Accession Number : ADA325170

Title :   Grain Boundary Development in Superplastic Aluminum Alloys.

Descriptive Note : Doctoral thesis,

Corporate Author : NAVAL POSTGRADUATE SCHOOL MONTEREY CA

Personal Author(s) : McMahon, Michael E.

PDF Url : ADA325170

Report Date : DEC 1996

Pagination or Media Count : 232

Abstract : Superplasticity may be defined as the capability of certain polycrystalline materials to deform to extensive plastic elongations prior to failure, often without formation of a neck. Typically, superplasticity refers to tensile elongations greater than 200%, although some elongations have been reported in excess of 5000% Ref 1. While it has been suggested that bronze metals in use in ancient civilizations may have possessed superplastic properties Ref 2, most historical reviews credit the modern-day documentation of superplastic behavior to a paper published in the Journal of the Institute of Metals by G.D. Bengough in 1912 which described extensive elongations in brass Ref 3. Recognition of a stress and strain-rate relationship was first presented qualitatively in a paper by Rosenhain in 1920 which examined a near eutectic Zn-Al-Cu alloy Ref 4. Photomicrographs detailing superplastic grain structures in eutectic Sn-Pb and Bi-Pb alloys deformed to elongations of 2000% were presented in 1934 by Pearson Ref 5. This study was the first to identify an equiaxed grain morphology in the deformed regions and suggest that grain boundary migration may be involved in the deformation processes.

Descriptors :   *ALUMINUM ALLOYS, *GRAIN BOUNDARIES, *SUPERPLASTICITY, METALS, DEFORMATION, TENSILE PROPERTIES, MORPHOLOGY, THESES, HIGH STRENGTH ALLOYS, STRAIN RATE, COPPER, ALUMINUM, ZINC, PLASTIC PROPERTIES, MIGRATION, ELONGATION, GRAIN STRUCTURES(METALLURGY), POLYCRYSTALLINE, PHOTOMICROGRAPHY, BISMUTH ALLOYS, LEAD ALLOYS, BRASS, BRONZE.

Subject Categories : Properties of Metals and Alloys
      Plastics
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE