr 2015
The microstructure of the Cu-Mn alloy was modified by thermomechanical treatment, i.e., cold working and subsequent heat treatment. The pore size of dealloyed copper and the dealloying kinetics of the Cu-Mn alloy were investigated for specimens with different microstructures.
- 150
(a)
-100 Current [mA] - 50
i
-0.5
'
'
i
i
i
i
-0.4
i
i
i
i
i
i
-0.3
i
i
-0.1
Potential (V, SCE)
(b)
- 15 -10 Curre
Data Loading...
