INFLUENCE OF PEAK PRESSURE AND TEMPERATURE ON THE STRUCTURE-PROPERTY RESPONSE OF SHOCK-LOADED TA AND TA-10W

The deformation behavior and substructure evolution of unalloyed-Ta and Ta-1OW under quasistatic conditions have been compared to their respective responses when shock prestrained to 20 GPa at 25 degrees C as well as to unalloyed-Ta shocked to 7 GPa at 25 degrees C, 200 degrees C, and 400 degrees C. The reload yield behavior of shock-prestrained Ta and Ta-1OW did not exhibit enhanced shock hardening when compared to their respective quasistatic stress-strain response at an equivalent strain level. In addition, the reload yield behavior of Ta shock prestrained to 7 GPa at 200 degrees C or 400 degrees C was found to exhibit increased hardening compared to the shock prestraining at 25 degrees C. The quasistatic substructure evolution and shock-hardening responses of Ta and Ta-10W were investigated via transmission electron microscopy (TEM). The dislocation substructures in both materials and at each strain rate condition and temperature were similar and consisted primarily of long, straight, (a/2) [111] type screw dislocations. The propensity for long, straight screw dislocations, irrespective of the loading condition, supports the theory of strong Peierls stress control on defect generation and defect storage. The substructure evolution and mechanical behavior of Ta and Ta-10W are discussed in terms of defect storage mechanisms and compared to the mechanisms operative in face-centered cubic (fcc) metals.