1982 年 31 巻 345 号 p. 553-558
An attempt was made to produce microduplex structures for Fe-Cr-Ni alloys with two different volume fractions of γ that is, 28%Cr-9%Ni and 32%Cr-8%Ni steels. The influences of grain size, ageing at 475°C and volume fraction of γ on their tensile properties and fracture were studied.
The main results obtained are as follows;
(1) A better combination of strength and ductility was obtained for 28%Cr-9%Ni steel (volume fraction of γ; 70%) than that for 32%Cr-8%Ni steel (volume fraction of γ; 30%). This results from the finer microstructures produced by the thermomechanical treatments in the former.
(2) The relation between σ0.2 and d-1/2 showed Petch's type equation for the aged specimens with high volume fraction of γ and all unaged specimens. On the other hand, d-1/2 dependence of σ0.2 for the large grained specimens differed from that of the fine ones when the volume fraction of γ was low. This may be caused by the difference in the deformation mode within the α matrix that is, twin or slip deformations.
(3) The influence of d on the ductility for the unaged specimens differed from that of the aged ones. The ductility decreased with the decrease in d in the former, whereas it increased in the latter.