Papers by Author: Y. Shiota

Abstract: Dislocation density and crystallite size of steel wires with various carbon concentrations and drawing strains were determined by profile analyses for neutron diffraction profiles. The density is found to increase while the size decreases with increasing of carbon concentration and/or drawing strain. Both of the Bailey-Hirsch relation and Hall-Petch relation hold for the present results to suggest that these two are not independent., i.e., indicating an identical strengthening mechanism from a different point of view.

Abstract: Neutron diffraction technique was employed to measure stress distribution in an interior region of a SUS304 rotating mechanical component with a fringe after solution treatment and after subsequently conducted stress-relief annealing. A coupon with 3x3x3 mm was prepared by spark cutting to determine stress-free spacing d0. The elastic strain was determined by using the measured (111) spacing d and d0 by (d - d0)/d0. Then the obtained strains were input into the general Hooke’s law to calculate stresses. The residual hoop stress near the surface is compressive which is lowered in the inner part. The residual stresses near the center of the component are hydrostatic tensile stresses. These residual stresses were not relaxed by the annealing treatment recommended in a handbook. Hence, more appropriate stress relief treatment has to be developed. In case of a cast specimen, coarse grains with a strong texture made it difficult to determine residual stresses precisely.

Abstract: The microstructural change with drawing and subsequent annealing for a patented pearlite steel was investigated by means of neutron diffraction. The dissolution of cementite plates with drawing and re-precipitation of spherical cementite particles with annealing after sever drawing were observed. In situ neutron diffraction during tensile loading was performed and it is revealed that the strengthening mechanism of the specimen without cementite differs from that for a ferrite-cementite steel where the load transfer is a main mechanism. The possible strengthening mechanism for the heavily drawn specimen is proposed.