Key Engineering Materials
Vols. 353-358
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Key Engineering Materials
Vols. 345-346
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Key Engineering Materials Vols. 345-346
Paper Title Page
Abstract: In this study, we try to investigate the asymmetric rolling process affects microstructure,
texture and formability of AZ31 Mg sheet. The deformation twins are clearly apparent, small and
recrystallized grains are visible along some grain boundary and twinned regions in the as-rolled
both samples. The symmetrically rolled sample tended to show peak inclined to the rolling direction.
On the other hand, the asymmetrically rolled sample tended to show peak slightly inclined to the
transverse direction. From the pole figure observation by EBSD, the intensity decrease of basal
fiber texture after asymmetric rolling should be attributed to the severe shear strain induced during
asymmetric process. The Erichsen value was measured to be 6.5 for asymmetrically rolled sample
and 5.2 for symmetrically rolled sample.
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Abstract: In this study, the elastic buckling strength of cubic open-cell foams subjected to uniaxial
compression is investigated using the homogenization framework developed by the present authors
(Ohno et al., JMPS 2002; Okumura et al., JMPS 2004). First of all, based on the framework, the
microscopic bifurcation and macroscopic instability of cubic open-cell foams are numerically
analyzed by performing finite element analysis. It is thus shown that long wavelength buckling is the
primary mode and occurs just after the onset of macroscopic instability. Then, a solution for
predicting the stress of long wavelength buckling is analytically derived from the onset condition of
macroscopic instability. The validity of this analytical solution is demonstrated by the finite element
results.
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Abstract: Evolution of crystallographic texture by hot rolling deformation at the temperature of
200°C was investigated by hot rolling tests on as-cast Al-5wt%Mg alloy fabricated by a new strip
cast technology. Texture variation through the thickness direction in the Al-5wt%Mg alloy was
examined experimentally. Macrotexture and microtexture measurements were conducted using
X-ray diffractometer and electron backscatter diffraction (EBSD), respectively. Experimental
investigation reveals that the evolution of texture and microstructure is strongly dependent on a
distance from center of the Al-5wt%Mg alloy sheet. It was found that the shear texture components
tend to be increased at the surface region of the hot-rolled specimen.
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Abstract: A new approach is proposed for description of autowave processes responsible for plastic
deformation localization in metals and alloys. It is postulated that to a localized flow autowave there
corresponds a quasi-particle. The characteristics of the quasi-particle have been determined. A direct
relationship has been established between the processes involved in the deformation on a
macro- and a micro-scale level.
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Abstract: This paper discusses ratchetting deformation of lead-free solder Sn/3Ag/0.5Cu and
lead-containing solder alloy Sn/37Pb with several stress amplitudes and stress ratios of the maximum
stress to the minimum stress. First the uniaxial ratchetting testsare conducted with three maximum
stresses and five stress ratios. The all tests are conducted using cylindrical bulk specimens of the
solder alloys at 313 K. The test results show that there is the difference in the viscoplastic deformation
behavior between two solder alloys. The relationship between ratchetting strain and time is estimated
by Biley-Norton law to explain that the uniaxial ratchetting deformation is strongly dominated by the
viscous deformation. Finally, the ratchetting deformation is simulated by the dislocation based
constitutive model proposed by Estrin [1]. The simulations show that there is a possibility to simulate
the uniaxial ratchetting by clarifying the dislocation mechanism of the solder alloys.
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Abstract: It is important to research activation of the slip systems in magnesium crystals to
understand deformation behavior of magnesium. In this study, pure magnesium, Mg-7.0at%Li and
Mg-0.1at%Zn single crystals were stretched in the [11-20] direction in the range of 77K to 573K to
investigate the deformation behavior by non-basal slip. The active slip system was investigated by
the observation of slip bands, etch pit bands and dislocations by TEM. {11-22} <-1-123> second
order pyramidal slip is activated in all magnesium and magnesium alloy single crystals, and its yield
stress shows anomalous temperature dependence in the range from 77K to 293K, however, the
yields stress decreased rapidly with increasing temperature above 293K. The yield stress due to
the pyramidal slip in Mg-Li and Mg-Zn alloy were lower than that of pure magnesium about 20MPa
whereas the stress of Mg-Zn at 77K was about two times higher than pure magnesium.
101
Abstract: The formability of several Zr-based bulk metallic glasses in the supercooled liquid region has been
estimated. Using the data obtained from compression tests, normalized processing maps based on a dynamic
materials model (DMM) have been constructed to evaluate feasible forming conditions. Laboratory-scale hot
extrusion of the Zr44Ti11Cu9.8Ni10.2Be25 BMG has also been carried out to clarify the effectiveness of the
normalized processing maps established in this study. The influence of thermal properties and
microstructural differences on the formability of BMGs is interpreted in terms of a normalized temperature
within the supercooled liquid region.
105
Effect of Aging Treatment Conditions on the Microstructure and Strength of Fe-36Ni Based Invar Alloy
Abstract: Strengthening method for the Fe-36Ni based Invar alloy for power transmission wire was
investigated in this study. High strength of 1300 MPa could be obtained in this alloy through solution
hardening, precipitation hardening and strain hardening by cold working. Phase equilibrium of the
Invar alloy was calculated using FactSage®, revealing that thermodynamically stable phases are
Mo2C, MoC, M23C6-type FeCrMo carbide, and M6C-type FeMo carbides. Aging treatments were
carried out at temperatures ranging from 400 to 900oC for time intervals from 3 min to 30 hrs. Peak
aging condition was obtained as 400oC and 1 hr. With temperature increased, peak hardness was
decreased abruptly. Microstructure observation was conducted by optical microscopy, scanning
electron microscopy, and transmission electron microscopy. By using the result from aging treatment,
high strength above 1300MPa was obtained in the cold rolled Invar alloy plate.
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Abstract: Equal channel angular extrusion (ECAE) was employed in an attempt to develop
nanostructural metal matrix composites with homogenized distribution of reinforcing particles. Zn-
Al metal matrix composites reinforced with 5 μm SiC particulates were produced by casting
method. A non-uniform distribution of the reinforcing particles was evident in the metal matrix.
With repetitive shear deformation imposed via the ECAE process, substantial structural
improvement was achieved and the reinforcing particulates were de-clustered into a finely dispersed
distribution throughout the metal matrix. The homogeneity of the particle distribution was studied
by the Quadrat method and the skew factors were determined. It was found that the skew factors
were substantially reduced after 8 extrusion passes, showing the homogeneity of the particle
distribution was greatly improved in the composites.
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