ELECTRICAL-RESISTANCE CHANGES OF CYCLICALLY DEFORMED CU 10-PERCENT NI AND CU 30-PERCENT NI

Previous measurements have shown that Cu-10% Ni exhibits an anomalous resistance decrease during the early stages of cyclic deformation. In an attempt to understand this behaviour polycrystalline foils of Cu-10% Ni and Cu-30% Ni have been cyclically deformed at constant total strain amplitude and the resulting resistance changes measured at room temperature and, for the 10% alloy, at 77 K. The effect of aging on the resistance of fatigued specimens has been determined in the range 77-770 K. The resistivity of the 10% alloy decreases with fatigue to a minimum value and subsequently increases before the formation of cracks, a behaviour very similar to that observed for the 20% Ni alloy. The resistivity of the 30% alloy increases monotonically with the number of cycles, which is similar to the behaviour of CuNi alloys with higher concentrations of nickel. It is concluded that the anomalous behaviour occurs over a range of nickel compositions. The results are interpreted in terms of the break-up of clusters of nickel atoms, the formation of persistent slip bands, and the production and motion of point defects. © 1979.