Microstructural evolution of a shaped-charge liner and target materials during ballistic tests
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I. INTRODUCTION
GENERALLY, the ballistic performance of shapedcharge jets is known to be influenced markedly by two important parameters: the maximum elongation prior to fragmentation and the density of liner materials. Although pure copper has successfully been used for the shaped-charge liner in the past few decades, developing a new liner material is required to defeat the recently improved armor plate. Accordingly, many researchers have focused on attempts to enhance the density and the maximum elongation of the shaped-charge liner.[1–5] One promising approach has been achieved from the addition of a high-density material such as tungsten into the copper matrix phase.[2,6,7] For instance, it has been reported[2,8] that a W-Cu shaped-charge liner containing 70 to 80 wt pct W exhibits not only an increased density (15 g/cm3) approximately 11/2 times that of the pure-copper one, but also a better elongation during the ballistic test. During the ballistic test, the W-Cu shaped-charge liner also tends to form a narrower jet compared to the pure-copper one,[6] which leads to a decreased hole diameter of the crater and, thereby, results in improved ballistic performance. However, despite such studies[1,2,6–8] on the behavior of pure-copper and W-Cu shaped-charge liners, nothing is known about the interaction between the jet and target, especially the microstructure of the target impacted against the pure-copper and W-Cu shaped-charge jets. The observation of the microstructure can provide us with some idea about the penetration mechanisms. Thus, in the present work, the microstructure of the mild-steel target in the region ahead of the crater, made by a pure-copper shaped-charge jet, is observed and compared to that made by a W-Cu shapedcharge jet. The microstructural change of the shaped-charge liners with ballistic impact is also investigated by using the SEONG LEE and MOON-HEE HONG, Senior Researchers, and JOONWOONG NOH and WOON HYOUNG BAEK, Principal Researchers, are with the Materials Science Division, Agency for Defense Development, Taejon 305-600, Korea. Contact e-mail: [email protected] Manuscript submitted June 30, 1999. METALLURGICAL AND MATERIALS TRANSACTIONS A
samples extracted from the liners and slugs that remained in the craters of the targets. The objective of the present work is to determine the different possible penetration mechanisms of pure-copper and W-Cu shaped-charge jets. II. EXPERIMENTAL PROCEDURE For fabricating a W-Cu shaped-charge liner, tungsten powder with an average particle size about 3 m is cold isostatically pressed into a cylindrical bar (30 mm in diameter ⫻ 20 mm in height). The pressed compacts are presintered at 1300 ⬚C for 1 hour under a flowing hydrogen gas to make a skeleton structure, and then copper is infiltrated into open pore channels of the skeleton at 1200 ⬚C for 1 hour. The final chemical composition of the specimen is designed to be 75W-25Cu by wt pct after the copper infiltration. The infiltrated specimen is forged to a conical shape by using a hydraulic press with
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