The Behavior of Ni, Ni-60Co, and Ni3Al during One-Dimensional Shock Loading

Abstract

The response of pure nickel (Ni), a binary Ni-60 at. pct cobalt (Co) alloy exhibiting a low stacking fault energy (SFE), and the ordered face-centered-cubic (fcc) alloy Ni-24Al-0.01B to shock loading has been studied using the technique of plate impact. Changes in the variation of mechanical properties with shock amplitude and pulse duration have been explained in terms of a shift from dislocation dominated to twin dominated plasticity in the case of the Ni-Co alloy and the increasing effect of brittle failure in the case of Ni 3 Al.

Contrasting the effects of cold rolling on the shock response of typical face centred cubic and body centred cubic metals

“…In the case of copper, similar results have been observed in pure nickel [14], and seen to occur over the same time scales that the shocked microstructure takes to reach a stable confirmation [15]. In both materials, shear strength increases with shock stress, as shown in Figure 1b.…”

Shear strength measurements in a shock loaded commercial silastomer

“…In a previous article, lateral stress gauge results in tungsten heavy alloy [20] have been shown to give the same results as those measured from pressure shear [35] or from differences between the Hugoniot and hydrostatic pressure [36]. Further, it has also been possible to relate changes in shear strength with both stress and pulse width to similar changes in shocked microstructure and spall strength [11], hence there is a high degree of confidence in the lateral gauge response. However, with Sylgard, it has been possible to cast the uncured material around the gauge itself without the need for sectioning.…”

“…Assuming that x is constant behind the shock front, then this implies, from equation 3, that the shear strength is increasing until releases enter the gauge location. Such a response has been seen in a number of materials, including face-centred cubic metals, where it was explained in terms of dislocation multiplication [11], and more pertinently polymers such as PMMA [33], PEEK [17], polycarbonate [34], epoxy [16] and polyethylene, polypropylene and polystyrene [18]. Clearly dislocation based mechanisms cannot be operating, especially as these materials represent a range of semi-crystalline (PE, will again lead to a high degree of steric interference.…”

“…However, from equation 2, it can be seen that shear strength can also be measured using suitably orientated manganin stress gauges. This methodology has been used by ourselves and others on a variety of materials including metals and alloys [10][11][12], ceramics and silicate glasses [13][14][15] and polymers [16][17][18]. It can be seen that this is an invasive procedure, in that a manganin stress gauge must be introduced into a sectioned target assembly, and as such, it has been suggested that in doing so, the lateral stress recorded by the gauge is more a function of the layer of adhesive it sits in due to target assembly [19].…”

Shock response of body centered cubic metals

“…This is in contrast to high stacking fault fcc metals such as nickel, where the opposite behaviour has been noted [10]. This has been explained in terms of rapid dislocation motion and generation during deformation [11].…”