EFFECTS OF SHOCK LOADING ON THE LATTICE OF A SILICON BRONZE WITH LOW STACKING FAULT ENERGY

摘要

Effects of shock loading on the lattice of silicon bronze with low stacking fault energy were studied by post-mortem analysis. Crystal imperfections intro¬duced by shock loading up to 420 kbar were studied primarily by X-ray dif¬fraction. Specimens were 30 mm long and 2x2 mm in cross-section;the shock pressure was applied to one of the 2 x 30 mm faces. By spinning the specimens at 200 rpm about the long axis, a Debye-Scherrer geometry could be employed for the X-ray work. The macroscopic plastic strains determined from dimensional changes of the specimens varied linearly with shock pres¬sure, whereas the slope of hardness versus pressure was initially steep and then asymptotically approached a limiting value. Analysis of the position and width of X-ray diffraction line profiles showed: (1) some formation of deforma¬tion stacking faults;(2) a decrease in domain size to a lower limiting value reached at fairly low (~100 kbar) shock pressures;(3) essentially no rms strain in any of the specimens even after loading to maximum shock pressure. Observations are consistent with the formation, by shock loading, of micro-twins and faults as the principal lattice imperfections. In addition, evidence was found for a polymorphic transformation between 130 and 200 kbar.