METALLIZATION AND INSULIZATION DURING IMPACT

It is pointed out that the large strains produced by hypervelocity imp acts can be expected to produce dramatic changes in the chemical bondi ng (electronic structures) of materials. This will change the mechanic al behavior towards increased ductility when a semi-conductor is compr essed until it becomes metallic; and towards increased brittleness whe n a transition metal is expanded so as to localize its d-band electron s. Both isotropic compression (expansion) and shear strains can cause these transformations. Critical deformation criteria are given based o n the observed cubic to tetragonal transformations in compressed semic onductors,