THE ROLE OF ELASTIC INTERACTION STRESSES ON THE ONSET OF SLIP IN POLYCRYSTALLINE ALPHA BRASS

oarse grained (alpha)-Brass specimens with grain size of 2.4mm (as-cast), 0.86 (wrought), 0.52 (as-cast) and 0.19 (wrought) were compressed to the proportional limit. The orientation of a number of grains, including 67 which revealed cross slip were determined by the back reflection Laue technique. Trace analysis of cross slipping systems permitted the determination of the operating slip systems. Of the 195 slip systems determined, 118 were primary or strongly operating. The remainder were either cross slip or secondary slip systems. Of the 118 primary slip systems only 30 had the highest Schmid factor based on the applied stress. This indicates that internal stresses, arising from the elastic interaction of neighboring grains, provided the necessary additional stress to permit the observed slip system to operate. A qualitative analysis, based on the elastic contribution of surrounding grains gave to slip in a given grain, indicated that elastic assistance could provide the additional stress to cause the operation of lower Schmid factor slip systems.;the stress in 11 grains of 2.4mm grain size specimen. Resolved shear.;stresses were not uniformly distributed. However, the predicted slip.;system based on the highest total resolved shear stress was found to.;A three dimensional finite element method was used to calculate.;operate in 9 of the 11 grains. In the other two cases it was not.;possible to predict which slip system would operate because the.;resolved shear stresses were too close for the two highest resolved.;shear stress slip systems. Resolved shear stresses at which slip.;occurred were compatible with those found by other investigators.;and measured slip offsets were generally higher where the stresses.;were higher. Second highest resolved shear stress or lower slip.;systems which did not form strong obstacles with the primary slip.;systems were found to operate. Slip was found to occur within.;grains more frequently as grain size increased. On the basis of.;available evidence, it must be concluded that elastic interaction.;stresses play an important role in the yield process and for strains.;of at least several percent.;*This was supported on NSF Grant...