Microstructural modifications in an explosively welded Ti/Ti clad material: II. Deformation structures around bonding in
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I.
INTRODUCTION
THE morphological features o f the bonding interface in an explosively welded T i / T i clad material have been reported from macro- and microscopic points o f view in the previous article.~1~ These features were remarkably changed with increasing flyer plate speed (i.e., the collision pressure o f the flyer to the parent plates) and were different from those o f such clad materials o f cubic metals and alloys as C u / C u ,[2~ Cu/Cu-2Be,[3] A1-3Cu/A13Cu, [4] and T Z M - M o / M o[41 systems. This may be related to the difference o f deformation mechanism in cubic and hexagonal close-packed (hcp) structures and the low thermal conductivity o f titanium. It is likely that the former is more influential on the microstructural modifications around the bonding interface at w h i c h severe plastic deformation is induced by shock loading. Accordingly, this article describes the observation o f the residual deformation structures around the bonding interface, dislocations, deformation twins, and adiabatic shear bands (ASB) in an explosively welded Ti/Ti clad material. II.
EXPERIMENTAL PROCEDURE
The specimens used in the present study were mainly systems II and IV o f T i / T i clad materials described in the companion article.[~l The estimated collision pressure f o r the former is about 4.6 GPa and that for the latter is about 8.9 GPa, as listed in Table II o f the companion article. The specimen preparations and TEM observations have also been described. M . N I S H I D A , Associate Professor, A. C H I B A , Professor, S. ANDO, Research Associate, and K. IMAMURA, Technician, are with the Department of Materials Science and Resource Engineering, Faculty of Engineering, Kumamoto University, Kumamoto 8 6 0 , Japan. H. MINATO, formerly Graduate Student, Department of Materials Science and Resource Engineering, Kumamoto University, is Research Engineer, the Nippon Steel Corporation, Kitakyushu 8 0 5 , Japan. Manuscript submitted April 2 2 , 1992. METALLURGICAL TRANSACTIONS A
III.
RESULTS A N D D I S C U S S I O N
Macroscopic deformation structures around the bonding interface have been presented in Figure 4 in the previous article. [~ There were many accommodated deformation twins in all systems. Adiabatic shear bands were also seen in systems IV and VI. It is easily supposed that a large n u m b e r o f dislocations were also induced by shock loading. The crystallographic characterizations o f these defects are described in Sections A through C. A . Deformation Structures in System H Figure l(a) shows a bright-field image o f the deformation structures just near the bonding interface, which consists o f slightly elongated fine grains, [~] as indicated by the a r r o w on the left-hand side. There are deformation twins instead o f extremely elongated grains as reported on such cubic metal and alloy systems as mentioned in Section I. The twinning plane is the (01T2), as shown in Figure l(b). This is one o f the dominant twinning modes within 5 0 / x m o f the bonding interface, as well as {11ft.1} and
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