Plastic Deformations in Single Crystals of FePd with the L1 0 Structure
- PDF / 179,055 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 27 Downloads / 232 Views
1128-U09-07
Plastic Deformations in Single Crystals of FePd with the L10 Structure Katsushi Tanaka, Wang Chen, Kyosuke Kishida, Norihiko L. Okamoto and Haruyuki Inui Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 6068501, Japan. ABSTRACT Compressive deformations of L10-ordered single crystals of FePd have been investigated from room temperature to 873 K. The critical resolved shear stress for superlattice dislocations is hard to determine resulting from buckling that occurs after a small amount of conventional plastic deformation. The CRSS for superlattice dislocations determined from yield stress is significantly larger than that of ordinary dislocations. The CRSS for octahedral glide of ordinary and superlattice dislocations are virtually independent of the temperature, and the positive temperature dependence of the yield stress is not observed for both, ordinary and superlattice dislocations, by the present experiments. INTRODUCTION Intermetallic compounds and ordered alloys with the L10 structure are of considerable commercial interests for both, structural and functional applications. Owing to their technological interests, extensive investigations have been performed on the mechanical properties of the compound TiAl [1]. The studies of Ti-56 at.% Al show a positive temperature dependence of the yield stress from room temperature up to a peak temperature at about 900 K and both, ordinary and super dislocations, contribute to the anomaly. The CRSS for the superlattice slip system is slightly larger than that for the ordinary slip system in equiatomic compounds but significantly smaller than that for the ordinary slip system in Al-rich compounds [2]. On the other hand, a study of the deformation behavior of poly-crystalline FePt shows a monotonic decrease in the yield stress over the temperature range from 77 to 873 K [3]. A study of the deformation behavior of FePd poly-crystals shows a positive temperature dependence from room temperature up to a peak temperature at about 650 K [4]. Since the latter two studies had been carried out with poly-crystals, however, the contributions of ordinary and super dislocations to the plastic deformation have not been clarified yet. In the Co-Pt, Fe-Pd and Fe-Pt systems, the ordered L10 phase forms in conjunction with a cubic (fcc) to tetragonal (L10) transformation, resulting in a microstructure with so-called polytwinned morphology, that is a lamellar structure consisting of {101} thin twin plates. This microstructure makes investigations of mechanical properties of single crystals of these compounds difficult. Recently, one of the authors has found that single crystals of CoPt, FePd and FePt with the L10 structure form from single crystals with the fcc-disordered phase under an appropriate strength of a compressive stress or of a magnetic field [5]. Using samples obtained by these methods, physical properties of L10-ordered FePd single crystals have been investigated [6, 7]. Although we have reported our preliminary results of the plasti
Data Loading...
