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A study of slip line lengths in aluminum single crystals during transient deformation De Larios, John Martin

Abstract

Slip line length measurements have been carried out on oriented single crystals of high purity aluminum to qualitatively check the predictions of a new theory of plastic flow in strain hardened metals. This theory states that the slip line length L will be a function of the stress, σ, the yield strength, Ty, and the magnitude of the variation in the obstacle spacing, Tv. To achieve this purpose, the specimens were prestrained at room temperature to the same stress level insuring that they had the same structure. They were then electropolished and given a small increment of strain at a temperature between 298°K and 4°K or a strain rate from ɛ = 1x10⁻⁴ /min to ɛ = 2x10⁻¹ /min. The slip line lengths for these increments were found to increase with increasing strain rate and to decrease with increasing temperature, in agreement with the theory. By applying the increment of strain in small, divisions, the slip line length was found to increase during the region of transient deformation following a quench. This increase in L was due to an increase in stress. Lowering the prestrain temperature showed that the slip line length depended on the structure parameter Tv. A low temperature prestrain resulted in a smaller Tv and therefore shorter slip lines. From the 4°K increment, the parameters characterizing the prestrained structure and the structure after the increment could be determined. Using equations of the theory, these values were related to the experimental slip line length data with good quantitative agreement.

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