Residual Microstructure - Mechanical Property Relationships in Shock-Loaded Metals and Alloys

Abstract

This chapter reviews the results of a large number of shook loading experiments utilizing a common design and a constant shock pulse duration of 2 µs. It is shown that dislocations, dislocation cells, planar dislocation arrays, stacking faults, twins, twin faults, and point defects all contribute in specific systems to residual shock strengthening. Shock-induced microstructures are determined primarily by the stacking fault free energy. High stacking-fault free energy metals and alloys are characterized by dislocation cell structures while low stacking-fault free energy metals and alloys (with the fcc structure) are characterized by planar dislocation arrays, stacking faults and twins in {111} planes. High stacking-fault free energy metals and alloys also twin according to critical shear stress criteria, and the (001) orientation is the initial orientation where twinning occurs. Residual shock microstructures and specific lattice defects induced by the peak shock pressure are shown to be related to resisdual hardness and engineering yield stress. Body-centered cubic metals and alloys are characterized by irregular dislocation arrays as a result of the more numerous slip planes, although twinning also occurs in bcc metals.