Mechanical behavior of a bulk nanostructured iron alloy
- PDF / 665,678 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 80 Downloads / 217 Views
I.
INTRODUCTION
THE mechanical behavior of bulk nanostructured metals is not well understood or documented. A large volume fraction of boundary material might cause anomalous behavior, and for this reason, nanostructured solids have been regarded as composite materials made of a crystalline ‘‘phase’’ with long-range order and a more disordered grain boundary phase.[1,2,3] Further, reports on the deformation behavior of nanostructured thin films of gold and silver have indicated that mechanisms other than dislocation motion, for example, grain boundary sliding and grain rotation, may become dominant in thin films, even at room temperature, for grain sizes of 25 nm and lower.[4,5] However, studies of bulk nanostructured metals have been limited by poor densification, grain growth during consolidation, and contamination of materials. The purpose of this study was to investigate the mechanical behavior of a fully dense, ‘‘bulk’’ nanostructured metal. The iron-copper system was selected for study in this research for several reasons. First, materials of immiscible systems such as Cu-Nb, Cu-Ta, and Cu-Fe have been J.E. CARSLEY, formerly Graduate Student, Department of Metallurgical and Materials Engineering, Michigan Technological University, is Senior Research Engineer, General Motors, NAO Technical Center, Warren, MI 48090. A. FISHER, formerly Graduate Student, Department of Metallurgical and Materials Engineering, Michigan Technological University, is Materials Engineer, Robert Bosch Corporation, Charleston, SC 29418. W.W. MILLIGAN, Professor, Department of Metallurgical and Materials Engineering, and E.C. AIFANTIS, Professor, Department of Mechanical Engineering and Engineering Mechanics, are with Michigan Technological University, Houghton, MI 49931. This article is based on a presentation made in the symposium ‘‘Mechanical Behavior of Bulk Nanocrystalline Solids,’’ presented at the 1997 Fall TMS Meeting and Materials Week, September 14–18, 1997, in Indianapolis, Indiana, under the auspices of the Mechanical Metallurgy (SMD), Powder Materials (MDMD), and Chemistry and Physics of Materials (EMPMD/SMD) Committees. METALLURGICAL AND MATERIALS TRANSACTIONS A
shown to have desirable combinations of physical and mechanical properties.[6–10] Johnson and co-workers[11–15] reported on the mechanical alloying behavior of several binary compositions of the iron-copper system, which responded favorably to mechanical alloying. Although the equilibrium solubility of copper in iron is very small (,0.05 pct) near room temperature, ball milling of these powders led to the formation of supersaturated solid solutions with nanoscaled grain sizes (5 to 20 nm).[12] The copper atoms were incorporated into the bcc iron lattice, forming a homogeneous, single-phase nanostructured powder alloy. Another reason for choosing the iron-copper system was that contamination by the steel balls and ball mill walls during processing would have a minimal effect on material composition and behavior. A composition of Fe with 10 at. pct Cu was selected so
Data Loading...