Abstract: Precipitation phenomena in an austenitic stainless steel, SUS316L cold-rolled with
various reduction rates were studied by transmission electron microscopy and synchrotron radiation
diffractmetry. After the aging at 573 K for 15000 h, two of precipitates were observed, which
were identified as M7C3 and M23C6 by SR diffraction and electro diffraction measurements. The
precipitates M7C3 were formed at both innergranular and grain boundary, while the precipitate
M23C6 was formed at innergranular. The precipitation was promoted with increasing cold rolling
reduction. Also segregation of phosphorous was detected along grain boundaries. Besides, the
residual stresses were measured with side inclination method using a synchrotron radiation facility,
SPring-8. The residual stresses were increased with increasing the cold rolling reduction rate.
Abstract: The high pressure simple hexagonal structure of silicon, which has not been synthesized,
is quenched using femtosecond laser-driven shock wave. Any high-pressure phases of silicon do not
remain after the pressure release in the case of the hydrostatic and conventional shock compression
methods. We found the existence of the simple hexagonal structure after the intense femtosecond
laser irradiation to silicon by analyzing the crystalline structures using a synchrotron
grazing-incidence XRD method. Femtosecond laser-driven shock wave is a useful tool for the
synthesis of non-equilibrium high-pressure phases.
Abstract: α-phase forming on the surface layer and precipitation of α-phase inside a Ti-Mo alloy
during annealing in air has been investigated thermodynamically. α-phase layer is increased rapidly
when annealing temperature exceeds 700°C. When the 850°C solution-treated specimen annealed at
400°C for 1 hour, there is no α-phase precipitates. As annealing temperature increased to 800°C, the
amount of α-phase precipitates first increased to a maximum at 600°C, then decreased.
Abstract: The strain aging of heavily drawn pearlitic steel wires has been studied by means of
electrical resistivity mearsurement. The kinetic of the early stage of strain aging after being drawn to
true strain 2.89 is described by a Johnson-Mehl equation. The apparent activation energy ΔH is
estimated as 31.7kJ/mol. The results indicate that the mechanism of the early stage of strain aging of
heavily drawn pearlitic steel correlates with the formation of interstitial solute atoms-vacancy pairs.
Abstract: This study examined the phase changes, nitride precipitation and variations in hardness
of Fe-18Cr-1Mo-0.2Ti (436L) ferritic stainless steels after a nitrogen permeation heat treatment at
temperatures ranging from 1050°C to 1150°C. The strong affinity between nitrogen and Ti/Cr
enabled the permeation of nitrogen into the 436L ferritic stainless steels. The nitrogen content of the
surface layers ranged from 0.40% to 0.87%, depending on the nitrogen permeation temperatures.
The nitrogen-permeated surface layers changed into martensite plus retained austenite(RA) with rod
type M2N and square type TiN precipitates. Ups and downs of hardness with increasing depth
below the surface was observed, depending on the volume fraction of the RA, nitrogen content and
quantity of precipitates. The maximum hardness of the nitrogen permeated surface layer was 700Hv.
Abstract: It is generally accepted that Si promotes kinetics of polygonal ferrite due to
thermodynamic factors such as Ae3 and maximum amount of ferrite formed. However, in this study, it
was found that the difference between the measured rates of ferrite formation in C-Mn steel and Si
added steel was much larger than that expected considering only thermodynamic factors. The
classical nucleation theory with pillbox model was adopted to figure out what is the most controlling
factor in formation of ferrite. The volume free energy change was calculated by use of the dilute
solution model. The diffusivity of carbon (DC) was formulated as functions of C, Mn and Si by using
experimental data. It was found that the volume free energy change was still predominant but the
kinetic factors such as interfacial energy and the diffusivity of carbon by addition of Si were not
negligible at lower undercooling. However, with increasing undercooling, the diffusivity of C was
the most effective on the ferrite kinetics, though the ambiguity of treating interfacial energy was not
Abstract: In Ni-13.0at%Si-3.1at%Fe alloy, when γ/γ’ two-phase microstructure formed at 1123 K is
isothermally heated at 923 K which is lower than the temperature where the initial γ/γ’ microstructure
forms, the phase-separation of γ/γ’ precipitate phase occurs and γ particles newly appear in each
cuboidal γ’ precipitate. While in Ni-10.2at%Al-10.8at%Fe alloy, when γ/γ’ two-phase microstructure
formed at 1023 K is isothermally heated at 1123 K which is higher than the temperature where the
initial γ/γ’ microstructure forms, the phase-separation of γ’ precipitate phase takes place and γ
particles newly appear in each cuboidal γ’ precipitate. Such appearance of new γ particles in γ’
precipitates can be explained by the difference in the volume fraction of γ phase that should exist in
the γ/γ’ two-phase system depending on the heating temperature.
Abstract: A fatigue crack growth test was conducted in a polycrystalline copper. Dislocation
structure formed near an intergranular fatigue crack was investigated by electron channelling contrast
imaging (ECCI) method. The ECCI method enables us to observe dislocations lying under surface
using a scanning electron microscope. The fatigue crack in the copper specimen was grown along
both grain boundaries and slip bands inside grain. The ECCI observations revealed that both the vein
dislocation structure and the cell structures were formed near the grain boundaries. The formations of
different dislocation structures near boundaries could be interpreted in terms of the plastic strain
Abstract: Microstructures of Ni/Cu and Ni-Co/Cu multilayers were investigated by X-ray diffraction
analysis. These multilayered structures were fabricated on copper substrates using electrodeposition
technique. At an as-deposited Ni/Cu multilayer with the layer thickness of h=5nm, a single diffraction
peak appeared, although the multilayer of h=100nm exhibited the diffractions splitting into two peaks
which resulted from both the Ni and Cu layers. In the Ni-Co/Cu multilayers, it was found that
composition of the Ni-Co layer depended on an electric potential applied during deposition. The fcc
and hcp structures were detected at the Ni-rich and the Co-rich deposits, respectively. The Vickers
hardness of the Co-Ni/Cu multilayer was higher than that of the Ni/Cu multilayer.
Abstract: High velocity oxy-fuel (HVOF) spray coating of WC base cermet has been studied as a
promising candidate in some hard coating area for a replacement of the long traditional electrolytic
hard chrome (EHC) plating, which has been raising public health and environmental problems.
Micron size WC-Co (mWC-Co) has been coated on Inconel 718 substrate by HVOF thermal spray
coating process. Surface properties of coating layer and friction behavior have been investigated for
durability improvement coating on the sliding machine component surface.