The relation between macroscopic and microscopic strain hardening in F.C.C. polycrystals

Abstract The validity of using an ‘equivalence criterion’ to describe the plastic properties of polycrystals at large strains is addressed here from the point of view of the microscopic properties of the constituent grains. Proper account is taken of the grain reorientation as deformation proceeds and of the different amounts of hardening experienced by each grain. The averaged grain behavior is compared with the results of experiments on OFHC copper in three deformation modes: torsion, compression and diametrically controlled large strain tension. An attempt to explain the three different stress/strain curves on the basis of a unique microscopic hardening law using the above theory was only partially successful, and it is concluded that the microscopic hardening mechanisms depend on the deformation mode. Physical mechanisms for such a dependence are discussed and evaluated according to the observed statistics of grain behavior.

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