Fe-4.1 at%Mo合金の高温クリープ組織

Abstract

Substructures developed during the steady-state creep of Fe-4.1 at%Mo bcc solid solution at 1100∼1200 K under 6∼40 MPa have been observed by transmission electron microscopy. The stress exponent, n, of the steady-state creep rates is 3.2±0.2. This result means that this alloy shows Class I behavior under the present creep condition.Sub-boundaries consisting of dislocation networks as well as rather homogeneously-distributed dislocations within subgrains are always observed. This fact suggests that the presence or the absence of sub-boundaries does not necessarily indicate the importance of viscous gliding of dislocations during steady-state creep deformation of solid solution alloys.Dislocation density within subgrains, ρG, and total dislocation density, ρT, increase with increase in the applied stress, σa : ρG∝σ1.5a and ρT∝σ1.3a. The length of sub-boundaries per unit area, L, which is reciprocally proportional to the subgrain diameter, increases with σa:L∝σ0.5a. The mean spacing of dislocations within sub-boundaries, l, decreases with σa:l∝σ−0.6a. The average internal stresses, ‾σi obtained by stress-transient dip-tests using a back-extrapolation technique are roughly proportional to \sqrtρG, \sqrtρT, and 1⁄l.