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Title: Atom probe study of grain boundary segregation in technically pure molybdenum

Molybdenum, a metal with excellent physical, chemical and high-temperature properties, is an interesting material for applications in lighting-technology, high performance electronics, high temperature furnace construction and coating technology. However, its applicability as a structural material is limited because of the poor oxidation resistance at high temperatures and a brittle-to-ductile transition around room temperature, which is influenced by the grain size and the content of interstitial impurities at the grain boundaries. Due to the progress of the powder metallurgical production during the last decades, the amount of impurities in the current quality of molybdenum has become so small that surface sensitive techniques are not applicable anymore. Therefore, the atom probe, which allows the detection of small amounts of impurities as well as their location, seems to be a more suitable technique. However, a site-specific specimen preparation procedure for grain boundaries in refractory metals with a dual focused ion beam/scanning electron microscope is still required. The present investigation describes the development and successful application of such a site-specific preparation technique for grain boundaries in molybdenum, which is significantly improved by a combination with transmission electron microscopy. This complimentary technique helps to improve the visibility of grain boundaries during the last preparation stepsmore » and to evidence the presence of grain and subgrain boundaries without segregants in atom probe specimens. Furthermore, in industrially processed and recrystallized molybdenum sheets grain boundary segregation of oxygen, nitrogen and potassium is successfully detected close to segregated regions which are believed to be former sinter pores. - Highlights: • First study of grain boundary segregation in molybdenum by atom probe • Site-specific preparation technique by FIB and TEM successfully developed • Grain boundary segregation of oxygen, nitrogen and potassium found • Segregation in former sinter-pores detected • Presence of grain boundaries without segregation evidenced.« less
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [1] ;  [1]
  1. Montanuniversität Leoben, Department of Physical Metallurgy and Materials Testing, Franz-Josef Straße 18, 8700 Leoben (Austria)
  2. Chalmers University of Technology, Department of Applied Physics, 412 96 Gothenburg (Sweden)
  3. PLANSEE SE, Metallwerk-Plansee-Straße 71, 6600 Reutte (Austria)
Publication Date:
OSTI Identifier:
22288723
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 87; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BRITTLE-DUCTILE TRANSITIONS; GRAIN BOUNDARIES; GRAIN SIZE; IMPURITIES; ION BEAMS; MOLYBDENUM; OXYGEN; POTASSIUM; POWDER METALLURGY; SCANNING ELECTRON MICROSCOPY; SEGREGATION; SINTERS; TEMPERATURE RANGE 0400-1000 K; TOMOGRAPHY; TRANSMISSION ELECTRON MICROSCOPY