Accession Number : AD0629500

Title :   AN EXPERIMENTAL INVESTIGATION OF THE PORTEVIN-LE CHATELIER EFFECT IN DEAD ANNEALED COMMERCIAL PURITY ALUMINUM.

Descriptive Note : Technical rept.,

Corporate Author : JOHNS HOPKINS UNIV BALTIMORE MD DEPT OF MECHANICS

Personal Author(s) : Sharpe,William N. ,Jr.

Report Date : FEB 1966

Pagination or Media Count : 112

Abstract : The purpose of the investigation is to determine whether or not macroscopic grain boundaries affect the Portevin-Le Chatelier behavior. Polycrystal, single crystal, and bicrystal specimens of commercial purity aluminum are subjected to constant tensile loading at room temperature. The polycrystalline samples are discovered to exhibit continual repeated yield till failure. In contrast, the single crystals exhibit two groups of steps, each beginning at a reproducible value of resolved shear stress. Thus the existence of the two group behavior is independent of orientation. The resolved shear stress of the initial step in a single crystal, when related through the Taylor aggregate theory, predicts the observed initial step stress in the polycrystals. Consideration of bicrystals and crystals with stray grains shows that the presence of grain boundaries tends to proliferate repeated yield, i.e. they show continual steps. However, the initial step is not affected by these boundaries. Hence, the initial step of a specimen is the result of intragranular yielding, but the following stepare affected by grain boundaries. (Author)

Descriptors :   (*GRAIN BOUNDARIES, DEFORMATION), (*ALUMINUM, DEFORMATION), (*METAL CRYSTALS, FAILURE(MECHANICS)), SINGLE CRYSTALS, STRESSES, STRAIN(MECHANICS), SHEAR STRESSES, METALLOGRAPHY

Subject Categories : Metallurgy and Metallography
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE