Microstructural evolution and room-temperature mechanical properties of as-cast and heat-treated Fe50Al50-nNbn alloys (n=1, 3, 5, 7, and 9 at%)


Yıldırım M., Akdeniz M. V. , Mekhrabov A.

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, vol.664, pp.17-25, 2016 (Peer-Reviewed Journal) identifier identifier

  • Publication Type: Article / Article
  • Volume: 664
  • Publication Date: 2016
  • Doi Number: 10.1016/j.msea.2016.03.128
  • Journal Name: MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Page Numbers: pp.17-25
  • Keywords: Iron aluminides (based on FeAl), Microstructure, Mechanical properties at ambient temperatures, Compressive properties, ORDERED INTERMETALLIC ALLOYS, AL-NB SYSTEM, FE-AL, HIGH-STRENGTH, TENSILE PROPERTIES, DEFORMATION-BEHAVIOR, DIRECTIONAL GROWTH, ELEMENTS ADDITION, PHASE-EQUILIBRIA, IRON ALUMINIDES

Abstract

The microstructural evolution and room-temperature mechanical properties of Fe50Al50-nNbn alloys (n=1, 3, 5, 7, and 9 at%) were investigated after solidification and subsequent heat treatment. For all the compositions, the (Fe, Al)(2)Nb Laves phase formed because of the incomplete solid solubility of Nb in the Fe-Al-based phases and tended to develop an eutectic mixture with the Fe-Al-based phase. According to the results of EDS analysis and microstructural investigations, the Nb concentration of the eutectic composition was 9 at%, and the solid solubility of Nb in the B2-type Fe-Al-based phase was 3 at%. In addition, the eutectic phase transition temperature was approximately 1265 degrees C. Compared with the as cast state, all the heat-treated alloys exhibited ultrahigh compressive strength and considerably increased compressive fracture strains. The heat-treated hypoeutectic Fe50Al42Nb3 alloy exhibited the highest compressive strength and fracture strain of 3.02 GPa and 33.1%, respectively, and the eutectic Fe(50)oAl(41)Nb(9) alloy exhibited the lowest compressive strength and fracture strain of 2.66 GPa and 21.8%, respectively, because of the absence of the comparably softer Fe-Al-based primary dendrites. The superior mechanical properties of the heat-treated alloys were attributed to the bimodal distribution of the microstructure, structural incoherency between the crystalline phases, and elimination of solidification artifacts and lattice defects. (C) 2016 Elsevier B.V. All rights reserved.