Abstract
The behaviour of metals under mechanical loading, including shock loading conditions is strongly influenced by effects such as impurity levels, grain size, initial dislocation density and texture. The work discussed here is part of a wider study on the effects of orientation of aluminium single crystals to one dimensional shock loading, including the Hugoniot Elastic Limit and spall strength. In this work, specimens with three principle directions (<100>, <110> and <111>) parallel to the loading axis have been shock loaded and recovered under conditions of purely one-dimensional strain, with their post shock response monitored by quasi-static compression tests. Results show that the <100> crystal demonstrates a significant degree of post shock hardening, whilst the <111> crystal shows virtually none, and the <110> intermediate between the two. These results are consistent with the ordering of both the HELs and spall strengths observed in a previous paper, and have been explained in terms of the Schmidt factors.
Highlights
The high strain-rate response of aluminium based alloys has been the subject of intensive study over the past decades, due to their applications as light weight armour materials, and as structural components in the aerospace industry [1, 2]. Such studies are often constrained to specific alloy compositions, and properties will vary significantly due to differences in dislocation density, distribution of additional phases and grain size
The logical extension of this philosophy lies with the study of single crystals and assuming that the relationship between loading axis and crystal orientation is known, the generated data is more fundamental in nature and suitable for input in crystal plasticity models
After shock loading to 9.8 GPa for one microsecond, at -135 °C, the orientation was shown to show the greatest degree of post shock hardening, followed by with showing the least
Summary
The high strain-rate response of aluminium based alloys has been the subject of intensive study over the past decades, due to their applications as light weight armour materials, and as structural components in the aerospace industry [1, 2]. Similar measurements in copper by Minich et al [5] gave the same ordering of spall strength with orientation as Chen et al [3], whilst measurements of the HEL in aluminium by Huang and Asay [6] reversed the ordering again They were able to confirm the ordering of their results through consideration of the elastic constants. This method was used to explain the ordering of HEL versus crystal orientation in copper [7], showing that the mechanical response of single crystals, even in face centred cubic lattices requires more than just geometric considerations
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