Abstract: Tensile test of TiAl alloy was carried out in 700oC gas environment(H2, pure air, Ar,
vacuum) at three strain rates, 2.8x10-4, 2.8x10-5, and 2.8x10-6s-1. With decreasing strain rate, the
ultimate tensile strength decreased in all environments similarly. However, elongation to fracture
differed from each environment. With decreasing strain rate, the elongation to fracture in vacuum
and Ar increased slightly, that in H2 increased much and that in pure air significantly. The reasons
of such behaviour are not known. One of the reasons for high elongation to fracture would be
formation of multiple microcracks in H2 and pure air on the gauge surface of the specimen during
Abstract: Oxide dispersion strengthened (ODS) materials is leading candidates for blanket/first-wall
structures of the fusion reactor. ODS materials for structure application in fusion rector would allow
to increase the operating temperature to approximately 650. Therefore, this work focused on the
optimization of metallurgical features to improve high temperature strength and elongation through
understanding of contents of Cr and Al. In the study, the three kinds of ODS steels such as 19Cr-ODS
(K1), 13Cr-Al-ODS (K2) and 19Cr-Al-ODS (K4) with Y2O3 content of 0.37wt% have been produced.
And tensile test were performed on three ODS ferritic/martensitic steel between RT, 300, 400 and
600Dispersion hardening represents an interesting approach to improve the mechanical properties
at elevated temperature, as they are foreseen in the future fusion reactor It has been successfully
demonstrated that it is possible to expanse the temperature range for the application of fusion reactor.
Abstract: In this study, Nano Infiltration Transient Eutectic Phase SiC ceramics (NITE-SiC) was
fabricated by hot press method with nano-SiC powder which a particle size is about 30nm, and
alumina, yttria and silica were used for sintering additives. Process condition of NITE-SiC was given
temperature of 1800oC, pressure of 20Mpa and holding time of 1Hr. NITE-SiC was optimization for
densification and good mechanical properties by preceding researches. As a result, weight loss was
occurred heat treatment temperature of all. Surface of heat treated specimens was occurred reacting of
oxidation or erosion. All Point was occurred residual stress, but residual Stress was show Relaxant
properties by effect of heat treatment.
Abstract: Microstructure can have a significant effect on the resistance to intergranular stress
corrosion cracking. Certain grain boundaries are susceptible to corrosion while others have high
resistance and may form crack bridging ligaments as the crack deviates around them. To investigate
the mechanics of crack bridging, 3D computational model has been previously developed. An
extension to the model, to include stress corrosion crack growth kinetics is presented in this paper.
An analysis of the effects of resistant grain boundary fraction demonstrates that the bridging
ligaments can significantly retard short crack propagation rates. Increasing the fraction of resistant
boundaries is shown to improve microstructure resistance by reducing the crack propagation rate.
Abstract: Effect of ceramic coating (TiN, TiCN, TiAlN or Al2O3) on the wear resistance and
thermal oxidation behavior of Inconel 617 alloy (Ni-22Cr-12.5Co-9Mo-1Al) have been examined.
TiAlN and Al2O3 coatings showed lower wear loss than bare Inconel 617 and the enhanced thermal
oxidation resistance at 1000oC by suppressing the inhomogeneous formation of Cr2O3 at the surface
region through the reaction between oxygen and grain boundary-diffused Cr, one of the main
component of Inconel 617 alloy, while TiN and TiCN coatings showed poor temperature stability at
the temperature region above 600 oC.
Abstract: The long-term corrosion strength properties for the carbon steels under pressurized water
atmosphere have been investigated, in the conjunction with the detailed analysis of their
microstructures. The corrosion test for carbon steels was carried out at the temperature of 200°C
under a water pressure of 10 MPa. The corrosion test samples were maintained up to 50 weeks in the
tube shaped reactor. The mechanical strength and the microstucture of carbon steels suffered from the
long term corrosion test were evaluated by SEM, XRD and tensile test. The weight loss of carbon
steel by the corrosion test was also examined. The tensile strength of carbon steels decreased with the
increase of corrosion time under a pressurized water atmosphere, accompanying the creation of severe
corrosion damages like stress corrosion crack.
Abstract: The interaction between two or more independent causes of materials degradation results
in a duplex mode of materials degradation. The materials degradation rate whether expressed in
loss of material or loss of mechanical strength is often faster than the sum of each form of materials
degradation acting separately. For this reason, duplex modes of materials degradation are of great
practical importance. Synergisms between unrelated forms of materials degradation are not
immediately obvious and have in some instances been only recently recognized. In this paper a
chemically aggressive environment over a geo-synthetic polymeric membrane is investigated. The
membrane free energy depends upon the mono-axial strain and the degree of reaction with an
external agent. We suppose chemical potential assigned and the minimization problem is
formulated. Practically the minimum problem is non-convex, and coexistence of equilibrium phases
is possible. The proposed general model is able to describe the complex phenomenon when
polymeric geo-synthetic membrane are undergoing to heterogeneous and complex action of the
package system built in dump of urban waste. Finally a FEM simulation is compared with
minimization problem theoretical results.
Abstract: Thermal barrier coating (TBC) of a gas turbine blade suffers from high temperature
oxidation. It is known that thermally growth oxidation (TGO) grows at the interface between ZrO2-
8%Y2O3 and CoNiCrAlY, and the TGO degrades the adhesive strength. The purpose of this study is
to clarify the TGO growth process. Thermal aging tests of ZrO2-8%Y2O3 / CoNiCrAlY TBC
systems under various temperature conditions were carried out. TGO growth process was observed
by an electron probe micro analyzer (EPMA). Both TGO of Al and TGO of other elements were
examined, and the thickness of the TGOs were examined. Results are summarized as follows. (1)
The delamination occurred at a ZrO2-8%Y2O3 layer beside the interface. (2) The growth rate of
complicated TGO which consisted of Co, Ni and Cr increased with an increase of temperature.
However, the complicated TGO wasn’t related with the delamination life. (3) The delamination
could occur if the thickness of Al TGO increased more than about 3 μm.
Abstract: The low cycle fatigue tests of SA508 Gr.1a low alloy steel were carried out to investigate
the fatigue crack growth mechanisms in high temperature water. The fatigue life in 310oC
deoxygenated water was shorter than that in air. Furthermore, the reduction in the fatigue life in 310oC
deoxygenated water was enhanced with a decreasing strain rate, from 0.4 to 0.008 %/s. The ductile
striations with the streamed down features, which may indicate the occurrence of the metal
dissolution, were mainly observed at the strain rate of 0.008 %/s. And the flat facets and the brittle
cracks, which may be evidences for the HIC, were primarily observed in the strain rate range from
0.04 to 0.4 %/s. From the analysis of microstructure, it is thought that the HIC contribute dominantly
to the reduction in the fatigue life in the strain rate range from 0.04 to 0.4 %/s and the metal
dissolution is mainly responsible for the reduction in the fatigue life at the strain rate of 0.008 %/s.
Abstract: In this research, corrosion fatigue tests using 490MPa TMCP steel were performed in
synthetic seawater condition to investigate the corrosion fatigue crack propagation characteristics of
TMCP steel plate which is often used for ships and offshore structures from its weldability and weight
reduction purpose. In addition, relationships between boundary correlation factor F(α,β) and α(=
2a/W) of the fracture mechanics formula for the test specimen which was exerted by the pin load were
calculated for the evaluation of da/dN-.K. To get the boundary correlation factor F(α,β), the
calculation of J as a path-independent line integral was carried out. The solutions of J integral showed
similar value in spite of the different path. Crack propagation tests for the same steel in air condition
was carried out also for comparison. Finally, it was clear from the crack propagation test results that
the propagation rate of TMCP steel plate in synthetic seawater condition is faster than that of in air
condition at least twice.