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Materials science and engineering

Description: During FY-96, work within the Materials Science and Engineering Thrust Area was focused on material modeling. Our motivation for this work is to develop the capability to study the structural response of materials as well as material processing. These capabilities have been applied to a broad range of problems, in support of many programs at Lawrence Livermore National Laboratory. These studies are described in (1) Strength and Fracture Toughness of Material Interfaces; (2) Damage Evolution in Fiber Composite Materials; (3) Flashlamp Envelope Optical Properties and Failure Analysis; (4) Synthesis and Processing of Nanocrystalline Hydroxyapatite; and (5) Room Temperature Creep Compliance of Bulk Kel-E.
Date: February 1, 1997
Creator: Lesuer, D.R.
Partner: UNT Libraries Government Documents Department

Nanoscale Synthesis and Characterization Laboratory Annual Report 2005

Description: The Nanoscale Synthesis and Characterization Laboratory's (NSCL) primary mission is to create and advance interdisciplinary research and development opportunities in nanoscience and technology. The initial emphasis of the NSCL has been on development of scientific solutions in support of target fabrication for the NIF laser and other stockpile stewardship experimental platforms. Particular emphasis has been placed on the design and development of innovative new materials and structures for use in these targets. Projects range from the development of new high strength nanocrystalline alloys to graded density materials to high Z nanoporous structures. The NSCL also has a mission to recruit and train personnel for Lab programs such as the National Ignition Facility (NIF), Defense and Nuclear Technologies (DNT), and Nonproliferation, Arms control and International security (NAI). The NSCL continues to attract talented scientists to the Laboratory.
Date: January 3, 2006
Creator: Hamza, A V & Lesuer, D R
Partner: UNT Libraries Government Documents Department

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

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

Ancient and Modern Laminated Composites - From the Great Pyramid of Gizeh to Y2K

Description: Laminated metal composites have been cited in antiquity; for example, a steel laminate that may date as far back as 2750 B.C., was found in the Great Pyramid in Gizeh in 1837. A laminated shield containing bronze, tin, and gold layers, is described in detail by Homer. Well-known examples of steel laminates, such as an Adze blade, dating to 400 B.C. can be found in the literature. The Japanese sword is a laminated composite at several different levels and Merovingian blades were composed of laminated steels. Other examples are also available, including composites from China, Thailand, Indonesia, Germany, Britain, Belgium, France, and Persia. The concept of lamination to provide improved properties has also found expression in modern materials. Of particular interest is the development of laminates including high carbon and low carbon layers. These materials have unusual properties that are of engineering interest; they are similar to ancient welded Damascus steels. The manufacture of collectable knives, labeled ''welded Damascus'', has also been a focus of contemporary knifemakers. Additionally, in the Former Soviet Union, laminated composite designs have been used in engineering applications. Each of the above areas will be briefly reviewed, and some of the metallurgical principles will be described that underlie improvement in properties by lamination. Where appropriate, links are made between these property improvements and those that may have been present in ancient artifacts.
Date: March 14, 2000
Creator: Wadsworth, J. & Lesuer, D.R.
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

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

Liquid-metal embrittlement of refractory metals by molten plutonium

Description: Embrittlement by molten plutonium of the refractory metals and alloys W-25 wt % Re, tantalum, molybdenum, and Ta-10 wt % W was studied. At 900/sup 0/C and a strain rate of 10/sup -4/ s/sup -1/, the materials tested may be ranked in order of decreasing susceptibility to liquid-plutonium embrittlement as follows: molybdenum, W-25 wt % Re, Ta-10 wt % W, and tantalum. These materials exhibited a wide range in susceptibility. Embrittlement was found to exhibit a high degree of temperature and strain-rate dependence, and we present arguments that strongly support a stress-assisted, intergranular, liquid-metal corrosion mechanism. We also believe microstructure plays a key role in the extent of embrittlement. In the case of W-25 wt % Re, we have determined that a dealloying corrosion takes place in which rhenium is selectively withdrawn from the alloy.
Date: July 1, 1980
Creator: Lesuer, D.R.; Bergin, J.B.; McInturff, S.A. & Kuhn, B.A.
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

Forming of superplastic ceramics

Description: Superplasticity in ceramics has now advanced to the stage that technologically viable superplastic deformation processing can be performed. In this paper, examples of superplastic forming and diffusion bonding of ceramic components are given. Recent work in biaxial gas-pressure forming of several ceramics is provided. These include yttria-stabilized, tetragonal zirconia (YTZP), a 20% alumina/YTZP composite, and silicon. In addition, the concurrent superplastic forming and diffusion bonding of a hybrid ceramic-metal structure are presented. These forming processes offer technological advantages of greater dimensional control and increased variety and complexity of shapes than is possible with conventional ceramic shaping technology.
Date: May 1, 1994
Creator: Lesuer, D. R.; Wadsworth, J. & Nieh, T. G.
Partner: UNT Libraries Government Documents Department

Warm formability of aluminum-magnesium alloys

Description: Manufacturers have become increasingly interested in near-net-shape forming of aluminum alloys as a means to reduce production costs and the weight of aircraft and automotive structures. To achieve the ductilities required for this process, we have examined extended ductility of Al-Mg alloys in the warm forming, or Class I creep, regime. We have studied a high-purity, binary alloy of Al-2.8Mg and ternary alloys of Al-xMg-0.5Mn with Mg concentrations from 1.0 to 6.6 wt. %. Tensile tests, including strain rates-change tests, have been performed with these materials at temperatures of 300 and 400C over a range 10{sup {minus}4} to 2 {times} 10{sup {minus}2} s{sup {minus}1}. A maximum tensile failure strain of 325% for the binary alloy and a maximum of 125% in the ternary alloys have been measured. The experimental results have been used to evaluate the effects of solute concentration, microstructure, temperature, and strain rate on flow stress ({sigma}), elongation to failure (e{sub f}), and strain-rate sensitivity (m) of these alloys.
Date: May 27, 1994
Creator: Taleff, E. M.; Henshall, G. A.; Lesuer, D. R. & Nieh, T. G.
Partner: UNT Libraries Government Documents Department

Modeling microstructural evolution and the mechanical response of superplastic materials

Description: A model has been developed that accounts for grain growth during, superplastic flow and its subsequent influence on stress-strain-strain rate behavior. These studies are experimentally based and have involved two different types of superplastic materials -- a quasi-single phase metal (Coronze 638) and a microduplex metal (ultrahigh-carbon steel - UHCS). In both materials the kinetics of strain-enhanced grain growth have been studied as a function of strain, strain rate and temperature. An equation for the rate of grain growth has been developed that incorporates the influence of temperature. The evolution of the grain size distribution during superplastic deformation has also been investigated. Our model integrates grain growth laws derived from these studies with two mechanism based, rate dependent constitutive laws to predict the stress-strainstrain rate behavior of materials during superplastic deformation. The influence of crain size distribution and its evolution with strain and strain rate on the stress-strain-strain rate behavior has been represented through the use of distributed parameters. The model can capture the stress-strain-strain rate behavior over a wide range of strains and strain rates with a single set of parameters. Many subtle features of the mechanical response of these materials can be adequately predicted.
Date: January 11, 1993
Creator: Lesuer, D. R.; Syn, C. K.; Cadwell, K. L. & Preuss, C. S.
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