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971.
During the last ten years, techniques have been developed to measure the distribution of grain boundaries in polycrystals
as a function of both lattice misorientation and grain boundary plane orientation. This paper presents a brief overview of
the techniques used for these measurements and the principle findings of studies implementing these techniques. The most significant
findings are that grain boundary plane distributions are anisotropic, that they are scale invariant during normal grain growth,
that the most common grain boundary planes are those with low surface energies, that the grain boundary populations are inversely
correlated with the grain boundary energy, and that the coincident site lattice number is a poor predictor of the grain boundary
energy and population. 相似文献
972.
A set of device for electromagnetic separation (EMS) was designed and applied to process the continuous flowing melt. Tensile test was employed to compare effect of electromagnetic separation with that of the traditional processes. Compared with filtration by ceramic foam filter and process without filtration, multiple process combined with filtration and electromagnetic separation can effectively remove most of inclusions with diameter finer than 10μm in A356 alloy casting, hence improve its tensile properties. After being processed by electromagnetic filtration,the tensile strength of A356 scrap is enhanced by 8.27%, approaching the level of fresh A356 alloy. 相似文献
973.
Some months ago the submarine Nautilus was in dock for refueling. It had traveled 60,000 miles, but the total uranium used would make a lump smaller than a light bulb. This is only one example that the Atomic Age is here with us, now! How and where does this incredible Atomic Age challenge the first and greatest of America’s basic industries? 相似文献
974.
Biaxial forming behavior is investigated for three aluminum sheet alloys (Al 5182 containing 1% Mn (5182+Mn), Al 5754, and
6111-T4) using a heated die and punch in the warm forming temperature range of 200–350 °C. It is found that, while all three
alloys exhibit significant improvement in their formability compared with that at room temperature, the non-heat-treatable
alloys 5182 + Mn and 5754 give higher part depths than that of heat-treatable 6111-T4. The formability generally increases
with decreasing BHP (BHP), but increasing the forming temperature and/or BHP minimizes the wrinkling tendency and improves
the forming performance. The stretchability of the sheet alloys increase with increasing temperature and increasing BHP. For
the alloys and forming conditions involved in the current study, the formability, measured in terms of part depth, comes mainly
from the drawing of metal into the die cavity, although stretching effects do influence the overall forming behavior. The
optimum formability is achieved by setting the die temperature 50 °C higher than the punch temperature to enhance the drawing
component. Setting the die temperature higher than the punch temperature also improves the strain distribution in a part in
such a manner that postpones necking and fracture by altering the location of greatest thinning. 相似文献
975.
Jung-Chel Chang Cheol Choi Jae-Chul Kim Young-Hoon Yun 《Journal of Materials Engineering and Performance》2003,12(4):420-425
Effects of the hot-isostatic pressing (HIP) process on microstructures and mechanical properties of Ni-base single crystal
superalloy CMSX-4 were investigated. In the overall heat treatment process, the HIP treatment remarkably induced the healing
behavior of micropores and decreased the pore size and porosity of superalloy CMSX-4 compared with normally treated specimens.
The microstructure of γ′ phase after the HIP process showed rather a coarsening tendency and could be developed by the partially solution and aging
treatment. Consequently, the elimination of cast micropores using the HIP step resulted in the inhibition of crack initiation
in microstructure and improved the stress-rupture lives of Ni-base single crystal superalloy by 185%. 相似文献
976.
Phosphorus was added to Fe-50 wt.% Ni in the form of a coated composite powder via an electroless plating process. Addition
of phosphorus to Fe-50 wt.% Ni facilitated increases in density and grain size, both of which were beneficial to magnetic
performance. Because of the homogeneous distribution of phosphorus in the powder, the optimal phosphorus addition was much
lower than for those using Fe3P as the phosphorus precursor. The optimal phosphorus addition was close to its maximum solubility in Fe-50 wt.% Ni (about
0.5 wt.%), above which precipitation of excessive phosphorus in the form of iron nickel phosphide, (Fe,Ni)3P, effectively degraded the magnetic properties of Fe-50 wt.% Ni. Without the addition of phosphorus, good magnetic properties
could be achieved only when the sintering temperature was high enough (>1200 °C) to result in a high sintered density and
large grains in the sintered structure. 相似文献
977.
Pil-Ryung Cha Ho-Seok Nam Dae-Yeong Jeon Jong-Kyu Yoon 《Metals and Materials International》2002,8(1):119-127
This study presents a simple and robust algorithm for the optimal design of the system with coupled complex transport phenomena:
the transport phenomena comprise fluid flow, heat and mass transfer. The (1+1)-Evolution Strategy method is adopted as the optimization method. In order to analyze the transport phenomena in the complex geometry generated
during the optimization procedure, thefinite volume method with a boundary fitted curvilinear coordinate system is used. To confirm the validity of the present method, the optimal
design for the inner shape of the simplified two-dimensionalSubmerged Entry Nozzle in the continuous slab caster is conducted. It is shown that the resulting design of the nozzle is consistent with the purpose
and constraints of the design. 相似文献
978.
Mingru Zhang Jianqing Qian Haicheng Gu 《Journal of Materials Engineering and Performance》2007,16(5):635-639
Metallographic structures of carbide-free bainite steel wheel rim are mainly composed of supersaturated lath ferrite and retained
austenite film among bainitic ferrite laths. It is suspected that supersaturated ferrite and retained austenite are likely
to decompose under the influence of temperature change and mechanical stress. Stability of wheel rim structure is studied
by means of x-ray diffraction, dye microscopy, and micro-hardness test. When the samples are tempered in the range of 150-350 °C,
the retained austenite films are at the state of relative stability. Fifty percent of retained austenite is decomposed when
the sample is tempered at 400 °C. Microhardness increases when the sample is tempered at 150 °C. The decrease in hardness
is mild when the samples are tempered from 200 to 500 °C. The mechanical stability of retained austenite film is studied with
tensile sample under the effect of tensile stress. The retained austenite appears to be stable in low and middle degree of
deformation, and decomposition occurs at great amount of deformation. Diffraction peak of carbide is not found in all above
experiments. The steel enriched silicon prevents the carbide precipitation during the transformation. It indicates the carbide-free
bainite wheel steels have an excellent thermal and mechanical stability. 相似文献
979.
Patricia Muñoz-Escalona Shreyes Melkote Kai Liu 《Journal of Materials Engineering and Performance》2005,14(5):582-590
In recent years, the finite element method (FEM) has become the main tool for simulating the metal cutting process because
research based on trial and error is time consuming and requires high investment. Early studies were done by different investigators.
In this research AISI 52100, hardened steel (62 HRC) was selected for an orthogonal machining process as well as metal cutting
simulation using the software DEFORM-2D. This software is based on a forging process and has been adapted to an orthogonal
machining process. The results of simulated cutting forces were compared with experimental cutting force data to validate
the orthogonal cut simulation. Also, the surface roughness was measured, and the influence of the stress, strain, and temperature
on the surface roughness was studied. 相似文献
980.
2—甲基—1,4—萘醌对DNA光敏损伤的诱导作用 总被引:3,自引:0,他引:3
选择波长337nm的激光作为激励光源,借助凝胶电泳研究了2-甲基-1,4-萘醌诱导的DNA光敏损伤。结果表明:在氧气饱和、脱氧条件下光敏损伤显著,DNA损伤主要与光子剂量、核酸与萘醌浓度比及DNA存在形式有关。 相似文献