450 research outputs found
Dynamic and Postdeformation Recrystallization of Nuclear-Grade 316LN Stainless Steel
Nuclear-grade 316LN stainless steel was subjected to single and double compressions at 1173β1473 K and strain rates of 0.01β10 sβ»ΒΉ. The dynamic and postdeformation recrystallization was investigated through analysis of the stressβstrain curves and microstructure evolution. The thermal deformation equation and the quantitative relationships between the critical stress for the initiation of dynamic recrystallization and the ZenerβHollomon parameter, Z, and between the dynamic recrystallization grain size D and Z were derived. Dynamic recrystallization developed through an ordinary mechanism at low Z values and through a necklace mechanism at high Z values, with a critical Z value of about 3.6 10ΒΉβΆ . At 1273β1473 K, softening of 316LN stainless steel after deformation was characterized by an Avrami-type equation, where the Avrami parameter, n, has no appreciable temperature dependence, and an average value of n and the activation energy, Qrex , were 0.68 and 129 kJ/mol, respectively.ΠΠ΅ΡΠΆΠ°Π²Π΅ΡΡΠ°Ρ ΡΡΠ°Π»Ρ 316LN ΡΠ΄Π΅ΡΠ½ΠΎΠ³ΠΎ ΠΊΠ»Π°ΡΡΠ° ΠΏΠΎΠ΄Π²Π΅ΡΠ³Π°Π»Π°ΡΡ ΠΎΠ΄Π½ΠΎ- ΠΈ Π΄Π²ΡΠΊΡΠ°ΡΠ½ΠΎΠΌΡ ΡΠΆΠ°ΡΠΈΡ ΠΏΡΠΈ 1173...1473 Π ΠΈ ΡΠΊΠΎΡΠΎΡΡΠΈ Π΄Π΅ΡΠΎΡΠΌΠ°ΡΠΈΠΈ 0,01...10 Ρβ»ΒΉ. ΠΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠ°Ρ ΠΈ ΠΏΠΎΡΡΠ΄Π΅ΡΠΎΡΠΌΠ°ΡΠΈΠΎΠ½Π½Π°Ρ ΡΠ΅ΠΊΡΠΈΡΡΠ°Π»Π»ΠΈΠ·Π°ΡΠΈΡ ΠΈΠ·ΡΡΠ°Π»Π°ΡΡ Ρ ΠΏΠΎΠΌΠΎΡΡΡ Π°Π½Π°Π»ΠΈΠ·Π° Π·Π°Π²ΠΈΡΠΈΠΌΠΎΡΡΠΈ Π΄Π΅ΡΠΎΡΠΌΠ°ΡΠΈΠΈ ΠΎΡ Π½Π°ΠΏΡΡΠΆΠ΅Π½ΠΈΡ ΠΈ ΡΠ°Π·Π²ΠΈΡΠΈΡ ΠΌΠΈΠΊΡΠΎΡΡΡΡΠΊΡΡΡΡ. ΠΡΠ»ΠΈ Π²ΡΠ²Π΅Π΄Π΅Π½Ρ ΡΡΠ°Π²Π½Π΅Π½ΠΈΠ΅ ΡΠ΅ΠΏΠ»ΠΎΠ²ΠΎΠΉ Π΄Π΅ΡΠΎΡΠΌΠ°ΡΠΈΠΈ ΠΈ ΠΊΠΎΠ»ΠΈΡΠ΅ΡΡΠ²Π΅Π½Π½ΡΠ΅ Π·Π°Π²ΠΈΡΠΈΠΌΠΎΡΡΠΈ ΠΌΠ΅ΠΆΠ΄Ρ ΠΊΡΠΈΡΠΈΡΠ΅ΡΠΊΠΈΠΌ Π½Π°ΠΏΡΡΠΆΠ΅Π½ΠΈΠ΅ΠΌ ΠΈΠ½ΠΈΡΠΈΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΎΠΉ ΡΠ΅ΠΊΡΠΈΡΡΠ°Π»Π»ΠΈΠ·Π°ΡΠΈΠΈ ΠΈ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠΎΠΌ ΠΠ΅Π½Π΅ΡΠ° Π₯ΠΎΠ»Π»ΠΎΠΌΠΎΠ½Π° Z, Π° ΡΠ°ΠΊΠΆΠ΅ ΠΌΠ΅ΠΆΠ΄Ρ ΡΠ°Π·ΠΌΠ΅ΡΠΎΠΌ Π·Π΅ΡΠ½Π° D ΠΏΡΠΈ Π΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΎΠΉ ΡΠ΅ΠΊΡΠΈΡΡΠ°Π»Π»ΠΈΠ·Π°ΡΠΈΠΈ ΠΈ Z. ΠΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠ°Ρ ΡΠ΅ΠΊΡΠΈΡΡΠ°Π»Π»ΠΈΠ·Π°ΡΠΈΡ ΡΠ°Π·Π²ΠΈΠ²Π°Π»Π°ΡΡ ΠΏΠΎ ΠΎΠ±ΡΡΠ½ΠΎΠΌΡ ΠΌΠ΅Ρ
Π°Π½ΠΈΠ·ΠΌΡ ΠΏΡΠΈ Π½ΠΈΠ·ΠΊΠΈΡ
Π·Π½Π°ΡΠ΅Π½ΠΈΡΡ
Z ΠΈ ΠΏΠΎ ΠΌΠ΅Ρ
Π°Π½ΠΈΠ·ΠΌΡ ΠΎΠΆΠ΅ΡΠ΅Π»ΡΡ ΠΏΡΠΈ Π²ΡΡΠΎΠΊΠΈΡ
Π·Π½Π°ΡΠ΅Π½ΠΈΡΡ
Z, ΠΏΡΠΈ ΠΊΡΠΈΡΠΈΡΠ΅ΡΠΊΠΎΠΌ Π·Π½Π°ΡΠ΅Π½ΠΈΠΈ Z ΠΏΡΠΈΠΌΠ΅ΡΠ½ΠΎ 3 6 10ΒΉβΆ. ΠΡΠΈ 1273...1473 Π ΡΠ°Π·ΡΠΏΡΠΎΡΠ½Π΅Π½ΠΈΠ΅ Π½Π΅ΡΠΆΠ°Π²Π΅ΡΡΠ΅ΠΉ ΡΡΠ°Π»ΠΈ 316LN ΠΏΠΎΡΠ»Π΅ Π΄Π΅ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΎΠΏΠΈΡΡΠ²Π°Π΅ΡΡΡ ΡΡΠ°Π²Π½Π΅Π½ΠΈΠ΅ΠΌ ΠΠ²ΡΠ°ΠΌΠΈ, Π³Π΄Π΅ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡ ΠΠ²ΡΠ°ΠΌΠΈ n Π½Π΅ ΠΏΡΠΎΡΠ²Π»ΡΠ΅Ρ Π²ΡΡΠ°ΠΆΠ΅Π½Π½ΠΎΠΉ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ½ΠΎΠΉ Π·Π°Π²ΠΈΡΠΈΠΌΠΎΡΡΠΈ, Π° Π΅Π³ΠΎ ΡΡΠ΅Π΄Π½Π΅Π΅ Π·Π½Π°ΡΠ΅Π½ΠΈΠ΅ ΠΈ ΡΠ½Π΅ΡΠ³ΠΈΡ Π°ΠΊΡΠΈΠ²Π°ΡΠΈΠΈ Qrex ΡΠΎΡΡΠ°Π²Π»ΡΡΡ 0,68 ΠΈ 129 ΠΊΠΠΆ/ΠΌΠΎΠ»Ρ ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²Π΅Π½Π½ΠΎ
Gold slows down the growth of helium bubble in iron
We predict by first-principles calculations that Au have strong affinity to
He in bcc Fe. The Au-Au bonding in the segregated Au layer at the He bubble
surface is stronger than Fe-Fe and Au-Fe interactions; therefore this layer
becomes an effective barrier to further He and slows down the bubble growth.Comment: 9 pages, 4 figures, 1 tabl
Combined effect of rapid nitriding and plastic deformation on the surface strength, toughness and wear resistance of steel 38CrMoAlA
Carbonaceous nanomaterial reinforced Ti-6Al-4V matrix composites: Properties, interfacial structures and strengthening mechanisms
For conventional titanium matrix composites (TiMCs), there is always a trade-off issue between enhanced strength and ductility of these materials. In this study, we explore a new design methodology by reinforcing titanium alloy matrix with carbonaceous nanomaterials and investigate the mechanisms for achieving a good balance of their strength and ductility. The TiMCs were synthesized through a low-cost powder metallurgy route using pre-mixed Ti-6Al-4V (TC4) powders and various carbon based nanofillers, including graphite powders (GPs), graphene oxide nanosheets (GONs) and graphene nanoplates (GNPs), and were further rolled at a temperature of 1173 K with a deformation of 66.7%. Among these three types of carbon reinforcing sources, the GNPs are more easily reacted with TC4 matrix and form more contents of TiC phases after sintering owing to their larger amounts of defects than those of the GPs and GONs. TiC products are identified to play a bridging role for not only connecting the TC4 matrix but also forming coherent interfaces with the TC4 matrix, thus facilitating a strong interfacial bonding of the composites. The as-rolled GNPs/TC4 composites exhibit a 0.2% yield strength of 1146.36 MPa (with an elongation of βΌ8.1%), which is 24.6%, 9.22% and 5.62% higher than those of pure TC4, GPs/TC4 and GONs/TC4 composites. The GNPs/TC4 nanocomposites show a better balance of strength and ductility than those of the other two types of nanocomposites. The synergetic strengthening mechanisms are identified to be Orowan strengthening effect, effective load transfer capability of GNPs, and in-situ formation of interfacial TiC structures, which provide optimum interfacial microstructures to achieve good mechanical properties of the TiMCs
Analysis of Gas Nitriding Characteristics under Different Cold Hardening and Nitriding Pressure Conditions for Low-Carbon Low-Alloy Steel
A new approach to quick preparation of a nitrided case for low-carbon low-alloy steels was proposed. It is based on cold hardening and pressurized gas nitriding. The microstructure, surface hardness, thickness, and corrosion resistance of the nitrided layer on low-carbon low-alloy steel (20CrMnTi) were investigated after the nitriding at 510Β°C for 5 h under different cold rolling reduction (0β60% CR) and nitriding pressure (1β5 atm).ΠΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½ Π½ΠΎΠ²ΡΠΉ ΡΠΏΠΎΡΠΎΠ± ΠΏΠΎΠ»ΡΡΠ΅Π½ΠΈΡ Π°Π·ΠΎΡΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ³ΠΎ ΡΠ»ΠΎΡ Π½Π° ΠΌΠ°Π»ΠΎΡΠ³Π»Π΅ΡΠΎΠ΄ΠΈΡΡΡΡ
Π½ΠΈΠ·ΠΊΠΎΠ»Π΅Π³ΠΈΡΠΎΠ²Π°Π½Π½ΡΡ
ΡΡΠ°Π»ΡΡ
Ρ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ Ρ
ΠΎΠ»ΠΎΠ΄Π½ΠΎΠ³ΠΎ Π΄Π΅ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΈ Π³Π°Π·ΠΎΠ²ΠΎΠ³ΠΎ Π°Π·ΠΎΡΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π΄Π°Π²Π»Π΅Π½ΠΈΠ΅ΠΌ. ΠΠ·ΡΡΠ΅Π½Ρ ΠΌΠΈΠΊΡΠΎΡΡΡΡΠΊΡΡΡΠ°, ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠ½Π°Ρ ΡΠ²Π΅ΡΠ΄ΠΎΡΡΡ, ΡΠΎΠ»ΡΠΈΠ½Π° ΠΈ ΠΊΠΎΡΡΠΎΠ·ΠΈΠΎΠ½Π½Π°Ρ ΡΡΠΎΠΉΠΊΠΎΡΡΡ Π°Π·ΠΎΡΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ³ΠΎ ΡΠ»ΠΎΡ Π½Π° ΡΡΠ°Π»ΠΈ 20CrMnTi ΠΏΠΎΡΠ»Π΅ Π°Π·ΠΎΡΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΏΡΠΈ 510Β°Π‘ Π² ΡΠ΅ΡΠ΅Π½ΠΈΠ΅ 5 Ρ Π² ΡΠ°Π·Π»ΠΈΡΠ½ΡΡ
ΡΡΠ»ΠΎΠ²ΠΈΡΡ
ΠΎΠ±ΠΆΠ°ΡΠΈΡ ΠΏΡΠΈ Ρ
ΠΎΠ»ΠΎΠ΄Π½ΠΎΠΉ ΠΏΡΠΎΠΊΠ°ΡΠΊΠ΅ (0-60% Π‘R) ΠΈ Π΄Π°Π²Π»Π΅Π½ΠΈΠΈ Π°Π·ΠΎΡΠΈΡΠΎΠ²Π°Π½ΠΈΡ (1-5 Π°ΡΠΌ)
Interface engineering of graphene/copper matrix composites decorated with tungsten carbide for enhanced physico-mechanical properties
For metal matrix composites (MMCs), introduction of low-dimensional nano-carbon materials (NCMs) into three dimensional metallic matrix is commonly applied to enhance mechanical and physical properties of metals and thus significantly extend their wide range applications. However, the interfaces between the NCMs and metal matrix are always a major issue for achieving the best enhancement effects. In this paper, we investigated interfacial structures of graphene nanoplates (GNPs) reinforced Cu matrix composites fabricated using a simple and industrially scalable strategy, through integration of interface engineering design methodology and a spark plasma sintering (SPS) process. We then systematically evaluated their physico-mechanical properties, interfacial characteristics and strengthening mechanisms. The in-situ formed WxCy nano-layers and carbide nanoparticles on the surfaces of GNPs and near the interfaces of Cu grains promote strong interfacial bonding and improves the cohesive strength of Cu based nanocomposites. The GNPs-W/Cu composites show a good balance between strength and electrical conductivity. Their 0.2% yield strength and ultimate tensile strength have been improved up to 239.13% (112.73%) and 197.76% (72.51%), respectively, when compared with those of pure copper (or GNPs/Cu composites). Electrical conductivity of GNPs-W/Cu composites shows no apparent changes after the addition of the GNPs. The dislocation strengthening, refinement strengthening and load transfer strengthening were achieved simultaneously through the engineered interfaces in GNPs-W/Cu matrix composites. This work has provided a new strategy to fabricate high-performance NCMs enhanced MMCs by using the interface engineering methodology
The Random Quadratic Assignment Problem
Optimal assignment of classes to classrooms \cite{dickey}, design of DNA
microarrays \cite{carvalho}, cross species gene analysis \cite{kolar}, creation
of hospital layouts cite{elshafei}, and assignment of components to locations
on circuit boards \cite{steinberg} are a few of the many problems which have
been formulated as a quadratic assignment problem (QAP). Originally formulated
in 1957, the QAP is one of the most difficult of all combinatorial optimization
problems. Here, we use statistical mechanical methods to study the asymptotic
behavior of problems in which the entries of at least one of the two matrices
that specify the problem are chosen from a random distribution .
Surprisingly, this case has not been studied before using statistical methods
despite the fact that the QAP was first proposed over 50 years ago
\cite{Koopmans}. We find simple forms for and , the
costs of the minimal and maximum solutions respectively. Notable features of
our results are the symmetry of the results for and
and the dependence on only through its mean and standard deviation,
independent of the details of . After the asymptotic cost is determined for
a given QAP problem, one can straightforwardly calculate the asymptotic cost of
a QAP problem specified with a different random distribution
Production and Decay of D_1(2420)^0 and D_2^*(2460)^0
We have investigated and final states and
observed the two established charmed mesons, the with mass
MeV/c and width MeV/c and
the with mass MeV/c and width
MeV/c. Properties of these final states, including
their decay angular distributions and spin-parity assignments, have been
studied. We identify these two mesons as the doublet predicted
by HQET. We also obtain constraints on {\footnotesize } as a function of the cosine of the relative phase of the two
amplitudes in the decay.Comment: 15 pages in REVTEX format. hardcopies with figures can be obtained by
sending mail to: [email protected]
Measurement of the branching fraction for
We have studied the leptonic decay of the resonance into tau
pairs using the CLEO II detector. A clean sample of tau pair events is
identified via events containing two charged particles where exactly one of the
particles is an identified electron. We find . The result is consistent with
expectations from lepton universality.Comment: 9 pages, RevTeX, two Postscript figures available upon request, CLNS
94/1297, CLEO 94-20 (submitted to Physics Letters B
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