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Evaluation of waterjet-machined metal matrix composite tensile specimens

Description: Four magnesium/boron carbide metal matrix composite (MMC) tensile specimens fabricated using the waterjet machining method were evaluated in order to determine the effects of the waterjet material removal process on the composite material surface structure and properties. These results were then compared with data from material conventionally machined. Results showed that while waterjet cutting produces a rough surface finish and does not meet specified dimensional tolerances, the technique appears to be suitable for sectioning and rough machining of metal matrix composites.
Date: April 1, 1986
Creator: Lavender, C.A. & Smith, M.T.
Partner: UNT Libraries Government Documents Department

Effects of rolling on the ductility of 80% tungsten heavy alloy

Description: Relations between transverse tensile ductility and rolling and annealing schedules were investigated for solid-state sintered and annealed 80%W8%Ni-2%Fe heavy alloy rolled at 900C or 1150C with varying reductions between anneals at either 1150C or 1400C. Final anneals and a solution heat treatment were employed prior to tensile testing. Metallographic and fractographic analyses were performed to determine relations between microstructure and physical properties. Multiple 1400C intermediate anneals with a maximum 60% rolling reduction produced higher transverse tensile elongations than rolled with a higher final reduction, 86%. Tensile elongation differences were attributed to the recrystallized intra-particle W grain sizes achieved during the final anneal. Materials given a maximum of 60% reduction before final anneal had fewer intra-particle W grains and therefore higher ductilities. For materials rolled at 900C or 1150C, no differences in transverse tensile elongation were observed. 1150C intermediate anneals had consistently lower ductility. 900C rolling produced slightly higher elongations than 1150C rolling, but only when the material was annealed at 1455C. Tensile yield and ultimate strengths did not vary greatly with rolling and intermediate annealing conditions. The edge cracking correlated with observed lateral spread and the material softness.
Date: November 1, 1992
Creator: Lavender, C. A. & Gurwell, W. E.
Partner: UNT Libraries Government Documents Department

Effects of rolling on the ductility of 80% tungsten heavy alloy

Description: Relations between transverse tensile ductility and rolling and annealing schedules were investigated for solid-state sintered and annealed 80%W8%Ni-2%Fe heavy alloy rolled at 900C or 1150C with varying reductions between anneals at either 1150C or 1400C. Final anneals and a solution heat treatment were employed prior to tensile testing. Metallographic and fractographic analyses were performed to determine relations between microstructure and physical properties. Multiple 1400C intermediate anneals with a maximum 60% rolling reduction produced higher transverse tensile elongations than rolled with a higher final reduction, 86%. Tensile elongation differences were attributed to the recrystallized intra-particle W grain sizes achieved during the final anneal. Materials given a maximum of 60% reduction before final anneal had fewer intra-particle W grains and therefore higher ductilities. For materials rolled at 900C or 1150C, no differences in transverse tensile elongation were observed. 1150C intermediate anneals had consistently lower ductility. 900C rolling produced slightly higher elongations than 1150C rolling, but only when the material was annealed at 1455C. Tensile yield and ultimate strengths did not vary greatly with rolling and intermediate annealing conditions. The edge cracking correlated with observed lateral spread and the material softness.
Date: November 1, 1992
Creator: Lavender, C.A. & Gurwell, W.E.
Partner: UNT Libraries Government Documents Department

Interfacial segregation and deformation of superplastically deformed Al-Mg-Mn alloys

Description: Microstructural and microchemical studies have been carried out on superplastically deformed Al-Mg-Mn (AA5083-type) alloys. Grain boundary composition was measured using a Scanning Auger Microprobe (SAM) and an Analytical Transmission Electron Microscope (ATEM), while conventional TEM was used for microstructural evaluation. Non-equilibrium segregation of Si to grain boundaries following deformation was measured by both techniques. Significant interfacial Si enrichment was only detected in gage sections of tensile specimens after uniaxial strains from 50 to 200%. Grip regions which experience identical thermal histories, but without plastic deformation, did not reveal Si segregation. Selected samples also showed a slight depletion of Mg at grain boundaries after deformation. The only reproducible observation of equilibrium segregation was in Zr-modified alloys, where Sn was detected by SAM in both the deformed and undeformed sections of the sample. Microstructural analysis documented subgrain formation and subgrain-precipitate interactions during superplastic deformation. In addition, many grain boundaries and precipitate interfaces contained small (5 to 20 nm) voids. Compositional analysis of these nano-voids revealed that they were enriched in Mg with the adjacent boundary regions correspondingly depleted.
Date: March 1, 1995
Creator: Vetrano, J.S.; Lavender, C.A. & Bruemmer, S.M.
Partner: UNT Libraries Government Documents Department

Accuracy issues in modeling superplastic metal forming

Description: The utility of finite element modeling in optimizing superplastic metal forming is dependent on accurate representation of the material constitutive behavior and the frictional response of the sheet against the die surface. This paper presents work conducted to estimate the level of precision that is necessary in constitutive relations for finite element analysis to accurately predict the deformation history of actual SPF components. Previous work identified errors in SPF testing methods that use short tensile specimens with gauge length-to-width ratios of 2:1 or less. The analysis of the present paper was performed to estimate the error in predicted stress that results from using the short specimens. Stress correction factors were developed and an improved constitutive relation was implemented in the MARC finite element code to simulate the forming of a long, rectangular tray. The coefficient of friction in a Coulomb friction model was adjusted to reproduce the amount of material draw-in observed in the forming experiments. Comparisons between the finite element predictions and the forming experiments are presented.
Date: February 1, 1995
Creator: Johnson, K.I.; Khaleel, M.A.; Lavender, C.A. & Smith, M.T.
Partner: UNT Libraries Government Documents Department

Technology maturation project on optimization of sheet metal forming of aluminum for use in transportation systems: Final project report

Description: Using aluminum instead of steel in transportation systems could dramatically reduce the weight of vehicles--an effective way of decreasing energy consumption and emissions. The current cost of SMF aluminum alloys (about $4 per pound) and the relatively long forming times of current materials are serious drawbacks to the widespread use of SMF in industry. The interdependence of materials testing and model development is critical to optimizing SMF since the current process is conducted in a heated, pressurized die where direct measurement of critical SMF parameters is extremely difficult. Numerical models provide a means of tracking the forming process, allowing the applied gas pressure to be adjusted to maintain the optimum SMF behavior throughout the forming process. Thus, models can help produce the optimum SMF component in the least amount of time. The Pacific Northwest Laboratory is integrating SMF model development with research in improved aluminum alloys for SMF. The objectives of this research are: develop and characterize competitively priced aluminum alloys for SMF applications in industry; improve numerical models to accurately predict the optimum forming cycle for reduced forming time and improved quality; verify alloy performance and model accuracy with forming tests conducted in PNL`s Superplastic Forming User Facility. The activities performed in this technology maturation project represent a critical first step in achieving these objectives through cooperative research among industry, PNL, and universities.
Date: October 1, 1994
Creator: Johnson, K. I.; Smith, M. T.; Lavender, C. A. & Khalell, M. A.
Partner: UNT Libraries Government Documents Department

Effect of precipitate structure on hot deformation of Al-Mg-Mn alloys

Description: The size and nature of precipitates have strong effects on microstructural evolution from the cold-worked state through the course of deformation at high temperatures. Through selected heat treatments and minor alloying alterations the precipitate structure of AA5083 has been manipulated. Minor additions of Zr have been used to create fine (50 to 100 nm) precipitates. The number and size distribution of medium-sized (<1 {mu}m) Mn-rich precipitates were modified by increasing the Mn concentration in conjunction with several heat treatment paths. Effects of these precipitates on the dislocation structure, recrystallization behavior and grain growth during high-temperature deformation have been elucidated.
Date: October 1, 1993
Creator: Vetrano, J. S.; Lavender, C. A.; Smith, M. T. & Bruemmer, S. M.
Partner: UNT Libraries Government Documents Department

Bend Ductility of Tungsten Heavy Alloys

Description: A bend ductility test is used to indicate the formability of tungsten heavy alloys sheet. The primary test bends a notchless Charpy impact specimen to a bend angle of approximately 100C. This can be augmented by a bend-completion test. Finite element modeling as well as strain-gaged bend specimens elucidate the strain distribution in the specimen as a function of material thickness and bend angle. The bend ductilities of 70%W, 807.W and 90%W alloys are characterized. As expected, decreasing thickness or tungsten content enhances bend ductility. Oxidation is not detrimental; therefore, controlled atmosphere is not required for cooling. The potentially detrimental effects of mechanical working (e.g., rolling, roller-leveling, grit blasting, and peening) and machining (e.g., cutting and sanding) are illustrated.
Date: November 1992
Creator: Gurwell, W. E.; Garnich, M. R.; Dudder, G. B. & Lavender, C. A.
Partner: UNT Libraries Government Documents Department

Bend ductility of tungsten heavy alloys

Description: A bend ductility test is used to indicate the formability of tungsten heavy alloys sheet. The primary test bends a notchless Charpy impact specimen to a bend angle of approximately 100C. This can be augmented by a bend-completion test. Finite element modeling as well as strain-gaged bend specimens elucidate the strain distribution in the specimen as a function of material thickness and bend angle. The bend ductilities of 70%W, 807.W and 90%W alloys are characterized. As expected, decreasing thickness or tungsten content enhances bend ductility. Oxidation is not detrimental; therefore, controlled atmosphere is not required for cooling. The potentially detrimental effects of mechanical working (e.g., rolling, roller-leveling, grit blasting, and peening) and machining (e.g., cutting and sanding) are illustrated.
Date: November 1, 1992
Creator: Gurwell, W. E.; Garnich, M. R.; Dudder, G. B. & Lavender, C. A.
Partner: UNT Libraries Government Documents Department

Development of superplasticity in 5083 aluminum with additions of Mn and Zr

Description: The superplastic behavior of the 5083 aluminum alloy with additions of Mn and Zr was studied by uniaxial tensile testing and microstructural evaluations. Additions of up to 0.2% Zr and 0.8% Mn were made to a base 5083 aluminum alloy to decrease the grain size and improve superplastic behavior. Constant strain-rate tensile test data were used to determine strain-rate sensitivity (m values) and elongations-to-failure for the alloys at strain rates ranging from 4 {times} 10{sup {minus}4} to 1 {times} 10{sup {minus}1} s{sup {minus}1} at temperatures of 450 to 550C. Elongations-to-failure of up to 400% at 1 {times} 10{sup {minus}2} s{sup {minus}1} were achieved for the modified alloys. The strain-rate sensitivity for the alloys as a function of strain was determined and two distinct behaviors were observed. For the alloys having composition close to the base 5083 alloy, the m value steadily decreased with increasing strain; however, in alloys with higher levels of Zr, the m value remained stable. A maximum m value of 0.65 was achieved at 0.7 strain for the 1.6% Mn and 0.2% Zr alloy at 1 {times} 10{sup {minus}3} s{sup {minus}1}.
Date: May 1, 1994
Creator: Lavender, C. A.; Vetrano, J. S.; Smith, M. T.; Bruemmer, S. M. & Hamilton, C. H.
Partner: UNT Libraries Government Documents Department

Simulation for analysis and control of superplastic forming. Final report

Description: A joint study was conducted by Oak Ridge National Laboratory (ORNL) and the Pacific Northwest Laboratory (PNL) for the U.S. Department of Energy-Lightweight Materials (DOE-LWM) Program. the purpose of the study was to assess and benchmark the current modeling capabilities with respect to accuracy of predictions and simulation time. Two modeling capabilities with respect to accuracy of predictions and simulation time. Two simulation platforms were considered in this study, which included the LS-DYNA3D code installed on ORNL`s high- performance computers and the finite element code MARC used at PNL. both ORNL and PNL performed superplastic forming (SPF) analysis on a standard butter-tray geometry, which was defined by PNL, to better understand the capabilities of the respective models. The specific geometry was selected and formed at PNL, and the experimental results, such as forming time and thickness at specific locations, were provided for comparisons with numerical predictions. Furthermore, comparisons between the ORNL simulation results, using elasto-plastic analysis, and PNL`s results, using rigid-plastic flow analysis, were performed.
Date: August 1, 1996
Creator: Zacharia, T.; Aramayo, G.A.; Simunovic, S.; Ludtka, G.M.; Khaleel, M.; Johnson, K.I. et al.
Partner: UNT Libraries Government Documents Department