EFFECT OF GRAIN SIZE ON FLOW STRESS OF POLYCRYSTALLIE CADMIUM UNDER HYDROSTATIC PRESSURE.

The effect of grainsize on the increase of flow stress of polycrystalline cadmium due to hydrostatic pressure was investigated. Tensile tests and pressure change tests were carried out under 10 MPa and 600 MPa on various specimens with different grain sizes. The results obtained are summarized as follows. A strain softening phenomenon was observed on the specimens when hydrostatic pressure was changed from 10 MPa to 600 MPa. The amount of decrease of the flow stress under 600 MPa decreased with increasing prestrain at 10 MPa, and it was larger for the 18 mu m grain size specimen than for the 36 mu m one. The flow stress at a particular strain value was able to be related to the grain size d by the same form as the Hall-Petch equation sigma equals sigma //0// EPSILON plus kappa // EPSILON d** minus ** one-half where the intercept sigma //0// EPSILON and the slope kappa // EPSILON are experimental constants.