Creep behaviour at 1100 K has been studied in and . Steady state creep characteristics have been analysed together with data reported previously for Fe-2.1moL %Mo alloy and results obtained in conventional tensile tests of these materials.
The existence of two transitions in the deformation behaviour becomes evident in b.c.c. Fe-Mo solid solutions as in fc.c. AI-Mg alloys. Typical class 1 behaviour can be observed only under the intermediate stress range. The condition of the upper transition is well described by the Cottrell model for the breakaway of the solute atmosphere as in fc.c. AI-Mg alloys. The condition of the lower transition has some common features in Fe-Mo and AI-Mg alloys, though the creep process in the lower stress range has not been well understood.
behaviour of Fe-(1.3-4.2)mol.%Mo alloys under 5-200 MPa at 873-1233 K. They reported that the stress exponent n for the steady state creep rates, which was close to four under low stresses, increased monotonically with stress up to 14. Oikawa et al. [6] reported that n, which was about five in dilute alloys, decreased gradually, as the molybdenum concentration increased, down to about three in 4-6mol.%Mo [7]. Therefore the generality of the transition in creep characteristics in the power-law creep regime observed in AI-Mg alloys remained to be checked [8].
Recently, the authors [9] have reported the existence of the upper transition in creep of an Fe-2.1mol.%Mo alloy. In this paper, experimental results on the creep characteristics of a-Fe-Mo alloys reveal the existence of upper and lower transitions in the power-law creep of b.c.c, solid solutions.