Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

We report evidence for graphene layer rearrangements in heavy ion interactions with carbon onions at 140 MeV and 70 MeV per nucleon kinetic energies. Graphene layer rearrangements have been recently predicted in spherical and cylindrical multi-layer graphene systems. The implications of graphene layer rearrangement on the tribological performance of multi-layer nano-carbons in extreme environments are discussed.

Single shear lap specimens were subjected to creep, isothermal aging, and thermomechanical fatigue (TMF). Scanning electron microscopy micrographs of previously polished specimens revealed changes in surface morphology. Orientation imaging microscopy was carried out on the same specimens to study the microstructural evolution and crystal orientation changes. As-fabricated joints consistently show a preferred crystal orientation with a few minority orientations with highly preferred misorientations. Alloy additions caused an increase in the number of statistically significant crystal orientations and misorientations. The solidification microstructure was unchanged due to room-temperature creep. Aging caused development and motion of well-defined subgrain boundaries and removal of most minority orientations. TMF causes heterogeneous refinement of the microstructure that accounts for the localized grain boundary sliding in regions of high strain concentration. This study implies that the lead-free solder joints are not polycrystals, but multicrystals, so that deformation is very heterogeneous and sensitive to strain and temperature history.

Nanoindentation testing was used to obtain mechanical properties on realistic Sn-Ag solder joints made with (i) eutectic Sn-3.5Ag solder and (ii) in-situ Cu6Sn5 particle reinforced, eutectic Sn-Ag matrix composite solder. The composite solder joint contained ˜20 volume percent of intentionally-added Cu6Sn5 intermnetallic particles which were ∼5 microns in size. The Cu6Sn5 particles were dispersed in-situ in eutectic Sn-3.5Ag matrix alloy as a reinforcement phase to stabilize the microstructure by acting as a non-coarsening microconstituent phase. Mechanical properties characterization and deformation behavior were assessed on the bulk microstructure and on microconstituents in the actual solder joints. Mechanical property data obtained on constituents included hardness, elastic modulus, strain rate, and creep behavior. The pushing and rotation of the reinforcement particles that often occurred when contacted by the indenter provided a means for evaluating the interfacial shear strength of reinforcement particles in the solder matrix.

Most research about creep has focused on minimum creep rate or stress rupture properties, but primary creep is important for practical applications. In this paper, we compare how interstitial content and heat treatments of shorter duration than used in past studies affect the microstructure and primary creep resistance of a particular alloy containing TiB2 particles. More time and temperature in heat treatment homogenizes the microstructure and reduces the scatter of creep times to 0.5% strain. Increasing interstitial content increases the time to 0.5% creep, and it stabilizes the a2 phase. Preliminary evidence for large mechanical twinning strains parallel to lamellar interfaces shortly following loading is provided.

Extrusion textures in monolithic NiAl and an NiAl/AlN particle composite are compared. The NiAl has a generally increasing grain size with extrusion temperature, and a corresponding transition from <110> to <111> fiber texture. The results suggests that <110> is more closely related to the deformation texture, while the <111> is a recrystallization orientation formed by preferential growth. The composite exhibits <311> fiber texture, and this is consistent with slip in <100> directions. The effect of the AlN particles is to prevent the orientation changes observed in the monolithic NiAl during recrystallization.

The tensile behavior of IN90211 was characterized at strain rates between 0.0001/sec and 340/sec at temperatures between 425 and 475 °C. At strain rates below 0.1/sec, the strain rate sensitivity m is about 0.027, with corresponding low elongation (<100%). At strain rates above 0.1/sec, the strain rate sensitivity increases to 0.26. A maximum elongation of 500% was obtained at 475 °C at a strain rate of 2.5/sec. Grain boundary sliding and rotation was observed on the highly elongated specimens and fracture surfaces exhibited intergranular fracture. Experimental data in the high strain rate regime (superplastic) revealed the existence of a temperature dependent threshold stress that seemed unrelated to the low stress deformation regime. This result is consistent with stress relaxation experiments. These threshold stresses are generally lower than those typically observed in other oxide dispersion strengthened (ODS) alloys. This observation is not expected from conventional superplastic creep theory.

The following list includes books and articles on Irish history in which the year 1970 is given in the work itself as the date of publication, together with Addenda for 1965-9. The list excludes current works of reference, parliamentary publications, writings on contemporary politics, and items in newspapers; reports of archaeological finds and literary and linguistic studies, presented without reference to their historical context; and writings of little scholarly value. Reviews or short notices of many of the items listed will be found in this journal.

The following list includes books and articles on Irish history in which the year 1969 is given in the work itself as the date of publication, together with Addenda for 1965–8. The list excludes current works of reference, parliamentary publications, writings on contemporary politics, and items in newspapers; reports of archaeological finds and literary and linguistic studies, presented without reference to their historical context; and writings of little scholarly value. Reviews or short notices of many of the items listed will be found in this journal.