Abstract
The Precipitation processes in supersaturated Fe-5W-(0-34)Cr (at%) alloys during the aging between 823 and 1173 K have been studied mainly by means of X-ray diffraction, electron diffraction and electron microscopic observations. The major results obtained are as follows:
(1) During the aging at 823-1173 K, a metastable R-phase, which is similar to that in Fe-Mo binary alloys, is found in the early stage in Fe-5W-(12-34)Cr alloys, which is transformed to the Laves-phase, the χ-phase or the σ-phase in the later stage depending on the alloy composition and aging temperature. The composition of metastable R-phase is Fe-31W-(9-21)Cr.
(2) At 1173 K, the existence of χ-phase is confirmed but its composition is somewhat different from that in the literature. The three-phase region of (α+Laves+χ) exists near the Fe-corner in the 1173 K-isothermal section of the phase diagram.
(3) In the early stage of aging, there is an increase in hardness which might be due to the precipitation of metastable R-phase. In the later stage of aging, the successive hardening occurs in the high Cr alloys probably due to the transformation to the σ-Phase.
