EFFECT OF GRAIN SIZE AND DEFORMATION SUB-STRUCTURE ON MECHANICAL PROPERTIES OF POLYCRYSTALLINE COPPER AND Cu-Al ALLOYS.

Abstract

The grain size effect on apparent yield and flow stresses up to 20% strain was investigated at 77 and 293 K on polycrystalline copper and Cu-2. 16 Al and Cu-6. 11 Al alloys. The apparent yield stresses satisfied the Hall-Petch relation in all specimens, but for copper the flow stresses did not. They could be represented roughly by a single linear function of the inverse of the cell size induced by deformation. The flow stresses of the 2. 16% Al alloy deviated at 77 but not at 293 K, and those of the 6. 11% Al alloy satisfied the relation. The discrepancy between copper and Cu-Al alloys is discussed in terms of the effect of stacking fault energy on macroscopic and microscopic deformation modes.