Internal friction in lotus-structured porous copper with hydrogen pores

Porous copper whose long cylindrical pores are aligned in one direction has been fabricated by unidirectional solidification of the melt in a pressurized mixture gas of hydrogen and argon. Internal friction has been measured by a forced torsional vibration technique in the frequency range of 0.1–2 Hz in vacuum atmosphere in the temperature range up to 1173 K. A very large relaxation type peak, which is about 0.1 as Q inverse, was observed at around 700 K on heating and on cooling. After annealing in vacuum at 1173 K for 43.2 ks the relaxation peak was not detected up to 1173 K. The disappearance of the peak may be due to desorption of hydrogen from the porous copper. Thus, it is concluded that the large internal friction peak is attributed to hydrogen in the porous copper.