About the 1996 TMS Annual Meeting: Wednesday Afternoon Sessions (February 7)

Wednesday, PM Room: Orange County 1

February 7, 1996 Location: Anaheim Marriott Hotel

Session Chairperson:TBA

2:00 pm

TENSILE BEHAVIOR OF Alloy 800H AS AFFECTED BY AGEING, STRAIN RATE AND NOTCHES: A. M. Eleiche, Mech. Eng. Dept. of Mech. Design & Production, Cairo University, Egypt; M. F. Aly, National Center for Atomic Safety, Cairo, Egypt; M. A. Adly, Dept. of Mech. Design & Production, Cairo, Egypt; M. M. Ghoneim, Atomic Energy Authority, Egypt

The objective of this work was characterizing the mechanical behavior in tension of INCOLOY 800H at the ambient temperature. Quasi-static tests were performed using an electro-mechanical universal testing machine, while a tensile split-Hopkinson-bar apparatus was used in the dynamic tests. The testing program was designed to elucidate the following: (a) The effect of material ageing: by carrying out tests at strain rates of 7.5 E-5 and 7.5 E-3/s on solution-treated material and on material thermally-aged at 900deg.C for 24 hrs. (b) The effect of strain rate: by carrying tests in the range 7.5E-5 to 400 /s on solution-treated material. (c) The effect of strain-rate history: by quasi-statically deforming solution-treated specimens to strain amplitudes of 5, 7.7, 11.3 and 13.6 % followed by dynamic reloading.(d) The effect of notches: by carrying tests at 7.5 E-5/s on specimens, in both the solution-treated and the aged conditions, having two types of notches, namely circular and B.S. notch. Reference: M. F. Aly, The behaviour of Alloy 800H at 20deg. C using a novel tensile split-Hopkinson bar apparatus, M.Sc. Thesis, Dept. of Mechanical Design and Production, Faculty of Engineering, Cairo University, 1993.

2:20 pm

TEMPERATURE AND GRAIN SIZE DEPENDENCE OF MICROSTRUCTURAL CREEP MECHANISMS IN A P/M NI-BASE SUPERALLOY: Dr. Charles P. Blankenship. Jr., Dr. Ernest L. Hall, GE Corporate Research & Development, P.O. Box 8, Schenectady, NY 12301

Creep deformation studies were conducted in polycrystalline René 88 at 1200,1400, and 1500°F. Samples with grain sizes of 7, 15, and 90m and identical ' sizes and distributions were tested at each temperature in order to isolate the grain size contribution to creep resistance. After deformation to 0.5% and to failure, transmission electron microscopy was used to characterize the microstructure. Individual dislocation segments and extended faults are observed under all creep conditions. The density of these intergranular defects generally decreases with test temperature at a given grain size, but is not strongly affected by grain size. The amount of mass transport along grain boundaries, as evidenced by discontinuous ' precipitation and grain boundary precipitate coarsening, increases with increasing temperature and decreasing grain size. The nature of the matrix dislocations and associated faults appears to be similar at 1400 and 1500°F, but different from those at 1200°F and room temperature. The relationship of these results to the observed creep behavior will be discussed.

2:40 pm

DEFORMATION BEHAVIOR AND MECHANICAL PROPERTIES OF L12 ALLOYS BASED ON (Ni,Pt)3Al: J. L. Kamm, W. W. Milligan, Department of Metallurgical and Materials Engineering, Michigan Technological University, Houghton, MI 49931

Ternary alloys based on Ni3Al, containing up to 25 atomic percent Pt substituted for Ni, were prepared. The alloys possessed the L12 structure, and were single-phase. The temperature dependence of the mechanical properties was similar to that of Ni₃Al, although the peak strength was higher and occurred at much lower temperatures. Dislocation behavior was also similar to Ni₃Al, except the density of trapped screws at room temperature was much higher for the Pt-bearing alloys. The results are consistent with increasing ease of cross slip with increasing Pt content, and not with solution hardening. Sponsored by the National Science Foundation under grant DMR-9257465.

3:00 pm

EFFECT OF COMPOSITION ON CRYSTALLOGRAPHIC TEXTURE IN HOT ROLLED Al-Li-Cu ALLOYS: M. A. Przystupa, Dept. of Materials, Science and Engineering, University of California, Los Angeles, CA 90024; A. K. Vasud van, Office of Naval Research, Code-332, 800 N. Quincy St., Arlington, VA 22217; W. G. Fricke, Jr. (Deceased), Alcoa Technical Center, Alcoa Center, PA 15069

The hot-rolling textures of ternary Al-Li- Cu alloys have been characterized to determine their effects on yield strength anisotropy. The alloys used in the study had (Li/Cu) ratios varying from 0 to infinity and were hot-rolled in the 520-400°C temperature range. All alloys developed beta-fibers, with maximum intensity at Brass, and a weak background alfa-fiber. The Brass components were the strongest for the alloys with intermediate(Li/Cu)ratios. All alloy compositions showed weak Cube or rotated Cube recrystallization texture components. The texture results were used to predict yield strength anisotropies. The predictions were in agreement with the experimental results for the high (Li/Cu) alloys. In the low (Li/Cu) alloys, the discrepancies between the predicted and the measured yield strength anisotropies have been attributed to the modifying effect of the directional precipitates on deformation.

3:20 pm BREAK

3:30 pm

HIGH-TEMPERATURE RUPTURE OF 7075 AL ALLOY UNDER MULTIAXIAL STRESS STATES: Ahmadali Yousefiani, Al-Badrawy Abo Elnasr, Farghalli A. Mohamed, James C. Earthman, Materials Science and Engineering, Dept. of Chemical and Biochemical Engineering, University of California, Irvine, CA 92717

Experiments were performed on 7075 Al alloy under three different stress states: uniaxial tension, biaxial shear and triaxial tension. Rupture times are compared for the three states with respect to the maximum principal stress, von Mises effective stress, and the principal facet stress. The results of this comparison along with microstructural observations regarding the cavitation behavior of the alloy are discussed.

3:50 pm

CHARACTERIZATION OF THE DEFORMATION MECHANISMS IN PURE ALUMINUM AND COPPER AND Cu-2.2%Al AND Cu-4.5%Al ALLOYS DURING TENSILE TESTING AT ROOM TEMPERATURE: Veronica Caballero, Arturo De La Cruz, S. K. Varma, Department of Metallurgical and Materials Engineering, The University of Texas at El Paso, El Paso, TX 79968-0520

The differences in the deformation mechanisms for the pure metals aluminum and copper and -the Cu-2.2%Al and Cu-4.5%Al alloys during the room temperature tensile testing has been explored. The choice of materials provides for a stacking fault energy values in a range from 4 to 166 mJ/m². The influence of grain size and strain rate on the development of microstructures during the deformation has been investigated. While pure aluminum, with a SFE value of 166 mJ/m², deforms by a process of slip leading to the cell formation and cell size refinement, the mechanisms change from the development of cellular structure to slip band, microband and deformation twin formation as the SFE decreases, corresponding to those for pure copper to the very low values (up to 4 mJ/m²) for the dilute alloys. This research has been supported by the National Science Foundation through the grant number HRD-9353547.

4:10 pm

INVESTIGATION OF CD SEGREGATION AT BOUNDARIES IN THE PB-62% Sn EUTECTIC: Souping Yan, Farghalli A. Mohamed, Materials Science and Engineeling, Department of Chemical and Biochemical Engineering, University of California, Irvine, CA 92717

A detailed microstructure investigation was performed on the Pb-62%Sn eutectic doped with 890ppm Cd. In conducting the investigation, SEM, EDS and AES surface analysis techniques were used. The data have shown that Cd segregation occurs along Sn-Sn intercrystalline boundaries and Pb-Sn interphase boundaries. The data are discussed in reference to recent results regarding the effects of impurities on superplastic flow at low stresses.

4:30 pm

ELEVATED-TEMPERATURE DEFORMATION OF (Lal x,Srx)MnO3: J. Wolfenstine, Department of Chemical and Biochemical Engineering, University of California, Irvine, CA 92717-2575; M. A. Boling-Risser, K. C. Goretta, J. L. Routbort, Energy Technology Division, Argonne National Laboratory, Argonne, IL 60439-4838

The compression creep behavior of fine-grained (La1-xSrx)MnO₃ (with x from 0.1 to 0.25) materials with relative theoretical densities between 85-90% was investigated over the temperature range 1150-1300°C. The fine-grain size, brief creep transients, stress exponent close to unity and absence of deformation induced dislocations, suggested that the deformation is controlled by a diffusional creep mechanism. A comparison of the activation energy for creep with existing diffusion and creep data for pervoskite oxides suggested, that the diffusional creep of (La 1-x,Srx)MnO₃ is controlled by lattice diffusion of either lanthanum or manganese. This is confirmed by the dependence of the steady-state creep rate on Sr composition.