Influence of cold rolling and strain rate on plastic response of powder metallurgy and chemical vapor deposition rhenium
- PDF / 1,104,420 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 63 Downloads / 162 Views
I. INTRODUCTION
RHENIUM is a refractory metal with a hexagonal closed pack (hcp) crystal structure. It is one of the heaviest metals (density of 21 g/cm3) and is known to possess the highest modulus (460 GPa) among metals, the second highest melting point (second only to tungsten), creep strength superior to any other metal, high strength at elevated temperatures, good ductility, and corrosion and wear resistance.[1,2] In recent years, the interest in rhenium metal has grown considerably due to its wide spread use in high-temperature applications. Currently, rhenium is primarily used with platinum in the manufacture of catalysts for the petroleum refining process[3] and for the production of nickel-cobalt–based superalloys.[4] It is also used as an alloying element in molybdenum- and tungsten-based alloys for increasing their yield strength and ductility, sometimes referred to as the “rhenium effect.”[5,6] Other applications that have taken advantage of its unique combination of properties include heating elements, heat exchangers, high-temperature thermocouples, electrical contacts, large lamp filaments, nuclear fuel cladding, and bearing alloys.[7,8,9] Due to its superior high-temperature properties, rhenium rocket thrust chambers weighing more than 450 N were also used in space applications.[4,10] Most recently, rhenium has been used in SP-100 Space Nuclear Reactor design as a barrier between the uranium nitride nuclear fuel and the niobium alloy cladding.[11] However, its scarcity, prohibitive cost (currently 50 to 100 times the cost of gold), high density, and, most importantly, poor oxidation resistance have limited its use in most structural applications. Some of the earliest studies on rhenium were focused on its deformation mechanisms, work hardening, and creep behavior.[12–18] More recently, Carlson and Bryskin[3,19] B.J. KOEPPEL, formerly Graduate Student, ME-EM Department, Michigan Technological University, is Research Scientist, Pacific Northwest National Laboratories, Richland, WA 99352. G. SUBHASH, Associate Professor, is with the ME-EM Department, Michigan Technological University, Houghton, MI 49931. Manuscript submitted October 28, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS A
investigated cold forming characteristics and work hardening behavior of rhenium. To the author’s knowledge, literature on high strain-rate plastic response of rhenium is very limited. Accordingly, the objective of this article is to present the plastic behavior of rhenium as a function of cold work and strain rate. II. MATERIALS Rhenium plates of various thicknesses ranging from 1.5 to 5 mm were obtained from Ultramet (Pacoima, CA). These plates were either prepared by powder metallurgy (PM) or chemical vapor deposition (CVD). The chemical compositions of these materials were supplied by Ultramet and are reported in Table I. The PM rhenium was fabricated from high-purity (99.995 pct) powders by cold pressing at 415 MPa, presintering at 1200 8C, and finally sintering at 2700 8C in hydrogen atmosphere. It was then repeat
Data Loading...
