Influence of Stacking Faults and Alloy Composition on Irradiation Induced Amorphization of Zrcr 2 , Zrfe 2 And Zr 3 (Fei
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3 2 Joseph A.Faldowski and Arthur T.Motta1, Lawrence M. Howe and Paul R. Okamoto 1. Dept. of Nuclear Engineering, Pennsylvania State University, University Park, PA, 16802 USA. 2. AECL Research, Reactor Materials Research Branch, Chalk River Laboratories, Chalk River, Ontario, Canada, KOJ iJ0. 3. Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.
ABSTRACT
The Zr-based intermetallic compounds ZrCr 2, ZrFe 2 and Zr 3 (Fe1 _x,Ni,) were irradiated with high energy electrons at the HVEM/Tandem facility at Argonne National Laboratory to study their amorphization behavior. The results show that although ZrCr 2 and ZrFe 2 have the same Laves phase C15 fcc crystal structure, their critical temperatures for amorphization under electron irradiation were 180 K and 80 K, showing that the substitution of Cr for Fe in the sublattice had a marked effect on the annealing characteristics of the material. The low temperature dose to amorphization was higher in ZrFe 2 than in ZrCr 2 by a factor of two. The presence of a high density of stacking faults had a strong effect on amorphization in both compounds causing the critical temperature to be increased by 10-15 K. By contrast, the addition of Ni to Zr3(Fel-,,Nix) had no effect on amorphization behavior for x=0. 1 and 0.5. These results are discussed in terms of current models of amorphization based on defect accumulation and the attainment of a critical damage level, such as given by the Lindemann criterion.
INTRODUCTION Amorphization of intermetallic compounds under irradiation is still a topic of great interest. It consists of the loss of long range topological order, as measured by the disappearance of the spot diffraction pattern and the appearance of a ring pattern characteristic of the amorphous phase [I]. The conditions under which this transfprmation occurs under electron, ion and neutron irradiation have been extensively studied [2,3]. It has been shown that a minimum dose which increases exponentially with temperature is required before amorphization can occur. Amorphization has also been shown to occur preferentially at lattice defects such as dislocations [4], anti-phase boundaries [5] and free surfaces [6]. In this paper we report on experiments that were conducted with the aim of increasing this base of knowledge. We first studied the amorphization behavior of ZrFe 2 and ZrCr 2 under electron irradiation. These compounds are of interest to the nuclear industry [3] and have also been proposed as possible hydrogen storage compounds [7]. We determined the amorphization kinetics and the dose to amorphization versus temperature. We also assessed the influence of a high 183 Mat. Res. Soc. Symp. Proc. Vol. 398 01996 Materials Research Society
density of stacking faults on the amorphization process. We also report on our study of the influence of internal stoichiometry x on amorphization behavior of Zr3(Fe-.,,Ni.) under electron irradiation. These results are discussed in terms of current amorphization models.
EXPERIMENTAL METHODS Thin foil s
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