共查询到20条相似文献,搜索用时 15 毫秒
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The deformation characteristics contributing to the superior cavitation erosion properties of HCP cobalt single crystals have
been determined. Results indicate that its erosion response is highly orientation sensitive. A homogeneous distribution of
and
glide occurs in {0110} crystals, whereas slip in the (0001) crystals is much more heterogeneous and consists mainly of
dislocations. Continued exposure to cavitation nucleates a large number of twins, predominantly on the
and
planes in the
and (0001) crystals respectively. The former twins are finer and more needle-like than the latter. The
crystals are also significantly more erosion resistant than the (0001) crystals. The twin density increases continuously
with cavitation exposure until a dense network of twins spans the entire exposed area. This fine-scale twinning is considered
responsible for the superior erosion resistance of the metal. 相似文献
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The crystallographic direction of growth in directionally solidified magnesium alloy AZ91 has been studied by TEM and EBSP
techniques in SEM. The main direction of growth is found to be
. The dendrites have sixfold symmetry around the main direction, with secondary arms lying along the traces of the (0001),
, and
-planes, respectively. The secondary arms lying in the basal plane are crystallographically of the same type as the main direction:
and
. 相似文献
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Z.H. Nie Y.D. Wang G.Y. Wang J.W. Richardson G. Wang Y.D. Liu P.K. Liaw L. Zuo 《Metallurgical and Materials Transactions A》2008,39(13):3113-3119
The phase transition and influence of the applied stress on the texture evolution in the as-cast Ni-Mn-Ga ferromagnetic shape-memory
alloys were studied by the time-of-flight (TOF) neutron diffraction technique. The neutron diffraction experiments were performed
on the General Purpose Powder Diffractometer (Argonne National Laboratory). Inverse pole figures were determined from the
neutron data for characterizing the orientation distributions and variant selections of polycrystalline Ni-Mn-Ga alloys subjected
to different uniaxial compression deformations. Texture analyses reveal that the initial texture for the parent phase in the
as-cast specimen was composed of
, , , and , which was weakened after the compression deformation. Moreover, a strong preferred selection of martensitic-twin variants
(and ) was observed in the transformed martensite after a compression stress applied on the parent phase along the cyclindrical
axis of the specimens. The preferred selection of variants can be well explained by considering the grain/variant-orientation-dependent
Bain-distortion energy.
This article is based on a presentation given in the symposium entitled “Neutron and X-Ray Studies for Probing Materials Behavior,”
which occurred during the TMS Spring Meeting in New Orleans, LA, March 9–13, 2008, under the auspices of the National Science
Foundation, TMS, the TMS Structural Materials Division, and the TMS Advanced Characterization, Testing, and Simulation Committee. 相似文献
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S. Hata T. Nakano N. Kuwano M. Itakura S. Matsumura Y. Umakoshi 《Metallurgical and Materials Transactions A》2008,39(7):1610-1617
The ordering mechanism of long-period superstructures (LPSs) in Al-rich TiAl alloys has been investigated by high-resolution
transmission electron microscopy (HRTEM). The LPSs are classified in terms of arrangements of base clusters with different
shapes and compositions formed in Ti-rich (002) layers of L10-TiAl matrix: square Ti4Al, fat rhombus Ti3Al, and lean rhombus Ti2Al type clusters. The HRTEM observations revealed that antiphase boundaries of long-range-ordered LPS domains and short-range-ordered
microdomains are constructed by various space-filling arrangements of the base clusters. Such a microscopic property characterized
by the base clusters and their arrangements is markedly analogous to that of the
* special-point ordering alloys such as Ni-Mo.
This article is based on a presentation given in the symposium entitled “Materials Behavior: Far from Equilibrium” as part
of the Golden Jubilee Celebration of Bhabha Atomic Research Centre, which occurred December 15–16, 2006 in Mumbai, India.
相似文献
S. Hata (Associate Professor)Email: |
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Sungsoo Kim 《Metallurgical and Materials Transactions A》2006,37(1):59-68
Recently, it was proven that delayed hydride cracking (DHC) is accompanied by deformation twinning through the texture analysis
of a fractured surface. Thus, in order to understand the operation of deformation twinning, the texture variations by rolling
were investigated using Zr-2.5 pct Nb alloy with {11
0} 〈10
0〉 texture. It was observed that deformation twinning was operated predominantly in the range of a 5 to 15 pct strain. The
basal poles were rotated in the normal direction of a rolling plane with the strain, and the (0002) texture was fully reversed
after 15 pct strain. This finding was established to be due to the operation of the {10
2} and {11
1} twinning systems through the analysis of the inverse pole figure. It appeared that the degree and easiness of the twinning
operation was affected by changing the direction of compression during rolling with respect to the initial {11
0} 〈10
0〉 texture. The contribution of deformation twinning to strain was quantitatively calculated using the change in the basal
pole components.
This article is based on a presentation made in the symposium entitled “Processing and Properties of Structural Materials,”
which occurred during the Fall TMS meeting in Chicago, Illinois, November 9–12, 2003, under the auspices of the Structural
Materials Committee. 相似文献
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R. Bai C. L. Briant D. C. Paine J. R. Beresford 《Metallurgical and Materials Transactions A》1998,29(3):757-764
This article presents a study of the evolution of the annealing texture in hafnium, as measured by electron backscattering
diffraction patterns (EBSPs). It was found that the annealing texture of asreceived extruded rod depended on the annealing
temperature. After low-temperature recrystallization, the deformation axis was parallel to
or
and the basal planes were approximately parallel to the deformation axis. These orientations were deduced by the position
of the points in the standard stereographic triangle used to produce the inverse pole figure. As the annealing temperature
was raised to 1700 °C, the direction parallel to the rolling direction changed to
and the grain size increased. It appeared that the increase in grain size occurred by a process of abnormal grain growth,
and this abnormal grain growth appeared to be the cause of the change in the texture. Texture was also examined in samples
that had been warm rolled to thickness reductions between 10 and 90 pct and then annealed at 1700 °C. In these samples, the
main feature of the texture was that the basal plane became parallel to the rolling plane as the amount of rolling increased.
The maximum grain size was observed in samples that had been rolled to a reduction in thickness of 50 pct. 相似文献