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Title: Effect of processing conditions on microstructural features in Mn–Si sintered steels

Sintering of steels containing oxidation sensitive elements is possible if such elements are alloyed with others which present lower affinity for oxygen. In this work, a master alloy powder containing Fe–Mn–Si–C, specifically designed to create a liquid phase during sintering, has been used for such purpose. The effect of processing conditions such as sintering temperature and atmosphere was studied with the aim of describing the microstructural evolution as well as the morphology and distribution of oxides in the sintered material, evaluating the potential detrimental effect of such oxides on mechanical properties. Chemical analyses, metallography and fractography studies combined with X-ray photoelectron spectroscopy analyses on the fracture surfaces were used to reveal the main mechanism of fracture and their correlation with the chemical composition of the different fracture surfaces. The results indicate that the main mechanism of failure in these steels is brittle fracture in the surrounding of the original master alloy particles due to degradation of grain boundaries by the presence of oxide inclusions. Mn–Si oxide inclusions were observed on intergranular decohesive facets. The use of reducing atmospheres and high sintering temperatures reduces the amount and size of such oxide inclusions. Besides, high heating and cooling rates reduce significantly themore » final oxygen content in the sintered material. A model for microstructure development and oxide evolution during different stages of sintering is proposed, considering the fact that when the master alloy melts, the liquid formed can dissolve some of the oxides as well as the surface of the surrounding iron base particles. - Highlights: • Oxide distribution in steels containing oxidation-sensitive elements • Mn, Si introduced in a master alloy powder, mixed with a base iron powder • Selective oxidation of Mn and Si on iron grain boundaries • Decohesive fracture caused by degradation of grain boundaries by oxide inclusions • Reducing agents efficient at low temperatures critical for avoiding oxide inclusions.« less
Authors:
 [1] ;  [1] ;  [2] ;  [2] ;  [3]
  1. Department of Materials and Manufacturing Technology, Chalmers University of Technology, Rännvägen 2A, SE-41296 Gothenburg (Sweden)
  2. Department of Materials Science and Engineering, IAAB, Universidad Carlos III de Madrid, Av. Universidad 30, 28911 Leganés, Madrid (Spain)
  3. (Spain)
Publication Date:
OSTI Identifier:
22403539
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 95; Other Information: Copyright (c) 2014 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; CHEMICAL ANALYSIS; CHEMICAL COMPOSITION; FRACTOGRAPHY; FRACTURES; GRAIN BOUNDARIES; IRON ALLOYS; MANGANESE ALLOYS; MECHANICAL PROPERTIES; METALLOGRAPHY; OXIDATION; OXIDES; POWDER METALLURGY; SILICON ALLOYS; SINTERED MATERIALS; SINTERING; STEELS; X-RAY PHOTOELECTRON SPECTROSCOPY