Martensite-to-austenite reverse transformation in Fe-Ni-Co alloys

The reverse martensitic transformation was investigated in three Fe-Ni-Co alloys containing acicular martensite by means of dilatometry and coercive force (H_c) measurements. Two maxima were observed in the H_c -T relationships: the first H_c peak occurred at the Curie temperature of the austenite and is attributable to magnetic effects in a material containing two ferromagnetic phases; the second H_c peak, with values near 400 oe, is caused by reverse transformation wherein the remaining ferromagnetic martensite has increased coercivity due to decreased particle size and increased shape anisotropy. Dilatometric measurements display a gradual decrease in expansivity in the early stages of reversal. This observation is explained by a two-step process for shear-type transformation in which the first austenite formed has high magnetostriction and low expansivity. As the magnetostriction is lost by further heating, a large expansion occurs which counteracts contraction due to the crystallographic phase change.     

Die Ästigkeit des in den Leimbaubetrieben verwendeten Schmittholzes

The KAR-values of the occuring knots from 456 boards, as well as their position in the boards were investigated. The boards came from three different growth areas; two various board widths of each grade were examined. The results showed that neither the growth area, nor the board width have a statistically based influence on the knot distribution, and that the difference between grades is not as important as expected.     

Einfluß keilgezinkter Lamellen auf die Biegefestigkeit von Brettschichtholzträgern

With the computer model explained in the proceding paper, the load-carrying capacity of straight glulam beams of certain configuration can be predicted. In this part the basis for simulating the built-up of a beam is described. The stiffness and strength values of each 15 cm long board section are determined using regression equations. Based on 239 tension tests with finger-jointed boards the strength values of finger-joints needed for the computer model were achieved. Thus, with a finite element programme the bending strength of straight glulam beams can be predicted.     

Biohydrometallurgical/UV production of ferrous sulphate heptahydrate crystals from pyrite present in coal tailings

The objective of this work was to develop a biohydrometallurgical/UV radiation route to produce ferrous sulphate heptahydrate (melanterite) from the pyrite present in coal tailings. The experimental work was carried out with a pyrite concentrate obtained from gravimetric processing of coal tailing. At laboratory scale it was performed the oxidation of pyrite in an aqueous medium in packed bed leaching columns in an oxidising environment with the presence of acidophilic bacteria (Acidithiobacillus ferrooxidans). The recirculation of the liquor allowed obtaining an iron-rich extract. The conversion of Fe³⁺ to Fe²⁺ was performed using ultraviolet irradiation (UV). Finally, the solution was evaporated allowing the formation of iron sulphate crystals. The results demonstrated that it is possible to produce high purity ferrous sulphate heptahydrate crystals using coal tailings as raw material.     

Munich dark matter search

We plan a dark matter search using cryogenic calorimetric detectors with superconducting phase transition thermometers. We discuss such an experiment, compare its estimated sensitivity range with other dark matter searches, and discuss its planned realization.     

Bestimmung von purinhaltigen Verbindungen und Purinbasen in Lebensmitteln

Zusammenfassung In handelsüblichen rohen Lebensmitteln wird der Gesamtpuringehalt Bowie der Gehalt der jeweiligen Einzelkomponenten DNS, RNS, Nucleotide, Nucleoside und freie Purinbasen ermittelt. Der Gesamtpuringehalt wird nach Säurehydrolyse der Lebensmittel enzymatisch als Harnsäure bestimmt. Für die Bestimmung des Nucleinsduregehalts wird eine Methode gewählt, welche die direkte Analyse der Nucleinsäurezusammensetzung ermöglicht. Die Anteile der in Nucleinsäuren gebundenen Purine und der Anteil der Purine aus. Nucleosiden, Nucleosiden und Purinbasen am Gesamtpuringehalt variieren sehr stark. Besonders nucleinsäurereich sind die Innereien von Kalb, Schwein und Rind. Der Purinanteil aus Nucleotiden, Nucleosiden und Basen am Gesamtpuringehalt ist in diesen Proben gering. Demgegenüber übertrifft in Hering und Forelle der genannte Anteil deutlich den aus DNS- und RNS-Purinen. Das gleiche gilt für Muskelgewebe von Reh, Rind and Schwein. In Erbsen und Bohnen liegt der niedrigste Gesamtpuringehalt der untersuchten Proben vor.

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Determination of purine compounds and purine bases in food

Summary The total purine content and the content of RNA, DNA, nucleotides, nucleosides and free purine bases has been determined in commercial raw food. After hydrolysing food samples with acid, the total purine content is enzymatically determined as uric acid. For the determination of the nucleic acid content, a method is chosen that allows for the analysis of the composition of nucleic acids. The amount of purine bound in nucleic acids and of purine bound in nucleotides, nucleosides and free bases is very different. The content of nucleic acids is especially high in the innards of veal, pork and beef. In these samples the quantity of purine bound in nucleotides, nucleosides and bases is very small. In trout and herring, however, more purine is bound in RNA and DNA. The same is true of roe, pork and beef muscle. Peas and beans have the lowest total purine content of all the samples examined.

     

Use of proximity effect in iridium-gold superconducting phase transition thermometers

We have studied the proximity effect in bilayers of thin films of iridium covered by gold. These structures were evaporated onto sapphire single crystals for use as phase transition thermometers in cryogenic particle detectors. By varying the thicknesses of the iridium and gold layers, we achieved critical temperatures as low as 33 mK. The critical temperature of the bilayers is lower than predicted by the theory of de Gennes-Werthamer, but adding a free parameter to the theory allows good agreement. The transitions of the bilayers typically had widths of a few mK, with the narrowest reaching 0.2 mK, and were always sharper than those of pure iridium films evaporated simultaneously.     

Einfluß des Volumens und der Spannungsverteilung auf die Festigkeit eines Rechteckträgers

In this part, possibilities for the determination of the fullness-parameters are given. With the help of some examples it is shown, that the strength of a material is not only determined by the size of the stressed volume, but also by the stress distribution over this volume.     

Correlation of coercive force to microstructure in cyclic martensite → austenite transformations in an fe-ni-co alloy

Microstructural changes which occur in an Fe-29 Ni-18 Co alloy during cyclic martensite austenite transformations have been monitored by coercive force measurements and transmission electron microscopy. Cycling was performed between liquid nitrogen and temperatures between 400°C (just aboveAs) and 800°C (about 100°C above A_f). For all temperatures belowAf, there was no measurable change in the value ofHc following immersion in liquid nitrogen; changes inHc occurred only in a subsequent high temperature cycle. This stabilization of the reversed austenite was attributed to transformation-induced strains. On the other hand, for temperatures of 700° and 800°C and any given cycle,Hc following liquid nitrogen immersion indicated formation of new martensite. At 800°C, transformation-induced strains were sufficient to promote recrystallization of the reversed austenite. An irrational martensitic habit plane for the nucleation of the reversed austenite was identified. Formerly Senior Engineer, Westinghouse Research and Development Center