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991.
992.
Daniel G. Sanders Mamidala Ramulu 《Journal of Materials Engineering and Performance》2004,13(6):744-752
Superplastic forming (SPF) combined with diffusion bonding (DB) has been used successfully for the fabrication of titanium
aerospace hardware. Many of these applications have been for military aircraft, whereby a complex built-up structure has been
replaced with monolithic parts. Several methods for applying the two- and four-sheet titanium SPF/DB processes have been devised,
including the welding of sheets prior to forming and the use of silk-screened stop-off (yttria) to prevent bonding where it
is undesirable. Very little progress has been made in the past few years toward understanding and modeling the SPF/DB process
using constitutive equations and data by laboratory testing. Concerns that engineers face in designing for fatigue life, acceptable
design loads, and damage tolerance are currently being studied, but the database is very limited. This is a summary of past
work found in the literature and forms the foundation for additional research.
This paper was presented at the International Symposium on Superplasticity and Superplastic Forming sponsored by the Manufacturing
Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium
was organized by Daniel G. Sanders, The Boeing Company. 相似文献
993.
Yang Gao Lian-Tong An Cheng-Qi Sun Zhi-Jun Yan 《Journal of Thermal Spray Technology》2004,13(4):521-525
The effects of the composition of plasma gases (Ar-N2, Ar-H2), arc current, and voltage on the temperature and velocity of a low-power (5 kW) plasma torch in the arc field free region
has been investigated using an enthalpy probe. Coatings of Al2O3-13TiO2 were deposited under different conditions. The results show that in the Ar-N2 plasma, the enthalpy, temperature, and velocity change little with arc current and voltage when regulating the nitrogen proportion
in the plasma gas. The hardness of the resulting coatings is 800 to 900 kg/mm2 HV.300. For Ar-H2 plasma, however, increases in the H2 content in the mixture of the gases remarkably enhanced the velocity and heat transfer ability of the plasma jet, with the
result that the coatings showed high hardness up to 1200 HV. 相似文献
994.
Uma Batra S. Ray S. R. Prabhakar 《Journal of Materials Engineering and Performance》2003,12(5):597-601
A ductile iron containing 0.6% copper as the main alloying element was austempered at a fixed austempering temperature of
330 °C for a fixed austempering time of 60 min after austenitization at 850 °C for different austenitization periods of 60,
90, and 120 min. The austempering process was repeated after changing austenitization temperature to 900 °C. The effect of
austenitization temperature and time was studied on the carbon content and its distribution in the austenite after austenitization.
The effect of austenitization parameters was also studied on austempered microstructure, structural parameters like volume
fraction of austenite, X
γ
, carbon content C
γ
, and X
γ
C
γ
, and bainitic ferrite needle size, d
α
after austempering. The average carbon content of austenite increases linearly with austenitization time and reaches a saturation
level. Higher austenitization temperature results in higher carbon content of austenite. As regards the austempered structure,
the lowering austenitization temperature causes significant refinement and more uniform distribution of austempered structure,
and a decrease in the volume fraction of retained austenite. 相似文献
995.
Désirée Risch Alexander Brosius Matthias Kleiner 《Journal of Materials Engineering and Performance》2007,16(3):327-330
Electromagnetic sheet metal forming is a high speed forming process using pulsed magnetic fields to form metals with high
electrical conductivity such as aluminum. Thereby, workpiece velocities of more than 300 m/s are achievable, which can cause
difficulties when forming into a die. The kinetic energy, which is related to the workpiece velocity, must be dissipated in
a short time slot when the workpiece hits the die; otherwise undesired effects, for example rebound can occur. One possibility
to handle this shortcoming is to locally increase the stiffness of the workpiece. A modal analysis is carried out in order
to determine the stiffness of specific regions of the workpiece so that an estimation concerning the feasibility of the desired
geometry is possible in advance without doing cost and time consuming experiments. Thereby, the desired geometry of the workpiece
will be fractionized in significant sectors. This approach has to define the internal force variables acting on the cutting
edge, which are required to constrain the numerical model. Finally, a method will be developed with the objective of calculating
the stiffness of each sector. The numerical results will be verified by experiments.
This article was presented at Materials Science & Technology 2006, Innovations in Metal Forming symposium held in Cincinnati,
OH, October 15-19, 2006. 相似文献
996.
Zhongning Shi Junli Xu Zhuxian Qiu Zhaowen Wang Bingliang Gao 《JOM Journal of the Minerals, Metals and Materials Society》2003,55(11):63-65
The superalloys Cu-Ni-Al, Cu-Ni-Fe, and Cu-Ni-Cr were studied as anodes for aluminum electrolysis. The alloys were tested
for corrosion in acidic electrolyte molten salt and for oxidation in both air and oxygen. The results showed that the Cu-Ni-Al
anodes possess excellent resistance to oxidation and corrosion, and the oxidation rates of Cu-Ni-Fe and Cu-Ni-Al anodes were
slower than those of pure copper or nickel. During electrolysis, the cell voltage of the Cu-Ni-Al anode was affected most
by the concentration of alumina in cryolite molten salt. The Cu-Ni-Fe anode exhibited corrosion resistance in electrolyte
molten salt. Comparatively, the Cu-Ni-Cr anode showed poor resistance to oxidation and corrosion. The testing found that further
study is warranted on the use of Cu-Ni-Al and Cu-Ni-Fe as inert alloy anodes.
For more information, contact Zhongning Shi, Northeastern University, School of Materials and Metallurgy, WenhuiRoad No. 3,
Shenynag, Liaoning 110004 China; e-mail znshi@163.com 相似文献
997.
Dong-il Shin François Gitzhofer Christian Moreau 《Journal of Thermal Spray Technology》2007,16(1):118-127
Metal-based thermal barrier coatings (MBTBCs) have been produced using high frequency induction plasma spraying (IPS) of iron-based
nanostructured alloy powders. The study of MBTBCs has been initiated to challenge issues associated with current TBC materials
such as difficult prediction of their “in-service” lifetime. Reliability of TBCs is an important aspect besides the economical
consideration. Therefore, the study of MBTBCs, which should posses higher toughness than the current TBC materials, has been
initiated to challenge the mechanical problems of ceramic-based TBCs (CBTBCs) to create a new generation of TBCs. The thermal
diffusivity (TD) (α) properties of the MBTBCs were measured using a laser flash method, and density (ρ) and specific heat
(C
p) of the MBTBCs were also measured for their thermal conductivity (k) calculation (k = αρ
C
p). 相似文献
998.
在许多情况下,只应用一种NDT技术存在不足,这就迫使NDT操作人员使用一种以上的技术以保证检测出危害被检物使用寿命或功能的缺陷。但分别实施多种技术的检测,就会延长检验时间。介绍了一种新的NDT设施,采用两种不同的非接触无损检测技术进行互补,即电磁声换能器(EMAT)和脉冲涡流(PEC)探头。检测结果表明,脉冲涡流和电磁声换能器因是非接触,所以可应用于材料生产过程中的自动在线检验,也可用于在役检验。 相似文献
999.
Advances in fabricating superplastically formed and diffusion bonded components for aerospace structures 总被引:1,自引:0,他引:1
Larry D. Hefti 《Journal of Materials Engineering and Performance》2004,13(6):678-682
Superplastic forming and diffusion bonding (SPF/DB) production hardware is being fabricated today for aerospace applications.
Metal tooling is being used to bring the titanium sheets into contact so diffusion bonding can occur. However, due to material
sheet and tooling tolerances, good bond quality is difficult to achieve over large areas. A better method for achieving DB
is to use “stop-off” inside sealed sheets of titanium, which constitutes a pack, and then the pack is bonded using external
gas pressure. A good method for heating the pack for this process is to use induction heating. Components using “stop-off”
that were diffusion bonded first and then superplastically formed have shown much better bond quality than components that
were produced using matched metal tooling. This type of tooling has been successful at bonding small areas as long as the
exerted pressure is concentrated on the area where bonding is required. Finite element modeling is providing weight effect
solutions for titanium SPF/DB aerospace structures.
This paper was presented at the International Symposium on Superplasticity and Superplastic Forming, sponsored by the Manufacturing
Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium
was organized by Daniel G. Sanders, The Boeing Company. 相似文献
1000.
The wear resistance of plasma sprayed molybdenum blend coatings applicable to synchronizer rings or piston rings was investigated
in this study. Four spray powders, one of which was pure molybdenum and the others blended powders of bronze and aluminum-silicon
alloy powders mixed with molybdenum powders, were sprayed on a low-carbon steel substrate by atmospheric plasma spraying.
Microstructural analysis of the coatings showed that the phases formed during spraying were relatively homogeneously distributed
in the molybdenum matrix. The wear test results revealed that the wear rate of all the coatings increased with increasing
wear load and that the blended coatings exhibited better wear resistance than the pure molybdenum coating, although the hardness
was lower. In the pure molybdenum coatings, splats were readily fractured, or cracks were initiated between splats under high
wear loads, thereby leading to the decrease in wear resistance. On the other hand, the molybdenum coating blended with bronze
and aluminum-silicon alloy powders exhibited excellent wear resistance because hard phases such as CuAl2 and Cu9Al4 formed inside the coating. 相似文献