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Designing ultrastrong maraging stainless steels with improved uniform plastic strain via controlled precipitation of coherent nanoparticles

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Journal of Materials Science & technology 2021年第34期93卷 60-70页

作者： Z.H.Wang B.Niu Q.Wang C.Dong J.C.Jie t.M.Wang t.g.nieh Key Laboratory of Materials Modification by Laser Ion and Electron Beams(Ministry of Education)School of Materials Science and EngineeringDalian University of TechnologyDalian116024China Department of Materials Science and Engineering The University of TennesseeKnoxville37996TennesseeUSA

the development of ultrastrong maraging stainless steels(MSSs)is always in high ***,traditional high-strength MSSs generally exhibit early plastic instability with a low uniform strain since the precipitated nanoparticles are non-coherent with the body-centered-cubic(BCC)lath martensitic ***,we design a novel ultrahigh strength MSS(Fe-5.30 Cr-13.47 Ni-3.10 Al-1.22 Mo-0.50 W-0.23 Nb-0.03 C-0.005 B,wt.%)using a cluster formula approach.A fabulous microstructure consisting of a uniform distribution of high-density coherent B2-Ni Al nanoprecipitates(3-5 nm)in BCC martensitic matrix was successfully *** alloy has not only an exceedingly high ultimate tensile strength of 2.0 gPa,but also a decent uniform elongation of 4.2%-5.1%,which is almost triple of the value observed in existing *** present an in-depth discussion on the origins of ultrahigh strength and uniform plastic strain in the new alloy to validate our design strategy and further offer a new pathway to exploit highperformance MSSs.

关键词： Maraging stainless steel Ultrahigh strength Coherent precipitation Strengthening mechanisms Uniform deformation

Deformation of metallic glasses with special emphasis in supercooled liquid region

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中国有色金属学会会刊：英文版 2002年第4期12卷 726-733页

作者： t.g.nieh (Lawrence Livermore National Laboratory, L 350, PO Box 808, Livermore, CA 94551, USA) Lawrence Livermore National Laboratory 美国 Livermore CA 94551

Upon deforming a metallic glass at low temperatures, shear tends to localize and this leads to a brittle behavior. However, in the high temperature, and particularly in the supercooled liquid region, homogeneous deformation begins to take place. A bulk amorphous Zr 10Al 5ti 17.9Cu 14.6Ni alloy was observed to exhibit the Newtonian behavior at low strain rates but becomes non Newtonian at high strain rates in the supercooled liquid region. Structures of the amorphous material, both before and after deformation, were examined using X ray diffraction and high resolution electron microscopy. Results showed the presence of nanocrystallites in the deformed samples. thus, the non Newtonian behavior is attributable to the concurrent crystallization of the amorphous structure during deformation. A mechanistic model is presented to interpret the observed non Newtonian result. A phenomenological approach is also used to develop the deformation map for bulk metallic glasses in the supercooled liquid region.

关键词：非晶合金金属玻璃超塑性过度冷却液体层

Unveiling anneal hardening in dilute Al-doped Al_(x)CoCrFeMnNi(x = 0,0.1) high-entropy alloys

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Journal of Materials Science & technology 2021年第32期91卷 270-277页

作者： Q.Cheng X.D.Xu P.Xie L.L.Han J.Y.He X.Q.Li J.Zhang Z.t.Li Y.P.Li B.Liu t.g.nieh M.W.Chen J.H.Chen Centre for High Resolution Electron Microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China Applied Materials Physics Department of Materials Science and EngineeringKTH-Royal Institute of TechnologyStockholm SE10044Sweden Department of Materials Science and Engineering University of TennesseeKnoxvilleTN37996United States Department of Materials Science and Engineering Johns Hopkins UniversityBaltimoreMD 21214USA

Anneal hardening has been one of the approaches to improve mechanical properties of solid solution alloys with the face-centered cubic(FCC) structure,whereby a considerable strengthening can be attained by annealing of cold-worked alloys below the recrystallization temperature(t_(rx)).Microscopically,this hardening effect has been ascribed to several mechanisms,*** segregation to defects(dislocation and stacking fault) and short-range chemical ordering,***,none of these mechanisms can well explain the anneal hardening recently observed in phase-pure and coarse-grained FCC-structured high-entropy alloys(HEAs).Here we report the observations,using high-resolution electron channeling contrast imaging and transmission electron microscopy,of profuse and stable dislocation substructures in a cold-rolled CoCrFeMnNi HEA subject to an annealing below t_(rx).the dislocation substructures are observed to be thermally stable up to t_(rx),which could arise from the chemical complexity of the high-entropy system where certain elemental diffusion retardation *** microstructure feature is markedly different from that of conventional dilute solid solution alloys,in which dislocation substructures gradually vanish by recovery during annealing,leading to a strength ***,dilute addition of 2 at.% Al leads to a reduction in both microhardness and yield strength of the cold-rolled and subsequently annealed(≤500℃) *** Al induced softening effect,could be associated with the anisotropic formation of dislocation substructure,resulting from enhanced dislocation planar slip due to glide plane softening *** findings suggest that the strength of HEAs can be tailored through the anneal hardening effect from dislocation substructure strengthening.

关键词： Annealing hardening Dislocation substructure strengthening High-entropy alloy Solid solution structure

CONtROLLINg HIgHtEMPERAtURE DEFORMAtION BY VARYINg MICROStRUCtURE IN A ti47Al2Cr2Nb ALLOY

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中国有色金属学会会刊：英文版 1999年第S1期9卷 254-262页

作者： t.g.nieh and J.Wadsworth Lawrence Livermore National Laboratory, L-369, P.O.Box 808, Livermore, CA 94550, U.S.A.

A ti 47Al 2Cr 2Nb alloy was made by powder extrusion methods. By varying extrusion temperature, different microstructures were produced. At an extrusion temperature of 1 400 ℃ (above α transus), a uniform, fully lamellar structure was observed. In contrast, when powders were extruded at 1 150 ℃, an inhomogeneous microstructure consisting of γ,α 2 and metastable β phases was obtained. It was demonstrated that, while alloy extruded at 1 400 ℃ exhibited an excellent creep resistance, alloy with the same composition extruded at 1 150 ℃ exhibited superplasticity. the good creep resistance was resulted from the presence of fine lamellae which restrict dislocation slip within γ grains. these fine lamellae also promote the nucleation of deformation twins which impede dislocation glide along the interfaces ( γ/γ and γ/α 2) and, thus, reduces creep rate. In the case of low temperature extrusion, an elongation value of over 300% was obtained at a strain rate of 2×10 -5 s -1 and at a temperature as low as 800 ℃, which is close to the ductile to brittle transition temperature. this is in contrast to the prior major observations of superplastic behaviors in tiAl in which typical temperatures of 1 000 ℃ have usually been required for superplasticity. It was proposed that the occurrence of superplasticity at 800 ℃ is caused by the presence of a B2 phase which, during superplastic deformation (grain boundary sliding), accommodates sliding strains to reduce the propensity for cavitation at grain triple junctions and, thus, delays the fracture process.

关键词： ti 47Al 2Cr 2Nb alloy microstructures high temperature deformation

金属基复合材料中高应变速率超塑性的流变学观点

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铝加工 1993年第4期16卷 52-54页

作者： t.g.nieh J.Wadsworth 章四琪

超塑成形是实用而有效的制造技术。然而,超塑性变形速率低,典型速率为10-5～10-3S-1,是其存在的主要问题之一。最近的一些研究表明,以非常高的应变速率(大于10-1S-1,最高达102S-1)也能出现超塑性。一特定实例是应变速率为lS-1时,抗拉伸... 详细信息

超塑成形是实用而有效的制造技术。然而,超塑性变形速率低,典型速率为10-5～10-3S-1,是其存在的主要问题之一。最近的一些研究表明,以非常高的应变速率(大于10-1S-1,最高达102S-1)也能出现超塑性。一特定实例是应变速率为lS-1时,抗拉伸长率超过1250％。迄今,由本文作者发现的这种高应变速率超塑性（HSRS）现象,在某些材料中已有报导,这类材料包括金属合金。

关键词：超塑性高应变速率金属基复合材料超塑成形伸长率变形速率金属合金固相线温度基体合金固态材料

EFFECtS OF ALLOYINg ELEMENtS ON CREEP OF tiAl ALLOYS WItH FINELAMELLAR StRUCtURES

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中国有色金属学会会刊：英文版 1999年第S1期9卷 263-273页

作者： J.N.Wang, B.Y.Huang and t.g.nieh  National Key Laboratory for Powder Metallurgy, Central South University of technology, Changsha 410083, China  Lawrence Livermore National Laboratory, P.O.Box 808, Livermore, CA 94550, U.S.A.

Creep experiments have been conducted on five powder metallurgy tiAl alloys with fine grains (65～80 μm), fine lamellar spacings (0.1～0.16 μm), and different compositions [ti 47Al(+Cr, Nb, ta, W, Si)] at temperatures of 760 ℃ and 815 ℃ and stresses from 35 to 723 MPa. Results show that at a given lamellar spacing 1% Nb(mole fraction) with 1% ta and replacing 0.2% ta with 0.2% W induced little effect, but addition of 0.3% Si decreased the creep resistance by a factor of 3～4 under otherwise identical conditions. these different effects of different alloying elements are interpreted in terms of the interaction of alloy segregants with misfit and/or misorientaion dislocations at the lamellar interface. that is, the interaction retards or facilitates the climb of interfacial dislocations, which is rate controlling during creep, depending on the size of the segregants relative to the host atoms.

关键词： tiAl alloys fine lamellar structures creep alloying elements

Calculations and Sensitivity Analysis of Chlorine-,NO_(x)-,and Bromine-Depleting Cycles of Stratospheric Ozone

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Journal of Environmental Science and Engineering(B) 2024年第2期13卷 53-69页

作者： Ibraheem Alelmi Sen nieh Department of Mechanical Engineering the Catholic University of AmericaWashington DC 20064the United States College of Engineering Yuan Ze UniversityTaoyuan 32003Taiwan

this paper presents an engineering system approach using a 2D model of conservation of mass to study the dynamics of ozone and concerned chemical species in the *** considering all fourteen photolysis,ozone-generating,and-depleting chemical reactions,the model calculated the transient,spatial changes of ozone under different physical-chemical-radiative *** against the measured data demonstrated good accuracy,close match of our model with the observed ozone concentrations at both 20°S and 90°N *** deviation in the average concentration was less than 1% and in ozone profiles less than 17%.the impacts of various chlorine-(Cl),nitrogen oxides-(NO_(x)),and bromine-(Br)depleting cycles on ozone concentrations and distribution were *** chlorine catalytic depleting cycle was found to exhibit the most significant impact on ozone dynamics,confirming the key role of chlorine in the problem of ozone *** analysis was conducted with levels of 25%,50%,100%,200%,and 400% of the baseline *** combined cycles(Cl+NO_(x)+Br)showed the most significant influence on ozone *** total ozone abundance above the South Pole could decrease by a small 3%,from 281 DU(Dubson Units)to 273 DU for the 25% level,or by a huge thinning of 60%to 114 DU for the 400% concentration *** the level of chlorine gases increased beyond 200%,it would cause ozone depletion to a level of ozone hole(below 220 DU).the 2D Ozone Model presented in this paper demonstrates robustness,convenience,efficiency,and executability for analyzing complex ozone phenomena in the stratosphere.

关键词： Ozone depletion 2-D model chlorine bromine nitrogen oxides sensitivity analysis total ozone abundance DU

Effects of Chlorine and Chlorine Monoxide on Stratospheric Ozone Depletion

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Atmospheric and Climate Sciences 2024年第1期14卷 136-153页

作者： Laurie Wei Ibraheem Alelmi Sen nieh Department of Mechanical Engineering The Catholic University of America Washington DC USA

this paper presents a system approach of mass balance calculations of ozone and other species under diffusion-convection-reaction processes to study the impacts of major ozone-depleting chemicals, chlorine (Cl) and chlorine monoxide (ClO), and the effect of photolysis on ozone concentrations, ozone depletion, total ozone abundance, and ozone layer along the altitude in the stratosphere. the calculated ozone concentrations and profile of the layer followed a similar trend and were generally in good agreement with the measurements above the tropical area. the calculated peak of the layer was at the same mid-stratosphere at Z = 30 km with a peak concentration and total ozone abundance about 20% higher than the measured peak concentration of 8.0 ppm and total abundance of 399 DU. In the presence of Cl and ClO, the calculated ozone concentrations and total abundance were substantially reduced. Cl generally depleted more uniformly of ozone across the altitude, while ClO reduced substantially the ozone in the upper stratosphere and thus shifted the peak of the layer to a much lower elevation at Z = 14 km. Although both ClO and Cl are active ozone-depleting chemicals, ClO was found to have a more pronounced impact on ozone depletion and distribution than Cl. the possible explanations of these interesting phenomena were discussed and elaborated. the approach and calculations in this paper were shown to be useful in providing an initial insight into the structure and behavior of the complex ozone layer.

关键词： Ozone Ozone Depletion Chlorine Chlorine Monoxide Photolysis Dobson Unit

2-D Modeling and Calculations of Stratospheric Ozone and Influences of Convection, Diffusion, and time

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Atmospheric and Climate Sciences 2024年第2期14卷 250-276页

作者： Ibraheem Alelmi Laurie Wei Sen nieh Department of Mechanical Engineering The Catholic University of America Washington DC USA School of Engineering The Catholic University of America Washington DC USA College of Engineering Yuan Ze University Taoyuan

An engineering system approach of 2-D cylindrical model of transient mass balance calculations of ozone and other concerned chemicals along with fourteen photolysis, ozone-generating and ozone-depleting chemical reaction equations was developed, validated, and used for studying the ozone concentrations, distribution and peak of the layer, ozone depletion and total ozone abundance in the stratosphere. the calculated ozone concentrations and profile at both the Equator and a 60˚N location were found to follow closely with the measured data. the calculated average ozone concentration was within 1% of the measured average, and the deviation of ozone profiles was within 14%. the monthly evolution of stratospheric ozone concentrations and distribution above the Equator was studied with results discussed in details. the influences of slow air movement in both altitudinal and radial directions on ozone concentrations and profile in the stratosphere were explored and discussed. Parametric studies of the influences of gas diffusivities of ozone DO3 and active atomic oxygen DO on ozone concentrations and distributions were also studied and delineated. Having both influences through physical diffusion and chemical reactions, the diffusivity (and diffusion) of atomic oxygen DO was found to be more sensitive and important than that of ozone DO3 on ozone concentrations and distribution. the 2-D ozone model present in this paper for stratospheric ozone and its layer and depletion is shown to be robust, convenient, efficient, and executable for analyzing the complex ozone phenomena in the stratosphere. .

关键词： Stratospheric Ozone 2-D Model Ozone Layer Ozone Depletion Convection Diffusion