Lead induced intergranular fracture in aluminum alloy AA6262

The influence of lead on the fracture behavior of aluminum alloy AA6262 is investigated. Under certain conditions, the mode of fracture changes from transgranular microvoid coalescence to an intergranular mechanism. Three different intergranular fracture mechanisms are observed: liquid metal embrittlement, dynamic embrittlement at temperatures below the melting temperature of lead, and intergranular microvoid coalescence. An attempt is made to examine the dependence of these three mechanisms on temperature, strain rate, and stress state using in situ scanning electron microscopy (SEM). Liquid metal embrittlement occurs when the alloy is fractured at temperatures above the melting temperature of lead and at low strain rates. At lower temperatures, the occurrence of dynamic embrittlement depends largely on strain rate, stress state, and temperature. Intergranular microvoid coalescence is not often observed.

Scattered wave functions of dislocated lattices

Using a Wannier function approach and a transformation of the coordinate system it is shown that a method can be set up to calculate the scattered wave function of a dislocated lattice

Competitive segregation of gallium and indium at heterophase Cu–MnO interfaces studied with transmission electron microscopy

This paper concentrates on the possible segregation of indium and gallium and competitive segregation of gallium and indium at atomically flat parallel {111}-oriented Cu–MnO interfaces. The segregation of gallium at Cu–MnO interfaces after introduction of gallium in the copper matrix of internally oxidized Cu–1 at.%Mn could be hardly detected with energy-dispersive spectrometry in a field emission gun transmission electron microscope. After a heat treatment to dissolve indium in the copper matrix, gallium has a weak tendency to segregate, that is 2.5 at.% Ga per monolayer at the interface compared with 2 at.% in the copper matrix. The striking result is that this gallium segregation is observable because it does not occur at the metal side of the interface but in the first two monolayers at the oxide side. Using the same heat treatment as for introducing indium in the sample, but without indium present, gallium segregates strongly at the oxide side of the Cu–MnO interface with a concentration of about 14.3 at.% in each monolayer of the two. In contrast, the presence of gallium has no influence on the segregation of indium towards Cu–MnO interfaces, because the outermost monolayer at the metal side of the interface contains 17.6 at.% In, that is similar to previously found results. This leads to the intriguing conclusions, firstly, that, in contrast with antimony and indium, gallium segregates at the oxide side of the interface and, secondly, that the presence of indium strongly hampers gallium segregation. The results from analytical transmission electron microscopy on gallium segregation are supported by high-resolution transmission electron microscopy observations.

Is the pull-out force of the Meniscus Arrow in bone affected by the inward curling of the barbs during biodegradation? An in vitro study

Background: Inward curling of the barbs of Meniscus Arrows during degradation was observed in a previous study, in which swelling, distention, and water uptake by Meniscus Arrows was evaluated. This change of configuration could have consequences with respect to anchorage capacity in bone. Material/Methods: Eight non-degraded Meniscus Arrows in the original configuration were pulled out of thawed, fresh-frozen human femoral condyle, and pull-out force was measured and compared with that of 6 Meniscus Arrows after 31 days of degradation under controlled conditions. Results: No significant difference was found between the 2 groups with respect to the required pull-out force (t test), the distribution of the data, or the interaction between degradation and location, as evaluated by mann-Whitney test, and no significant difference was found between the 2 groups with respect to the degradation state or position in the coudyles, as evaluated by 2-way analysis of variance. Conclusions: Our results indicate that the decrease in barb-barb diameter during the first month of degradation of the Meniscus Arrows has no significant effect on the tensile pull-out force required for removal from human femur condyle. Further research should be undertaken to examine whether the same is true for other biodegradable devices with barbs

Some aspects of nanocrystalline nickel and zinc ferrites processed using microemulsion technique

Nanocrystalline nickel and zinc ferrites synthesised using a microemulsion technique were characterised by high resolution transmission electron microscopy and vibrating sample magnetometry. A narrow and uniform distribution of crystals of size range 5 – 8 nm, distinguished by a clear lack of saturation magnetisation at 9 kOe, were obtained. Also, no coercivity or remanence was observed.