High Strain Rate Properties of Tantalum Processed by Equal Channel Angular Pressing

Current ingot refinement and solidification techniques used in tantalum processing often result in inconsistent mechanical properties. Subsequent processing by equal channel angular pressing (ECAP) has been shown to reduce or eliminate internal structural variations as well as part-to-part variability [2]. This paper presents the effects of ECAP processing on the properties of tantalum. The materials of interest are 2.5-inch round bar tantalum supplied by H.C. Starck and Cabot Supermetals. Three metallurgical conditions were examined for each material: as worked, fine-grain annealed, and large-grain annealed. Prior to annealing, each bar was processed eight times through a 135-degree ECAP die using route C and then forged into 0.25-inch thick plates. Mechanical property specimens were subsequently removed from the plates for low and high-rate uniaxial compression experiments. Orientation dependence was characterized by orienting specimen load axes through the thickness or in the plane of the forged plate. Wave propagation and anisotropy were studied using Taylor impact experiments. Presented at the APS Topical Conference (15th) on Shock Compression of Condensed Matter held in Kohala Coast, HI on 24-29 June 2007. Paper only to be published by the American Physical Society. Conf. paper no. AAC/PA 07-30-07-499, dated 30 Jul 2007 and briefing charts no. AAC/PA 06-15-07-453, dated 15 Jun 2007.