Microstructures, mechanical properties, and electrical resistivity of rapidly quenched Fe-Cr-Al alloys
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I.
INTRODUCTION
THE alloys
Fe-Cr-A1 have been practically used as resistance materials owing to the high electrical resistivity, l However, the composition ranges of the conventional materials are limited to less than 15 at. pct Cr and 6 at. pct A1 because of their poor cold workability. ~It is welt known that the electrical resistivity, heat resistance, corrosion resistance, and strength of Fe-Cr-A1 alloys increase with increasing chromium and aluminum contents, 2 and hence the production of ductile Fe-Cr-A1 alloys containing large amounts of chromium and aluminum, which can be formed into a sheet or wire shape by cold working, has been expected from the industrial point of view. A rapid quenching technique has been known to be useful for the extension of solid solubilities of chromium and aluminum, the refinement of grain size, and the uniform distribution of precipitates. It is therefore expected that the application of the rapid quenching technique to Fe-Cr-A1 alloys results in an improvement of strength and ductility and an increase of electrical resistivity. From this point of view, the present authors have examined the quenching effect on their properties and have found that the supersaturated ferrite phase containing more than about 15 at. pct Cr and 5 at. pct A1, produced by the rapid quenching technique, exhibits high strengt h combined with good ductility despite the fact that conventionally cast alloys are extremely brittle, having a mixed structure of ferrite, Fe3A1, FeA1, and/or Cr2A1 phase. T. NAOHARA, formerly with the Research Staff of Tohoku University, is now Research Assistant, Faculty of Engineering, Ehime University, Matsuyama 790, Japan. A. INOUE is Research Assistant, The Research Institute for Iron, Steel, and Other Metals, Tohoku University, Sendai 980, Japan. T. MINEMURA, formerly Graduate Student of Tohoku University, is now with Research Staff, Hitachi Research Laboratory, Hitachi Ltd., Hitachi 317, Japan. T. MASUMOTO is Professor, The Research Institute for Iron, Steel, and Other Metals, Tohoku University, Sendai 980, Japan. K. KUMADA is Professor, Faculty of Engineering, Ehime University, Matsuyama 790, Japan. Manuscript submitted May 22, 1981. METALLURGICAL TRANSACTIONS A
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The purpose of this paper is to present the composition ranges in which this supersaturated ferrite forms, the compositional dependences of the microstructures, mechanical and electrical properties of the ferrite phase, and the changes in its properties during tempering.
II.
EXPERIMENTAL PROCEDURES
The specimens used in the present work are Fe-Cr and Fe-A1 binary and Fe-Cr-AI ternary alloys in the composition ranges of 10 to J0 at. pct Cr and J to 40 at. pct A1. Mixtures. of pure metals (iron, chromium, and aluminum) were melted under an argon atmosphere in an induction furnace to prepare the test alloys. The melts were sucked up into quartz tubes of about 3 mm inner diameter and solidified in the tubes. The compositions were determined by the weighed values in at. pct, since the difference between the wei
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