• PDF / 524,511 Bytes
• 9 Pages / 612 x 792 pts (letter) Page_size
• 60 Downloads / 197 Views

DOWNLOAD

REPORT

---

alloys (Fe-Al) and iron aluminides (Fe3Al and FeAl) are of interest in structural applications due to their lightweight characteristics, high strength at elevated temperatures, oxidation resistance, and low material cost.[1,2] Although this material has been considered a potential industrial material for a considerable time, efforts in this regard have been unsuccessful, as evidenced by the few applications of this alloy. The primary reason for this is that conventional process equipment cannot be applied to deform these alloys due to their fairly brittle behavior at ambient temperatures and a sharp drop in strength above 600 °C.[3,4] This deformation deficiency of iron aluminides is explained by the crack generation behavior due to the dislocation structure, where a perfect dislocation Æ111æ dissociates into partial dislocations that remain on the same slip planes, thereby increasing the local strain and stress concentrations.[5,6] Furthermore, environmental embrittlement caused by the interaction between the Al atoms and moisture in the air promotes crack nucleation and propagation,[7,8,9] wherein the presence of hydrogen in air changes the elastic energy of the Æ100æ edge dislocation and promotes a crack nucleus that results in a {100} cleavage.[10] The topical discovery of superplasticity in iron aluminides is of great importance,[11,12] while the tensile properties at a considerably slow strain rate are usually not considered as the technological plasticity.[13] With the exception of the aggressive studies by the Oak Ridge groups, there have been few recent publications with regard to the application of this material.[14–17] From the viewpoint of material processing for structural applications, the fabrication of iron aluminide intermetallics to arbitrary shapes, N. MASAHASHI, Professor, S. WATANABE, Research Assistant, and S. HANADA, Emeritus Professor, are with the Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba, Sendai 980-8577, Japan. Contact e-mail: [email protected] K. KOMATSU, Graduate Student, and G. KIMURA, Graduate Student, are with the Department of Materials Science, Graduate School, Tohoku University Katahira 2-1-1, Aoba, Sendai 980-8577, Japan. Manuscript submitted August 29, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS

such as that of a sheet or rod, using conventional equipment, might be rather difficult. With these considerations as a background, the authors have proposed that composite laminates of an Fe-Al alloy and a certain type of steel can impart additional properties to the steel, such as corrosion resistance, strength, and light weight.[18–21] This laminate can be produced by the cladrolling technique, wherein a ductile plate (steel) is sandwiched by brittle plates (Fe-Al alloy). This integration prevents the local accumulation of induced strain by absorbing it in soft materials, thereby resulting in the simultaneous deformation of a laminate. In this case, for the preparation of a plate for the laminate by conventional rolling, the aluminum content of