Stress-modified electrochemical reactivity of metallic surfaces: atomic force microscopy imaging studies of nickel and alloyed aluminum

In this paper, we demonstrate that externally applied tensile and compressi ve stresses can systematically modify the electrochemical surface reactivit y of pure and alloyed metals. Atomic force microscopy (AFM) is used to stat istically characterize the extent and nature of interface change for nickel and aluminum alloy 2024-T3 subjected to electrochemical conditions under V arious levels of stress. Statistical analysis of AFM images reveals that th e extent of electrochemical reactivity is significantly enhanced when subje cting the sample to tensile as opposed to compressive stress; this enhancem ent increases monotonically as the level of applied stress is systematicall y increased. Surface morphologies differ on the pure nickel and alloyed alu minum samples, with the nickel interfaces exhibiting facetted features whic h are aligned 120 degrees from one another while the surface features on al uminum alloy 2024-T3 are circular pores. These results unambiguously indica te that the kinetics for electrochemical metallic processes, which nucleate at surface defects and grain boundaries, can be significantly modified by the presence of external stress fields. (C) 2000 Elsevier Science B.V. All rights reserved.