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排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
A. Phillion H. W. Zurob C. R. Hutchinson H. Guo D. V. Malakhov J. Nakano G. R. Purdy 《Metallurgical and Materials Transactions A》2004,35(4):1237-1242
We have evaluated controlled decarburization as a method for probing the effect of alloying elements on ferrite growth from
austenite. The technique permits the exploration of longer-time ferrite layer growth; it minimizes the effects of interface
structure on ferrite growth; and it permits the isolation of the effects of temperature and alloying element concentration
on ferrite/austenite interface motion. The study of the decarburization of initially homogeneous Fe-C-Ni alloys was complemented
by experiments using specimens with a controlled nickel concentration gradient. Although the decarburization method yields
consistent results at longer times, it is found to be less appropriate for the study of initial ferrite growth. Nucleation
in the gas/solid interface region, coupled with uncertainties about the precise time of decarburization, leads to large relative
errors at the earliest times. For these reasons, the method is considered a valuable complement to studies based on precipitation
boundary conditions.
This article is based on a presentation given in the symposium “The Effects of Alloying Elements on the Gamma to Alpha Transformation
in Steels,” October 6, 2002, at the TMS Fall Meeting in Columbus, Ohio, under the auspices of the McMaster Centre for Steel
Research and the TMS-ASM Phase Transformations Committee. 相似文献
992.
Chul-Hwan Choi Sung-Koo Jo Seon-Hyo Kim Kwang-Ro Lee Jeong-Tae Kim 《Metallurgical and Materials Transactions B》2004,35(1):115-120
To address the role of CaF2 in the CaO-CaF2-SiO2(-MgO) slag system employed for the production of low-pressure rotor steels, the thermodynamic aspects of the slag were investigated
by equilibrating it with liquid iron at 1873 K in CaO or MgO crucibles. Presaturation of slag with an oxide block piece of
CaO or MgO in a Pt crucible and application of a carbon paste to the outside of an oxide crucible were designed to prevent
crucible failure during the slag-metal experiments. The liquidus isotherm and phase boundary of the preceding slag system
were investigated using the slag-metal equilibria. Also, the effect of CaF2 on the sulfide capacity and the activity coefficient of Fe
t
O were of particular interest in controlling the sulfur level and cleanliness of low-pressure rotor steels. 相似文献
993.
Yaojun Lin Yizhang Zhou Enrique J. Lavernia Kevin M. McHugh 《Metallurgical and Materials Transactions A》2004,35(11):3633-3635
From the geometrical standpoint, this article presents a qualitative theoretical analysis and prediction of the transient
to steady-state transition during the spray-rolling process, a novel manufacturing technique for aluminum strips. The analytical
results indicate that, when the deposited materials at the specific points on one roll surface overlap their counterparts
on the other roll surface, spray rolling transits from the transient state to the steady state. The specific points are the
limiting deposition positions of the atomized droplets on the roll surface initially. 相似文献
994.
Theoretical and experimetal methods have been developed to characterize the effect of mechanical loading on the mesoscopic
and macroscopic mechanical state of polycrystalline materials. Ferritic and austenitic single-phase materials were first analyzed,
then phase interaction was studied in a multiductile phase material (austeno-ferritic duplex steel) and a natural reinforced
composite (pearlitic steel). The theoretical method is based on the self-consistent approach in which elastic and plastic
characteristics of the phases have been applied through the micromechanical behavior of single-crystal-using slip systems
and microscopic hardening. The effects of a crystallographic texture and phase interaction during loading and after unloading
were studied. The elastic and plastic anisotropy of the grains having the same crystallographic orientation were assessed
by diffraction strain analysis. The simulation was compared with the experiments performed using the X-ray diffraction technique.
In the considered duplex and pearlitic steels, it was observed that the ferrite stress state is much lower than the austenite
and cementite ones. The results of diffraction strain distribution have showed the pertinence of the models and give valuable
information, for example, for the yield stress and the hardening parameters of each phase in a two-phase material. 相似文献
995.
996.
Cyclic oxidation response of multiphase niobium-based alloys 总被引:4,自引:0,他引:4
Kwai S. Chan 《Metallurgical and Materials Transactions A》2004,35(2):589-597
Cyclic oxidation tests were performed on multiphase Nb-based alloys containing silicide, Laves, and Nb solid solution phases.
In particular, the oxidation resistance of six alloys with various compositions (Nb, Ti, Hf, Cr, Ge, and Si) and microstructures
was characterized by thermal cycling from ambient temperature to a peak temperature that ranges from 900 °C to 1400 °C. Weight
change data were obtained and the corresponding spalled oxides were collected and identified by X-ray diffraction. The results
indicated that Nb-based alloys formed a mixture of CrNbO4, Nb2O5, and Nb2O5 · TiO2, with possibly small amounts of SiO2 or GeO2. The oxidation resistance was improved when CrNbO4 formed instead of Nb2O5 and Nb2O5 · TiO2. These results were used to assess the influence of microstructure and composition on the oxidation resistance of multiphase
Nb-based alloys. 相似文献
997.
998.
I. M. Martynenko 《Journal of Engineering Physics and Thermophysics》2007,80(2):420-424
We have derived a Fredholm-type equation of the second kind for a directional derivative problem arising in the stationary
theory of heat conduction. One result of Ya. B. Lopatinskii has been refined.
__________
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 197–200, March–April, 2007. 相似文献
999.
Kernel Spectral Matched Filter for Hyperspectral Imagery 总被引:1,自引:0,他引:1
In this paper a kernel-based nonlinear spectral matched filter is introduced for target detection in hyperspectral imagery,
which is implemented by using the ideas in kernel-based learning theory. A spectral matched filter is defined in a feature
space of high dimensionality, which is implicitly generated by a nonlinear mapping associated with a kernel function. A kernel
version of the matched filter is derived by expressing the spectral matched filter in terms of the vector dot products form
and replacing each dot product with a kernel function using the so called kernel trick property of the Mercer kernels. The proposed kernel spectral matched filter is equivalent to a nonlinear matched filter in the original input space,
which is capable of generating nonlinear decision boundaries. The kernel version of the linear spectral matched filter is
implemented and simulation results on hyperspectral imagery show that the kernel spectral matched filter outperforms the conventional
linear matched filter. 相似文献
1000.