INTRAGRANULAR AND INTERGRANULAR HETEROGENEITIES IN THE PLASTIC-DEFORMATION OF BRASS DURING ROLLING

Brass (with 15% zinc) rolled to moderate reductions (up to 37%) is investigated by transmission electron microscopy. In about every second grain one observes (after 37% reduction) platelets or "bundles" consisting of a composite of deformation-twin lamellae and matrix. These bundles are zones with very intense shear. Even though the bundles are the predominant microstructural feature, the total volume fraction of twin lamellae is rather small (of the order of few percents). Investigation of the deviation of the twin lamellae from the {111} plane on which they originally formed shows that the grains with twins deform by slip on one predominant slip plane, viz. that parallel to the twin lamellae. This behaviour obviously reflects a deformation pattern radically different from that of the Taylor model. The "modified Sachs model" may be used as a first approximation. © 1990.