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Laminated metal composite formed from low flow stress layers and high flow stress layers using flow constraining elements and method of making same

Description: This invention relates to a laminated metal composite, comprising alternating layers of low flow stress material and high flow stress material, and formed using flow constraining elements around each low flow stress layer; and a method of making same. A composite is a combination of at least two chemically distinct materials with a distinct interface separating the two materials. A metal matrix composite (MMC) is a composite material composed of a metal and a nonmetallic reinforcing agent such as silicon carbide (SiC) or graphite in continuous or discontinuous fiber, whisker, or discrete particulate form. A laminate is a material composed of several bonded layers. It is possible to have a laminate composed of multi-layers of a single type of material bonded to each other. However, such a laminate would not be considered to be a composite. The term {open_quotes}laminated metal composite{close_quotes} (LMC), as used herein, is intended to include a structural material composed of: (1) layers of metal or metal alloys interleaved with (2) a different metal, a metal alloy, or a metal matrix composite (MMC) containing strengthening agents.
Date: December 31, 1994
Creator: Syn, C.K. & Lesuer, D.R.
Partner: UNT Libraries Government Documents Department

Advances in the heat treatment of steels

Description: A number of important recent advances in the processing of steels have resulted from the sophisticated uses of heat treatment to tailor the microstructure of the steels so that desirable properties are established. These new heat treatments often involve the tempering or annealing of the steel to accompish a partial or complete reversion from martensite to austenite. The influence of these reversion heat treatments on the product microstructure and its properties may be systematically discussed in terms of the heat treating temperature in relation to the phase diagram. From this perspective, four characteristic heat treatments are defined: (1) normal tempering, (2) inter-critical tempering, (3) intercritical annealing, and (4) austenite reversion. The reactions occurring during each of these treatments are described and the nature and properties of typical product microstructures discussed, with specific reference to new commercial or laboratory steels having useful and exceptional properties.
Date: June 1, 1978
Creator: Morris, J.W. Jr.; Kim, J.I. & Syn, C.K.
Partner: UNT Libraries Government Documents Department

Influence of Iron Oxide Particles on the Strength of Ball-Milled Iron

Description: Detailed microstructural and mechanical property studies of ball-milled iron, in the powder and consolidated states, are reviewed and assessed. The analyses cover three and one-half orders of magnitude of grain size (from 6 nm to 20 mm) and focus on the influence of oxide particles on the strength. The study includes the early work of Koch and Yang, Kimura and Takaki and continues with the more recent work of Umemoto et al and Belyakov, Sakai et al. It is shown that the major contributors to strength are the nanooxide particles. These particles are created by adiabatic shear banding during ball-milling leading to a bimodal distribution of particles. The predicted strength from particles, {sigma}{sub p}, is given by {sigma}{sub p} = B {center_dot} (D*{sub S}){sup -1/2} where D*{sub S} is the surface-to-surface interparticle spacing, and B = 395 MPa {center_dot} {micro}m{sup -1/2}. A model is proposed that accounts for the influence of the bimodal particle size distribution on strength.
Date: December 7, 2005
Creator: Lesuer, D R; Syn, C K & Sherby, O D
Partner: UNT Libraries Government Documents Department

Nano-subgrain Strengthening in Ball-milled Iron

Description: The strength and deformation behavior of ball-milled, iron-base materials containing nano-scale subgrains have been evaluated. As reported by several authors, nanosubgrains form during the early stages of ball milling as a result of severe plastic deformation inherent in the ball milling process. The strength for these nano-scale subgrains are compared with the strength of larger-scale subgrains in iron and iron-base alloys produced by traditional mechanical working. The data covers over 2 orders of magnitude in subgrain size (from 30 nm to 6 {micro}m) and shows a continuous pattern of behavior. For all materials studied, the strength varied as {lambda}{sup -1}, where {lambda} is the subgrain size. Strengthening from subgrains was found to breakdown at a much smaller subgrain size than strengthening from grains. In addition, the ball-milled materials showed significant strengthening contributions from nano-scale oxide particles. Shear bands are developed during testing of ball-milled materials containing ultra-fine subgrains. A model for shear band development in nano-scale subgrains during deformation has also been developed. The model predicts a strain state of uniaxial compression in the shear band with a strain of -1.24. Subgrains are shown to offer the opportunity for high strength and good work hardening with the absence of yield point behavior.
Date: March 23, 2006
Creator: Lesuer, D R; Syn, C K & Sherby, O D
Partner: UNT Libraries Government Documents Department

MICROSTRUCTURE IN ADIABATIC SHEAR BANDS IN A PEARLITIC ULTRAHIGH CARBON STEEL

Description: Adiabatic shear bands, obtained in compression deformation at a strain rate of 4000 s{sup -1}, in a pearlitic 1.3%C steel, were investigated. Shear-bands initiated at 55% compression deformation with the width of the band equal to 14 {micro}m. Nano-indentor hardness of the shear band was 11.5 GPa in contrast to the initial matrix hardness of 3.5 GPa. The high strength of the shear band is attributed to its creation from two sequential events. First, large strain deformation, at a high strain rate, accompanied by adiabatic heating, led to phase transformation to austenite. Second, retransformation upon rapid cooling occurred by a divorced eutectoid transformation. The result is a predicted microstructure consisting of nano-size carbide particles within a matrix of fine ferrite grains. It is proposed that the divorced eutectoid transformation occurs in iron-carbon steels during high rate deformation in ball milling, ball drop tests and in commercial wire drawing.
Date: September 22, 2003
Creator: Syn, C K; Lesuer, D R & Sherby, O D
Partner: UNT Libraries Government Documents Department

Mechanical behavior of ultrahigh strength ultrahigh carbon steel wire and rod

Description: Ultrahigh-carbon steels (UHCSS) can achieve very high strengths in wire or rod form. These high strengths result from the mechanical work introduced during wire and rod processing. These strengths have been observed to increase with carbon content. In wire form, tensile strengths approaching 6000 MPa are predicted for UHCS containing 1. 8%C. In this paper, we will discuss the influence of processing (including rapid transformation during wire patenting) and micros ct- ure on the mechanical behavior of UHCS wire. The tensile properties of as- extruded rods are described as a function of extrusion temperature and composition. For spheroidized steels, yield and ultimate tensile strength are a function of grain size, interparticle spacing and particle size. For pearlitic steels, yield and ultimate strength were found to be functions of colony size, carbide size and plate spacing and orientation. Alloying additions (such as C, Cr, Si, Al and Co) can influence the effect of processing on these microstructural features. For spheroidized steels, fracture was found to be a function of the size of coarse carbides and of composition.
Date: July 22, 1997
Creator: Lesuer, D.R.; Syn, C.K.; Sberby, O.D. & Whittenherger, W.D.
Partner: UNT Libraries Government Documents Department

Damage initiation and propagation in metal laminates

Description: The metal laminates proposed here for aircraft structures are Al alloy interlayers between Al alloy based metal matrix composite (MMC) plates reinforced with Si carbide particles. Properties to be tailored for jet engine fan containment and wing and auxiliary support structures include the important property fracture toughness. A method was developed for simulating and predicting crack initiation/growth using finite element analysis and fracture mechanics. An important key in predicting the failure is the tie- break slideline with prescribed (chosen based on J Integral calculations) effective plastic strain to failure in elements along the slideline. More development of the method is needed, particularly in its correlation with experimental data from various fracture toughness and strength tests of metal laminates. Results show that delamination at the interface of the ductile interlayer and MMC material can add significantly to the energy required to propagate a crack through a metal laminate. 11 figs, 7 refs.
Date: July 26, 1996
Creator: Riddle, R.A.; Lesuer, D.R. & Syn, C.K.
Partner: UNT Libraries Government Documents Department

Thermo-Mechanical Processing and Properties of a Ductile Iron

Description: Thermo-mechanical processing of ductile irons is a potential method for enhancing their mechanical properties. A ductile cast iron containing 3.6% C, 2.6% Si and 0.045% Mg was continuously hot-and-warm rolled or one-step press-forged from a temperature in the austenite range (900{degrees}C-1100{degrees}C) to a temperature below the A, temperature. Various amounts of reduction were used (from 60% to more than 90%) followed by a short heat ent at 600`C. The heat ent lead to a structure of fine graphite in a matrix of ferrite and carbides. The hot-and- warm worked materials developed a pearlitic microstructure while the press-forged material developed a spheroidite-like carbide microstructure in the matrix. Cementite-denuded ferrite zones were developed around graphite stringers in the hot-and-warm worked materials, but such zones were absent in the press-forged material. Tensile properties including tensile strength and total elongation were measured along the direction parallel and transverse to the rolling direction and along the direction transverse to the press-forging direction. The tensile ductility and strength both increased with a decrease in the amount of hot-and-warm working. The press- forged materials showed higher strength (645 MPa) than the hot-and-warrn worked materials (575 MPa) when compared at the same ductility level (22% elongation).
Date: July 14, 1997
Creator: Syn, C.K.; Lesuer, R.R. & Sherby, O.D.
Partner: UNT Libraries Government Documents Department

Ultrahigh carbon steel for automotive applications

Description: Ultrahigh carbon steels (UHCSs), which contain 1--2.1% carbon, have remarkable structural properties for automotive application when processed to achieve fine ferrite grains with fine spheroidized carbides. When processed for high room temperature ductility, UHCS can have good tensile ductility but significantly higher strength than current automotive high strength steels. The material can also be made superplastic at intermediate temperatures and exhibits excellent die fill capability. Furthermore, they can be made hard with high compression ductility. In wire form it is projected that UHCS can exhibit extremely high strengths (5,000 MPa) for tire cord applications. Examples of structural components that have been formed from fine-grained spheroidized UHCSs are illustrated.
Date: December 4, 1995
Creator: Lesuer, D.R.; Syn, C.K. & Sherby, O.D.
Partner: UNT Libraries Government Documents Department

Creep fracture during solute-drag creep and superplastic deformation

Description: Creep fracture behavior has been studied in Al-Mg and Al-Mg-Mn alloys undergoing solute-drag creep and in microduplex stainless steel undergoing both solute-drag creep and superplastic deformation. Failure in these materials is found to be controlled by two mechanisms, neck formation and cavitation. The mechanism of creep fracture during solute-drag creep in Al-Mg is found to change from necking-controlled fracture to cavitation-controlled fracture as Mn content is increased. Binary Al-Mg material fails by neck formation during solute-drag creep, and cavities are formed primarily in the neck region due to high hydrostatic stresses. Ternary alloys of Al-Mg- Mn containing 0.25 and 0.50 wt % Mn exhibit more uniform cavitation, with the 0.50 Mn alloy clearly failing by cavity interlinkage. Failure in the microduplex stainless steel is dominated by neck formation during solute-drag creep deformation but is controlled by cavity growth and interlinkage during superplastic deformation. Cavitation was measured at several strains, and found to increase as an exponential function of strain. An important aspect of cavity growth in the stainless steel is the long latency time before significant cavitation occurs. For a short latency period, cavitation acts to significantly reduce ductility below that allowed by neck growth alone. This effect is most pronounced in materials with a high strain-rate sensitivity, for which neck growth occurs very slowly.
Date: October 1, 1996
Creator: Taleff, E.M.; Lesuer, D.R.; Syn, C.K. & Henshall, G.A.
Partner: UNT Libraries Government Documents Department

Processing and mechanical behavior of hypereutectoid steel wires

Description: Hypereutectoid steels have the potential for dramatically increasing the strength of wire used in tire cord and in other high strength wire applications. The basis for this possible breakthrough is the elimination of a brittle proeutectoid network that can form along grain boundaries if appropriate processing procedures and alloy additions are used. A review is made of work done by Japanese and other researchers on eutectoid and mildly hypereutectoid wires. A linear extrapolation of the tensile strength of fine wires predicts higher strengths at higher carbon contents. The influence of processing, alloy additions and carbon content in optimizing the strength, ductility and fracture behavior of hypereutectoid steels is presented. It is proposed that the tensile strength of pearlitic wires is dictated by the fracture strength of the carbide lamella at grain boundary locations in the carbide. Methods to improve the strength of carbide grain boundaries and to decrease the carbide plate thickness will contribute to enhancing the ultrahigh strength obtainable in hypereutectoid steel wires. 23 refs., 13 figs., 1 tab.
Date: June 25, 1996
Creator: Lesuer, D.R.; Syn, C.K.; Sherby, O.D. & Kim, D.K.
Partner: UNT Libraries Government Documents Department

Superplastic deformation in two microduplex stainless steels

Description: The deformation behavior and mechanisms of superplastic flow in two microduplex stainless steels (SuperDux64 and Nitronic 19D) were studied at {similar_to}0.7T{sub m}. The two steels differed in initial grain size by a factor of 3. Both steels exhibited solute-drag-controlled grain boundary sliding in a high temperature {gamma}+{delta} phase field. In a lower temperature {gamma}+{sigma} phase field, the fine-grained steel ({bar L}=5{mu}m) exhibited climb-controlled grain boundary sliding and the coarser- grained steel ({bar L}=15{mu}m) exhibited solute-drag-controlled slip creep.
Date: September 1, 1996
Creator: Lesuer, D.R.; Nieh, T.G.; Syn, C.K. & Taleff, E.M.
Partner: UNT Libraries Government Documents Department

Laminated metals composites fracture and ballistic impact behavior

Description: Recent advances in the fracture and ballistic impact response of laminated metal composites (LMCs) are reviewed. The laminate structure can provide significant improvements to these properties relative to the component materials. Typical fracture and ballistic impact properties in LMCs are illustrated for systems containing Al alloys and Al matrix composites. The unique mechanisms operating in a layered structure that contribute to fracture or ballistic impact resistance are discussed. The influence of laminate architecture, component material properties and interface strength on mechanisms and properties are briefly reviewed for these Al-based LMCs.
Date: January 20, 1998
Creator: Lesuer, D. R.; Syn, C. K.; Sherby, O. D. & Wadsworth, J.
Partner: UNT Libraries Government Documents Department

Evolution of grain size distribution during deformation of superplastic materials

Description: Grain size distribution and its evolution during superplastic deformation has been studied for two materials- ultrahigh carbon steel, which has a two phase microstructure, and a copper alloy, which has a quasi-single phase microstructure. For both materials the distribution of initial grain size is very accurately represented by a lognormal throughout the deformation history. The evolution of the parameters characterizing the log normal distribution have also been studied and found to vary in a systematic manner results. Results can be used to specify the grain size distribution as a function of strain during superplastic deformation and thus should prove useful for computational studies in which grain size distribution is evaluated.
Date: October 28, 1997
Creator: Lesuer, D. R.; Glaser, R. & Syn, C. K.
Partner: UNT Libraries Government Documents Department

Enhancing tensile ductility of a particulate-reinforced aluminum MMC by lamination with Mg-9% Li alloy

Description: A laminated metal composite has been made by press bonding alternating layers of a particulate-reinforced aluminum MMC, 6090/SiC/25p, and a Mg-9%Li alloy. The mechanical properties including tensile ductility were evaluated. The tensile ductility of the Al MMC was found to increase from 3.5% to 11.5%. In contrast to other laminates based on ultrahigh carbon, steel, the laminate of this study and other Al MMC laminates exhibited tensile yield strengths that did not follow the rule of averages. This is attributed to interlayer reaction products developed during processing of the Al MMC laminates.
Date: May 1995
Creator: Syn, C. K.; Lesuer, D. R. & Sherby, O. D.
Partner: UNT Libraries Government Documents Department

Consequences of the re-transformation of precipitated austenite in ferritic cryogenic steels. Technical report No. 8

Description: The re-transformation of precipitated austenite (..gamma../sub R/) in Fe-(6-9)%Ni steels has been investigated, with particular emphasis on the influence of transformation characteristics on alloy toughness at cryogenic temperature. In all cases studied the precipitated austenite re-transforms, either during cooling to cryogenic temperature or during deformation prior to fracture of the alloy. When the re-transformation is thermally induced the product martensite tends to form in a variant identical to that present before precipitation of the austenite; no significant refinement of the microstructure is achieved. On the other hand, mechanical transformation of the austenite produces a distribution of martensite variants determined by the local strain, hence preserving a refined microstructure conducive to low temperature toughness.
Date: June 1, 1979
Creator: Morris, J.W. Jr.; Syn, C.K.; Kim, J.I. & Fultz, B.
Partner: UNT Libraries Government Documents Department

Influence of volume fraction of component materials and interlayer bond strength on fracture toughness of multi-layer Al 6090-25 vol % SiCp and Al 5182 laminates

Description: Multilayer laminates of Al 6090/SiC/25p MMC and Al 5182 were prepared by hot pressing alternating layers of the component materials at 450{degree}C in an argon gas atmosphere. Tensile properties, interlayer normal and shear bond strengths, and fracture toughness were measured in the T6-treated and untreated conditions. Fracture toughness was also measured as a function of the volume fraction of the MMC component. Yield and tensile strengths increased substantially by the T6 treatment while the total-elongation and interlayer bond strengths decreased even more substantially. Fracture toughness, on the other hand, did not change appreciably by the T6 treatment. The fracture toughness increased perceptibly with an increase in the volume percent of the MMC component.
Date: November 1, 1993
Creator: Syn, C. K.; Stoner, S.; Lesuer, D. R. & Sherby, O. D.
Partner: UNT Libraries Government Documents Department

Explosively driven facture and fragmentation of metal cylinders and rings

Description: Cylinders and rings fabricated from AerMet{reg_sign} 100 alloy and AISI 1018 steel have been explosively driven to fragmentation in order to determine the fracture strains for these materials under plane strain and uniaxial stress conditions. The phenomena associated with the dynamic expansion and subsequent break up of the cylinders are monitored with high-speed diagnostics. In addition, complementary experiments are performed in which fragments from the explosively driven cylinder are recovered and analyzed to determine the statistical distribution associated with the fragmentation process as well as to determine failure mechanisms. The data are used to determine relevant coefficients for the Johnson-Cook (Hancock-McKenzie) fracture model. Metallurgical analysis of the fragments provides information on damage and failure mechanisms.
Date: January 3, 2007
Creator: Goto, D; Becker, R C; Orzechowski, T J; Springer, H K; Sunwoo, A J & Syn, C K
Partner: UNT Libraries Government Documents Department

Mechanical and Thermal Properties of Ultra-High Carbon Steel Containing Aluminum

Description: The properties of ultrahigh carbon steels (UHCS) are strongly influenced by aluminum additions. Hardness studies of quenched UHCS-Al alloys reveal that the temperature for the start of transformation increases with increases in aluminum content. It is shown that this change is a function of the atomic percent of solute and of the valence state when comparisons are made with UHCSs containing silicon and tin as solutes. The thermal expansion of UHCSs with dilute aluminum additions shows no discontinuity in the vicinity of the ferrite-austenite transformation temperature. This is the result of a three phase region of ferrite, carbides and austenite. The slope of the expansion curve is higher in the austenite range than in the ferrite range as a result of the dissolution of carbon in austenite with temperature. Processing to achieve a fine grain size in UHCS-Al alloys was principally by hot and warm working (HWW) followed by isothermal warm working (IWW). The high temperature mechanical properties of a UHCS-10Al-1.5C material show nearly Newtonian-viscous behavior at 900 to 1000 C. Tensile elongations of 1200% without failure were achieved in the 1.5%C material. The high oxidation corrosion resistance of the UHCS-10Al materials is described.
Date: January 31, 2006
Creator: Syn, C K; Lesuer, D R; Goldberg, A; Tsai, H & Sherby, O D
Partner: UNT Libraries Government Documents Department

Mechanical and Thermal Properties of Ultra-High Carbon Steel Containing Aluminum

Description: The properties of ultrahigh carbon steels (UHCS) are strongly influenced by aluminum additions. Hardness studies of quenched UHCS-Al alloys reveal that the temperature for the start of transformation increases with increases in aluminum content. It is shown that this change is a function of the atomic percent of solute and of the valence state when comparisons are made with UHCSs containing silicon and tin as solutes. The thermal expansion of UHCSs with dilute aluminum additions shows no discontinuity in the vicinity of the ferrite-austenite transformation temperature. This is the result of a three phase region of ferrite, carbides and austenite. The slope of the expansion curve is higher in the austenite range than in the ferrite range as a result of the dissolution of carbon in austenite with temperature. Processing to achieve a fine grain size in UHCS-Al alloys was principally by hot and warm working (HWW) followed by isothermal warm working (IWW). The high temperature mechanical properties of a UHCS-10Al-1.5C material show nearly Newtonian-viscous behavior at 900 to 1000 C. Tensile elongations of 1200% without failure were achieved in the 1.5%C material. The high oxidation corrosion resistance of the UHCS-10Al materials is described.
Date: October 3, 2005
Creator: Syn, C K; Lesuer, D R; Goldberg, A; Tsai, H C & Sherby, O D
Partner: UNT Libraries Government Documents Department

An Evaluation of Power Law Breakdown in Metals, Alloys, Dispersion Hardened Materials and Compounds

Description: Creep at high stresses often produces strain rates that exceed those that would be predicted by a power law relationship. In this paper, we examine available high stress creep data for pure metals, solid solution alloys, dispersion strengthened powder metallurgy materials and compounds for power law breakdown (PLB). The results show that, if PLB is observed, then the onset of PLB is generally observed at about {epsilon}/D{sub eff} = 10{sup 13} m{sup -2}, where D{sub eff} is the effective diffusion coefficient incorporating lattice and dislocation pipe diffusion. The common origins of PLB for the various systems studied can be found in the production of excess vacancies by plastic deformation. Anomalous behavior in two pure metals (nickel and tungsten) and a solid solution alloy (Fe-25Cr and Fe-26Cr-1Mo) has been analyzed and provides insight into this excess vacancy mechanism. In metal systems, the onset of PLB is related to a change in the nature of the subgrain structure developed. In the PLB region, subgrains become imperfect containing dislocation tangles adjacent to the sub-boundary, and dislocation cells are evident. The dislocation tangles and cells are the source of excess vacancies and increase the creep rate above that predicted from power law creep. If subgrains do not form then PLB is not observed. In solid solution alloys, in which the dominant deformation resistance results from the interaction of solute atoms with moving dislocations, excess vacancies influence the diffusion of these solute atoms. PLB is not observed in many systems. This is attributed either to the presence of a high equilibrium vacancy concentration (because of a low activation energy for vacancy formation) or to the inability to form subgrains.
Date: October 20, 1999
Creator: Lesuer, D.R.; Syn, C.K. & Sherby, O.D.
Partner: UNT Libraries Government Documents Department

Fracture toughness and impact properties of laminated metal composites

Description: Laminated metal composites consist of alternating metal (or metal matrix composite) layers bonded together. These materials can provide fracture toughness and impact properties superior to those of the component materials. These properties are a function of component material properties, laminate architecture (volume fraction, thickness) and interface properties. Properties are compared for seven lightweight materials.
Date: March 4, 1996
Creator: Lesuer, D.R.; Riddle, R.A.; Gogolewski, R.P.; Syn, C.K. & Cunningham, B.J.
Partner: UNT Libraries Government Documents Department

Machinability study of Aermet 100

Description: Machinability of Aermet 100, an ultrahigh strength alloy developed for Navy by Carpenter Technology as a candidate material for aircraft landing gear application, was studied by performing single-point turning tests. Coated and uncoated carbides, ceramic, and cermet cutting tool inserts of a square geometry (SNG 432 type) were used. Round stock workpieces were tested in the as - received, unaged condition and without using any cutting fluid. The turning tests for each tool material were conducted by (i) first establishing the cutting conditions that would allow the continued generation of broken chips during a given cutting test, (ii) measuring intermittently the flank wear as a function of cutting time under such established cutting conditions for discontinuous broken chips, and (iii) determining the tool life using the criteria specified in the ISO Standard 3685: 1993(E). Cutting tools except some uncoated carbide and ceramic were used with a mechanical chip breaker to induce chip breakage and avoid the generation of long continuous chips. The results obtained include the optimal cutting conditions for discontinuous chips, tool wear - cutting time curves, and records of tool life and tool failure mode for each tool material. From the measured tool life and cutting conditions, the amount of material removed by each cutting material was calculated. Coated carbide with CVD tri-phase coating showed the longest tool life that exceeded the twelve minute criterion and removed the highest amount of material per tool. Other tools failed by cutting edge chipping and their lives were shorter.
Date: February 8, 1995
Creator: Squire, D. V.; Syn, C. K. & Fix, B. L.
Partner: UNT Libraries Government Documents Department

Influence of severe plastic deformation on the structure and properties of ultrahigh carbon steel wire

Description: Ultrahigh-carbon steel wire can achieve very high strength after severe plastic deformation, because of the fine, stable substructures produce. Tensile strengths approaching 6000 MPa are predicted for UHCS containing 1.8%C. This paper discusses the microstructural evolution during drawing of UHCS wire, the resulting strength produced and the factors influencing fracture. Drawing produces considerable alignment of the pearlite plates. Dislocation cells develop within the ferrite plates and, with increasing strain, the size normal to the axis ({lambda}) decreases. These dislocation cells resist dynamic recovery during wire drawing and thus extremely fine substructures can be developed ({lambda} < 10 nm). Increasing the carbon content reduces the mean free ferrite path in the as-patented wire and the cell size developed during drawing. For UHCS, the strength varies as {lambda}{sup {minus}5}. Fracture of these steels was found to be a function of carbide size and composition. The influence of processing and composition on achieving high strength in these wires during severe plastic deformation is discussed.
Date: July 1, 1999
Creator: Leseur, D R; Sherby, O D & Syn, C K
Partner: UNT Libraries Government Documents Department