Gd Gerard Rieck

Diffusion in the titanium-aluminium system—I. Interdiffusion between solid Al and Ti or Ti-Al alloys☆

Pure Ti as well as Ti—Al alloys have been coated in various ways with a pure solid Al layer and interdiffusion in the temperature range between 516 and 642°C has been investigated. In each case, a well adherent layer of TiAl3 is formed, growing according to a peculiar time-dependence. No other intermetallic compounds show up and no solid solution of Al in Ti arises. Two types of crystal structure of the TiAl3 layer have been found, depending on the temperature at which the layer was formed and on the composition of the starting alloy.

Diffusion in the titanium-aluminium system—II. Interdiffusion in the composition range between 25 and 100 at.% Ti

Abstract Interdiffusion phenomena have been investigated m the Ti-Al system in the region from 25 to 100 at.% Ti at temperatures between 700 and 1200°C. The phase diagram of the Ti-Al system has been constructed using data from concentration-penetration curves recorded for various types of diffusion couples. In the composition range ≲ 25 at.% Al, the phase diagram is found to agree with that proposed by Blackburn. In the Al-rich part of the diagram a phase Ti 2 Al 5 was found which is probably the same as the compound Ti 5 Al 11 reported by Schubert et al . The growth of the various diffusion layers is non-parabolic; the reason is supposed to be the influence of grain boundary diffusion. The latter decreases steadily with increasing annealing time as a result of grain growth in the layer. Ti is the most mobile element in the Ti 3 Al phase at temperatures between 768–865°C, whereas in the Al-richer compounds Al is the most mobile element at temperatures between 784–972°C.

Thermotransport of oxygen in β-zirconium☆

Abstract A method is described by which the thermotransport of oxygen in β-ziroonium has been studied. The heat of transport turns out to be 20 kcal/g-atom with a standard deviation of 2 kcal/g-atom. The periods of time which are necessary to reach a nearly-steady state distribution of the oxygen under various conditions have been calculated by a method analogous to the one given by Sawatsky and Vogt. The heat of transport of nitrogen in β-zirconium is proved to be positive.

Thermotransport of nitrogen and oxygen in β-zirconium

Abstract An investigation of thermotransport of nitrogen in β-zirconium is reported. Using a method previously described, the heat of transport turned out to be 25.1 kcal/mole with a standard deviation of 2.5 kcal/mole. The formerly published value of the heat of transport of oxygen in β-zirconium, viz. 20 kcal/mole (standard deviation 2 kcal/mole), has been readjusted to 21.3 kcal/mole (standard deviation 2.9 kcal/mole).

THERMOTRANSPORT OF OXYGEN AND NITROGEN IN TITANIUM, NIOBIUM, AND TANTALUM: A QUALITATIVE INVESTIGATION.

Abstract Thermotransport of oxygen and nitrogen in β-titanium, niobium and tantalum has been studied in a qualitative way using a method previously described. The heat of transport of oxygen and nitrogen in β-titanium is positive. The heat of transport of oxygen, and probably also that of nitrogen, in niobium is very slight. The heat of transport of oxygen in tantalum is negative: a rough estimate has yielded a value of approximately −10 kcal/mole. Strong evidence was obtained that the heat of transport of oxygen and nitrogen in α-titanium is also negative.

The use of standards in the quantitative electron probe micro analysis of binary metal systems

SummaryFor the binary metal systems investigated, the Ziebold-Ogilvie relation has been found to be valid. It has been shown that polyphase alloys may be used as calibration standards if some specific conditions are fulfilled. In connection with a long-term instability of the microprobe apparatus, the Ziebold-Ogilvie constant of the calibration curve may vary with time. There is no reason for assuming that this instability is restricted to the particular instrument used. Therefore it is recommended that one or two standard alloys be used together with the pure reference metal to determine that constant every time concentration measurements have to be performed. The effect of the long-term instability can hardly be taken into account in the usual theoretically-based correction procedures.ZusammenfassungFür die hier untersuchten binären Metallsysteme hat sich die von Ziebold und Ogilvie angegebene Beziehung als gültig erwiesen. Wie sich zeigen ließ, kann man mehrphasige Legierungen als Eichstandards verwenden, wenn gewisse Voraussetzungen erfüllt sind. In Zusammenhang mit der Langzeit-Instabilität der Mikrosonde kann es sein, daß sich die Konstante der Ziebold-Ogilvie-Kurve mit der Zeit ändert. Es besteht kein Grund zur Annahme, daß diese Instabilität auf das eine benutzte Instrument beschränkt ist. Daher wird empfohlen, ein oder zwei Standardlegierungen zusammen mit dem reinen Bezugsmetall zu verwenden, um jederzeit die Gewähr für einwandfreie Meßergebnisse zu haben. Die Auswirkung der Langzeit-Instabilität kann bei dem üblichen, theoretisch ermittelten Korrekturverfahren nur schwer in Rechnung gestellt werden.