Chi phase

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The Chi phase (χ phase) is an intermetallic phase (Fe 36 Cr 12 Mo 10 ), which can arise, among other things, when welding high-alloy steels with a chromium content of over 15 percent. It is very similar in its formation and properties to the sigma phase .

The Chi phase arises when heated for a long time between 400 and 550 ° C and leads to 475 ° C embrittlement. It has a body- centered cubic structure .

The chi phase reduces the ductility , corrosion resistance and toughness of the material. As a countermeasure, the heat input (energy per unit length) can be limited during welding; the operating temperature during operation.

The Chi phase arises during welding because of its temperature range before the sigma phase and is usually also converted into this.

It is also found in other intermetallic compounds.

Individual evidence

  1. ↑ a b vhi GmbH: embrittlement , accessed on February 14, 2017
  2. ↑ a b Ulrich Dilthey: Welding production processes 2 Behavior of materials during welding . Springer-Verlag, 2006, ISBN 978-3-540-27402-5 , pp. 172 ( limited preview in Google Book search).
  3. ^ Bargel, Schulze: Material Science. 10th edition, p. 238
  4. ↑ HS Khatak, Baldev Raj: Corrosion of Austenitic Stainless Steels Mechanism, Mitigation and Monitoring . Woodhead Publishing, 2002, ISBN 978-1-85573-613-9 , pp. 18 ( limited preview in Google Book search).
  5. ↑ Joseph Ki Leuk Lai, Chan Hung Shek, Kin Ho Lo: Stainless Steels An Introduction and Their Recent Developments . Bentham Science Publishers, 2012, ISBN 978-1-60805-305-6 , pp. 97 ( limited preview in Google Book search).
  6. ↑ J.-M. Joubert, M. Phejar: Crystal chemistry and Calphad modeling of the χ phase. In: Progress in Materials Science. 54, 2009, p. 945, doi : 10.1016 / j.pmatsci.2009.04.002 .
  7. ^ JS Kasper: The ordering of atoms in the chi-phase of the iron-chromium-molybdenum system. In: Acta Metallurgica. 2, 1954, p. 456, doi : 10.1016 / 0001-6160 (54) 90066-8 .
  8. ↑ N. Eswara Prasad, TR Ramachandran: Aluminum-Lithium Alloys Chapter 3. Phase Diagrams and Phase Reactions in Al-Li alloys . Elsevier Inc. Chapters, 2013, ISBN 0-12-806841-8 ( limited preview in Google Book Search).