The first representation theorem establishes a correspondence between positive, self-adjoint operators and closed, positive
forms on Hilbert spaces. The aim of this paper is to show that some of the results remain true if the underlying space is
a reflexive Banach space. In particular, the construction of the Friedrichs extension and the form sum of positive operators
can be carried over to this case.
The phase changes in the solid state in E AlMgSi alloy are discussed. The dissolution and precipitation processes are investigated by DTA, and the results can be applied to control the technological parameters of dissolution heat treatments.