In shape-memory alloys a first-order martensitic phase transition is responsible for pseudo-elastic and for ferro-elastic stress-strain relations. To describe this behaviour a modified Landau theory is proposed in which the free energy of the crystal depends on the temperature and on the full strain tensor. The energy is invariant with respect to the cubic point group Oh of the high-temperature phase. To predict the cubic-to-monoclinic phase transitionofb-phaseshape-memory alloysanexpansion uptosixthorder instrain isnecessary for which, for the class of alloys considered, odd terms may be neglected. For a CuAlNi alloy the expansion coefficients are determined by comparison with experimental results. In contrast to classical Landau theory of second-order phase transitions, not only a single second-order but also a fourth-order expansion coefficient depend on temperature.

Non-uniformity of superconductor properties, e.g. a critical current reduction close to the edge of a coated conductor (CC) tape could degrade its performance in some power applications. Reliable characterization of such non-uniformity and understanding of its mechanism requires investigation of the character and causes of degradation. In this paper spatial distribution of critical current density across the width of a CC tape is studied. Three different experimental methods allowing estimation of the local current density were utilized for this purpose: (i) magnetic field mapping above the tape through which a DC current is flowing, (ii) measurement of the critical current of separate strips prepared by patterning of the CC tape, and (iii) magnetization measurements of the pieces cut from various positions within the tape width. Very good agreement between the results obtained by these methods was found, showing a reduction of the critical current density at the tape edges with respect to its centre. Moreover, structural investigation by scanning electron microscopy revealed a correlation between the morphology and the critical current density across the tape width. Insertion of such real non-uniform distribution of critical current density into AC loss calculation resulted in a dramatic improvement in the agreement with experimental results.

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Superconducting layer in coated conductor was investigated to assess the inhomogeneities present in its structure and to get better insight into the effect of inhomogeneities on degradation of electric properties. In the investigation scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron backscattered diffraction, and laser scanning confocal microscopy were used. The results obtained showed good correlation between the density of inhomogeneities across the tape width and the degradation of current transport properties determined by measurements of the current density