A general expression is derived for the residual electrical resistivity for alloys with arbitrary gradients of the concentration and the degree of order. It is applied to disordered alloys, to spinodally decomposed ones as well as for two phase structures, taking care of the finiteness of the electron mean free path A. I n the latter case maxima of the residual resistivity appear, if the precipitate size is of the order of magnitude of the electron mean free path A. This agrees well with a very critical experiment, in which one and the same microstructure is analysed with electrons of varying mean free path A.Es wird ein allgemeiner Ausdruck fur den elektrischen Restwiderstand von Legierungen mit beliebigen Gradienten der Konzentration und des Ordnungsgrades abgeleitet. Er wird sowohl fur ungeordnete und fur spinodal entmischte Legierungen, als auch fur Zweiphasensysteme angewandt, wobei die Endlichkeit c?er mittleren freien Elektronenwegliinge berucksichtigt wird. Im letzten Fall treten Maxima des Restwiderstandes auf, wenn die AusscheidungsgroDe die GroSenordnung der mittleren freien Elektronenwegliinge hat. Das stimmt mit einem sehr kritischen Experiment uberein, in dem die Mikrostruktur mit Elektronen verschiedener freier Elektronenweglinge analysiert wird.

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The stability of a precipitated two phase structure is analysed with respect to changes in number and size of the precipitated domains, using the equilibrium interfacial concentration profile and width of part I of this paper, and keeping the precipitate volume fraction at a constant value. Thereby the total system energy may show an absolute minimum at a finite precipitate size, if the ratio η out of the interfacial self energy component and of the pair potential strength stays below a certain value in the case of ordering alloys. This is caused by an increase of the absolute value of the negative pair interaction energy component during coarsening, leading to a drop of the interface energy density. η is fitted to parts of the FeAl and the CuAl phase diagrams, leading to a transition region between classical one and two phase zones of the phase diagram, that is characterized by an unorthodox kinetic behaviour of the microstructure. This microstructure might interpret several experiments.

Ordering and disordering to a short‐range ordered (SRO) state was studied by suddenly changing the annealing temperature by 5 deg after establishment of equilibrium. The measurement of residual resistivity indicates the existence of two kinetic processes. This and an ordering rate, that is smaller than the disordering rate harmonize better with inhomogeneous SRO, than with homogeneous SRO, often assumed in α‐CuAl. A quantitative comparison of experimental results with an inhomogeneous SRO‐model is given.