Accession Number : ADA320602

Title :   Micro-Mechanisms of Corrosion Fatigue Using Atomic Force Microscopy at Active Microstructural Sites on 2024-T3 Aluminum.

Descriptive Note : Final rept. May 95-May 96,

Corporate Author : PENNSYLVANIA UNIV PHILADELPHIA

Personal Author(s) : Laird, Campbell ; DeLuccia, John J.

PDF Url : ADA320602

Report Date : 22 OCT 1996

Pagination or Media Count : 45

Abstract : This is a final report summarizing a one-year effort to define the micro-mechanisms of corrosion fatigue of 2024-T3 sheet aluminum alloy in low pH environments using in-situ and ex-situ instrumentation, e. g., atomic force microscopy (AFM), scanning electron microscopy, and Auger spectroscopy. Constant stress, flexure fatigue specimens cycled in a unique mechanically driven, environmentally controlled, deformation stage, are electrochemically polished to exhibit uniform quality metallographic surfaces. Pertinent surface microstructural features of crack nucleation were determined by AFM on specimens fatigued in air, .01 M and 0.1 M HCl. Imposed cathodic polarization potentials during corrosion fatigue indicate a hydrogen embrittlement contribution to the fatigue process at potentials not affording sufficient cathodic protection. Enhanced embrittlement (approx. 40% decreased in cycles to failure) was observed when 1.5 mg/ml of NaAsO2 was added to 0.1M HCl solution at open circuit voltages (freely corroding). Other results from the subject program previously reported in the open literature are referenced here, but not reported again.

Descriptors :   *MICROSTRUCTURE, *CORROSION, *ALUMINUM ALLOYS, *FATIGUE(MECHANICS), STRESSES, POLARIZATION, SCANNING ELECTRON MICROSCOPES, ENVIRONMENTS, DEFORMATION, CRACKS, SITES, FAILURE, ELECTROCHEMISTRY, VOLTAGE, NUCLEATION, ELECTRON MICROSCOPY, SURFACES, CATHODES, OXIDES, CIRCUITS, CATHODIC PROTECTION, HYDROGEN EMBRITTLEMENT, ARSENIC, AUGER ELECTRON SPECTROSCOPY, FLEXURAL PROPERTIES, PH FACTOR, METALLOGRAPHY, POLISHING, SODIUM COMPOUNDS, CATHODES(ELECTROLYTIC CELL).

Subject Categories : Properties of Metals and Alloys
      Inorganic Chemistry
      Physical Chemistry
      Atomic and Molecular Physics and Spectroscopy
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE