Investigation of the structure and composition of a {111} incoherent Zr/ZrN interface containing ledges by high-resoluti
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I. INTRODUCTION
THE formation of facets and ledges at interfaces between the massive and parent phases in the massive transformation has led some researchers to propose that such interfaces are partly coherent.[1,2] For example, superledges and facets were found to form at the interface between the (hcp) and massive m (fcc) phases with a high-index orientation relationship (OR) and high-index interface plane in near-TiAl alloys by transmission electron microscopy (TEM), and all the interfaces were considered to be partly coherent.[2] In contrast, Li et al.[3] have recently shown that microscopic and atomic facets and ledges can be associated with type-3 incoherent interfaces (i.e., highindex OR and low-index interface plane in only one phase),[3,4] which were recently found in Zr-N alloy. The role of bonding on interfacial structure and the migration mechanisms of faceted incoherent interfaces are becoming increasingly important issue in phase transformation and interface research (e.g., see the General Discussion in these proceedings). Type-3 interfaces in Zr-N offer an opportunity P. LI, Postdoctoral Research Associate, is with the Center for Solid State Science, Arizona State University, Tempe, AZ 85287-1704. Contact e-mail: [email protected] J.M. HOWE, Professor, is with the Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA 229044745. W.T. REYNOLDS, Jr., Professor, is with the Department of Materials Science and Engineering, Virginia Polytechnic Institute, Blacksburg, VA 24060. This article is based on a presentation made in the “Hume-Rothery Symposium on Structure and Diffusional Growth Mechanisms of Irrational Interphase Boundaries,” which occurred during the TMS Winter meeting, March 15–17, 2004, in Charlotte, NC, under the auspices of the TMS Alloy Phases Committee and the co-sponsorship of the TMS-ASM Phase Transformations Committee. METALLURGICAL AND MATERIALS TRANSACTIONS A
to understand these topics in greater detail. However, a variety of complementary TEM techniques are needed to fully understand the structure and composition of such interfaces and reliably interpret their properties. This paper attempts to perform such studies on a second Zr/ZrN interface with a high-index OR and {111}ZrN interface plane. This article focuses on the study of ledges and facets at a {111}ZrN interface using conventional TEM, high-resolution TEM (HRTEM), electron energy-loss spectroscopy (EELS), energy-filtering TEM (EFTEM), and near-coincidence-site (NCS) atomic modeling. This set of complementary techniques provides a more complete set of data on such interfaces than previously analyzed by Li et al.[3] The formation of ledges with different atomic heights at the {111} Zr/ZrN interface is presented, and several important issues related to facets and ledges at the {111} incoherent interface described in Li et al.[3] are discussed. Both EELS and EFTEM techniques were used to determine the N composition changes across the interface in order to investigate the compositional abru
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